Add VCF/BCF support for POS=0 coordinate

Review of `bcftools merge` code and possibly others is necessary because it is relying
on uninitialized POS==-1 in synced_bcf_reader

This should resolve #1571

Author: pd3

hts.c

@@ -2205,6 +2205,8 @@ static inline int insert_to_l(lidx_t *l, int64_t _beg, int64_t _end, uint64_t of
 {
     int i;
     hts_pos_t beg, end;
+    if ( _beg<0 ) _beg = 0;
+    if ( _end<=_beg ) _end = _beg+1;
     beg = _beg >> min_shift;
     end = (_end - 1) >> min_shift;
     if (l->m < end + 1) {
@@ -2905,6 +2907,8 @@ static inline int reg2bins(int64_t beg, int64_t end, hts_itr_t *itr, int min_shi
 {
     int l, t, s = min_shift + (n_lvls<<1) + n_lvls;
     if (beg >= end) return 0;
+    if (beg < 0 ) beg = 0;
+    if (beg==end) end = 1;
     if (end >= 1LL<<s) end = 1LL<<s;
     for (--end, l = 0, t = 0; l <= n_lvls; s -= 3, t += 1<<((l<<1)+l), ++l) {
         hts_pos_t b, e;
@@ -3086,7 +3090,7 @@ hts_itr_t *hts_itr_query(const hts_idx_t *idx, int tid, hts_pos_t beg, hts_pos_t
         } else if (tid >= idx->n || (bidx = idx->bidx[tid]) == NULL) {
             iter->finished = 1;
         } else {
-            if (beg < 0) beg = 0;
+            if (beg < -1) beg = -1;
             if (end < beg) {
               free(iter);
               return NULL;
@@ -3103,7 +3107,7 @@ hts_itr_t *hts_itr_query(const hts_idx_t *idx, int tid, hts_pos_t beg, hts_pos_t
 
             if ( !kh_size(bidx) ) { iter->finished = 1; return iter; }
 
-            rel_off = beg>>idx->min_shift;
+            rel_off = (beg>=0 ? beg : 0) >> idx->min_shift;
             // compute min_off
             bin = hts_bin_first(idx->n_lvls) + rel_off;
             do {
@@ -3138,8 +3142,6 @@ hts_itr_t *hts_itr_query(const hts_idx_t *idx, int tid, hts_pos_t beg, hts_pos_t
                         min_off = kh_val(bidx, k).loff;
                 }
             } else if (unmapped) { //CSI index
-                if (k != kh_end(bidx))
-                    min_off = kh_val(bidx, k).loff;
             }
 
             // compute max_off: a virtual offset from a bin to the right of end

htslib/synced_bcf_reader.h

@@ -64,6 +64,8 @@ DEALINGS IN THE SOFTWARE.  */
 extern "C" {
 #endif
 
+#define CSI_COOR_EMPTY   -2
+
 /*
     When reading multiple files in parallel, duplicate records within each
     file will be reordered and offered in intuitive order. For example,

synced_bcf_reader.c

@@ -371,7 +371,7 @@ int bcf_sr_add_reader(bcf_srs_t *files, const char *fname)
             if ( !files->regions )
                 files->regions = _regions_init_string(names[i]);
             else
-                _regions_add(files->regions, names[i], -1, -1);
+                _regions_add(files->regions, names[i], CSI_COOR_EMPTY, CSI_COOR_EMPTY);
         }
         free(names);
         _regions_sort_and_merge(files->regions);
@@ -555,7 +555,7 @@ static int _readers_next_region(bcf_srs_t *files)
     int prev_iseq = files->regions->iseq;
     hts_pos_t prev_end = files->regions->end;
     if ( bcf_sr_regions_next(files->regions)<0 ) return -1;
-    files->regions->prev_end = prev_iseq==files->regions->iseq ? prev_end : -1;
+    files->regions->prev_end = prev_iseq==files->regions->iseq ? prev_end : CSI_COOR_EMPTY;
 
     for (i=0; i<files->nreaders; i++)
         _reader_seek(&files->readers[i],files->regions->seq_names[files->regions->iseq],files->regions->start,files->regions->end);
@@ -616,7 +616,7 @@ static int _reader_fill_buffer(bcf_srs_t *files, bcf_sr_t *reader)
             {
                 reader->buffer[reader->mbuffer-i] = bcf_init1();
                 reader->buffer[reader->mbuffer-i]->max_unpack = files->max_unpack;
-                reader->buffer[reader->mbuffer-i]->pos = -1;    // for rare cases when VCF starts from 1
+                reader->buffer[reader->mbuffer-i]->pos = CSI_COOR_EMPTY;    // for rare cases when VCF starts from 1 or 0
             }
         }
         if ( files->streaming )
@@ -656,7 +656,6 @@ static int _reader_fill_buffer(bcf_srs_t *files, bcf_sr_t *reader)
             if ( ret < 0 ) break; // no more lines or an error
             bcf_subset_format(reader->header,reader->buffer[reader->nbuffer+1]);
         }
-
         // Prevent creation of duplicates from records overlapping multiple regions
         // and recognize true variant overlaps vs record overlaps (e.g. TA>T vs A>-)
         if ( files->regions )
@@ -676,7 +675,6 @@ static int _reader_fill_buffer(bcf_srs_t *files, bcf_sr_t *reader)
                 hts_log_error("This should never happen, just to keep clang compiler happy: %d",BCF_SR_AUX(files)->targets_overlap);
                 exit(1);
             }
-
             if ( beg <= files->regions->prev_end || end < files->regions->start || beg > files->regions->end ) continue;
         }
 
