diff ezBAMQC/src/htslib/vcf.c @ 0:dfa3745e5fd8

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author youngkim
date Thu, 24 Mar 2016 17:12:52 -0400
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--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/ezBAMQC/src/htslib/vcf.c	Thu Mar 24 17:12:52 2016 -0400
@@ -0,0 +1,3212 @@
+/*  vcf.c -- VCF/BCF API functions.
+
+    Copyright (C) 2012, 2013 Broad Institute.
+    Copyright (C) 2012-2014 Genome Research Ltd.
+    Portions copyright (C) 2014 Intel Corporation.
+
+    Author: Heng Li <lh3@sanger.ac.uk>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.  */
+
+#include <zlib.h>
+#include <stdio.h>
+#include <ctype.h>
+#include <assert.h>
+#include <string.h>
+#include <stdlib.h>
+#include <limits.h>
+#include "htslib/kstring.h"
+#include "htslib/bgzf.h"
+#include "htslib/vcf.h"
+#include "htslib/tbx.h"
+#include "htslib/hfile.h"
+#include "htslib/khash_str2int.h"
+
+#include "htslib/khash.h"
+KHASH_MAP_INIT_STR(vdict, bcf_idinfo_t)
+typedef khash_t(vdict) vdict_t;
+
+#include "htslib/kseq.h"
+KSTREAM_DECLARE(gzFile, gzread)
+
+uint32_t bcf_float_missing    = 0x7F800001;
+uint32_t bcf_float_vector_end = 0x7F800002;
+uint8_t bcf_type_shift[] = { 0, 0, 1, 2, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
+static bcf_idinfo_t bcf_idinfo_def = { .info = { 15, 15, 15 }, .hrec = { NULL, NULL, NULL}, .id = -1 };
+
+/*************************
+ *** VCF header parser ***
+ *************************/
+
+int bcf_hdr_sync(bcf_hdr_t *h);
+
+int bcf_hdr_add_sample(bcf_hdr_t *h, const char *s)
+{
+    if ( !s ) return 0;
+
+    const char *ss = s;
+    while ( !*ss && isspace(*ss) ) ss++;
+    if ( !*ss )
+    {
+        fprintf(stderr,"[E::%s] Empty sample name: trailing spaces/tabs in the header line?\n", __func__);
+        abort();
+    }
+
+    vdict_t *d = (vdict_t*)h->dict[BCF_DT_SAMPLE];
+    int ret;
+    char *sdup = strdup(s);
+    int k = kh_put(vdict, d, sdup, &ret);
+    if (ret) { // absent
+        kh_val(d, k) = bcf_idinfo_def;
+        kh_val(d, k).id = kh_size(d) - 1;
+    } else {
+        if (hts_verbose >= 2)
+        {
+            fprintf(stderr, "[E::%s] Duplicated sample name '%s'\n", __func__, s);
+            abort();
+        }
+        free(sdup);
+        return -1;
+    }
+    int n = kh_size(d);
+    h->samples = (char**) realloc(h->samples,sizeof(char*)*n);
+    h->samples[n-1] = sdup;
+    h->dirty = 1;
+    return 0;
+}
+
+int bcf_hdr_parse_sample_line(bcf_hdr_t *h, const char *str)
+{
+    int ret = 0;
+    int i = 0;
+    const char *p, *q;
+    // add samples
+    for (p = q = str;; ++q) {
+        if (*q != '\t' && *q != 0 && *q != '\n') continue;
+        if (++i > 9) {
+            char *s = (char*)malloc(q - p + 1);
+            strncpy(s, p, q - p);
+            s[q - p] = 0;
+            if ( bcf_hdr_add_sample(h,s) < 0 ) ret = -1;
+            free(s);
+        }
+        if (*q == 0 || *q == '\n') break;
+        p = q + 1;
+    }
+    bcf_hdr_add_sample(h,NULL);
+    return ret;
+}
+
+int bcf_hdr_sync(bcf_hdr_t *h)
+{
+    int i;
+    for (i = 0; i < 3; i++)
+    {
+        vdict_t *d = (vdict_t*)h->dict[i];
+        khint_t k;
+
+        // find out the largest id, there may be holes because of IDX
+        int max_id = -1;
+        for (k=kh_begin(d); k<kh_end(d); k++)
+        {
+            if (!kh_exist(d,k)) continue;
+            if ( max_id < kh_val(d,k).id ) max_id = kh_val(d,k).id;
+        }
+        if ( max_id >= h->n[i] )
+        {
+            h->id[i] = (bcf_idpair_t*)realloc(h->id[i], (max_id+1)*sizeof(bcf_idpair_t));
+            for (k=h->n[i]; k<=max_id; k++)
+            {
+                h->id[i][k].key = NULL;
+                h->id[i][k].val = NULL;
+            }
+            h->n[i] = max_id+1;
+        }
+        for (k=kh_begin(d); k<kh_end(d); k++)
+        {
+            if (!kh_exist(d,k)) continue;
+            h->id[i][kh_val(d,k).id].key = kh_key(d,k);
+            h->id[i][kh_val(d,k).id].val = &kh_val(d,k);
+        }
+    }
+    h->dirty = 0;
+    return 0;
+}
+
+void bcf_hrec_destroy(bcf_hrec_t *hrec)
+{
+    free(hrec->key);
+    if ( hrec->value ) free(hrec->value);
+    int i;
+    for (i=0; i<hrec->nkeys; i++)
+    {
+        free(hrec->keys[i]);
+        free(hrec->vals[i]);
+    }
+    free(hrec->keys);
+    free(hrec->vals);
+    free(hrec);
+}
+
+// Copies all fields except IDX.
+bcf_hrec_t *bcf_hrec_dup(bcf_hrec_t *hrec)
+{
+    bcf_hrec_t *out = (bcf_hrec_t*) calloc(1,sizeof(bcf_hrec_t));
+    out->type = hrec->type;
+    if ( hrec->key ) out->key = strdup(hrec->key);
+    if ( hrec->value ) out->value = strdup(hrec->value);
+    out->nkeys = hrec->nkeys;
+    out->keys = (char**) malloc(sizeof(char*)*hrec->nkeys);
+    out->vals = (char**) malloc(sizeof(char*)*hrec->nkeys);
+    int i, j = 0;
+    for (i=0; i<hrec->nkeys; i++)
+    {
+        if ( hrec->keys[i] && !strcmp("IDX",hrec->keys[i]) ) continue;
+        if ( hrec->keys[i] ) out->keys[j] = strdup(hrec->keys[i]);
+        if ( hrec->vals[i] ) out->vals[j] = strdup(hrec->vals[i]);
+        j++;
+    }
+    if ( i!=j ) out->nkeys -= i-j;   // IDX was omitted
+    return out;
+}
+
+void bcf_hrec_debug(FILE *fp, bcf_hrec_t *hrec)
+{
+    fprintf(fp, "key=[%s] value=[%s]", hrec->key, hrec->value?hrec->value:"");
+    int i;
+    for (i=0; i<hrec->nkeys; i++)
+        fprintf(fp, "\t[%s]=[%s]", hrec->keys[i],hrec->vals[i]);
+    fprintf(fp, "\n");
+}
+
+void bcf_header_debug(bcf_hdr_t *hdr)
+{
+    int i, j;
+    for (i=0; i<hdr->nhrec; i++)
+    {
+        if ( !hdr->hrec[i]->value )
+        {
+            fprintf(stderr, "##%s=<", hdr->hrec[i]->key);
+            fprintf(stderr,"%s=%s", hdr->hrec[i]->keys[0], hdr->hrec[i]->vals[0]);
+            for (j=1; j<hdr->hrec[i]->nkeys; j++)
+                fprintf(stderr,",%s=%s", hdr->hrec[i]->keys[j], hdr->hrec[i]->vals[j]);
+            fprintf(stderr,">\n");
+        }
+        else
+            fprintf(stderr,"##%s=%s\n", hdr->hrec[i]->key,hdr->hrec[i]->value);
+    }
+}
+
+void bcf_hrec_add_key(bcf_hrec_t *hrec, const char *str, int len)
+{
+    int n = ++hrec->nkeys;
+    hrec->keys = (char**) realloc(hrec->keys, sizeof(char*)*n);
+    hrec->vals = (char**) realloc(hrec->vals, sizeof(char*)*n);
+    assert( len );
+    hrec->keys[n-1] = (char*) malloc((len+1)*sizeof(char));
+    memcpy(hrec->keys[n-1],str,len);
+    hrec->keys[n-1][len] = 0;
+    hrec->vals[n-1] = NULL;
+}
+
+void bcf_hrec_set_val(bcf_hrec_t *hrec, int i, const char *str, int len, int is_quoted)
+{
+    if ( !str ) { hrec->vals[i] = NULL; return; }
+    if ( hrec->vals[i] ) free(hrec->vals[i]);
+    if ( is_quoted )
+    {
+        hrec->vals[i] = (char*) malloc((len+3)*sizeof(char));
+        hrec->vals[i][0] = '"';
+        memcpy(&hrec->vals[i][1],str,len);
+        hrec->vals[i][len+1] = '"';
+        hrec->vals[i][len+2] = 0;
+    }
+    else
+    {
+        hrec->vals[i] = (char*) malloc((len+1)*sizeof(char));
+        memcpy(hrec->vals[i],str,len);
+        hrec->vals[i][len] = 0;
+    }
+}
+
+void hrec_add_idx(bcf_hrec_t *hrec, int idx)
+{
+    int n = ++hrec->nkeys;
+    hrec->keys = (char**) realloc(hrec->keys, sizeof(char*)*n);
+    hrec->vals = (char**) realloc(hrec->vals, sizeof(char*)*n);
+    hrec->keys[n-1] = strdup("IDX");
+    kstring_t str = {0,0,0};
+    kputw(idx, &str);
+    hrec->vals[n-1] = str.s;
+}
+
+int bcf_hrec_find_key(bcf_hrec_t *hrec, const char *key)
+{
+    int i;
+    for (i=0; i<hrec->nkeys; i++)
+        if ( !strcasecmp(key,hrec->keys[i]) ) return i;
+    return -1;
+}
+
+static inline int is_escaped(const char *min, const char *str)
+{
+    int n = 0;
+    while ( --str>=min && *str=='\\' ) n++;
+    return n%2;
+}
+
+bcf_hrec_t *bcf_hdr_parse_line(const bcf_hdr_t *h, const char *line, int *len)
+{
+    const char *p = line;
+    if (p[0] != '#' || p[1] != '#') { *len = 0; return NULL; }
+    p += 2;
+
+    const char *q = p;
+    while ( *q && *q!='=' ) q++;
+    int n = q-p;
+    if ( *q!='=' || !n ) { *len = q-line+1; return NULL; } // wrong format
+
+    bcf_hrec_t *hrec = (bcf_hrec_t*) calloc(1,sizeof(bcf_hrec_t));
+    hrec->key = (char*) malloc(sizeof(char)*(n+1));
+    memcpy(hrec->key,p,n);
+    hrec->key[n] = 0;
+
+    p = ++q;
+    if ( *p!='<' ) // generic field, e.g. ##samtoolsVersion=0.1.18-r579
+    {
+        while ( *q && *q!='\n' ) q++;
+        hrec->value = (char*) malloc((q-p+1)*sizeof(char));
+        memcpy(hrec->value, p, q-p);
+        hrec->value[q-p] = 0;
+        *len = q-line+1;
+        return hrec;
+    }
+
+    // structured line, e.g. ##INFO=<ID=PV1,Number=1,Type=Float,Description="P-value for baseQ bias">
+    int nopen = 1;
+    while ( *q && *q!='\n' && nopen )
+    {
+        p = ++q;
+        while ( *q && isalnum(*q) ) q++;
+        n = q-p;
+        if ( *q!='=' || !n )
+        {
+            // wrong format
+            while ( *q && *q!='\n' ) q++;
+            kstring_t tmp = {0,0,0};
+            kputsn(line,q-line,&tmp);
+            fprintf(stderr,"Could not parse the header line: \"%s\"\n", tmp.s);
+            free(tmp.s);
+            *len = q-line+1;
+            bcf_hrec_destroy(hrec);
+            return NULL;
+        }
+        bcf_hrec_add_key(hrec, p, q-p);
+        p = ++q;
+        int quoted = *p=='"' ? 1 : 0;
+        if ( quoted ) p++, q++;
+        while (1)
+        {
+            if ( !*q ) break;
+            if ( quoted ) { if ( *q=='"' && !is_escaped(p,q) ) break; }
+            else
+            {
+                if ( *q=='<' ) nopen++;
+                if ( *q=='>' ) nopen--;
+                if ( !nopen ) break;
+                if ( *q==',' && nopen==1 ) break;
+            }
+            q++;
+        }
+        bcf_hrec_set_val(hrec, hrec->nkeys-1, p, q-p, quoted);
+        if ( quoted ) q++;
+        if ( *q=='>' ) { nopen--; q++; }
+    }
+    *len = q-line+1;
+    return hrec;
+}
+
+// returns: 1 when hdr needs to be synced, 0 otherwise
+int bcf_hdr_register_hrec(bcf_hdr_t *hdr, bcf_hrec_t *hrec)
+{
+    // contig
+    int i,j,k, ret;
+    char *str;
+    if ( !strcmp(hrec->key, "contig") )
+    {
+        hrec->type = BCF_HL_CTG;
+
+        // Get the contig ID ($str) and length ($j)
+        i = bcf_hrec_find_key(hrec,"length");
+        if ( i<0 ) j = 0;
+        else if ( sscanf(hrec->vals[i],"%d",&j)!=1 ) return 0;
+
+        i = bcf_hrec_find_key(hrec,"ID");
+        if ( i<0 ) return 0;
+        str = strdup(hrec->vals[i]);
+
+        // Register in the dictionary
+        vdict_t *d = (vdict_t*)hdr->dict[BCF_DT_CTG];
+        k = kh_put(vdict, d, str, &ret);
+        if ( !ret ) { free(str); return 0; }    // already present
+
+        int idx = bcf_hrec_find_key(hrec,"IDX");
+        if ( idx!=-1 )
+        {
+            char *tmp = hrec->vals[idx];
+            idx = strtol(hrec->vals[idx], &tmp, 10);
+            if ( *tmp )
+            {
+                fprintf(stderr,"[%s:%d %s] Error parsing the IDX tag, skipping.\n", __FILE__,__LINE__,__FUNCTION__);
+                return 0;
+            }
+        }
+        else
+        {
+            idx = kh_size(d) - 1;
+            hrec_add_idx(hrec, idx);
+        }
+
+        kh_val(d, k) = bcf_idinfo_def;
+        kh_val(d, k).id = idx;
+        kh_val(d, k).info[0] = j;
+        kh_val(d, k).hrec[0] = hrec;
+
+        return 1;
+    }
+
+    if ( !strcmp(hrec->key, "INFO") ) hrec->type = BCF_HL_INFO;
+    else if ( !strcmp(hrec->key, "FILTER") ) hrec->type = BCF_HL_FLT;
+    else if ( !strcmp(hrec->key, "FORMAT") ) hrec->type = BCF_HL_FMT;
+    else if ( hrec->nkeys>0 ) { hrec->type = BCF_HL_STR; return 1; }
+    else return 0;
+
+    // INFO/FILTER/FORMAT
+    char *id = NULL;
+    int type = -1, num = -1, var = -1, idx = -1;
+    for (i=0; i<hrec->nkeys; i++)
+    {
+        if ( !strcmp(hrec->keys[i], "ID") ) id = hrec->vals[i];
+        else if ( !strcmp(hrec->keys[i], "IDX") )
+        {
+            char *tmp = hrec->vals[i];
+            idx = strtol(hrec->vals[i], &tmp, 10);
+            if ( *tmp )
+            {
+                fprintf(stderr,"[%s:%d %s] Error parsing the IDX tag, skipping.\n", __FILE__,__LINE__,__FUNCTION__);
+                return 0;
+            }
+        }
+        else if ( !strcmp(hrec->keys[i], "Type") )
+        {
+            if ( !strcmp(hrec->vals[i], "Integer") ) type = BCF_HT_INT;
+            else if ( !strcmp(hrec->vals[i], "Float") ) type = BCF_HT_REAL;
+            else if ( !strcmp(hrec->vals[i], "String") ) type = BCF_HT_STR;
+            else if ( !strcmp(hrec->vals[i], "Character") ) type = BCF_HT_STR;
+            else if ( !strcmp(hrec->vals[i], "Flag") ) type = BCF_HT_FLAG;
+            else
+            {
+                fprintf(stderr, "[E::%s] The type \"%s\" not supported, assuming \"String\"\n", __func__, hrec->vals[i]);
+                type = BCF_HT_STR;
+            }
+        }
+        else if ( !strcmp(hrec->keys[i], "Number") )
+        {
+            if ( !strcmp(hrec->vals[i],"A") ) var = BCF_VL_A;
+            else if ( !strcmp(hrec->vals[i],"R") ) var = BCF_VL_R;
+            else if ( !strcmp(hrec->vals[i],"G") ) var = BCF_VL_G;
+            else if ( !strcmp(hrec->vals[i],".") ) var = BCF_VL_VAR;
+            else
+            {
+                sscanf(hrec->vals[i],"%d",&num);
+                var = BCF_VL_FIXED;
+            }
+            if (var != BCF_VL_FIXED) num = 0xfffff;
+        }
+    }
+    uint32_t info = (uint32_t)num<<12 | var<<8 | type<<4 | hrec->type;
+
+    if ( !id ) return 0;
+    str = strdup(id);
+
+    vdict_t *d = (vdict_t*)hdr->dict[BCF_DT_ID];
+    k = kh_put(vdict, d, str, &ret);
+    if ( !ret )
+    {
+        // already present
+        free(str);
+        if ( kh_val(d, k).hrec[info&0xf] ) return 0;
+        kh_val(d, k).info[info&0xf] = info;
+        kh_val(d, k).hrec[info&0xf] = hrec;
+        if ( idx==-1 ) hrec_add_idx(hrec, kh_val(d, k).id);
+        return 1;
+    }
+    kh_val(d, k) = bcf_idinfo_def;
+    kh_val(d, k).info[info&0xf] = info;
+    kh_val(d, k).hrec[info&0xf] = hrec;
+    kh_val(d, k).id = idx==-1 ? kh_size(d) - 1 : idx;
+
+    if ( idx==-1 ) hrec_add_idx(hrec, kh_val(d, k).id);
+
+    return 1;
+}
+
+int bcf_hdr_add_hrec(bcf_hdr_t *hdr, bcf_hrec_t *hrec)
+{
+    if ( !hrec ) return 0;
+
+    hrec->type = BCF_HL_GEN;
+    if ( !bcf_hdr_register_hrec(hdr,hrec) )
+    {
+        // If one of the hashed field, then it is already present
+        if ( hrec->type != BCF_HL_GEN )
+        {
+            bcf_hrec_destroy(hrec);
+            return 0;
+        }
+
+        // Is one of the generic fields and already present?
