diff bwa-0.6.2/bwase.c @ 2:a294fbfcb1db draft default tip

Uploaded BWA

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/bwa-0.6.2/bwase.c	Fri Jul 18 07:55:59 2014 -0400
@@ -0,0 +1,683 @@
+#include <unistd.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#include <time.h>
+#include "stdaln.h"
+#include "bwase.h"
+#include "bwtaln.h"
+#include "bntseq.h"
+#include "utils.h"
+#include "kstring.h"
+
+int g_log_n[256];
+char *bwa_rg_line, *bwa_rg_id;
+
+void bwa_print_sam_PG();
+
+void bwa_aln2seq_core(int n_aln, const bwt_aln1_t *aln, bwa_seq_t *s, int set_main, int n_multi)
+{
+	int i, cnt, best;
+	if (n_aln == 0) {
+		s->type = BWA_TYPE_NO_MATCH;
+		s->c1 = s->c2 = 0;
+		return;
+	}
+
+	if (set_main) {
+		best = aln[0].score;
+		for (i = cnt = 0; i < n_aln; ++i) {
+			const bwt_aln1_t *p = aln + i;
+			if (p->score > best) break;
+			if (drand48() * (p->l - p->k + 1 + cnt) > (double)cnt) {
+				s->n_mm = p->n_mm; s->n_gapo = p->n_gapo; s->n_gape = p->n_gape;
+				s->score = p->score;
+				s->sa = p->k + (bwtint_t)((p->l - p->k + 1) * drand48());
+			}
+			cnt += p->l - p->k + 1;
+		}
+		s->c1 = cnt;
+		for (; i < n_aln; ++i) cnt += aln[i].l - aln[i].k + 1;
+		s->c2 = cnt - s->c1;
+		s->type = s->c1 > 1? BWA_TYPE_REPEAT : BWA_TYPE_UNIQUE;
+	}
+
+	if (n_multi) {
+		int k, rest, n_occ, z = 0;
+		for (k = n_occ = 0; k < n_aln; ++k) {
+			const bwt_aln1_t *q = aln + k;
+			n_occ += q->l - q->k + 1;
+		}
+		if (s->multi) free(s->multi);
+		if (n_occ > n_multi + 1) { // if there are too many hits, generate none of them
+			s->multi = 0; s->n_multi = 0;
+			return;
+		}
+		/* The following code is more flexible than what is required
+		 * here. In principle, due to the requirement above, we can
+		 * simply output all hits, but the following samples "rest"
+		 * number of random hits. */
+		rest = n_occ > n_multi + 1? n_multi + 1 : n_occ; // find one additional for ->sa
+		s->multi = calloc(rest, sizeof(bwt_multi1_t));
+		for (k = 0; k < n_aln; ++k) {
+			const bwt_aln1_t *q = aln + k;
+			if (q->l - q->k + 1 <= rest) {
+				bwtint_t l;
+				for (l = q->k; l <= q->l; ++l) {
+					s->multi[z].pos = l;
+					s->multi[z].gap = q->n_gapo + q->n_gape;
+					s->multi[z++].mm = q->n_mm;
+				}
+				rest -= q->l - q->k + 1;
+			} else { // Random sampling (http://code.activestate.com/recipes/272884/). In fact, we never come here. 
