+ return (rg == 0)? 0 : sam_tbl_get(h->rg2lib, (const char*)(rg + 1));
+}
+
+/************
+ * Remove B *
+ ************/
+
+int bam_remove_B(bam1_t *b)
+{
+ int i, j, end_j, k, l, no_qual;
+ uint32_t *cigar, *new_cigar;
+ uint8_t *seq, *qual, *p;
+ // test if removal is necessary
+ if (b->core.flag & BAM_FUNMAP) return 0; // unmapped; do nothing
+ cigar = bam1_cigar(b);
+ for (k = 0; k < b->core.n_cigar; ++k)
+ if (bam_cigar_op(cigar[k]) == BAM_CBACK) break;
+ if (k == b->core.n_cigar) return 0; // no 'B'
+ if (bam_cigar_op(cigar[0]) == BAM_CBACK) goto rmB_err; // cannot be removed
+ // allocate memory for the new CIGAR
+ if (b->data_len + (b->core.n_cigar + 1) * 4 > b->m_data) { // not enough memory
+ b->m_data = b->data_len + b->core.n_cigar * 4;
+ kroundup32(b->m_data);
+ b->data = (uint8_t*)realloc(b->data, b->m_data);
+ cigar = bam1_cigar(b); // after realloc, cigar may be changed
+ }
+ new_cigar = (uint32_t*)(b->data + (b->m_data - b->core.n_cigar * 4)); // from the end of b->data
+ // the core loop
+ seq = bam1_seq(b); qual = bam1_qual(b);
+ no_qual = (qual[0] == 0xff); // test whether base quality is available
+ i = j = 0; end_j = -1;
+ for (k = l = 0; k < b->core.n_cigar; ++k) {
+ int op = bam_cigar_op(cigar[k]);
+ int len = bam_cigar_oplen(cigar[k]);
+ if (op == BAM_CBACK) { // the backward operation
+ int t, u;
+ if (k == b->core.n_cigar - 1) break; // ignore 'B' at the end of CIGAR
+ if (len > j) goto rmB_err; // an excessively long backward
+ for (t = l - 1, u = 0; t >= 0; --t) { // look back
+ int op1 = bam_cigar_op(new_cigar[t]);
+ int len1 = bam_cigar_oplen(new_cigar[t]);
+ if (bam_cigar_type(op1)&1) { // consume the query
+ if (u + len1 >= len) { // stop
+ new_cigar[t] -= (len - u) << BAM_CIGAR_SHIFT;
+ break;
+ } else u += len1;
+ }
+ }
+ if (bam_cigar_oplen(new_cigar[t]) == 0) --t; // squeeze out the zero-length operation
+ l = t + 1;
+ end_j = j; j -= len;
+ } else { // other CIGAR operations
+ new_cigar[l++] = cigar[k];
+ if (bam_cigar_type(op)&1) { // consume the query
+ if (i != j) { // no need to copy if i == j
+ int u, c, c0;
+ for (u = 0; u < len; ++u) { // construct the consensus
+ c = bam1_seqi(seq, i+u);
+ if (j + u < end_j) { // in an overlap
+ c0 = bam1_seqi(seq, j+u);
+ if (c != c0) { // a mismatch; choose the better base
+ if (qual[j+u] < qual[i+u]) { // the base in the 2nd segment is better
+ bam1_seq_seti(seq, j+u, c);
+ qual[j+u] = qual[i+u] - qual[j+u];
+ } else qual[j+u] -= qual[i+u]; // the 1st is better; reduce base quality
+ } else qual[j+u] = qual[j+u] > qual[i+u]? qual[j+u] : qual[i+u];
+ } else { // not in an overlap; copy over
+ bam1_seq_seti(seq, j+u, c);
+ qual[j+u] = qual[i+u];
+ }
+ }
+ }
+ i += len, j += len;
+ }
+ }
+ }
+ if (no_qual) qual[0] = 0xff; // in very rare cases, this may be modified
+ // merge adjacent operations if possible
+ for (k = 1; k < l; ++k)
+ if (bam_cigar_op(new_cigar[k]) == bam_cigar_op(new_cigar[k-1]))
+ new_cigar[k] += new_cigar[k-1] >> BAM_CIGAR_SHIFT << BAM_CIGAR_SHIFT, new_cigar[k-1] &= 0xf;
+ // kill zero length operations
+ for (k = i = 0; k < l; ++k)
+ if (new_cigar[k] >> BAM_CIGAR_SHIFT)
+ new_cigar[i++] = new_cigar[k];
+ l = i;
+ // update b
+ memcpy(cigar, new_cigar, l * 4); // set CIGAR
+ p = b->data + b->core.l_qname + l * 4;
+ memmove(p, seq, (j+1)>>1); p += (j+1)>>1; // set SEQ
+ memmove(p, qual, j); p += j; // set QUAL
+ memmove(p, bam1_aux(b), b->l_aux); p += b->l_aux; // set optional fields
+ b->core.n_cigar = l, b->core.l_qseq = j; // update CIGAR length and query length
+ b->data_len = p - b->data; // update record length
+ return 0;
+
+rmB_err:
+ b->core.flag |= BAM_FUNMAP;
+ return -1;