+        int i;
+        for (i=0; i<hdr->nhrec; i++)
+        {
+            if ( hdr->hrec[i]->type!=BCF_HL_GEN ) continue;
+            if ( !strcmp(hdr->hrec[i]->key,hrec->key) && !strcmp(hrec->key,"fileformat") ) break;
+            if ( !strcmp(hdr->hrec[i]->key,hrec->key) && !strcmp(hdr->hrec[i]->value,hrec->value) ) break;
+        }
+        if ( i<hdr->nhrec )
+        {
+            bcf_hrec_destroy(hrec);
+            return 0;
+        }
+    }
+
+    // New record, needs to be added
+    int n = ++hdr->nhrec;
+    hdr->hrec = (bcf_hrec_t**) realloc(hdr->hrec, n*sizeof(bcf_hrec_t*));
+    hdr->hrec[n-1] = hrec;
+    hdr->dirty = 1;
+
+    return hrec->type==BCF_HL_GEN ? 0 : 1;
+}
+
+/*
+ *  Note that while querying of FLT,INFO,FMT,CTG lines is fast (the keys are hashed),
+ *  the STR,GEN lines are searched for linearly in a linked list of all header lines.
+ *  This may become a problem for VCFs with huge headers, we might need to build a
+ *  dictionary for these lines as well.
+ */
+bcf_hrec_t *bcf_hdr_get_hrec(const bcf_hdr_t *hdr, int type, const char *key, const char *value, const char *str_class)
+{
+    int i;
+    if ( type==BCF_HL_GEN )
+    {
+        for (i=0; i<hdr->nhrec; i++)
+        {
+            if ( hdr->hrec[i]->type!=type ) continue;
+            if ( strcmp(hdr->hrec[i]->key,key) ) continue;
+            if ( !value || !strcmp(hdr->hrec[i]->value,value) ) return hdr->hrec[i];
+        }
+        return NULL;
+    }
+    else if ( type==BCF_HL_STR )
+    {
+        for (i=0; i<hdr->nhrec; i++)
+        {
+            if ( hdr->hrec[i]->type!=type ) continue;
+            if ( strcmp(hdr->hrec[i]->key,str_class) ) continue;
+            int j = bcf_hrec_find_key(hdr->hrec[i],key);
+            if ( j>=0 && !strcmp(hdr->hrec[i]->vals[j],value) ) return hdr->hrec[i];
+        }
+        return NULL;
+    }
+    vdict_t *d = type==BCF_HL_CTG ? (vdict_t*)hdr->dict[BCF_DT_CTG] : (vdict_t*)hdr->dict[BCF_DT_ID];
+    khint_t k = kh_get(vdict, d, value);
+    if ( k == kh_end(d) ) return NULL;
+    return kh_val(d, k).hrec[type==BCF_HL_CTG?0:type];
+}
+
+void bcf_hdr_check_sanity(bcf_hdr_t *hdr)
+{
+    static int PL_warned = 0, GL_warned = 0;
+
+    if ( !PL_warned )
+    {
+        int id = bcf_hdr_id2int(hdr, BCF_DT_ID, "PL");
+        if ( bcf_hdr_idinfo_exists(hdr,BCF_HL_FMT,id) && bcf_hdr_id2length(hdr,BCF_HL_FMT,id)!=BCF_VL_G )
+        {
+            fprintf(stderr,"[W::%s] PL should be declared as Number=G\n", __func__);
+            PL_warned = 1;
+        }
+    }
+    if ( !GL_warned )
+    {
+        int id = bcf_hdr_id2int(hdr, BCF_HL_FMT, "GL");
+        if ( bcf_hdr_idinfo_exists(hdr,BCF_HL_FMT,id) && bcf_hdr_id2length(hdr,BCF_HL_FMT,id)!=BCF_VL_G )
+        {
+            fprintf(stderr,"[W::%s] GL should be declared as Number=G\n", __func__);
+            PL_warned = 1;
+        }
+    }
+}
+
+int bcf_hdr_parse(bcf_hdr_t *hdr, char *htxt)
+{
+    int len, needs_sync = 0;
+    char *p = htxt;
+
+    // Check sanity: "fileformat" string must come as first
+    bcf_hrec_t *hrec = bcf_hdr_parse_line(hdr,p,&len);
+    if ( !hrec || !hrec->key || strcasecmp(hrec->key,"fileformat") )
+        fprintf(stderr, "[W::%s] The first line should be ##fileformat; is the VCF/BCF header broken?\n", __func__);
+    needs_sync += bcf_hdr_add_hrec(hdr, hrec);
+
+    // The filter PASS must appear first in the dictionary
+    hrec = bcf_hdr_parse_line(hdr,"##FILTER=<ID=PASS,Description=\"All filters passed\">",&len);
+    needs_sync += bcf_hdr_add_hrec(hdr, hrec);
+
+    // Parse the whole header
+    while ( (hrec=bcf_hdr_parse_line(hdr,p,&len)) )
+    {
+        needs_sync += bcf_hdr_add_hrec(hdr, hrec);
+        p += len;
+    }
+    int ret = bcf_hdr_parse_sample_line(hdr,p);
+    bcf_hdr_sync(hdr);
+    bcf_hdr_check_sanity(hdr);
+    return ret;
+}
+
+int bcf_hdr_append(bcf_hdr_t *hdr, const char *line)
+{
+    int len;
+    bcf_hrec_t *hrec = bcf_hdr_parse_line(hdr, (char*) line, &len);
+    if ( !hrec ) return -1;
+    bcf_hdr_add_hrec(hdr, hrec);
+    return 0;
+}
+
+void bcf_hdr_remove(bcf_hdr_t *hdr, int type, const char *key)
+{
+    int i;
+    bcf_hrec_t *hrec;
+    while (1)
+    {
+        if ( type==BCF_HL_FLT || type==BCF_HL_INFO || type==BCF_HL_FMT || type== BCF_HL_CTG )
+        {
+            hrec = bcf_hdr_get_hrec(hdr, type, "ID", key, NULL);
+            if ( !hrec ) return;
+
+            for (i=0; i<hdr->nhrec; i++)
+                if ( hdr->hrec[i]==hrec ) break;
+            assert( i<hdr->nhrec );
+
+            vdict_t *d = type==BCF_HL_CTG ? (vdict_t*)hdr->dict[BCF_DT_CTG] : (vdict_t*)hdr->dict[BCF_DT_ID];
+            khint_t k = kh_get(vdict, d, key);
+            kh_val(d, k).hrec[type==BCF_HL_CTG?0:type] = NULL;
+        }
+        else
+        {
+            for (i=0; i<hdr->nhrec; i++)
+            {
+                if ( hdr->hrec[i]->type!=type ) continue;
+                if ( type==BCF_HL_GEN )
+                {
+                    if ( !strcmp(hdr->hrec[i]->key,key) ) break;
+                }
+                else
+                {
+                    // not all structured lines have ID, we could be more sophisticated as in bcf_hdr_get_hrec()
+                    int j = bcf_hrec_find_key(hdr->hrec[i], "ID");
+                    if ( j>=0 && !strcmp(hdr->hrec[i]->vals[j],key) ) break;
+                }
+            }
+            if ( i==hdr->nhrec ) return;
+            hrec = hdr->hrec[i];
+        }
+
+        hdr->nhrec--;
+        if ( i < hdr->nhrec )
+            memmove(&hdr->hrec[i],&hdr->hrec[i+1],(hdr->nhrec-i)*sizeof(bcf_hrec_t*));
+        bcf_hrec_destroy(hrec);
+        hdr->dirty = 1;
+    }
+}
+
+int bcf_hdr_printf(bcf_hdr_t *hdr, const char *fmt, ...)
+{
+    va_list ap;
+    va_start(ap, fmt);
+    int n = vsnprintf(NULL, 0, fmt, ap) + 2;
+    va_end(ap);
+
+    char *line = (char*)malloc(n);
+    va_start(ap, fmt);
+    vsnprintf(line, n, fmt, ap);
+    va_end(ap);
+
+    int ret = bcf_hdr_append(hdr, line);
+
+    free(line);
+    return ret;
+}
+
+
+/**********************
+ *** BCF header I/O ***
+ **********************/
+
+const char *bcf_hdr_get_version(const bcf_hdr_t *hdr)
+{
+    bcf_hrec_t *hrec = bcf_hdr_get_hrec(hdr, BCF_HL_GEN, "fileformat", NULL, NULL);
+    if ( !hrec )
+    {
+        fprintf(stderr,"No version string found, assuming VCFv4.2\n");
+        return "VCFv4.2";
+    }
+    return hrec->value;
+}
+
+void bcf_hdr_set_version(bcf_hdr_t *hdr, const char *version)
+{
+    bcf_hrec_t *hrec = bcf_hdr_get_hrec(hdr, BCF_HL_GEN, "fileformat", NULL, NULL);
+    if ( !hrec )
+    {
+        int len;
+        kstring_t str = {0,0,0};
+        ksprintf(&str,"##fileformat=%s", version);
+        hrec = bcf_hdr_parse_line(hdr, str.s, &len);
+        free(str.s);
+    }
+    else
+    {
+        free(hrec->value);
+        hrec->value = strdup(version);
+    }
+    hdr->dirty = 1;
+}
+
+bcf_hdr_t *bcf_hdr_init(const char *mode)
+{
+    int i;
+    bcf_hdr_t *h;
+    h = (bcf_hdr_t*)calloc(1, sizeof(bcf_hdr_t));
+    for (i = 0; i < 3; ++i)
+        h->dict[i] = kh_init(vdict);
+    if ( strchr(mode,'w') )
+    {
+        bcf_hdr_append(h, "##fileformat=VCFv4.2");
+        // The filter PASS must appear first in the dictionary
+        bcf_hdr_append(h, "##FILTER=<ID=PASS,Description=\"All filters passed\">");
+    }
+    return h;
+}
+
+void bcf_hdr_destroy(bcf_hdr_t *h)
+{
+    int i;
+    khint_t k;
+    for (i = 0; i < 3; ++i) {
+        vdict_t *d = (vdict_t*)h->dict[i];
+        if (d == 0) continue;
+        for (k = kh_begin(d); k != kh_end(d); ++k)
+            if (kh_exist(d, k)) free((char*)kh_key(d, k));
+        kh_destroy(vdict, d);
+        free(h->id[i]);
+    }
+    for (i=0; i<h->nhrec; i++)
+        bcf_hrec_destroy(h->hrec[i]);
+    if (h->nhrec) free(h->hrec);
+    if (h->samples) free(h->samples);
+    free(h->keep_samples);
+    free(h->transl[0]); free(h->transl[1]);
+    free(h->mem.s);
+    free(h);
+}
+
+bcf_hdr_t *bcf_hdr_read(htsFile *hfp)
+{
+    if (hfp->format.format == vcf)
+        return vcf_hdr_read(hfp);
+
+    BGZF *fp = hfp->fp.bgzf;
+    uint8_t magic[5];
+    bcf_hdr_t *h;
+    h = bcf_hdr_init("r");
+    if ( bgzf_read(fp, magic, 5)<0 )
+    {
+        fprintf(stderr,"[%s:%d %s] Failed to read the header (reading BCF in text mode?)\n", __FILE__,__LINE__,__FUNCTION__);
+        return NULL;
+    }
+    if (strncmp((char*)magic, "BCF\2\2", 5) != 0)
+    {
+        if (!strncmp((char*)magic, "BCF", 3))
+            fprintf(stderr,"[%s:%d %s] invalid BCF2 magic string: only BCFv2.2 is supported.\n", __FILE__,__LINE__,__FUNCTION__);
+        else if (hts_verbose >= 2)
+            fprintf(stderr, "[E::%s] invalid BCF2 magic string\n", __func__);
+        bcf_hdr_destroy(h);
+        return 0;
+    }
+    int hlen;
+    char *htxt;
+    bgzf_read(fp, &hlen, 4);
+    htxt = (char*)malloc(hlen);
+    bgzf_read(fp, htxt, hlen);
+    bcf_hdr_parse(h, htxt);
+    free(htxt);
+    return h;
+}
+
+int bcf_hdr_write(htsFile *hfp, bcf_hdr_t *h)
+{
+    if ( h->dirty ) bcf_hdr_sync(h);
+    if (hfp->format.format == vcf || hfp->format.format == text_format)
+        return vcf_hdr_write(hfp, h);
+
+    int hlen;
+    char *htxt = bcf_hdr_fmt_text(h, 1, &hlen);
+    hlen++; // include the \0 byte
+
+    BGZF *fp = hfp->fp.bgzf;
+    if ( bgzf_write(fp, "BCF\2\2", 5) !=5 ) return -1;
+    if ( bgzf_write(fp, &hlen, 4) !=4 ) return -1;
+    if ( bgzf_write(fp, htxt, hlen) != hlen ) return -1;
+
+    free(htxt);
+    return 0;
+}
+
+/********************
+ *** BCF site I/O ***
+ ********************/
+
+bcf1_t *bcf_init1()
+{
+    bcf1_t *v;
+    v = (bcf1_t*)calloc(1, sizeof(bcf1_t));
+    return v;
+}
+
+void bcf_clear(bcf1_t *v)
+{
+    int i;
+    for (i=0; i<v->d.m_info; i++)
+    {
+        if ( v->d.info[i].vptr_free )
+        {
+            free(v->d.info[i].vptr - v->d.info[i].vptr_off);
+            v->d.info[i].vptr_free = 0;
+        }
+    }
+    for (i=0; i<v->d.m_fmt; i++)
+    {
+        if ( v->d.fmt[i].p_free )
+        {
+            free(v->d.fmt[i].p - v->d.fmt[i].p_off);
+            v->d.fmt[i].p_free = 0;
+        }
+    }
+    v->rid = v->pos = v->rlen = v->unpacked = 0;
+    bcf_float_set_missing(v->qual);
+    v->n_info = v->n_allele = v->n_fmt = v->n_sample = 0;
+    v->shared.l = v->indiv.l = 0;
+    v->d.var_type = -1;
+    v->d.shared_dirty = 0;
+    v->d.indiv_dirty  = 0;
+    v->d.n_flt = 0;
+    v->errcode = 0;
+    if (v->d.m_als) v->d.als[0] = 0;
+    if (v->d.m_id) v->d.id[0] = 0;
+}
+
+void bcf_empty1(bcf1_t *v)
+{
+    bcf_clear1(v);
+    free(v->d.id);
+    free(v->d.als);
+    free(v->d.allele); free(v->d.flt); free(v->d.info); free(v->d.fmt);
+    if (v->d.var ) free(v->d.var);
+    free(v->shared.s); free(v->indiv.s);
+}
+
+void bcf_destroy1(bcf1_t *v)
+{
+    bcf_empty1(v);
+    free(v);
+}
+
+static inline int bcf_read1_core(BGZF *fp, bcf1_t *v)
+{
+    uint32_t x[8];
+    int ret;
+    if ((ret = bgzf_read(fp, x, 32)) != 32) {
+        if (ret == 0) return -1;
+        return -2;
+    }
+    bcf_clear1(v);