+				int j, i, k;
+				for (j = rest, i = q->l - q->k + 1, k = 0; j > 0; --j) {
+					double p = 1.0, x = drand48();
+					while (x < p) p -= p * j / (i--);
+					s->multi[z].pos = q->l - i;
+					s->multi[z].gap = q->n_gapo + q->n_gape;
+					s->multi[z++].mm = q->n_mm;
+				}
+				rest = 0;
+				break;
+			}
+		}
+		s->n_multi = z;
+	}
+}
+
+void bwa_aln2seq(int n_aln, const bwt_aln1_t *aln, bwa_seq_t *s)
+{
+	bwa_aln2seq_core(n_aln, aln, s, 1, 0);
+}
+
+int bwa_approx_mapQ(const bwa_seq_t *p, int mm)
+{
+	int n;
+	if (p->c1 == 0) return 23;
+	if (p->c1 > 1) return 0;
+	if (p->n_mm == mm) return 25;
+	if (p->c2 == 0) return 37;
+	n = (p->c2 >= 255)? 255 : p->c2;
+	return (23 < g_log_n[n])? 0 : 23 - g_log_n[n];
+}
+
+bwtint_t bwa_sa2pos(const bntseq_t *bns, const bwt_t *bwt, bwtint_t sapos, int len, int *strand)
+{
+	bwtint_t pos_f;
+	int is_rev;
+	pos_f = bns_depos(bns, bwt_sa(bwt, sapos), &is_rev); // pos_f
+	*strand = !is_rev;
+	/* NB: For gapped alignment, pacpos may not be correct, which will be fixed
+	 * in bwa_refine_gapped_core(). This line also determines the way "x" is
+	 * calculated in bwa_refine_gapped_core() when (ext < 0 && is_end == 0). */
+	if (is_rev) pos_f = pos_f + 1 < len? 0 : pos_f - len + 1; // mapped to the forward strand
+	return pos_f; // FIXME: it is possible that pos_f < bns->anns[ref_id].offset
+}
+
+/**
+ * Derive the actual position in the read from the given suffix array
+ * coordinates. Note that the position will be approximate based on
+ * whether indels appear in the read and whether calculations are
+ * performed from the start or end of the read.
+ */
+void bwa_cal_pac_pos_core(const bntseq_t *bns, const bwt_t *bwt, bwa_seq_t *seq, const int max_mm, const float fnr)
+{
+	int max_diff, strand;
+	if (seq->type != BWA_TYPE_UNIQUE && seq->type != BWA_TYPE_REPEAT) return;
+	max_diff = fnr > 0.0? bwa_cal_maxdiff(seq->len, BWA_AVG_ERR, fnr) : max_mm;
+	seq->seQ = seq->mapQ = bwa_approx_mapQ(seq, max_diff);
+	seq->pos = bwa_sa2pos(bns, bwt, seq->sa, seq->len, &strand);
+	seq->strand = strand;
+	seq->seQ = seq->mapQ = bwa_approx_mapQ(seq, max_diff);
+}
+
+void bwa_cal_pac_pos(const bntseq_t *bns, const char *prefix, int n_seqs, bwa_seq_t *seqs, int max_mm, float fnr)
+{
+	int i, j, strand, n_multi;
+	char str[1024];
+	bwt_t *bwt;
+	// load forward SA
+	strcpy(str, prefix); strcat(str, ".bwt");  bwt = bwt_restore_bwt(str);
+	strcpy(str, prefix); strcat(str, ".sa"); bwt_restore_sa(str, bwt);
+	for (i = 0; i != n_seqs; ++i) {
+		bwa_seq_t *p = &seqs[i];
+		bwa_cal_pac_pos_core(bns, bwt, p, max_mm, fnr);
+		for (j = n_multi = 0; j < p->n_multi; ++j) {
+			bwt_multi1_t *q = p->multi + j;
+			q->pos = bwa_sa2pos(bns, bwt, q->pos, p->len, &strand);
+			q->strand = strand;
+			if (q->pos != p->pos)