@@ -954,9 +952,9 @@ int bcf_sr_set_samples(bcf_srs_t *files, const char *fname, int is_file)
 // inclusive. Sorting and merging step needed afterwards: qsort(..,cmp_regions) and merge_regions().
 static int _regions_add(bcf_sr_regions_t *reg, const char *chr, hts_pos_t start, hts_pos_t end)
 {
-    if ( start==-1 && end==-1 )
+    if ( start==CSI_COOR_EMPTY && end==CSI_COOR_EMPTY )
     {
-        start = 0; end = MAX_CSI_COOR-1;
+        start = -1; end = MAX_CSI_COOR-1;
     }
     else
     {
@@ -1029,8 +1027,9 @@ void _regions_sort_and_merge(bcf_sr_regions_t *reg)
 static bcf_sr_regions_t *_regions_init_string(const char *str)
 {
     bcf_sr_regions_t *reg = (bcf_sr_regions_t *) calloc(1, sizeof(bcf_sr_regions_t));
-    reg->start = reg->end = -1;
-    reg->prev_start = reg->prev_end = reg->prev_seq = -1;
+    reg->start = reg->end = CSI_COOR_EMPTY;
+    reg->prev_start = reg->prev_end = CSI_COOR_EMPTY;
+    reg->prev_seq = -1;
 
     kstring_t tmp = {0,0,0};
     const char *sp = str, *ep = str;
@@ -1075,7 +1074,7 @@ static bcf_sr_regions_t *_regions_init_string(const char *str)
         }
         else
         {
-            if ( tmp.l ) _regions_add(reg, tmp.s, -1, -1);
+            if ( tmp.l ) _regions_add(reg, tmp.s, CSI_COOR_EMPTY, CSI_COOR_EMPTY);
             if ( !*ep ) break;
             sp = ++ep;
         }
@@ -1157,8 +1156,9 @@ bcf_sr_regions_t *bcf_sr_regions_init(const char *regions, int is_file, int ichr
     }
 
     reg = (bcf_sr_regions_t *) calloc(1, sizeof(bcf_sr_regions_t));
-    reg->start = reg->end = -1;
-    reg->prev_start = reg->prev_end = reg->prev_seq = -1;
+    reg->start = reg->end = CSI_COOR_EMPTY;
+    reg->prev_start = reg->prev_end = CSI_COOR_EMPTY;
+    reg->prev_seq = -1;
 
     reg->file = hts_open(regions, "rb");
     if ( !reg->file )
@@ -1253,7 +1253,8 @@ void bcf_sr_regions_destroy(bcf_sr_regions_t *reg)
 
 int bcf_sr_regions_seek(bcf_sr_regions_t *reg, const char *seq)
 {
-    reg->iseq = reg->start = reg->end = -1;
+    reg->iseq = -1;
+    reg->start = reg->end = CSI_COOR_EMPTY;
     if ( khash_str2int_get(reg->seq_hash, seq, &reg->iseq) < 0 ) return -1;  // sequence seq not in regions
 
     // using in-memory regions
@@ -1284,7 +1285,7 @@ static int advance_creg(region_t *reg)
 int bcf_sr_regions_next(bcf_sr_regions_t *reg)
 {
     if ( reg->iseq<0 ) return -1;
-    reg->start = reg->end = -1;
+    reg->start = reg->end = CSI_COOR_EMPTY;
     reg->nals = 0;
 
     // using in-memory regions
@@ -1442,7 +1443,7 @@ static int _bcf_sr_regions_overlap(bcf_sr_regions_t *reg, const char *seq, hts_p
             bcf_sr_regions_flush(reg);
 
         bcf_sr_regions_seek(reg, seq);
-        reg->start = reg->end = -1;
+        reg->start = reg->end = CSI_COOR_EMPTY;
     }
     if ( reg->prev_seq==iseq && reg->iseq!=iseq ) return -2;    // no more regions on this chromosome
     reg->prev_seq = reg->iseq;

tbx.c

@@ -107,12 +107,12 @@ int tbx_parse1(const tbx_conf_t *conf, size_t len, char *line, tbx_intv_t *intv)
                 if ( s==line+b ) return -1; // expected int
                 if (!(conf->preset&TBX_UCSC)) --intv->beg;
                 else ++intv->end;
-                if (intv->beg < 0) {
+                if (intv->beg < -1) {
                     hts_log_warning("Coordinate <= 0 detected. "
                                     "Did you forget to use the -0 option?");
                     intv->beg = 0;
                 }
-                if (intv->end < 1) intv->end = 1;
+                if (intv->end < intv->beg ) intv->end = intv->beg;
             } else {
                 if ((conf->preset&0xffff) == TBX_GENERIC) {
                     if (id == conf->ec)
@@ -171,7 +171,7 @@ int tbx_parse1(const tbx_conf_t *conf, size_t len, char *line, tbx_intv_t *intv)
             ++id;
         }
     }
-    if (intv->ss == 0 || intv->se == 0 || intv->beg < 0 || intv->end < 0) return -1;
+    if (intv->ss == 0 || intv->se == 0 || intv->beg < -1 || intv->end < -1) return -1;
     return 0;
 }
 
@@ -181,7 +181,7 @@ static inline int get_intv(tbx_t *tbx, kstring_t *str, tbx_intv_t *intv, int is_
         int c = *intv->se;
         *intv->se = '\0'; intv->tid = get_tid(tbx, intv->ss, is_add); *intv->se = c;
         if (intv->tid < 0) return -2;  // get_tid out of memory
-        return (intv->beg >= 0 && intv->end >= 0)? 0 : -1;
+        return (intv->beg >= -1 && intv->end >= -1)? 0 : -1;
     } else {
         char *type = NULL;
         switch (tbx->conf.preset&0xffff)