+    x[0] -= 24; // to exclude six 32-bit integers
+    ks_resize(&v->shared, x[0]);
+    ks_resize(&v->indiv, x[1]);
+    memcpy(v, x + 2, 16);
+    v->n_allele = x[6]>>16; v->n_info = x[6]&0xffff;
+    v->n_fmt = x[7]>>24; v->n_sample = x[7]&0xffffff;
+    v->shared.l = x[0], v->indiv.l = x[1];
+
+    // silent fix of broken BCFs produced by earlier versions of bcf_subset, prior to and including bd6ed8b4
+    if ( (!v->indiv.l || !v->n_sample) && v->n_fmt ) v->n_fmt = 0;
+
+    bgzf_read(fp, v->shared.s, v->shared.l);
+    bgzf_read(fp, v->indiv.s, v->indiv.l);
+    return 0;
+}
+
+#define bit_array_size(n) ((n)/8+1)
+#define bit_array_set(a,i)   ((a)[(i)/8] |=   1 << ((i)%8))
+#define bit_array_clear(a,i) ((a)[(i)/8] &= ~(1 << ((i)%8)))
+#define bit_array_test(a,i)  ((a)[(i)/8] &   (1 << ((i)%8)))
+
+static inline uint8_t *bcf_unpack_fmt_core1(uint8_t *ptr, int n_sample, bcf_fmt_t *fmt);
+int bcf_subset_format(const bcf_hdr_t *hdr, bcf1_t *rec)
+{
+    if ( !hdr->keep_samples ) return 0;
+    if ( !bcf_hdr_nsamples(hdr) )
+    {
+        rec->indiv.l = rec->n_sample = 0;
+        return 0;
+    }
+
+    int i, j;
+    uint8_t *ptr = (uint8_t*)rec->indiv.s, *dst = NULL, *src;
+    bcf_dec_t *dec = &rec->d;
+    hts_expand(bcf_fmt_t, rec->n_fmt, dec->m_fmt, dec->fmt);
+    for (i=0; i<dec->m_fmt; ++i) dec->fmt[i].p_free = 0;
+
+    for (i=0; i<rec->n_fmt; i++)
+    {
+        ptr = bcf_unpack_fmt_core1(ptr, rec->n_sample, &dec->fmt[i]);
+        src = dec->fmt[i].p - dec->fmt[i].size;
+        if ( dst )
+        {
+            memmove(dec->fmt[i-1].p + dec->fmt[i-1].p_len, dec->fmt[i].p - dec->fmt[i].p_off, dec->fmt[i].p_off);
+            dec->fmt[i].p = dec->fmt[i-1].p + dec->fmt[i-1].p_len + dec->fmt[i].p_off;
+        }
+        dst = dec->fmt[i].p;
+        for (j=0; j<hdr->nsamples_ori; j++)
+        {
+            src += dec->fmt[i].size;
+            if ( !bit_array_test(hdr->keep_samples,j) ) continue;
+            memmove(dst, src, dec->fmt[i].size);
+            dst += dec->fmt[i].size;
+        }
+        rec->indiv.l -= dec->fmt[i].p_len - (dst - dec->fmt[i].p);
+        dec->fmt[i].p_len = dst - dec->fmt[i].p;
+    }
+    rec->unpacked |= BCF_UN_FMT;
+
+    rec->n_sample = bcf_hdr_nsamples(hdr);
+    return 0;
+}
+
+int bcf_read(htsFile *fp, const bcf_hdr_t *h, bcf1_t *v)
+{
+    if (fp->format.format == vcf) return vcf_read(fp,h,v);
+    int ret = bcf_read1_core(fp->fp.bgzf, v);
+    if ( ret!=0 || !h->keep_samples ) return ret;
+    return bcf_subset_format(h,v);
+}
+
+int bcf_readrec(BGZF *fp, void *null, void *vv, int *tid, int *beg, int *end)
+{
+    bcf1_t *v = (bcf1_t *) vv;
+    int ret;
+    if ((ret = bcf_read1_core(fp, v)) >= 0)
+        *tid = v->rid, *beg = v->pos, *end = v->pos + v->rlen;
+    return ret;
+}
+
+static inline void bcf1_sync_id(bcf1_t *line, kstring_t *str)
+{
+    // single typed string
+    if ( line->d.id && strcmp(line->d.id, ".") ) bcf_enc_vchar(str, strlen(line->d.id), line->d.id);
+    else bcf_enc_size(str, 0, BCF_BT_CHAR);
+}
+static inline void bcf1_sync_alleles(bcf1_t *line, kstring_t *str)
+{
+    // list of typed strings
+    int i;
+    for (i=0; i<line->n_allele; i++)
+        bcf_enc_vchar(str, strlen(line->d.allele[i]), line->d.allele[i]);
+    if ( !line->rlen && line->n_allele ) line->rlen = strlen(line->d.allele[0]);
+}
+static inline void bcf1_sync_filter(bcf1_t *line, kstring_t *str)
+{
+    // typed vector of integers
+    if ( line->d.n_flt ) bcf_enc_vint(str, line->d.n_flt, line->d.flt, -1);
+    else bcf_enc_vint(str, 0, 0, -1);
+}
+
+static inline void bcf1_sync_info(bcf1_t *line, kstring_t *str)
+{
+    // pairs of typed vectors
+    int i, irm = -1;
+    for (i=0; i<line->n_info; i++)
+    {
+        bcf_info_t *info = &line->d.info[i];
+        if ( !info->vptr )
+        {
+            // marked for removal
+            if ( irm < 0 ) irm = i;
+            continue;
+        }
+        kputsn_(info->vptr - info->vptr_off, info->vptr_len + info->vptr_off, str);
+        if ( irm >=0 )
+        {
+            bcf_info_t tmp = line->d.info[irm]; line->d.info[irm] = line->d.info[i]; line->d.info[i] = tmp;
+            while ( irm<=i && line->d.info[irm].vptr ) irm++;
+        }
+    }
+    if ( irm>=0 ) line->n_info = irm;
+}
+
+static int bcf1_sync(bcf1_t *line)
+{
+    char *shared_ori = line->shared.s;
+    size_t prev_len;
+
+    kstring_t tmp = {0,0,0};
+    if ( !line->shared.l )
+    {
+        // New line created via API, BCF data blocks do not exist. Get it ready for BCF output
+        tmp = line->shared;
+        bcf1_sync_id(line, &tmp);
+        line->unpack_size[0] = tmp.l; prev_len = tmp.l;
+
+        bcf1_sync_alleles(line, &tmp);
+        line->unpack_size[1] = tmp.l - prev_len; prev_len = tmp.l;
+
+        bcf1_sync_filter(line, &tmp);
+        line->unpack_size[2] = tmp.l - prev_len;
+
+        bcf1_sync_info(line, &tmp);
+        line->shared = tmp;
+    }
+    else if ( line->d.shared_dirty )
+    {
+        // The line was edited, update the BCF data block, ptr_ori points
+        // to the original unchanged BCF data.
+        uint8_t *ptr_ori = (uint8_t *) line->shared.s;
+
+        assert( line->unpacked & BCF_UN_STR );
+
+        // ID: single typed string
+        if ( line->d.shared_dirty & BCF1_DIRTY_ID )
+            bcf1_sync_id(line, &tmp);
+        else
+            kputsn_(ptr_ori, line->unpack_size[0], &tmp);
+        ptr_ori += line->unpack_size[0];
+        line->unpack_size[0] = tmp.l; prev_len = tmp.l;
+
+        // REF+ALT: list of typed strings
+        if ( line->d.shared_dirty & BCF1_DIRTY_ALS )
+            bcf1_sync_alleles(line, &tmp);
+        else
+        {
+            kputsn_(ptr_ori, line->unpack_size[1], &tmp);
+            if ( !line->rlen && line->n_allele ) line->rlen = strlen(line->d.allele[0]);
+        }
+        ptr_ori += line->unpack_size[1];
+        line->unpack_size[1] = tmp.l - prev_len; prev_len = tmp.l;
+
+        if ( line->unpacked & BCF_UN_FLT )
+        {
+            // FILTER: typed vector of integers
+            if ( line->d.shared_dirty & BCF1_DIRTY_FLT )
+                bcf1_sync_filter(line, &tmp);
+            else if ( line->d.n_flt )
+                kputsn_(ptr_ori, line->unpack_size[2], &tmp);
+            else
+                bcf_enc_vint(&tmp, 0, 0, -1);
+            ptr_ori += line->unpack_size[2];
+            line->unpack_size[2] = tmp.l - prev_len;
+
+            if ( line->unpacked & BCF_UN_INFO )
+            {
+                // INFO: pairs of typed vectors
+                if ( line->d.shared_dirty & BCF1_DIRTY_INF )
+                {
+                    bcf1_sync_info(line, &tmp);
+                    ptr_ori = (uint8_t*)line->shared.s + line->shared.l;
+                }
+            }
+        }
+
+        int size = line->shared.l - (size_t)ptr_ori + (size_t)line->shared.s;
+        if ( size ) kputsn_(ptr_ori, size, &tmp);
+
+        free(line->shared.s);
+        line->shared = tmp;
+    }
+    if ( line->shared.s != shared_ori && line->unpacked & BCF_UN_INFO )
+    {
+        // Reallocated line->shared.s block invalidated line->d.info[].vptr pointers
+        size_t off_new = line->unpack_size[0] + line->unpack_size[1] + line->unpack_size[2];
+        int i;
+        for (i=0; i<line->n_info; i++)
+        {
+            uint8_t *vptr_free = line->d.info[i].vptr_free ? line->d.info[i].vptr - line->d.info[i].vptr_off : NULL;
+            line->d.info[i].vptr = (uint8_t*) line->shared.s + off_new + line->d.info[i].vptr_off;
+            off_new += line->d.info[i].vptr_len + line->d.info[i].vptr_off;
+            if ( vptr_free )
+            {
+                free(vptr_free);
+                line->d.info[i].vptr_free = 0;
+            }
+        }
+    }
+
+    if ( line->n_sample && line->n_fmt && (!line->indiv.l || line->d.indiv_dirty) )
+    {
+        // The genotype fields changed or are not present
+        tmp.l = tmp.m = 0; tmp.s = NULL;
+        int i, irm = -1;
+        for (i=0; i<line->n_fmt; i++)
+        {
+            bcf_fmt_t *fmt = &line->d.fmt[i];
+            if ( !fmt->p )
+            {
+                // marked for removal
+                if ( irm < 0 ) irm = i;
+                continue;
+            }
+            kputsn_(fmt->p - fmt->p_off, fmt->p_len + fmt->p_off, &tmp);
+            if ( irm >=0 )
+            {
+                bcf_fmt_t tfmt = line->d.fmt[irm]; line->d.fmt[irm] = line->d.fmt[i]; line->d.fmt[i] = tfmt;
+                while ( irm<=i && line->d.fmt[irm].p ) irm++;
+            }
+
+        }
+        if ( irm>=0 ) line->n_fmt = irm;
+        free(line->indiv.s);
+        line->indiv = tmp;
+
+        // Reallocated line->indiv.s block invalidated line->d.fmt[].p pointers
+        size_t off_new = 0;
+        for (i=0; i<line->n_fmt; i++)
+        {
+            uint8_t *p_free = line->d.fmt[i].p_free ? line->d.fmt[i].p - line->d.fmt[i].p_off : NULL;
+            line->d.fmt[i].p = (uint8_t*) line->indiv.s + off_new + line->d.fmt[i].p_off;
+            off_new += line->d.fmt[i].p_len + line->d.fmt[i].p_off;
+            if ( p_free )
+            {
+                free(p_free);
+                line->d.fmt[i].p_free = 0;
+            }
+        }
+    }
+    if ( !line->n_sample ) line->n_fmt = 0;
+    line->d.shared_dirty = line->d.indiv_dirty = 0;
+    return 0;
+}
+
+bcf1_t *bcf_copy(bcf1_t *dst, bcf1_t *src)
+{
+    bcf1_sync(src);
+
+    bcf_clear(dst);
+    dst->rid  = src->rid;
+    dst->pos  = src->pos;
+    dst->rlen = src->rlen;
+    dst->qual = src->qual;
+    dst->n_info = src->n_info; dst->n_allele = src->n_allele;
+    dst->n_fmt = src->n_fmt; dst->n_sample = src->n_sample;
+
+    dst->shared.m = dst->shared.l = src->shared.l;
+    dst->shared.s = (char*) malloc(dst->shared.l);
+    memcpy(dst->shared.s,src->shared.s,dst->shared.l);
+
+    dst->indiv.m = dst->indiv.l = src->indiv.l;
+    dst->indiv.s = (char*) malloc(dst->indiv.l);
+    memcpy(dst->indiv.s,src->indiv.s,dst->indiv.l);
+
+    return dst;
+}
+bcf1_t *bcf_dup(bcf1_t *src)
+{
+    bcf1_t *out = bcf_init1();
+    return bcf_copy(out, src);
+}
+
+int bcf_write(htsFile *hfp, const bcf_hdr_t *h, bcf1_t *v)
+{
+    if ( h->dirty )
+    {
+        // we could as well call bcf_hdr_sync here, not sure
+        fprintf(stderr,"FIXME: dirty header not synced\n");
+        exit(1);
+    }
+    if ( bcf_hdr_nsamples(h)!=v->n_sample )
+    {
+        fprintf(stderr,"[%s:%d %s] Broken VCF record, the number of columns at %s:%d does not match the number of samples (%d vs %d).\n",
+                __FILE__,__LINE__,__FUNCTION__,bcf_seqname(h,v),v->pos+1, v->n_sample,bcf_hdr_nsamples(h));
+        return -1;
+    }
+
+    if ( hfp->format.format == vcf || hfp->format.format == text_format )
+        return vcf_write(hfp,h,v);
+
+    if ( v->errcode )
+    {
+        // vcf_parse1() encountered a new contig or tag, undeclared in the
+        // header.  At this point, the header must have been printed,
+        // proceeding would lead to a broken BCF file. Errors must be checked
+        // and cleared by the caller before we can proceed.