+				p->multi[n_multi++] = *q;
+		}
+		p->n_multi = n_multi;
+	}
+	bwt_destroy(bwt);
+}
+
+/* is_end_correct == 1 if (*pos+len) gives the correct coordinate on
+ * forward strand. This happens when p->pos is calculated by
+ * bwa_cal_pac_pos(). is_end_correct==0 if (*pos) gives the correct
+ * coordinate. This happens only for color-converted alignment. */
+bwa_cigar_t *bwa_refine_gapped_core(bwtint_t l_pac, const ubyte_t *pacseq, int len, const ubyte_t *seq, bwtint_t *_pos,
+									int ext, int *n_cigar, int is_end_correct)
+{
+	bwa_cigar_t *cigar = 0;
+	ubyte_t *ref_seq;
+	int l = 0, path_len, ref_len;
+	AlnParam ap = aln_param_bwa;
+	path_t *path;
+	int64_t k, __pos = *_pos;
+
+	ref_len = len + abs(ext);
+	if (ext > 0) {
+		ref_seq = (ubyte_t*)calloc(ref_len, 1);
+		for (k = __pos; k < __pos + ref_len && k < l_pac; ++k)
+			ref_seq[l++] = pacseq[k>>2] >> ((~k&3)<<1) & 3;
+	} else {
+		int64_t x = __pos + (is_end_correct? len : ref_len);
+		ref_seq = (ubyte_t*)calloc(ref_len, 1);
+		for (l = 0, k = x - ref_len > 0? x - ref_len : 0; k < x && k < l_pac; ++k)
+			ref_seq[l++] = pacseq[k>>2] >> ((~k&3)<<1) & 3;
+	}
+	path = (path_t*)calloc(l+len, sizeof(path_t));
+
+	aln_global_core(ref_seq, l, (ubyte_t*)seq, len, &ap, path, &path_len);
+	cigar = bwa_aln_path2cigar(path, path_len, n_cigar);
+	
+	if (ext < 0 && is_end_correct) { // fix coordinate for reads mapped to the forward strand
+		for (l = k = 0; k < *n_cigar; ++k) {
+			if (__cigar_op(cigar[k]) == FROM_D) l -= __cigar_len(cigar[k]);
+			else if (__cigar_op(cigar[k]) == FROM_I) l += __cigar_len(cigar[k]);
+		}
+		__pos += l;
+	}
+
+	if (__cigar_op(cigar[0]) == FROM_D) { // deletion at the 5'-end
+		__pos += __cigar_len(cigar[0]);
+		for (k = 0; k < *n_cigar - 1; ++k) cigar[k] = cigar[k+1];
+		--(*n_cigar);
+	}
+	if (__cigar_op(cigar[*n_cigar-1]) == FROM_D) --(*n_cigar); // deletion at the 3'-end
+
+	// change "I" at either end of the read to S. just in case. This should rarely happen...
+	if (__cigar_op(cigar[*n_cigar-1]) == FROM_I) cigar[*n_cigar-1] = __cigar_create(3, (__cigar_len(cigar[*n_cigar-1])));
+	if (__cigar_op(cigar[0]) == FROM_I) cigar[0] = __cigar_create(3, (__cigar_len(cigar[0])));
+
+	*_pos = (bwtint_t)__pos;
+	free(ref_seq); free(path);
+	return cigar;
+}
+
+char *bwa_cal_md1(int n_cigar, bwa_cigar_t *cigar, int len, bwtint_t pos, ubyte_t *seq,
+				  bwtint_t l_pac, ubyte_t *pacseq, kstring_t *str, int *_nm)
+{
+	bwtint_t x, y;
+	int z, u, c, nm = 0;
+	str->l = 0; // reset
+	x = pos; y = 0;
+	if (cigar) {
+		int k, l;
+		for (k = u = 0; k < n_cigar; ++k) {
+			l = __cigar_len(cigar[k]);
+			if (__cigar_op(cigar[k]) == FROM_M) {
+				for (z = 0; z < l && x+z < l_pac; ++z) {
+					c = pacseq[(x+z)>>2] >> ((~(x+z)&3)<<1) & 3;