+        fprintf(stderr,"[%s:%d %s] Unchecked error (%d), exiting.\n", __FILE__,__LINE__,__FUNCTION__,v->errcode);
+        exit(1);
+    }
+    bcf1_sync(v);   // check if the BCF record was modified
+
+    BGZF *fp = hfp->fp.bgzf;
+    uint32_t x[8];
+    x[0] = v->shared.l + 24; // to include six 32-bit integers
+    x[1] = v->indiv.l;
+    memcpy(x + 2, v, 16);
+    x[6] = (uint32_t)v->n_allele<<16 | v->n_info;
+    x[7] = (uint32_t)v->n_fmt<<24 | v->n_sample;
+    if ( bgzf_write(fp, x, 32) != 32 ) return -1;
+    if ( bgzf_write(fp, v->shared.s, v->shared.l) != v->shared.l ) return -1;
+    if ( bgzf_write(fp, v->indiv.s, v->indiv.l) != v->indiv.l ) return -1;
+    return 0;
+}
+
+/**********************
+ *** VCF header I/O ***
+ **********************/
+
+bcf_hdr_t *vcf_hdr_read(htsFile *fp)
+{
+    kstring_t txt, *s = &fp->line;
+    bcf_hdr_t *h;
+    h = bcf_hdr_init("r");
+    txt.l = txt.m = 0; txt.s = 0;
+    while (hts_getline(fp, KS_SEP_LINE, s) >= 0) {
+        if (s->l == 0) continue;
+        if (s->s[0] != '#') {
+            if (hts_verbose >= 2)
+                fprintf(stderr, "[E::%s] no sample line\n", __func__);
+            free(txt.s);
+            bcf_hdr_destroy(h);
+            return 0;
+        }
+        if (s->s[1] != '#' && fp->fn_aux) { // insert contigs here
+            int dret;
+            gzFile f;
+            kstream_t *ks;
+            kstring_t tmp;
+            tmp.l = tmp.m = 0; tmp.s = 0;
+            f = gzopen(fp->fn_aux, "r");
+            ks = ks_init(f);
+            while (ks_getuntil(ks, 0, &tmp, &dret) >= 0) {
+                int c;
+                kputs("##contig=<ID=", &txt); kputs(tmp.s, &txt);
+                ks_getuntil(ks, 0, &tmp, &dret);
+                kputs(",length=", &txt); kputw(atol(tmp.s), &txt);
+                kputsn(">\n", 2, &txt);
+                if (dret != '\n')
+                    while ((c = ks_getc(ks)) != '\n' && c != -1); // skip the rest of the line
+            }
+            free(tmp.s);
+            ks_destroy(ks);
+            gzclose(f);
+        }
+        kputsn(s->s, s->l, &txt);
+        kputc('\n', &txt);
+        if (s->s[1] != '#') break;
+    }
+    if ( !txt.s )
+    {
+        fprintf(stderr,"[%s:%d %s] Could not read the header\n", __FILE__,__LINE__,__FUNCTION__);
+        return NULL;
+    }
+    bcf_hdr_parse(h, txt.s);
+
+    // check tabix index, are all contigs listed in the header? add the missing ones
+    tbx_t *idx = tbx_index_load(fp->fn);
+    if ( idx )
+    {
+        int i, n, need_sync = 0;
+        const char **names = tbx_seqnames(idx, &n);
+        for (i=0; i<n; i++)
+        {
+            bcf_hrec_t *hrec = bcf_hdr_get_hrec(h, BCF_HL_CTG, "ID", (char*) names[i], NULL);
+            if ( hrec ) continue;
+            hrec = (bcf_hrec_t*) calloc(1,sizeof(bcf_hrec_t));
+            hrec->key = strdup("contig");
+            bcf_hrec_add_key(hrec, "ID", strlen("ID"));
+            bcf_hrec_set_val(hrec, hrec->nkeys-1, (char*) names[i], strlen(names[i]), 0);
+            bcf_hdr_add_hrec(h, hrec);
+            need_sync = 1;
+        }
+        free(names);
+        tbx_destroy(idx);
+        if ( need_sync )
+            bcf_hdr_sync(h);
+    }
+    free(txt.s);
+    return h;
+}
+
+int bcf_hdr_set(bcf_hdr_t *hdr, const char *fname)
+{
+    int i, n;
+    char **lines = hts_readlines(fname, &n);
+    if ( !lines ) return 1;
+    for (i=0; i<n-1; i++)
+    {
+        int k;
+        bcf_hrec_t *hrec = bcf_hdr_parse_line(hdr,lines[i],&k);
+        if ( hrec ) bcf_hdr_add_hrec(hdr, hrec);
+        free(lines[i]);
+    }
+    bcf_hdr_parse_sample_line(hdr,lines[n-1]);
+    free(lines[n-1]);
+    free(lines);
+    bcf_hdr_sync(hdr);
+    return 0;
+}
+
+static void _bcf_hrec_format(const bcf_hrec_t *hrec, int is_bcf, kstring_t *str)
+{
+    if ( !hrec->value )
+    {
+        int j, nout = 0;
+        ksprintf(str, "##%s=<", hrec->key);
+        for (j=0; j<hrec->nkeys; j++)
+        {
+            // do not output IDX if output is VCF
+            if ( !is_bcf && !strcmp("IDX",hrec->keys[j]) ) continue;
+            if ( nout ) kputc(',',str);
+            ksprintf(str,"%s=%s", hrec->keys[j], hrec->vals[j]);
+            nout++;
+        }
+        ksprintf(str,">\n");
+    }
+    else
+        ksprintf(str,"##%s=%s\n", hrec->key,hrec->value);
+}
+
+void bcf_hrec_format(const bcf_hrec_t *hrec, kstring_t *str)
+{
+    _bcf_hrec_format(hrec,0,str);
+}
+char *bcf_hdr_fmt_text(const bcf_hdr_t *hdr, int is_bcf, int *len)
+{
+    int i;
+    kstring_t txt = {0,0,0};
+    for (i=0; i<hdr->nhrec; i++)
+        _bcf_hrec_format(hdr->hrec[i], is_bcf, &txt);
+
+    ksprintf(&txt,"#CHROM\tPOS\tID\tREF\tALT\tQUAL\tFILTER\tINFO");
+    if ( bcf_hdr_nsamples(hdr) )
+    {
+        ksprintf(&txt,"\tFORMAT");
+        for (i=0; i<bcf_hdr_nsamples(hdr); i++)
+            ksprintf(&txt,"\t%s", hdr->samples[i]);
+    }
+    ksprintf(&txt,"\n");
+
+    if ( len ) *len = txt.l;
+    return txt.s;
+}
+
+const char **bcf_hdr_seqnames(const bcf_hdr_t *h, int *n)
+{
+    vdict_t *d = (vdict_t*)h->dict[BCF_DT_CTG];
+    int tid, m = kh_size(d);
+    const char **names = (const char**) calloc(m,sizeof(const char*));
+    khint_t k;
+    for (k=kh_begin(d); k<kh_end(d); k++)
+    {
+        if ( !kh_exist(d,k) ) continue;
+        tid = kh_val(d,k).id;
+        assert( tid<m );
+        names[tid] = kh_key(d,k);
+    }
+    // sanity check: there should be no gaps
+    for (tid=0; tid<m; tid++)
+        assert(names[tid]);
+    *n = m;
+    return names;
+}
+
+int vcf_hdr_write(htsFile *fp, const bcf_hdr_t *h)
+{
+    int hlen;
+    char *htxt = bcf_hdr_fmt_text(h, 0, &hlen);
+    while (hlen && htxt[hlen-1] == 0) --hlen; // kill trailing zeros
+    int ret;
+    if ( fp->format.compression!=no_compression )
+        ret = bgzf_write(fp->fp.bgzf, htxt, hlen);
+    else
+        ret = hwrite(fp->fp.hfile, htxt, hlen);
+    free(htxt);
+    return ret<0 ? -1 : 0;
+}
+
+/***********************
+ *** Typed value I/O ***
+ ***********************/
+
+void bcf_enc_vint(kstring_t *s, int n, int32_t *a, int wsize)
+{
+    int32_t max = INT32_MIN + 1, min = INT32_MAX;
+    int i;
+    if (n == 0) bcf_enc_size(s, 0, BCF_BT_NULL);
+    else if (n == 1) bcf_enc_int1(s, a[0]);
+    else {
+        if (wsize <= 0) wsize = n;
+        for (i = 0; i < n; ++i) {
+            if (a[i] == bcf_int32_missing || a[i] == bcf_int32_vector_end ) continue;
+            if (max < a[i]) max = a[i];
+            if (min > a[i]) min = a[i];
+        }
+        if (max <= INT8_MAX && min > bcf_int8_vector_end) {
+            bcf_enc_size(s, wsize, BCF_BT_INT8);
+            for (i = 0; i < n; ++i)
+                if ( a[i]==bcf_int32_vector_end ) kputc(bcf_int8_vector_end, s);
+                else if ( a[i]==bcf_int32_missing ) kputc(bcf_int8_missing, s);
+                else kputc(a[i], s);
+        } else if (max <= INT16_MAX && min > bcf_int16_vector_end) {
+            bcf_enc_size(s, wsize, BCF_BT_INT16);
+            for (i = 0; i < n; ++i)
+            {
+                int16_t x;
+                if ( a[i]==bcf_int32_vector_end ) x = bcf_int16_vector_end;
+                else if ( a[i]==bcf_int32_missing ) x = bcf_int16_missing;
+                else x = a[i];
+                kputsn((char*)&x, 2, s);
+            }
+        } else {
+            bcf_enc_size(s, wsize, BCF_BT_INT32);
+            for (i = 0; i < n; ++i) {
+                int32_t x = a[i];
+                kputsn((char*)&x, 4, s);
+            }
+        }
+    }
+}
+
+void bcf_enc_vfloat(kstring_t *s, int n, float *a)
+{
+    bcf_enc_size(s, n, BCF_BT_FLOAT);
+    kputsn((char*)a, n << 2, s);
+}
+
+void bcf_enc_vchar(kstring_t *s, int l, const char *a)
+{
+    bcf_enc_size(s, l, BCF_BT_CHAR);
+    kputsn(a, l, s);
+}
+
+void bcf_fmt_array(kstring_t *s, int n, int type, void *data)
+{
+    int j = 0;
+    if (n == 0) {
+        kputc('.', s);
+        return;
+    }
+    if (type == BCF_BT_CHAR)
+    {
+        char *p = (char*)data;
+        for (j = 0; j < n && *p; ++j, ++p)
+        {
+            if ( *p==bcf_str_missing ) kputc('.', s);
+            else kputc(*p, s);
+        }
+    }
+    else
+    {
+        #define BRANCH(type_t, is_missing, is_vector_end, kprint) { \
+            type_t *p = (type_t *) data; \
+            for (j=0; j<n; j++) \
+            { \
+                if ( is_vector_end ) break; \
+                if ( j ) kputc(',', s); \
+                if ( is_missing ) kputc('.', s); \
+                else kprint; \
+            } \
+        }
+        switch (type) {
+            case BCF_BT_INT8:  BRANCH(int8_t,  p[j]==bcf_int8_missing,  p[j]==bcf_int8_vector_end,  kputw(p[j], s)); break;
+            case BCF_BT_INT16: BRANCH(int16_t, p[j]==bcf_int16_missing, p[j]==bcf_int16_vector_end, kputw(p[j], s)); break;
+            case BCF_BT_INT32: BRANCH(int32_t, p[j]==bcf_int32_missing, p[j]==bcf_int32_vector_end, kputw(p[j], s)); break;
+            case BCF_BT_FLOAT: BRANCH(float,   bcf_float_is_missing(p[j]), bcf_float_is_vector_end(p[j]), ksprintf(s, "%g", p[j])); break;
+            default: fprintf(stderr,"todo: type %d\n", type); exit(1); break;
+        }
+        #undef BRANCH
+    }
+}
+
+uint8_t *bcf_fmt_sized_array(kstring_t *s, uint8_t *ptr)
+{
+    int x, type;
+    x = bcf_dec_size(ptr, &ptr, &type);
+    bcf_fmt_array(s, x, type, ptr);
+    return ptr + (x << bcf_type_shift[type]);
+}
+
+/********************
+ *** VCF site I/O ***
+ ********************/
+
+typedef struct {
+    int key, max_m, size, offset;
+    uint32_t is_gt:1, max_g:15, max_l:16;
+    uint32_t y;
+    uint8_t *buf;
+} fmt_aux_t;
+
+static inline void align_mem(kstring_t *s)
+{
+    if (s->l&7) {
+        uint64_t zero = 0;
+        int l = ((s->l + 7)>>3<<3) - s->l;
+        kputsn((char*)&zero, l, s);
+    }
+}
+
+// p,q is the start and the end of the FORMAT field
+int _vcf_parse_format(kstring_t *s, const bcf_hdr_t *h, bcf1_t *v, char *p, char *q)
+{
+    if ( !bcf_hdr_nsamples(h) ) return 0;
+
+    char *r, *t;
+    int j, l, m, g;
+    khint_t k;
+    ks_tokaux_t aux1;
+    vdict_t *d = (vdict_t*)h->dict[BCF_DT_ID];
+    kstring_t *mem = (kstring_t*)&h->mem;
+    mem->l = 0;
+
+    // count the number of format fields
+    for (r = p, v->n_fmt = 1; *r; ++r)
+        if (*r == ':') ++v->n_fmt;
+    char *end = s->s + s->l;
+    if ( q>=end )
+    {
+        fprintf(stderr,"[%s:%d %s] Error: FORMAT column with no sample columns starting at %s:%d\n", __FILE__,__LINE__,__FUNCTION__,s->s,v->pos+1);
+        return -1;
+    }
+
+    fmt_aux_t *fmt = (fmt_aux_t*)alloca(v->n_fmt * sizeof(fmt_aux_t));
+    // get format information from the dictionary
+    for (j = 0, t = kstrtok(p, ":", &aux1); t; t = kstrtok(0, 0, &aux1), ++j) {
+        *(char*)aux1.p = 0;
+        k = kh_get(vdict, d, t);
+        if (k == kh_end(d) || kh_val(d, k).info[BCF_HL_FMT] == 15) {
+            fprintf(stderr, "[W::%s] FORMAT '%s' is not defined in the header, assuming Type=String\n", __func__, t);
+            kstring_t tmp = {0,0,0};
+            int l;
+            ksprintf(&tmp, "##FORMAT=<ID=%s,Number=1,Type=String,Description=\"Dummy\">", t);
+            bcf_hrec_t *hrec = bcf_hdr_parse_line(h,tmp.s,&l);
+            free(tmp.s);
+            if ( bcf_hdr_add_hrec((bcf_hdr_t*)h, hrec) ) bcf_hdr_sync((bcf_hdr_t*)h);
+            k = kh_get(vdict, d, t);
+            v->errcode = BCF_ERR_TAG_UNDEF;
+        }
+        fmt[j].max_l = fmt[j].max_m = fmt[j].max_g = 0;
+        fmt[j].key = kh_val(d, k).id;
+        fmt[j].is_gt = !strcmp(t, "GT");
+        fmt[j].y = h->id[0][fmt[j].key].val->info[BCF_HL_FMT];
+    }
+    // compute max
+    int n_sample_ori = -1;
+    r = q + 1;  // r: position in the format string
+    m = l = g = 1, v->n_sample = 0;  // m: max vector size, l: max field len, g: max number of alleles
+    while ( r<end )
+    {
+        // can we skip some samples?
+        if ( h->keep_samples )
+        {
+            n_sample_ori++;
+            if ( !bit_array_test(h->keep_samples,n_sample_ori) )
+            {
+                while ( *r!='\t' && r<end ) r++;
+                if ( *r=='\t' ) { *r = 0; r++; }
+                continue;
+            }
+        }
+
+        // collect fmt stats: max vector size, length, number of alleles
+        j = 0;  // j-th format field
+        for (;;)
+        {
+            if ( *r == '\t' ) *r = 0;
+            if ( *r == ':' || !*r )  // end of field or end of sample
+            {
+                if (fmt[j].max_m < m) fmt[j].max_m = m;
+                if (fmt[j].max_l < l - 1) fmt[j].max_l = l - 1;
+                if (fmt[j].is_gt && fmt[j].max_g < g) fmt[j].max_g = g;
+                l = 0, m = g = 1;
+                if ( *r==':' ) 
+                {
+                    j++;
+                    if ( j>=v->n_fmt ) 
+                    { 
+                        fprintf(stderr,"Incorrect number of FORMAT fields at %s:%d\n", h->id[BCF_DT_CTG][v->rid].key,v->pos+1);
+                        exit(1); 
+                    }
+                }
+                else break;
+            }
+            else if ( *r== ',' ) m++;
+            else if ( fmt[j].is_gt && (*r == '|' || *r == '/') ) g++;
+            if ( r>=end ) break;
+            r++; l++;
+        }
+        v->n_sample++;
+        if ( v->n_sample == bcf_hdr_nsamples(h) ) break;
+        r++;
+    }
+
+    // allocate memory for arrays
+    for (j = 0; j < v->n_fmt; ++j) {
+        fmt_aux_t *f = &fmt[j];
+        if ( !f->max_m ) f->max_m = 1;  // omitted trailing format field
+        if ((f->y>>4&0xf) == BCF_HT_STR) {
+            f->size = f->is_gt? f->max_g << 2 : f->max_l;
+        } else if ((f->y>>4&0xf) == BCF_HT_REAL || (f->y>>4&0xf) == BCF_HT_INT) {
+            f->size = f->max_m << 2;
+        } else
+        {
+            fprintf(stderr, "[E::%s] the format type %d currently not supported\n", __func__, f->y>>4&0xf);
+            abort(); // I do not know how to do with Flag in the genotype fields
+        }
+        align_mem(mem);
+        f->offset = mem->l;
+        ks_resize(mem, mem->l + v->n_sample * f->size);
+        mem->l += v->n_sample * f->size;
+    }
+    for (j = 0; j < v->n_fmt; ++j)
+        fmt[j].buf = (uint8_t*)mem->s + fmt[j].offset;
+    // fill the sample fields; at beginning of the loop, t points to the first char of a format
+    n_sample_ori = -1;
+    t = q + 1; m = 0;   // m: sample id
+    while ( t<end )
+    {
+        // can we skip some samples?
+        if ( h->keep_samples )
+        {
+            n_sample_ori++;
+            if ( !bit_array_test(h->keep_samples,n_sample_ori) )
+            {
+                while ( *t && t<end ) t++;
+                t++;
+                continue;
+            }
+        }
+        if ( m == bcf_hdr_nsamples(h) ) break;
+
+        j = 0; // j-th format field, m-th sample
+        while ( *t )
+        {
+            fmt_aux_t *z = &fmt[j];
+            if ((z->y>>4&0xf) == BCF_HT_STR) {
+                if (z->is_gt) { // genotypes
+                    int32_t is_phased = 0, *x = (int32_t*)(z->buf + z->size * m);
+                    for (l = 0;; ++t) {
+                        if (*t == '.') ++t, x[l++] = is_phased;
+                        else x[l++] = (strtol(t, &t, 10) + 1) << 1 | is_phased;
+#if THOROUGH_SANITY_CHECKS
+                        assert( 0 );    // success of strtol,strtod not checked
+#endif
+                        is_phased = (*t == '|');
+                        if (*t == ':' || *t == 0) break;
+                    }
+                    if ( !l ) x[l++] = 0;   // An empty field, insert missing value
+                    for (; l < z->size>>2; ++l) x[l] = bcf_int32_vector_end;
+                } else {
+                    char *x = (char*)z->buf + z->size * m;
+                    for (r = t, l = 0; *t != ':' && *t; ++t) x[l++] = *t;
+                    for (; l < z->size; ++l) x[l] = 0;
+                }
+            } else if ((z->y>>4&0xf) == BCF_HT_INT) {
+                int32_t *x = (int32_t*)(z->buf + z->size * m);
+                for (l = 0;; ++t) {
+                    if (*t == '.') x[l++] = bcf_int32_missing, ++t; // ++t to skip "."
+                    else x[l++] = strtol(t, &t, 10);
+                    if (*t == ':' || *t == 0) break;
+                }
+                if ( !l ) x[l++] = bcf_int32_missing;
+                for (; l < z->size>>2; ++l) x[l] = bcf_int32_vector_end;
+            } else if ((z->y>>4&0xf) == BCF_HT_REAL) {
+                float *x = (float*)(z->buf + z->size * m);
+                for (l = 0;; ++t) {
+                    if (*t == '.' && !isdigit(t[1])) bcf_float_set_missing(x[l++]), ++t; // ++t to skip "."