+					if (c > 3 || seq[y+z] > 3 || c != seq[y+z]) {
+						ksprintf(str, "%d", u);
+						kputc("ACGTN"[c], str);
+						++nm;
+						u = 0;
+					} else ++u;
+				}
+				x += l; y += l;
+			} else if (__cigar_op(cigar[k]) == FROM_I || __cigar_op(cigar[k]) == FROM_S) {
+				y += l;
+				if (__cigar_op(cigar[k]) == FROM_I) nm += l;
+			} else if (__cigar_op(cigar[k]) == FROM_D) {
+				ksprintf(str, "%d", u);
+				kputc('^', str);
+				for (z = 0; z < l && x+z < l_pac; ++z)
+					kputc("ACGT"[pacseq[(x+z)>>2] >> ((~(x+z)&3)<<1) & 3], str);
+				u = 0;
+				x += l; nm += l;
+			}
+		}
+	} else { // no gaps
+		for (z = u = 0; z < (bwtint_t)len && x+z < l_pac; ++z) {
+			c = pacseq[(x+z)>>2] >> ((~(x+z)&3)<<1) & 3;
+			if (c > 3 || seq[y+z] > 3 || c != seq[y+z]) {
+				ksprintf(str, "%d", u);
+				kputc("ACGTN"[c], str);
+				++nm;
+				u = 0;
+			} else ++u;
+		}
+	}
+	ksprintf(str, "%d", u);
+	*_nm = nm;
+	return strdup(str->s);
+}
+
+void bwa_correct_trimmed(bwa_seq_t *s)
+{
+	if (s->len == s->full_len) return;
+	if (s->strand == 0) { // forward
+		if (s->cigar && __cigar_op(s->cigar[s->n_cigar-1]) == FROM_S) { // the last is S
+			s->cigar[s->n_cigar-1] += s->full_len - s->len;
+		} else {
+			if (s->cigar == 0) {
+				s->n_cigar = 2;
+				s->cigar = calloc(s->n_cigar, sizeof(bwa_cigar_t));
+				s->cigar[0] = __cigar_create(0, s->len);
+			} else {
+				++s->n_cigar;
+				s->cigar = realloc(s->cigar, s->n_cigar * sizeof(bwa_cigar_t));
+			}
+			s->cigar[s->n_cigar-1] = __cigar_create(3, (s->full_len - s->len));
+		}
+	} else { // reverse
+		if (s->cigar && __cigar_op(s->cigar[0]) == FROM_S) { // the first is S
+			s->cigar[0] += s->full_len - s->len;
+		} else {
+			if (s->cigar == 0) {
+				s->n_cigar = 2;
+				s->cigar = calloc(s->n_cigar, sizeof(bwa_cigar_t));
+				s->cigar[1] = __cigar_create(0, s->len);
+			} else {
+				++s->n_cigar;
+				s->cigar = realloc(s->cigar, s->n_cigar * sizeof(bwa_cigar_t));
+				memmove(s->cigar + 1, s->cigar, (s->n_cigar-1) * sizeof(bwa_cigar_t));
+			}
+			s->cigar[0] = __cigar_create(3, (s->full_len - s->len));
+		}
+	}
+	s->len = s->full_len;
+}
+
+void bwa_refine_gapped(const bntseq_t *bns, int n_seqs, bwa_seq_t *seqs, ubyte_t *_pacseq, bntseq_t *ntbns)
+{
+	ubyte_t *pacseq, *ntpac = 0;
+	int i, j;
+	kstring_t *str;
+
+	if (ntbns) { // in color space
+		ntpac = (ubyte_t*)calloc(ntbns->l_pac/4+1, 1);
+		rewind(ntbns->fp_pac);
+		fread(ntpac, 1, ntbns->l_pac/4 + 1, ntbns->fp_pac);
+	}
+
+	if (!_pacseq) {
+		pacseq = (ubyte_t*)calloc(bns->l_pac/4+1, 1);
+		rewind(bns->fp_pac);
+		fread(pacseq, 1, bns->l_pac/4+1, bns->fp_pac);
+	} else pacseq = _pacseq;
+	for (i = 0; i != n_seqs; ++i) {
+		bwa_seq_t *s = seqs + i;
+		seq_reverse(s->len, s->seq, 0); // IMPORTANT: s->seq is reversed here!!!