+                    else x[l++] = strtod(t, &t);
+                    if (*t == ':' || *t == 0) break;
+                }
+                if ( !l ) bcf_float_set_missing(x[l++]);    // An empty field, insert missing value
+                for (; l < z->size>>2; ++l) bcf_float_set_vector_end(x[l]);
+            } else abort();
+            if (*t == 0) {
+                for (++j; j < v->n_fmt; ++j) { // fill end-of-vector values
+                    z = &fmt[j];
+                    if ((z->y>>4&0xf) == BCF_HT_STR) {
+                        if (z->is_gt) {
+                            int32_t *x = (int32_t*)(z->buf + z->size * m);
+                            x[0] = bcf_int32_missing;
+                            for (l = 1; l < z->size>>2; ++l) x[l] = bcf_int32_vector_end;
+                        } else {
+                            char *x = (char*)z->buf + z->size * m;
+                            if ( z->size ) x[0] = '.';
+                            for (l = 1; l < z->size; ++l) x[l] = 0;
+                        }
+                    } else if ((z->y>>4&0xf) == BCF_HT_INT) {
+                        int32_t *x = (int32_t*)(z->buf + z->size * m);
+                        x[0] = bcf_int32_missing;
+                        for (l = 1; l < z->size>>2; ++l) x[l] = bcf_int32_vector_end;
+                    } else if ((z->y>>4&0xf) == BCF_HT_REAL) {
+                        float *x = (float*)(z->buf + z->size * m);
+                        bcf_float_set_missing(x[0]);
+                        for (l = 1; l < z->size>>2; ++l) bcf_float_set_vector_end(x[l]);
+                    }
+                }
+                break;
+            }
+            else
+            {
+                if (*t == ':') ++j;
+                t++;
+            }
+        }
+        m++; t++;
+    }
+
+    // write individual genotype information
+    kstring_t *str = &v->indiv;
+    int i;
+    if (v->n_sample > 0) {
+        for (i = 0; i < v->n_fmt; ++i) {
+            fmt_aux_t *z = &fmt[i];
+            bcf_enc_int1(str, z->key);
+            if ((z->y>>4&0xf) == BCF_HT_STR && !z->is_gt) {
+                bcf_enc_size(str, z->size, BCF_BT_CHAR);
+                kputsn((char*)z->buf, z->size * v->n_sample, str);
+            } else if ((z->y>>4&0xf) == BCF_HT_INT || z->is_gt) {
+                bcf_enc_vint(str, (z->size>>2) * v->n_sample, (int32_t*)z->buf, z->size>>2);
+            } else {
+                bcf_enc_size(str, z->size>>2, BCF_BT_FLOAT);
+                kputsn((char*)z->buf, z->size * v->n_sample, str);
+            }
+        }
+    }
+
+    if ( v->n_sample!=bcf_hdr_nsamples(h) )
+    {
+        fprintf(stderr,"[%s:%d %s] Number of columns at %s:%d does not match the number of samples (%d vs %d).\n",
+                __FILE__,__LINE__,__FUNCTION__,bcf_seqname(h,v),v->pos+1, v->n_sample,bcf_hdr_nsamples(h));
+        v->errcode |= BCF_ERR_NCOLS;
+        return -1;
+    }
+
+    return 0;
+}
+
+int vcf_parse(kstring_t *s, const bcf_hdr_t *h, bcf1_t *v)
+{
+    int i = 0;
+    char *p, *q, *r, *t;
+    kstring_t *str;
+    khint_t k;
+    ks_tokaux_t aux;
+
+    bcf_clear1(v);
+    str = &v->shared;
+    memset(&aux, 0, sizeof(ks_tokaux_t));
+    for (p = kstrtok(s->s, "\t", &aux), i = 0; p; p = kstrtok(0, 0, &aux), ++i) {
+        q = (char*)aux.p;
+        *q = 0;
+        if (i == 0) { // CHROM
+            vdict_t *d = (vdict_t*)h->dict[BCF_DT_CTG];
+            k = kh_get(vdict, d, p);
+            if (k == kh_end(d))
+            {
+                // Simple error recovery for chromosomes not defined in the header. It will not help when VCF header has
+                // been already printed, but will enable tools like vcfcheck to proceed.
+                fprintf(stderr, "[W::%s] contig '%s' is not defined in the header. (Quick workaround: index the file with tabix.)\n", __func__, p);
+                kstring_t tmp = {0,0,0};
+                int l;
+                ksprintf(&tmp, "##contig=<ID=%s>", p);
+                bcf_hrec_t *hrec = bcf_hdr_parse_line(h,tmp.s,&l);
+                free(tmp.s);
+                if ( bcf_hdr_add_hrec((bcf_hdr_t*)h, hrec) ) bcf_hdr_sync((bcf_hdr_t*)h);
+                k = kh_get(vdict, d, p);
+                v->errcode = BCF_ERR_CTG_UNDEF;
+            }
+            v->rid = kh_val(d, k).id;
+        } else if (i == 1) { // POS
+            v->pos = atoi(p) - 1;
+        } else if (i == 2) { // ID
+            if (strcmp(p, ".")) bcf_enc_vchar(str, q - p, p);
+            else bcf_enc_size(str, 0, BCF_BT_CHAR);
+        } else if (i == 3) { // REF
+            bcf_enc_vchar(str, q - p, p);
+            v->n_allele = 1, v->rlen = q - p;
+        } else if (i == 4) { // ALT
+            if (strcmp(p, ".")) {
+                for (r = t = p;; ++r) {
+                    if (*r == ',' || *r == 0) {
+                        bcf_enc_vchar(str, r - t, t);
+                        t = r + 1;
+                        ++v->n_allele;
+                    }
+                    if (r == q) break;
+                }
+            }
+        } else if (i == 5) { // QUAL
+            if (strcmp(p, ".")) v->qual = atof(p);
+            else memcpy(&v->qual, &bcf_float_missing, 4);
+            if ( v->max_unpack && !(v->max_unpack>>1) ) return 0; // BCF_UN_STR
+        } else if (i == 6) { // FILTER
+            if (strcmp(p, ".")) {
+                int32_t *a;
+                int n_flt = 1, i;
+                ks_tokaux_t aux1;
+                vdict_t *d = (vdict_t*)h->dict[BCF_DT_ID];
+                // count the number of filters
+                if (*(q-1) == ';') *(q-1) = 0;
+                for (r = p; *r; ++r)
+                    if (*r == ';') ++n_flt;
+                a = (int32_t*)alloca(n_flt * sizeof(int32_t));
+                // add filters
+                for (t = kstrtok(p, ";", &aux1), i = 0; t; t = kstrtok(0, 0, &aux1)) {
+                    *(char*)aux1.p = 0;
+                    k = kh_get(vdict, d, t);
+                    if (k == kh_end(d))
+                    {
+                        // Simple error recovery for FILTERs not defined in the header. It will not help when VCF header has
+                        // been already printed, but will enable tools like vcfcheck to proceed.
+                        fprintf(stderr, "[W::%s] FILTER '%s' is not defined in the header\n", __func__, t);
+                        kstring_t tmp = {0,0,0};
+                        int l;
+                        ksprintf(&tmp, "##FILTER=<ID=%s,Description=\"Dummy\">", t);
+                        bcf_hrec_t *hrec = bcf_hdr_parse_line(h,tmp.s,&l);
+                        free(tmp.s);
+                        if ( bcf_hdr_add_hrec((bcf_hdr_t*)h, hrec) ) bcf_hdr_sync((bcf_hdr_t*)h);
+                        k = kh_get(vdict, d, t);
+                        v->errcode = BCF_ERR_TAG_UNDEF;
+                    }
+                    a[i++] = kh_val(d, k).id;
+                }
+                n_flt = i;
+                bcf_enc_vint(str, n_flt, a, -1);
+            } else bcf_enc_vint(str, 0, 0, -1);
+            if ( v->max_unpack && !(v->max_unpack>>2) ) return 0;    // BCF_UN_FLT
+        } else if (i == 7) { // INFO
+            char *key;
+            vdict_t *d = (vdict_t*)h->dict[BCF_DT_ID];
+            v->n_info = 0;
+            if (strcmp(p, ".")) {
+                if (*(q-1) == ';') *(q-1) = 0;
+                for (r = key = p;; ++r) {
+                    int c;
+                    char *val, *end;
+                    if (*r != ';' && *r != '=' && *r != 0) continue;
+                    val = end = 0;
+                    c = *r; *r = 0;
+                    if (c == '=') {
+                        val = r + 1;
+                        for (end = val; *end != ';' && *end != 0; ++end);
+                        c = *end; *end = 0;
+                    } else end = r;
+                    if ( !*key ) { if (c==0) break; r = end; key = r + 1; continue; }  // faulty VCF, ";;" in the INFO
+                    k = kh_get(vdict, d, key);
+                    if (k == kh_end(d) || kh_val(d, k).info[BCF_HL_INFO] == 15)
+                    {
+                        fprintf(stderr, "[W::%s] INFO '%s' is not defined in the header, assuming Type=String\n", __func__, key);
+                        kstring_t tmp = {0,0,0};
+                        int l;
+                        ksprintf(&tmp, "##INFO=<ID=%s,Number=1,Type=String,Description=\"Dummy\">", key);
+                        bcf_hrec_t *hrec = bcf_hdr_parse_line(h,tmp.s,&l);
+                        free(tmp.s);
+                        if ( bcf_hdr_add_hrec((bcf_hdr_t*)h, hrec) ) bcf_hdr_sync((bcf_hdr_t*)h);
+                        k = kh_get(vdict, d, key);
+                        v->errcode = BCF_ERR_TAG_UNDEF;
+                    }
+                    uint32_t y = kh_val(d, k).info[BCF_HL_INFO];
+                    ++v->n_info;
+                    bcf_enc_int1(str, kh_val(d, k).id);
+                    if (val == 0) {
+                        bcf_enc_size(str, 0, BCF_BT_NULL);
+                    } else if ((y>>4&0xf) == BCF_HT_FLAG || (y>>4&0xf) == BCF_HT_STR) { // if Flag has a value, treat it as a string
+                        bcf_enc_vchar(str, end - val, val);
+                    } else { // int/float value/array
+                        int i, n_val;
+                        char *t, *te;
+                        for (t = val, n_val = 1; *t; ++t) // count the number of values
+                            if (*t == ',') ++n_val;
+                        if ((y>>4&0xf) == BCF_HT_INT) {
+                            int32_t *z;
+                            z = (int32_t*)alloca(n_val * sizeof(int32_t));
+                            for (i = 0, t = val; i < n_val; ++i, ++t)
+                            {
+                                z[i] = strtol(t, &te, 10);
+                                if ( te==t ) // conversion failed
+                                {
+                                    z[i] = bcf_int32_missing;
+                                    while ( *te && *te!=',' ) te++;
+                                }
+                                t = te;
+                            }
+                            bcf_enc_vint(str, n_val, z, -1);
+                            if (strcmp(key, "END") == 0) v->rlen = z[0] - v->pos;
+                        } else if ((y>>4&0xf) == BCF_HT_REAL) {
+                            float *z;
+                            z = (float*)alloca(n_val * sizeof(float));
+                            for (i = 0, t = val; i < n_val; ++i, ++t)
+                            {
+                                z[i] = strtod(t, &te);
+                                if ( te==t ) // conversion failed
+                                {
+                                    bcf_float_set_missing(z[i]);
+                                    while ( *te && *te!=',' ) te++;
+                                }
+                                t = te;
+                            }
+                            bcf_enc_vfloat(str, n_val, z);
+                        }
+                    }
+                    if (c == 0) break;
+                    r = end;
+                    key = r + 1;
+                }
+            }
+            if ( v->max_unpack && !(v->max_unpack>>3) ) return 0;
+        } else if (i == 8) // FORMAT
+            return _vcf_parse_format(s, h, v, p, q);
+    }
+    return 0;
+}
+
+int vcf_read(htsFile *fp, const bcf_hdr_t *h, bcf1_t *v)
+{
+    int ret;
+    ret = hts_getline(fp, KS_SEP_LINE, &fp->line);
+    if (ret < 0) return -1;
+    return vcf_parse1(&fp->line, h, v);
+}
+
+static inline uint8_t *bcf_unpack_fmt_core1(uint8_t *ptr, int n_sample, bcf_fmt_t *fmt)
+{
+    uint8_t *ptr_start = ptr;
+    fmt->id = bcf_dec_typed_int1(ptr, &ptr);
+    fmt->n = bcf_dec_size(ptr, &ptr, &fmt->type);
+    fmt->size = fmt->n << bcf_type_shift[fmt->type];
+    fmt->p = ptr;
+    fmt->p_off  = ptr - ptr_start;
+    fmt->p_free = 0;
+    ptr += n_sample * fmt->size;
+    fmt->p_len = ptr - fmt->p;
+    return ptr;
+}
+
+static inline uint8_t *bcf_unpack_info_core1(uint8_t *ptr, bcf_info_t *info)
+{
+    uint8_t *ptr_start = ptr;
+    info->key = bcf_dec_typed_int1(ptr, &ptr);
+    info->len = bcf_dec_size(ptr, &ptr, &info->type);
+    info->vptr = ptr;
+    info->vptr_off  = ptr - ptr_start;
+    info->vptr_free = 0;
+    info->v1.i = 0;
+    if (info->len == 1) {
+        if (info->type == BCF_BT_INT8 || info->type == BCF_BT_CHAR) info->v1.i = *(int8_t*)ptr;
+        else if (info->type == BCF_BT_INT32) info->v1.i = *(int32_t*)ptr;
+        else if (info->type == BCF_BT_FLOAT) info->v1.f = *(float*)ptr;
+        else if (info->type == BCF_BT_INT16) info->v1.i = *(int16_t*)ptr;
+    }
+    ptr += info->len << bcf_type_shift[info->type];
+    info->vptr_len = ptr - info->vptr;
+    return ptr;
+}
+
+int bcf_unpack(bcf1_t *b, int which)
+{
+    if ( !b->shared.l ) return 0; // Building a new BCF record from scratch
+    uint8_t *ptr = (uint8_t*)b->shared.s, *ptr_ori;
+    int *offset, i;
+    bcf_dec_t *d = &b->d;
+    if (which & BCF_UN_FLT) which |= BCF_UN_STR;
+    if (which & BCF_UN_INFO) which |= BCF_UN_SHR;
+    if ((which&BCF_UN_STR) && !(b->unpacked&BCF_UN_STR))
+    {
+        kstring_t tmp;
+
+        // ID
+        tmp.l = 0; tmp.s = d->id; tmp.m = d->m_id;
+        ptr_ori = ptr;
+        ptr = bcf_fmt_sized_array(&tmp, ptr);
+        b->unpack_size[0] = ptr - ptr_ori;
+        kputc('\0', &tmp);
+        d->id = tmp.s; d->m_id = tmp.m;
+
+        // REF and ALT are in a single block (d->als) and d->alleles are pointers into this block
+        tmp.l = 0; tmp.s = d->als; tmp.m = d->m_als;
+        offset = (int*)alloca(b->n_allele * sizeof(int));
+        ptr_ori = ptr;
+        for (i = 0; i < b->n_allele; ++i) {
+            offset[i] = tmp.l;
+            ptr = bcf_fmt_sized_array(&tmp, ptr);
+            kputc('\0', &tmp);
+        }
+        b->unpack_size[1] = ptr - ptr_ori;
+        d->als = tmp.s; d->m_als = tmp.m;
+
+        hts_expand(char*, b->n_allele, d->m_allele, d->allele); // NM: hts_expand() is a macro
+        for (i = 0; i < b->n_allele; ++i)
+            d->allele[i] = d->als + offset[i];
+        b->unpacked |= BCF_UN_STR;
+    }
+    if ((which&BCF_UN_FLT) && !(b->unpacked&BCF_UN_FLT)) { // FILTER
+        ptr = (uint8_t*)b->shared.s + b->unpack_size[0] + b->unpack_size[1];
+        ptr_ori = ptr;
+        if (*ptr>>4) {
+            int type;
+            d->n_flt = bcf_dec_size(ptr, &ptr, &type);
+            hts_expand(int, d->n_flt, d->m_flt, d->flt);
+            for (i = 0; i < d->n_flt; ++i)
+                d->flt[i] = bcf_dec_int1(ptr, type, &ptr);
+        } else ++ptr, d->n_flt = 0;
+        b->unpack_size[2] = ptr - ptr_ori;
+        b->unpacked |= BCF_UN_FLT;
+    }
+    if ((which&BCF_UN_INFO) && !(b->unpacked&BCF_UN_INFO)) { // INFO
+        ptr = (uint8_t*)b->shared.s + b->unpack_size[0] + b->unpack_size[1] + b->unpack_size[2];
+        hts_expand(bcf_info_t, b->n_info, d->m_info, d->info);
+        for (i = 0; i < d->m_info; ++i) d->info[i].vptr_free = 0;
+        for (i = 0; i < b->n_info; ++i)
+            ptr = bcf_unpack_info_core1(ptr, &d->info[i]);
+        b->unpacked |= BCF_UN_INFO;
+    }
+    if ((which&BCF_UN_FMT) && b->n_sample && !(b->unpacked&BCF_UN_FMT)) { // FORMAT
+        ptr = (uint8_t*)b->indiv.s;
+        hts_expand(bcf_fmt_t, b->n_fmt, d->m_fmt, d->fmt);
+        for (i = 0; i < d->m_fmt; ++i) d->fmt[i].p_free = 0;
+        for (i = 0; i < b->n_fmt; ++i)
+            ptr = bcf_unpack_fmt_core1(ptr, b->n_sample, &d->fmt[i]);
+        b->unpacked |= BCF_UN_FMT;
+    }
+    return 0;
+}
+
+int vcf_format(const bcf_hdr_t *h, const bcf1_t *v, kstring_t *s)
+{
+    int i;
+    bcf_unpack((bcf1_t*)v, BCF_UN_ALL);
+    kputs(h->id[BCF_DT_CTG][v->rid].key, s); // CHROM
+    kputc('\t', s); kputw(v->pos + 1, s); // POS
+    kputc('\t', s); kputs(v->d.id ? v->d.id : ".", s); // ID
+    kputc('\t', s); // REF
+    if (v->n_allele > 0) kputs(v->d.allele[0], s);
+    else kputc('.', s);
+    kputc('\t', s); // ALT
+    if (v->n_allele > 1) {
+        for (i = 1; i < v->n_allele; ++i) {
+            if (i > 1) kputc(',', s);
+            kputs(v->d.allele[i], s);
+        }
+    } else kputc('.', s);
+    kputc('\t', s); // QUAL
+    if ( bcf_float_is_missing(v->qual) ) kputc('.', s); // QUAL
+    else ksprintf(s, "%g", v->qual);
+    kputc('\t', s); // FILTER
+    if (v->d.n_flt) {
+        for (i = 0; i < v->d.n_flt; ++i) {
+            if (i) kputc(';', s);
+            kputs(h->id[BCF_DT_ID][v->d.flt[i]].key, s);
+        }
+    } else kputc('.', s);
+    kputc('\t', s); // INFO
+    if (v->n_info) {
+        int first = 1;
+        for (i = 0; i < v->n_info; ++i) {
+            bcf_info_t *z = &v->d.info[i];
+            if ( !z->vptr ) continue;
+            if ( !first ) kputc(';', s); first = 0;
+            kputs(h->id[BCF_DT_ID][z->key].key, s);
+            if (z->len <= 0) continue;
+            kputc('=', s);
+            if (z->len == 1) 
+            {
+                switch (z->type) 
+                {
+                    case BCF_BT_INT8:  if ( z->v1.i==bcf_int8_missing ) kputc('.', s); else kputw(z->v1.i, s); break;
+                    case BCF_BT_INT16: if ( z->v1.i==bcf_int16_missing ) kputc('.', s); else kputw(z->v1.i, s); break;
+                    case BCF_BT_INT32: if ( z->v1.i==bcf_int32_missing ) kputc('.', s); else kputw(z->v1.i, s); break;
+                    case BCF_BT_FLOAT: if ( bcf_float_is_missing(z->v1.f) ) kputc('.', s); else ksprintf(s, "%g", z->v1.f); break;
+                    case BCF_BT_CHAR:  kputc(z->v1.i, s); break;
+                    default: fprintf(stderr,"todo: type %d\n", z->type); exit(1); break;
+                }
+            }
+            else bcf_fmt_array(s, z->len, z->type, z->vptr);
+        }
+        if ( first ) kputc('.', s);
+    } else kputc('.', s);
+    // FORMAT and individual information
+    if (v->n_sample)
+    {
+        int i,j;
+        if ( v->n_fmt)
+        {
+            int gt_i = -1;
+            bcf_fmt_t *fmt = v->d.fmt;
+            int first = 1;
+            for (i = 0; i < (int)v->n_fmt; ++i) {
+                if ( !fmt[i].p ) continue;
+                kputc(!first ? ':' : '\t', s); first = 0;
+                if ( fmt[i].id<0 ) //!bcf_hdr_idinfo_exists(h,BCF_HL_FMT,fmt[i].id) )
+                {
+                    fprintf(stderr, "[E::%s] invalid BCF, the FORMAT tag id=%d not present in the header.\n", __func__, fmt[i].id);
+                    abort();
+                }
+                kputs(h->id[BCF_DT_ID][fmt[i].id].key, s);
+                if (strcmp(h->id[BCF_DT_ID][fmt[i].id].key, "GT") == 0) gt_i = i;
+            }
+            if ( first ) kputs("\t.", s);
+            for (j = 0; j < v->n_sample; ++j) {
+                kputc('\t', s);
+                first = 1;
+                for (i = 0; i < (int)v->n_fmt; ++i) {
+                    bcf_fmt_t *f = &fmt[i];
+                    if ( !f->p ) continue;
+                    if (!first) kputc(':', s); first = 0;
+                    if (gt_i == i)
+                        bcf_format_gt(f,j,s);
+                    else
+                        bcf_fmt_array(s, f->n, f->type, f->p + j * f->size);
+                }
+                if ( first ) kputc('.', s);
+            }
+        }
+        else
+            for (j=0; j<=v->n_sample; j++)
+                kputs("\t.", s);
+    }
+    kputc('\n', s);
+    return 0;
+}
+
+int vcf_write_line(htsFile *fp, kstring_t *line)
+{
+    int ret;
+    if ( line->s[line->l-1]!='\n' ) kputc('\n',line);
+    if ( fp->format.compression!=no_compression )
+        ret = bgzf_write(fp->fp.bgzf, line->s, line->l);
+    else
+        ret = hwrite(fp->fp.hfile, line->s, line->l);
+    return ret==line->l ? 0 : -1;
+}
+
+int vcf_write(htsFile *fp, const bcf_hdr_t *h, bcf1_t *v)
+{
+    int ret;
+    fp->line.l = 0;
+    vcf_format1(h, v, &fp->line);
+    if ( fp->format.compression!=no_compression )
+        ret = bgzf_write(fp->fp.bgzf, fp->line.s, fp->line.l);
+    else
+        ret = hwrite(fp->fp.hfile, fp->line.s, fp->line.l);
+    return ret==fp->line.l ? 0 : -1;
+}
+
+/************************
+ * Data access routines *
+ ************************/
+
+int bcf_hdr_id2int(const bcf_hdr_t *h, int which, const char *id)
+{
+    khint_t k;
+    vdict_t *d = (vdict_t*)h->dict[which];
+    k = kh_get(vdict, d, id);
+    return k == kh_end(d)? -1 : kh_val(d, k).id;
+}
+
+
+/********************
+ *** BCF indexing ***
+ ********************/
+
+hts_idx_t *bcf_index(htsFile *fp, int min_shift)
+{
+    int n_lvls, i;
+    bcf1_t *b;
+    hts_idx_t *idx;
+    bcf_hdr_t *h;
+    int64_t max_len = 0, s;
+    h = bcf_hdr_read(fp);
+    if ( !h ) return NULL;
+    int nids = 0;
+    for (i = 0; i < h->n[BCF_DT_CTG]; ++i)
+    {
+        if ( !h->id[BCF_DT_CTG][i].val ) continue;
+        if ( max_len < h->id[BCF_DT_CTG][i].val->info[0] ) max_len = h->id[BCF_DT_CTG][i].val->info[0];
+        nids++;
+    }
+    if ( !max_len ) max_len = ((int64_t)1<<31) - 1;  // In case contig line is broken.
+    max_len += 256;
+    for (n_lvls = 0, s = 1<<min_shift; max_len > s; ++n_lvls, s <<= 3);
+    idx = hts_idx_init(nids, HTS_FMT_CSI, bgzf_tell(fp->fp.bgzf), min_shift, n_lvls);
+    b = bcf_init1();
+    while (bcf_read1(fp,h, b) >= 0) {
+        int ret;
+        ret = hts_idx_push(idx, b->rid, b->pos, b->pos + b->rlen, bgzf_tell(fp->fp.bgzf), 1);
+        if (ret < 0)
+        {
+            bcf_destroy1(b);
+            hts_idx_destroy(idx);
+            return NULL;
+        }
+    }
+    hts_idx_finish(idx, bgzf_tell(fp->fp.bgzf));
+    bcf_destroy1(b);
+    bcf_hdr_destroy(h);
+    return idx;
+}
+
+int bcf_index_build(const char *fn, int min_shift)
+{
+    htsFile *fp;
+    hts_idx_t *idx;
+    if ((fp = hts_open(fn, "rb")) == 0) return -1;
+    if ( fp->format.compression!=bgzf ) { hts_close(fp); return -1; }
+    idx = bcf_index(fp, min_shift);
+    hts_close(fp);
+    if ( !idx ) return -1;
+    hts_idx_save(idx, fn, HTS_FMT_CSI);
+    hts_idx_destroy(idx);
+    return 0;
+}
+
+/*****************
+ *** Utilities ***
+ *****************/
+
+int bcf_hdr_combine(bcf_hdr_t *dst, const bcf_hdr_t *src)
+{
+    int i, ndst_ori = dst->nhrec, need_sync = 0, ret = 0;
+    for (i=0; i<src->nhrec; i++)
+    {
+        if ( src->hrec[i]->type==BCF_HL_GEN && src->hrec[i]->value )
+        {
+            int j;
+            for (j=0; j<ndst_ori; j++)
+            {
+                if ( dst->hrec[j]->type!=BCF_HL_GEN ) continue;
+
+                // Checking only the key part of generic lines, otherwise
+                // the VCFs are too verbose. Should we perhaps add a flag
+                // to bcf_hdr_combine() and make this optional?
+                if ( !strcmp(src->hrec[i]->key,dst->hrec[j]->key) ) break;
+            }
+            if ( j>=ndst_ori )
+                need_sync += bcf_hdr_add_hrec(dst, bcf_hrec_dup(src->hrec[i]));
+        }
+        else if ( src->hrec[i]->type==BCF_HL_STR )
+        {
+            // NB: we are ignoring fields without ID
+            int j = bcf_hrec_find_key(src->hrec[i],"ID");
+            if ( j>=0 )
+            {
+                bcf_hrec_t *rec = bcf_hdr_get_hrec(dst, src->hrec[i]->type, "ID", src->hrec[i]->vals[j], src->hrec[i]->key);
+                if ( !rec )
+                    need_sync += bcf_hdr_add_hrec(dst, bcf_hrec_dup(src->hrec[i]));
+            }
+        }
+        else
+        {
+            int j = bcf_hrec_find_key(src->hrec[i],"ID");
+            assert( j>=0 ); // this should always be true for valid VCFs
+
+            bcf_hrec_t *rec = bcf_hdr_get_hrec(dst, src->hrec[i]->type, "ID", src->hrec[i]->vals[j], NULL);
+            if ( !rec )
+                need_sync += bcf_hdr_add_hrec(dst, bcf_hrec_dup(src->hrec[i]));
+            else if ( src->hrec[i]->type==BCF_HL_INFO || src->hrec[i]->type==BCF_HL_FMT )
+            {
+                // Check that both records are of the same type. The bcf_hdr_id2length
+                // macro cannot be used here because dst header is not synced yet.
+                vdict_t *d_src = (vdict_t*)src->dict[BCF_DT_ID];
+                vdict_t *d_dst = (vdict_t*)dst->dict[BCF_DT_ID];
+                khint_t k_src  = kh_get(vdict, d_src, src->hrec[i]->vals[0]);
+                khint_t k_dst  = kh_get(vdict, d_dst, src->hrec[i]->vals[0]);
+                if ( (kh_val(d_src,k_src).info[rec->type]>>8 & 0xf) != (kh_val(d_dst,k_dst).info[rec->type]>>8 & 0xf) )
+                {
+                    fprintf(stderr,"Warning: trying to combine \"%s\" tag definitions of different lengths\n", src->hrec[i]->vals[0]);
+                    ret |= 1;
+                }
+                if ( (kh_val(d_src,k_src).info[rec->type]>>4 & 0xf) != (kh_val(d_dst,k_dst).info[rec->type]>>4 & 0xf) )
+                {
+                    fprintf(stderr,"Warning: trying to combine \"%s\" tag definitions of different types\n", src->hrec[i]->vals[0]);
+                    ret |= 1;
+                }
+            }
+        }
+    }
+    if ( need_sync ) bcf_hdr_sync(dst);
+    return ret;
+}
+int bcf_translate(const bcf_hdr_t *dst_hdr, bcf_hdr_t *src_hdr, bcf1_t *line)
+{
+    int i;
+    if ( line->errcode )
+    {
+        fprintf(stderr,"[%s:%d %s] Unchecked error (%d), exiting.\n", __FILE__,__LINE__,__FUNCTION__,line->errcode);
+        exit(1);
+    }
+    if ( src_hdr->ntransl==-1 ) return 0;    // no need to translate, all tags have the same id
+    if ( !src_hdr->ntransl )  // called for the first time, see what needs translating
+    {
+        int dict;
+        for (dict=0; dict<2; dict++)    // BCF_DT_ID and BCF_DT_CTG
+        {
+            src_hdr->transl[dict] = (int*) malloc(src_hdr->n[dict]*sizeof(int));
+            for (i=0; i<src_hdr->n[dict]; i++)
+            {
+                if ( !src_hdr->id[dict][i].key || !dst_hdr->id[dict][i].key )    // gap left after removed BCF header lines
+                    src_hdr->transl[dict][i] = -1;
+                else if ( i>=dst_hdr->n[dict] || strcmp(src_hdr->id[dict][i].key,dst_hdr->id[dict][i].key) )
+                {
+                    src_hdr->transl[dict][i] = bcf_hdr_id2int(dst_hdr,dict,src_hdr->id[dict][i].key);
+                    src_hdr->ntransl++;
+                }
+                else
+                    src_hdr->transl[dict][i] = -1;
+            }
+        }
+        if ( !src_hdr->ntransl )
+        {
+            free(src_hdr->transl[0]); src_hdr->transl[0] = NULL;
+            free(src_hdr->transl[1]); src_hdr->transl[1] = NULL;
+            src_hdr->ntransl = -1;
+        }
+        if ( src_hdr->ntransl==-1 ) return 0;
+    }
+    bcf_unpack(line,BCF_UN_ALL);
+
+    // CHROM
+    if ( src_hdr->transl[BCF_DT_CTG][line->rid] >=0 ) line->rid = src_hdr->transl[BCF_DT_CTG][line->rid];
+
+    // FILTER
+    for (i=0; i<line->d.n_flt; i++)
+    {
+        int src_id = line->d.flt[i];
+        if ( src_hdr->transl[BCF_DT_ID][src_id] >=0 )
+            line->d.flt[i] = src_hdr->transl[BCF_DT_ID][src_id];
+        line->d.shared_dirty |= BCF1_DIRTY_FLT;
+    }
+
+    // INFO
+    for (i=0; i<line->n_info; i++)
+    {
+        int src_id = line->d.info[i].key;
+        int dst_id = src_hdr->transl[BCF_DT_ID][src_id];
+        if ( dst_id<0 ) continue;
+        int src_size = src_id>>7 ? ( src_id>>15 ? BCF_BT_INT32 : BCF_BT_INT16) : BCF_BT_INT8;
+        int dst_size = dst_id>>7 ? ( dst_id>>15 ? BCF_BT_INT32 : BCF_BT_INT16) : BCF_BT_INT8;
+        if ( src_size==dst_size )   // can overwrite
+        {
+            line->d.info[i].key = dst_id;
+            uint8_t *vptr = line->d.info[i].vptr - line->d.info[i].vptr_off;
+            if ( dst_size==BCF_BT_INT8 ) { vptr[1] = (uint8_t)dst_id; }
+            else if ( dst_size==BCF_BT_INT16 ) { *(uint16_t*)vptr = (uint16_t)dst_id; }
+            else { *(uint32_t*)vptr = (uint32_t)dst_id; }
+        }
+        else    // must realloc
+        {
+            bcf_info_t *info = &line->d.info[i];
+            assert( !info->vptr_free );
+            kstring_t str = {0,0,0};
+            bcf_enc_int1(&str, dst_id);
+            bcf_enc_size(&str, info->len,info->type);
+            info->vptr_off = str.l;
+            kputsn((char*)info->vptr, info->vptr_len, &str);
+            info->vptr = (uint8_t*)str.s + info->vptr_off;
+            info->vptr_free = 1;
+            info->key = dst_id;
+            line->d.shared_dirty |= BCF1_DIRTY_INF;
+        }
+    }
+
+    // FORMAT
+    for (i=0; i<line->n_fmt; i++)
+    {
+        int src_id = line->d.fmt[i].id;
+        int dst_id = src_hdr->transl[BCF_DT_ID][src_id];
+        if ( dst_id<0 ) continue;
+        int src_size = src_id>>7 ? ( src_id>>15 ? BCF_BT_INT32 : BCF_BT_INT16) : BCF_BT_INT8;
+        int dst_size = dst_id>>7 ? ( dst_id>>15 ? BCF_BT_INT32 : BCF_BT_INT16) : BCF_BT_INT8;
+        if ( src_size==dst_size )   // can overwrite
+        {
+            line->d.fmt[i].id = dst_id;
+            uint8_t *p = line->d.fmt[i].p - line->d.fmt[i].p_off;    // pointer to the vector size (4bits) and BT type (4bits)
+            if ( dst_size==BCF_BT_INT8 ) { p[1] = dst_id; }
+            else if ( dst_size==BCF_BT_INT16 ) { uint8_t *x = (uint8_t*) &dst_id; p[1] = x[0]; p[2] = x[1]; }
+            else { uint8_t *x = (uint8_t*) &dst_id; p[1] = x[0]; p[2] = x[1]; p[3] = x[2]; p[4] = x[3]; }
+        }
+        else    // must realloc
+        {
+            bcf_fmt_t *fmt = &line->d.fmt[i];
+            assert( !fmt->p_free );
+            kstring_t str = {0,0,0};
+            bcf_enc_int1(&str, dst_id);
+            bcf_enc_size(&str, fmt->n, fmt->type);
+            fmt->p_off = str.l;
+            kputsn((char*)fmt->p, fmt->p_len, &str);
+            fmt->p = (uint8_t*)str.s + fmt->p_off;
+            fmt->p_free = 1;
+            fmt->id = dst_id;
+            line->d.indiv_dirty = 1;
+        }
+    }
+    return 0;
+}
+
+bcf_hdr_t *bcf_hdr_dup(const bcf_hdr_t *hdr)
+{
+    bcf_hdr_t *hout = bcf_hdr_init("r");
+    char *htxt = bcf_hdr_fmt_text(hdr, 1, NULL);
+    bcf_hdr_parse(hout, htxt);
+    free(htxt);
+    return hout;
+}
+
+bcf_hdr_t *bcf_hdr_subset(const bcf_hdr_t *h0, int n, char *const* samples, int *imap)
+{
+    int hlen;
+    void *names_hash = khash_str2int_init();
+    char *htxt = bcf_hdr_fmt_text(h0, 1, &hlen);
+    kstring_t str;
+    bcf_hdr_t *h;
+    str.l = str.m = 0; str.s = 0;
+    h = bcf_hdr_init("w");
+    bcf_hdr_set_version(h,bcf_hdr_get_version(h0));
+    int j;
+    for (j=0; j<n; j++) imap[j] = -1;
+    if ( bcf_hdr_nsamples(h0) > 0) {
+        char *p;
+        int i = 0, end = n? 8 : 7;
+        while ((p = strstr(htxt, "#CHROM\t")) != 0)
+            if (p > htxt && *(p-1) == '\n') break;
+        while ((p = strchr(p, '\t')) != 0 && i < end) ++i, ++p;
+        if (i != end) {
+            free(h); free(str.s);
+            return 0; // malformated header
+        }
+        kputsn(htxt, p - htxt, &str);
+        for (i = 0; i < n; ++i) {
+            if ( khash_str2int_has_key(names_hash,samples[i]) )
+            {
+                fprintf(stderr,"[E::bcf_hdr_subset] Duplicate sample name \"%s\".\n", samples[i]);
+                free(str.s);
+                free(htxt);
+                khash_str2int_destroy(names_hash);
+                bcf_hdr_destroy(h);
+                return NULL;
+            }
+            imap[i] = bcf_hdr_id2int(h0, BCF_DT_SAMPLE, samples[i]);
+            if (imap[i] < 0) continue;
+            kputc('\t', &str);
+            kputs(samples[i], &str);
+            khash_str2int_inc(names_hash,samples[i]);
+        }
+    } else kputsn(htxt, hlen, &str);
+    while (str.l && (!str.s[str.l-1] || str.s[str.l-1]=='\n') ) str.l--; // kill trailing zeros and newlines
+    kputc('\n',&str);
+    bcf_hdr_parse(h, str.s);
+    free(str.s);
+    free(htxt);
+    khash_str2int_destroy(names_hash);
+    return h;
+}
+
+int bcf_hdr_set_samples(bcf_hdr_t *hdr, const char *samples, int is_file)
+{
+    if ( samples && !strcmp("-",samples) ) return 0;            // keep all samples
+
+    hdr->nsamples_ori = bcf_hdr_nsamples(hdr);
+    if ( !samples ) { bcf_hdr_nsamples(hdr) = 0; return 0; }    // exclude all samples
+
+    int i, narr = bit_array_size(bcf_hdr_nsamples(hdr));
+    hdr->keep_samples = (uint8_t*) calloc(narr,1);
+    if ( samples[0]=='^' )
+        for (i=0; i<bcf_hdr_nsamples(hdr); i++) bit_array_set(hdr->keep_samples,i);
+
+    int idx, n, ret = 0;
+    char **smpls = hts_readlist(samples[0]=='^'?samples+1:samples, is_file, &n);
+    if ( !smpls ) return -1;
+    for (i=0; i<n; i++)
+    {
+        idx = bcf_hdr_id2int(hdr,BCF_DT_SAMPLE,smpls[i]);
+        if ( idx<0 )
+        {
+            if ( !ret ) ret = i+1;
+            continue;
+        }
+        assert( idx<bcf_hdr_nsamples(hdr) );
+        if (  samples[0]=='^' )
+            bit_array_clear(hdr->keep_samples, idx);
+        else
+            bit_array_set(hdr->keep_samples, idx);
+    }
+    for (i=0; i<n; i++) free(smpls[i]);
+    free(smpls);
+
+    bcf_hdr_nsamples(hdr) = 0;
+    for (i=0; i<hdr->nsamples_ori; i++)
+        if ( bit_array_test(hdr->keep_samples,i) ) bcf_hdr_nsamples(hdr)++;
+    if ( !bcf_hdr_nsamples(hdr) ) { free(hdr->keep_samples); hdr->keep_samples=NULL; }
+    else
+    {
+        char **samples = (char**) malloc(sizeof(char*)*bcf_hdr_nsamples(hdr));
+        idx = 0;
+        for (i=0; i<hdr->nsamples_ori; i++)
+            if ( bit_array_test(hdr->keep_samples,i) ) samples[idx++] = strdup(hdr->samples[i]);
+        free(hdr->samples);
+        hdr->samples = samples;
+
+        // delete original samples from the dictionary
+        vdict_t *d = (vdict_t*)hdr->dict[BCF_DT_SAMPLE];
+        int k;
+        for (k = kh_begin(d); k != kh_end(d); ++k)
+            if (kh_exist(d, k)) free((char*)kh_key(d, k));
+        kh_destroy(vdict, d);
+
+        // add the subset back
+        hdr->dict[BCF_DT_SAMPLE] = d = kh_init(vdict);
+        for (i=0; i<bcf_hdr_nsamples(hdr); i++)
+        {
+            int ignore, k = kh_put(vdict, d, hdr->samples[i], &ignore);
+            kh_val(d, k) = bcf_idinfo_def;
+            kh_val(d, k).id = kh_size(d) - 1;
+        }
+        bcf_hdr_sync(hdr);
+    }
+
+    return ret;
+}
+
+int bcf_subset(const bcf_hdr_t *h, bcf1_t *v, int n, int *imap)
+{
+    kstring_t ind;
+    ind.s = 0; ind.l = ind.m = 0;
+    if (n) {
+        bcf_fmt_t *fmt;
+        int i, j;
+        fmt = (bcf_fmt_t*)alloca(v->n_fmt * sizeof(bcf_fmt_t));
+        uint8_t *ptr = (uint8_t*)v->indiv.s;
+        for (i = 0; i < v->n_fmt; ++i)
+            ptr = bcf_unpack_fmt_core1(ptr, v->n_sample, &fmt[i]);
+        for (i = 0; i < (int)v->n_fmt; ++i) {
+            bcf_fmt_t *f = &fmt[i];
+            bcf_enc_int1(&ind, f->id);
+            bcf_enc_size(&ind, f->n, f->type);
+            for (j = 0; j < n; ++j)
+                if (imap[j] >= 0) kputsn((char*)(f->p + imap[j] * f->size), f->size, &ind);
+        }
+        for (i = j = 0; j < n; ++j) if (imap[j] >= 0) ++i;
+        v->n_sample = i;
+    } else v->n_sample = 0;
+    if ( !v->n_sample ) v->n_fmt = 0;
+    free(v->indiv.s);
+    v->indiv = ind;
+    v->unpacked &= ~BCF_UN_FMT;    // only BCF is ready for output, VCF will need to unpack again
+    return 0;
+}
+
+int bcf_is_snp(bcf1_t *v)
+{
+    int i;
+    bcf_unpack(v, BCF_UN_STR);
+    for (i = 0; i < v->n_allele; ++i)
+    {
+        if ( v->d.allele[i][1]==0 ) continue;
+
+        // mpileup's <X> allele, see also below. This is not completely satisfactory,
+        // a general library is here narrowly tailored to fit samtools.
+        if ( v->d.allele[i][0]=='<' && v->d.allele[i][1]=='X' && v->d.allele[i][2]=='>' ) continue;
+
+        break;
+    }
+    return i == v->n_allele;
+}
+
+static void bcf_set_variant_type(const char *ref, const char *alt, variant_t *var)
+{
+    // The most frequent case
+    if ( !ref[1] && !alt[1] )
+    {
+        if ( *alt == '.' || *ref==*alt ) { var->n = 0; var->type = VCF_REF; return; }
+        if ( *alt == 'X' ) { var->n = 0; var->type = VCF_REF; return; }  // mpileup's X allele shouldn't be treated as variant
+        var->n = 1; var->type = VCF_SNP; return;
+    }
+    if ( alt[0]=='<' )
+    {
+        if ( alt[1]=='X' && alt[2]=='>' ) { var->n = 0; var->type = VCF_REF; return; }  // mpileup's X allele shouldn't be treated as variant
+        var->type = VCF_OTHER;
+        return;
+    }
+
+    const char *r = ref, *a = alt;
+    while (*r && *a && *r==*a ) { r++; a++; }
+
+    if ( *a && !*r )
+    {
+        while ( *a ) a++;
+        var->n = (a-alt)-(r-ref); var->type = VCF_INDEL; return;
+    }
+    else if ( *r && !*a )
+    {
+        while ( *r ) r++;
+        var->n = (a-alt)-(r-ref); var->type = VCF_INDEL; return;
+    }
+    else if ( !*r && !*a )
+    {
+        var->n = 0; var->type = VCF_REF; return;
+    }
+
+    const char *re = r, *ae = a;
+    while ( re[1] ) re++;
+    while ( ae[1] ) ae++;
+    while ( *re==*ae && re>r && ae>a ) { re--; ae--; }
+    if ( ae==a )
+    {
+        if ( re==r ) { var->n = 1; var->type = VCF_SNP; return; }
+        var->n = -(re-r);
+        if ( *re==*ae ) { var->type = VCF_INDEL; return; }
+        var->type = VCF_OTHER; return;
+    }
+    else if ( re==r )
+    {
+        var->n = ae-a;
+        if ( *re==*ae ) { var->type = VCF_INDEL; return; }
+        var->type = VCF_OTHER; return;
+    }
+
+    var->type = ( re-r == ae-a ) ? VCF_MNP : VCF_OTHER;
+    var->n = ( re-r > ae-a ) ? -(re-r+1) : ae-a+1;
+
+    // should do also complex events, SVs, etc...
+}
+
+static void bcf_set_variant_types(bcf1_t *b)
+{
+    if ( !(b->unpacked & BCF_UN_STR) ) bcf_unpack(b, BCF_UN_STR);
+    bcf_dec_t *d = &b->d;
+    if ( d->n_var < b->n_allele )
+    {
+        d->var = (variant_t *) realloc(d->var, sizeof(variant_t)*b->n_allele);
+        d->n_var = b->n_allele;
+    }
+    int i;
+    b->d.var_type = 0;
+    for (i=1; i<b->n_allele; i++)
+    {
+        bcf_set_variant_type(d->allele[0],d->allele[i], &d->var[i]);
+        b->d.var_type |= d->var[i].type;
+        //fprintf(stderr,"[set_variant_type] %d   %s %s -> %d %d .. %d\n", b->pos+1,d->allele[0],d->allele[i],d->var[i].type,d->var[i].n, b->d.var_type);
+    }
+}
+
+int bcf_get_variant_types(bcf1_t *rec)
+{
+    if ( rec->d.var_type==-1 ) bcf_set_variant_types(rec);
+    return rec->d.var_type;
+}
+int bcf_get_variant_type(bcf1_t *rec, int ith_allele)
+{
+    if ( rec->d.var_type==-1 ) bcf_set_variant_types(rec);
+    return rec->d.var[ith_allele].type;
+}
+
+int bcf_update_info(const bcf_hdr_t *hdr, bcf1_t *line, const char *key, const void *values, int n, int type)
+{
+    // Is the field already present?
+    int i, inf_id = bcf_hdr_id2int(hdr,BCF_DT_ID,key);
+    if ( !bcf_hdr_idinfo_exists(hdr,BCF_HL_INFO,inf_id) ) return -1;    // No such INFO field in the header
+    if ( !(line->unpacked & BCF_UN_INFO) ) bcf_unpack(line, BCF_UN_INFO);
+
+    for (i=0; i<line->n_info; i++)
+        if ( inf_id==line->d.info[i].key ) break;
+    bcf_info_t *inf = i==line->n_info ? NULL : &line->d.info[i];
+
+    if ( !n || (type==BCF_HT_STR && !values) )
+    {
+        if ( inf )
+        {
+            // Mark the tag for removal, free existing memory if necessary
+            if ( inf->vptr_free )
+            {
+                free(inf->vptr - inf->vptr_off);
+                inf->vptr_free = 0;
+            }
+            line->d.shared_dirty |= BCF1_DIRTY_INF;
+            inf->vptr = NULL;
+        }
+        return 0;
+    }
+
+    // Encode the values and determine the size required to accommodate the values
+    kstring_t str = {0,0,0};
+    bcf_enc_int1(&str, inf_id);
+    if ( type==BCF_HT_INT )
+        bcf_enc_vint(&str, n, (int32_t*)values, -1);
+    else if ( type==BCF_HT_REAL )
+        bcf_enc_vfloat(&str, n, (float*)values);
+    else if ( type==BCF_HT_FLAG || type==BCF_HT_STR )
+    {
+        if ( values==NULL )
+            bcf_enc_size(&str, 0, BCF_BT_NULL);
+        else
+            bcf_enc_vchar(&str, strlen((char*)values), (char*)values);
+    }
+    else
+    {
+        fprintf(stderr, "[E::%s] the type %d not implemented yet\n", __func__, type);
+        abort();
+    }
+
+    // Is the INFO tag already present
+    if ( inf )
+    {
+        // Is it big enough to accommodate new block?
+        if ( str.l <= inf->vptr_len + inf->vptr_off )
+        {
+            if ( str.l != inf->vptr_len + inf->vptr_off ) line->d.shared_dirty |= BCF1_DIRTY_INF;
+            uint8_t *ptr = inf->vptr - inf->vptr_off;
+            memcpy(ptr, str.s, str.l);
+            free(str.s);
+            int vptr_free = inf->vptr_free;
+            bcf_unpack_info_core1(ptr, inf);
+            inf->vptr_free = vptr_free;
+        }
+        else
+        {
+            assert( !inf->vptr_free );  // fix the caller or improve here: this has been modified before
+            bcf_unpack_info_core1((uint8_t*)str.s, inf);
+            inf->vptr_free = 1;
+            line->d.shared_dirty |= BCF1_DIRTY_INF;
+        }
+    }
+    else
+    {
+        // The tag is not present, create new one
+        line->n_info++;
+        hts_expand0(bcf_info_t, line->n_info, line->d.m_info , line->d.info);
+        inf = &line->d.info[line->n_info-1];
+        bcf_unpack_info_core1((uint8_t*)str.s, inf);
+        inf->vptr_free = 1;
+        line->d.shared_dirty |= BCF1_DIRTY_INF;
+    }
+    line->unpacked |= BCF_UN_INFO;
+    return 0;
+}
+
+int bcf_update_format_string(const bcf_hdr_t *hdr, bcf1_t *line, const char *key, const char **values, int n)
+{
+    if ( !n )
+        return bcf_update_format(hdr,line,key,NULL,0,BCF_HT_STR);
+
+    int i, max_len = 0;
+    for (i=0; i<n; i++)
+    {
+        int len = strlen(values[i]);
+        if ( len > max_len ) max_len = len;
+    }
+    char *out = (char*) malloc(max_len*n);
+    if ( !out ) return -2;
+    for (i=0; i<n; i++)
+    {
+        char *dst = out+i*max_len;
+        const char *src = values[i];
+        int j = 0;
+        while ( src[j] ) { dst[j] = src[j]; j++; }
+        for (; j<max_len; j++) dst[j] = 0;
+    }
+    int ret = bcf_update_format(hdr,line,key,out,max_len*n,BCF_HT_STR);
+    free(out);
+    return ret;
+}
+
+int bcf_update_format(const bcf_hdr_t *hdr, bcf1_t *line, const char *key, const void *values, int n, int type)
+{
+    // Is the field already present?
+    int i, fmt_id = bcf_hdr_id2int(hdr,BCF_DT_ID,key);
+    if ( !bcf_hdr_idinfo_exists(hdr,BCF_HL_FMT,fmt_id) )
+    {
+        if ( !n ) return 0;
+        return -1;  // the key not present in the header
+    }
+
+    if ( !(line->unpacked & BCF_UN_FMT) ) bcf_unpack(line, BCF_UN_FMT);
+
+    for (i=0; i<line->n_fmt; i++)
+        if ( line->d.fmt[i].id==fmt_id ) break;
+    bcf_fmt_t *fmt = i==line->n_fmt ? NULL : &line->d.fmt[i];
+
+    if ( !n )
+    {
+        if ( fmt )
+        {
+            // Mark the tag for removal, free existing memory if necessary
+            if ( fmt->p_free )
+            {
+                free(fmt->p - fmt->p_off);
+                fmt->p_free = 0;
+            }
+            line->d.indiv_dirty = 1;
+            fmt->p = NULL;
+        }
+        return 0;
+    }
+
+    line->n_sample = bcf_hdr_nsamples(hdr);
+    int nps = n / line->n_sample;  // number of values per sample
+    assert( nps && nps*line->n_sample==n );     // must be divisible by n_sample
+
+    // Encode the values and determine the size required to accommodate the values
+    kstring_t str = {0,0,0};
+    bcf_enc_int1(&str, fmt_id);
+    if ( type==BCF_HT_INT )
+        bcf_enc_vint(&str, n, (int32_t*)values, nps);
+    else if ( type==BCF_HT_REAL )
+    {
+        bcf_enc_size(&str, nps, BCF_BT_FLOAT);
+        kputsn((char*)values, nps*line->n_sample*sizeof(float), &str);
+    }
+    else if ( type==BCF_HT_STR )
+    {
+        bcf_enc_size(&str, nps, BCF_BT_CHAR);
+        kputsn((char*)values, nps*line->n_sample, &str);
+    }
+    else
+    {
+        fprintf(stderr, "[E::%s] the type %d not implemented yet\n", __func__, type);
+        abort();
+    }
+
+    if ( !fmt )
+    {
+        // Not present, new format field
+        line->n_fmt++;
+        hts_expand0(bcf_fmt_t, line->n_fmt, line->d.m_fmt, line->d.fmt);
+
+        // Special case: VCF specification requires that GT is always first
+        if ( line->n_fmt > 1 && key[0]=='G' && key[1]=='T' && !key[2] )
+        {
+            for (i=line->n_fmt-1; i>0; i--)
+                line->d.fmt[i] = line->d.fmt[i-1];
+            fmt = &line->d.fmt[0];
+        }
+        else
+            fmt = &line->d.fmt[line->n_fmt-1];
+        bcf_unpack_fmt_core1((uint8_t*)str.s, line->n_sample, fmt);
+        line->d.indiv_dirty = 1;
+        fmt->p_free = 1;
+    }
+    else
+    {
+        // The tag is already present, check if it is big enough to accomodate the new block
+        if ( str.l <= fmt->p_len + fmt->p_off )
+        {
+            // good, the block is big enough
+            if ( str.l != fmt->p_len + fmt->p_off ) line->d.indiv_dirty = 1;
+            uint8_t *ptr = fmt->p - fmt->p_off;
+            memcpy(ptr, str.s, str.l);
+            free(str.s);
+            int p_free = fmt->p_free;
+            bcf_unpack_fmt_core1(ptr, line->n_sample, fmt);
+            fmt->p_free = p_free;
+        }
+        else
+        {
+            assert( !fmt->p_free );  // fix the caller or improve here: this has been modified before
+            bcf_unpack_fmt_core1((uint8_t*)str.s, line->n_sample, fmt);
+            fmt->p_free = 1;
+            line->d.indiv_dirty = 1;
+        }
+    }
+    line->unpacked |= BCF_UN_FMT;
+    return 0;
+}
+
+
+int bcf_update_filter(const bcf_hdr_t *hdr, bcf1_t *line, int *flt_ids, int n)
+{
+    if ( !(line->unpacked & BCF_UN_FLT) ) bcf_unpack(line, BCF_UN_FLT);
+    line->d.shared_dirty |= BCF1_DIRTY_FLT;
+    line->d.n_flt = n;
+    if ( !n ) return 0;
+    hts_expand(int, line->d.n_flt, line->d.m_flt, line->d.flt);
+    int i;
+    for (i=0; i<n; i++)
+        line->d.flt[i] = flt_ids[i];
+    return 0;
+}
+
+int bcf_add_filter(const bcf_hdr_t *hdr, bcf1_t *line, int flt_id)
+{
+    if ( !(line->unpacked & BCF_UN_FLT) ) bcf_unpack(line, BCF_UN_FLT);
+    int i;
+    for (i=0; i<line->d.n_flt; i++)
+        if ( flt_id==line->d.flt[i] ) break;
+    if ( i<line->d.n_flt ) return 0;    // this filter is already set
+    line->d.shared_dirty |= BCF1_DIRTY_FLT;
+    if ( flt_id==0 )    // set to PASS
+        line->d.n_flt = 1;
+    else if ( line->d.n_flt==1 && line->d.flt[0]==0 )
+        line->d.n_flt = 1;
+    else
+        line->d.n_flt++;
+    hts_expand(int, line->d.n_flt, line->d.m_flt, line->d.flt);
+    line->d.flt[line->d.n_flt-1] = flt_id;
+    return 1;
+}
+int bcf_remove_filter(const bcf_hdr_t *hdr, bcf1_t *line, int flt_id, int pass)
+{
+    if ( !(line->unpacked & BCF_UN_FLT) ) bcf_unpack(line, BCF_UN_FLT);
+    int i;
+    for (i=0; i<line->d.n_flt; i++)
+        if ( flt_id==line->d.flt[i] ) break;
+    if ( i==line->d.n_flt ) return 0;   // the filter is not present
+    line->d.shared_dirty |= BCF1_DIRTY_FLT;
+    if ( i!=line->d.n_flt-1 ) memmove(line->d.flt+i,line->d.flt+i+1,(line->d.n_flt-i-1)*sizeof(*line->d.flt));
+    line->d.n_flt--;
+    if ( !line->d.n_flt && pass ) bcf_add_filter(hdr,line,0);
+    return 0;
+}
+
+int bcf_has_filter(const bcf_hdr_t *hdr, bcf1_t *line, char *filter)
+{
+    if ( filter[0]=='.' && !filter[1] ) filter = "PASS";
+    int id = bcf_hdr_id2int(hdr, BCF_DT_ID, filter);
+    if ( !bcf_hdr_idinfo_exists(hdr,BCF_HL_FLT,id) ) return -1;  // not defined in the header
+
+    if ( !(line->unpacked & BCF_UN_FLT) ) bcf_unpack(line, BCF_UN_FLT);
+    if ( id==0 && !line->d.n_flt) return 1; // PASS
+
+    int i;
+    for (i=0; i<line->d.n_flt; i++)
+        if ( line->d.flt[i]==id ) return 1;
+    return 0;
+}
+
+static inline int _bcf1_sync_alleles(const bcf_hdr_t *hdr, bcf1_t *line, int nals)
+{
+    line->d.shared_dirty |= BCF1_DIRTY_ALS;
+
+    line->n_allele = nals;
+    hts_expand(char*, line->n_allele, line->d.m_allele, line->d.allele);
+
+    char *als = line->d.als;
+    int n = 0;
+    while (n<nals)
+    {
+        line->d.allele[n] = als;
+        while ( *als ) als++;
+        als++;
+        n++;
+    }
+    return 0;
+}
+int bcf_update_alleles(const bcf_hdr_t *hdr, bcf1_t *line, const char **alleles, int nals)
+{
+    kstring_t tmp = {0,0,0};
+    char *free_old = NULL;
+
+    // If the supplied alleles are not pointers to line->d.als, the existing block can be reused.
+    int i;
+    for (i=0; i<nals; i++)
+        if ( alleles[i]>=line->d.als && alleles[i]<line->d.als+line->d.m_als ) break;
+    if ( i==nals )
+    {
+        // all alleles point elsewhere, reuse the existing block
+        tmp.l = 0; tmp.s = line->d.als; tmp.m = line->d.m_als;
+    }
+    else
+        free_old = line->d.als;
+
+    for (i=0; i<nals; i++)
+    {
+        kputs(alleles[i], &tmp);
+        kputc(0, &tmp);
+    }
+    line->d.als = tmp.s; line->d.m_als = tmp.m;
+    free(free_old);
+    return _bcf1_sync_alleles(hdr,line,nals);
+}
+
+int bcf_update_alleles_str(const bcf_hdr_t *hdr, bcf1_t *line, const char *alleles_string)
+{
+    kstring_t tmp;
+    tmp.l = 0; tmp.s = line->d.als; tmp.m = line->d.m_als;
+    kputs(alleles_string, &tmp);
+    line->d.als = tmp.s; line->d.m_als = tmp.m;
+
+    int nals = 1;
+    char *t = line->d.als;
+    while (*t)
+    {
+        if ( *t==',' ) { *t = 0; nals++; }
+        t++;
+    }
+    return _bcf1_sync_alleles(hdr, line, nals);
+}
+
+int bcf_update_id(const bcf_hdr_t *hdr, bcf1_t *line, const char *id)
+{
+    kstring_t tmp;
+    tmp.l = 0; tmp.s = line->d.id; tmp.m = line->d.m_id;
+    if ( id )
+        kputs(id, &tmp);
+    else
+        kputs(".", &tmp);
+    line->d.id = tmp.s; line->d.m_id = tmp.m;
+    line->d.shared_dirty |= BCF1_DIRTY_ID;
+    return 0;
+}
+
+bcf_fmt_t *bcf_get_fmt(const bcf_hdr_t *hdr, bcf1_t *line, const char *key)
+{
+    int id = bcf_hdr_id2int(hdr, BCF_DT_ID, key);
+    if ( !bcf_hdr_idinfo_exists(hdr,BCF_HL_FMT,id) ) return NULL;   // no such FMT field in the header
+    return bcf_get_fmt_id(line, id);
+}
+
+bcf_info_t *bcf_get_info(const bcf_hdr_t *hdr, bcf1_t *line, const char *key)
+{
+    int id = bcf_hdr_id2int(hdr, BCF_DT_ID, key);
+    if ( !bcf_hdr_idinfo_exists(hdr,BCF_HL_INFO,id) ) return NULL;   // no such INFO field in the header
+    return bcf_get_info_id(line, id);
+}
+
+bcf_fmt_t *bcf_get_fmt_id(bcf1_t *line, const int id) 
+{
+    int i;
+    if ( !(line->unpacked & BCF_UN_FMT) ) bcf_unpack(line, BCF_UN_FMT);
+    for (i=0; i<line->n_fmt; i++)
+    {
+        if ( line->d.fmt[i].id==id ) return &line->d.fmt[i];
+    }
+    return NULL;
+}
+
+bcf_info_t *bcf_get_info_id(bcf1_t *line, const int id) 
+{
+    int i;
+    if ( !(line->unpacked & BCF_UN_INFO) ) bcf_unpack(line, BCF_UN_INFO);
+    for (i=0; i<line->n_info; i++)
+    {
+        if ( line->d.info[i].key==id ) return &line->d.info[i];
+    }
+    return NULL;
+}
+
+
+int bcf_get_info_values(const bcf_hdr_t *hdr, bcf1_t *line, const char *tag, void **dst, int *ndst, int type)
+{
+    int i,j, tag_id = bcf_hdr_id2int(hdr, BCF_DT_ID, tag);
+    if ( !bcf_hdr_idinfo_exists(hdr,BCF_HL_INFO,tag_id) ) return -1;    // no such INFO field in the header
+    if ( bcf_hdr_id2type(hdr,BCF_HL_INFO,tag_id)!=type ) return -2;     // expected different type
+
+    if ( !(line->unpacked & BCF_UN_INFO) ) bcf_unpack(line, BCF_UN_INFO);
+
+    for (i=0; i<line->n_info; i++)
+        if ( line->d.info[i].key==tag_id ) break;
+    if ( i==line->n_info ) return ( type==BCF_HT_FLAG ) ? 0 : -3;       // the tag is not present in this record
+    if ( type==BCF_HT_FLAG ) return 1;
+
+    bcf_info_t *info = &line->d.info[i];
+    if ( type==BCF_HT_STR )
+    {
+        if ( *ndst < info->len+1 )
+        {
+            *ndst = info->len + 1;
+            *dst  = realloc(*dst, *ndst);
+        }
+        memcpy(*dst,info->vptr,info->len);
+        ((uint8_t*)*dst)[info->len] = 0;
+        return info->len;
+    }
+
+    // Make sure the buffer is big enough
+    int size1 = type==BCF_HT_INT ? sizeof(int32_t) : sizeof(float);
+    if ( *ndst < info->len )
+    {
+        *ndst = info->len;
+        *dst  = realloc(*dst, *ndst * size1);
+    }
+
+    if ( info->len == 1 )
+    {
+        if ( info->type==BCF_BT_FLOAT ) *((float*)*dst) = info->v1.f;
+        else 
+        {
+            #define BRANCH(type_t, missing) { \
+                if ( info->v1.i==missing ) *((int32_t*)*dst) = bcf_int32_missing; \
+                else *((int32_t*)*dst) = info->v1.i; \
+            }
+            switch (info->type)
+            {
+                case BCF_BT_INT8:  BRANCH(int8_t,  bcf_int8_missing ); break;
+                case BCF_BT_INT16: BRANCH(int16_t, bcf_int16_missing); break;
+                case BCF_BT_INT32: BRANCH(int32_t, bcf_int32_missing); break;
+            }
+            #undef BRANCH
+        }
+        return 1;
+    }
+
+    #define BRANCH(type_t, is_missing, is_vector_end, set_missing, out_type_t) { \
+        out_type_t *tmp = (out_type_t *) *dst; \
+        type_t *p = (type_t *) info->vptr; \
+        for (j=0; j<info->len; j++) \
+        { \
+            if ( is_vector_end ) return j; \
+            if ( is_missing ) set_missing; \
+            else *tmp = p[j]; \
+            tmp++; \
+        } \
+        return j; \
+    }
+    switch (info->type) {
+        case BCF_BT_INT8:  BRANCH(int8_t,  p[j]==bcf_int8_missing,  p[j]==bcf_int8_vector_end,  *tmp=bcf_int32_missing, int32_t); break;
+        case BCF_BT_INT16: BRANCH(int16_t, p[j]==bcf_int16_missing, p[j]==bcf_int16_vector_end, *tmp=bcf_int32_missing, int32_t); break;
+        case BCF_BT_INT32: BRANCH(int32_t, p[j]==bcf_int32_missing, p[j]==bcf_int32_vector_end, *tmp=bcf_int32_missing, int32_t); break;
+        case BCF_BT_FLOAT: BRANCH(float,   bcf_float_is_missing(p[j]), bcf_float_is_vector_end(p[j]), bcf_float_set_missing(*tmp), float); break;
+        default: fprintf(stderr,"TODO: %s:%d .. info->type=%d\n", __FILE__,__LINE__, info->type); exit(1);
+    }
+    #undef BRANCH
+    return -4;  // this can never happen
+}
+
+int bcf_get_format_string(const bcf_hdr_t *hdr, bcf1_t *line, const char *tag, char ***dst, int *ndst)
+{
+    int i,tag_id = bcf_hdr_id2int(hdr, BCF_DT_ID, tag);
+    if ( !bcf_hdr_idinfo_exists(hdr,BCF_HL_FMT,tag_id) ) return -1;    // no such FORMAT field in the header
+    if ( bcf_hdr_id2type(hdr,BCF_HL_FMT,tag_id)!=BCF_HT_STR ) return -2;     // expected different type
+
+    if ( !(line->unpacked & BCF_UN_FMT) ) bcf_unpack(line, BCF_UN_FMT);
+
+    for (i=0; i<line->n_fmt; i++)
+        if ( line->d.fmt[i].id==tag_id ) break;
+    if ( i==line->n_fmt ) return -3;                               // the tag is not present in this record
+    bcf_fmt_t *fmt = &line->d.fmt[i];
+
+    int nsmpl = bcf_hdr_nsamples(hdr);
+    if ( !*dst )
+    {
+        *dst = (char**) malloc(sizeof(char*)*nsmpl);
+        if ( !*dst ) return -4;     // could not alloc
+        (*dst)[0] = NULL;
+    }
+    int n = (fmt->n+1)*nsmpl;
+    if ( *ndst < n )
+    {
+        (*dst)[0] = realloc((*dst)[0], n);
+        if ( !(*dst)[0] ) return -4;    // could not alloc
+        *ndst = n;
+    }
+    for (i=0; i<nsmpl; i++)
+    {
+        uint8_t *src = fmt->p + i*fmt->n;
+        uint8_t *tmp = (uint8_t*)(*dst)[0] + i*(fmt->n+1);
+        memcpy(tmp,src,fmt->n);
+        tmp[fmt->n] = 0;
+        (*dst)[i] = (char*) tmp;
+    }
+    return n;
+}
+
+int bcf_get_format_values(const bcf_hdr_t *hdr, bcf1_t *line, const char *tag, void **dst, int *ndst, int type)
+{
+    int i,j, tag_id = bcf_hdr_id2int(hdr, BCF_DT_ID, tag);
+    if ( !bcf_hdr_idinfo_exists(hdr,BCF_HL_FMT,tag_id) ) return -1;    // no such FORMAT field in the header
+    if ( tag[0]=='G' && tag[1]=='T' && tag[2]==0 )
+    {
+        // Ugly: GT field is considered to be a string by the VCF header but BCF represents it as INT.
+        if ( bcf_hdr_id2type(hdr,BCF_HL_FMT,tag_id)!=BCF_HT_STR ) return -2;
+    }
+    else if ( bcf_hdr_id2type(hdr,BCF_HL_FMT,tag_id)!=type ) return -2;     // expected different type
+
+    if ( !(line->unpacked & BCF_UN_FMT) ) bcf_unpack(line, BCF_UN_FMT);
+
+    for (i=0; i<line->n_fmt; i++)
+        if ( line->d.fmt[i].id==tag_id ) break;
+    if ( i==line->n_fmt ) return -3;                               // the tag is not present in this record
+    bcf_fmt_t *fmt = &line->d.fmt[i];
+
+    if ( type==BCF_HT_STR )
+    {
+        int n = fmt->n*bcf_hdr_nsamples(hdr);
+        if ( *ndst < n )
+        {
+            *dst  = realloc(*dst, n);
+            if ( !*dst ) return -4;     // could not alloc
+            *ndst = n;
+        }
+        memcpy(*dst,fmt->p,n);
+        return n;
+    }
+
+    // Make sure the buffer is big enough
+    int nsmpl = bcf_hdr_nsamples(hdr);
+    int size1 = type==BCF_HT_INT ? sizeof(int32_t) : sizeof(float);
+    if ( *ndst < fmt->n*nsmpl )
+    {
+        *ndst = fmt->n*nsmpl;
+        *dst  = realloc(*dst, *ndst*size1);
+        if ( !dst ) return -4;     // could not alloc
+    }
+
+    #define BRANCH(type_t, is_missing, is_vector_end, set_missing, set_vector_end, out_type_t) { \
+        out_type_t *tmp = (out_type_t *) *dst; \
+        type_t *p = (type_t*) fmt->p; \
+        for (i=0; i<nsmpl; i++) \
+        { \
+            for (j=0; j<fmt->n; j++) \
+            { \
+                if ( is_missing ) set_missing; \
+                else if ( is_vector_end ) { set_vector_end; break; } \
+                else *tmp = p[j]; \
+                tmp++; \
+            } \
+            for (; j<fmt->n; j++) { set_vector_end; tmp++; } \
+            p = (type_t *)((char *)p + fmt->size); \
+        } \
+    }
+    switch (fmt->type) {
+        case BCF_BT_INT8:  BRANCH(int8_t,  p[j]==bcf_int8_missing,  p[j]==bcf_int8_vector_end,  *tmp=bcf_int32_missing, *tmp=bcf_int32_vector_end, int32_t); break;
+        case BCF_BT_INT16: BRANCH(int16_t, p[j]==bcf_int16_missing, p[j]==bcf_int16_vector_end, *tmp=bcf_int32_missing, *tmp=bcf_int32_vector_end, int32_t); break;
+        case BCF_BT_INT32: BRANCH(int32_t, p[j]==bcf_int32_missing, p[j]==bcf_int32_vector_end, *tmp=bcf_int32_missing, *tmp=bcf_int32_vector_end, int32_t); break;
+        case BCF_BT_FLOAT: BRANCH(float,   bcf_float_is_missing(p[j]), bcf_float_is_vector_end(p[j]), bcf_float_set_missing(*tmp), bcf_float_set_vector_end(*tmp), float); break;
+        default: fprintf(stderr,"TODO: %s:%d .. fmt->type=%d\n", __FILE__,__LINE__, fmt->type); exit(1);
+    }
+    #undef BRANCH
+    return nsmpl*fmt->n;
+}
+