+		for (j = 0; j < s->n_multi; ++j) {
+			bwt_multi1_t *q = s->multi + j;
+			int n_cigar;
+			if (q->gap == 0) continue;
+			q->cigar = bwa_refine_gapped_core(bns->l_pac, pacseq, s->len, q->strand? s->rseq : s->seq, &q->pos,
+										  (q->strand? 1 : -1) * q->gap, &n_cigar, 1);
+			q->n_cigar = n_cigar;
+		}
+		if (s->type == BWA_TYPE_NO_MATCH || s->type == BWA_TYPE_MATESW || s->n_gapo == 0) continue;
+		s->cigar = bwa_refine_gapped_core(bns->l_pac, pacseq, s->len, s->strand? s->rseq : s->seq, &s->pos,
+									  (s->strand? 1 : -1) * (s->n_gapo + s->n_gape), &s->n_cigar, 1);
+	}
+#if 0
+	if (ntbns) { // in color space
+		for (i = 0; i < n_seqs; ++i) {
+			bwa_seq_t *s = seqs + i;
+			bwa_cs2nt_core(s, bns->l_pac, ntpac);
+			for (j = 0; j < s->n_multi; ++j) {
+				bwt_multi1_t *q = s->multi + j;
+				int n_cigar;
+				if (q->gap == 0) continue;
+				free(q->cigar);
+				q->cigar = bwa_refine_gapped_core(bns->l_pac, ntpac, s->len, q->strand? s->rseq : s->seq, &q->pos,
+											  (q->strand? 1 : -1) * q->gap, &n_cigar, 0);
+				q->n_cigar = n_cigar;
+			}
+			if (s->type != BWA_TYPE_NO_MATCH && s->cigar) { // update cigar again
+				free(s->cigar);
+				s->cigar = bwa_refine_gapped_core(bns->l_pac, ntpac, s->len, s->strand? s->rseq : s->seq, &s->pos,
+											  (s->strand? 1 : -1) * (s->n_gapo + s->n_gape), &s->n_cigar, 0);
+			}
+		}
+	}
+#endif
+	// generate MD tag
+	str = (kstring_t*)calloc(1, sizeof(kstring_t));
+	for (i = 0; i != n_seqs; ++i) {
+		bwa_seq_t *s = seqs + i;
+		if (s->type != BWA_TYPE_NO_MATCH) {
+			int nm;
+			s->md = bwa_cal_md1(s->n_cigar, s->cigar, s->len, s->pos, s->strand? s->rseq : s->seq,
+								bns->l_pac, ntbns? ntpac : pacseq, str, &nm);
+			s->nm = nm;
+		}
+	}
+	free(str->s); free(str);
+
+	// correct for trimmed reads
+	if (!ntbns) // trimming is only enabled for Illumina reads
+		for (i = 0; i < n_seqs; ++i) bwa_correct_trimmed(seqs + i);
+
+	if (!_pacseq) free(pacseq);
+	free(ntpac);
+}
+
+int64_t pos_end(const bwa_seq_t *p)
+{
+	if (p->cigar) {
+		int j;
+		int64_t x = p->pos;
+		for (j = 0; j != p->n_cigar; ++j) {
+			int op = __cigar_op(p->cigar[j]);
+			if (op == 0 || op == 2) x += __cigar_len(p->cigar[j]);
+		}
+		return x;
+	} else return p->pos + p->len;
+}
+
+int64_t pos_end_multi(const bwt_multi1_t *p, int len) // analogy to pos_end()
+{
+	if (p->cigar) {
+		int j;
+		int64_t x = p->pos;
+		for (j = 0; j != p->n_cigar; ++j) {
+			int op = __cigar_op(p->cigar[j]);
+			if (op == 0 || op == 2) x += __cigar_len(p->cigar[j]);
+		}
+		return x;
+	} else return p->pos + len;
+}
+
+static int64_t pos_5(const bwa_seq_t *p)
+{
+	if (p->type != BWA_TYPE_NO_MATCH)
+		return p->strand? pos_end(p) : p->pos;
+	return -1;
+}
+
+void bwa_print_sam1(const bntseq_t *bns, bwa_seq_t *p, const bwa_seq_t *mate, int mode, int max_top2)
+{
+	int j;
+	if (p->type != BWA_TYPE_NO_MATCH || (mate && mate->type != BWA_TYPE_NO_MATCH)) {
+		int seqid, nn, am = 0, flag = p->extra_flag;
+		char XT;
+
+		if (p->type == BWA_TYPE_NO_MATCH) {
+			p->pos = mate->pos;
+			p->strand = mate->strand;
+			flag |= SAM_FSU;
+			j = 1;
+		} else j = pos_end(p) - p->pos; // j is the length of the reference in the alignment
+
+		// get seqid
+		nn = bns_cnt_ambi(bns, p->pos, j, &seqid);
+		if (p->type != BWA_TYPE_NO_MATCH && p->pos + j - bns->anns[seqid].offset > bns->anns[seqid].len)
+			flag |= SAM_FSU; // flag UNMAP as this alignment bridges two adjacent reference sequences
+
+		// update flag and print it
+		if (p->strand) flag |= SAM_FSR;
+		if (mate) {
+			if (mate->type != BWA_TYPE_NO_MATCH) {
+				if (mate->strand) flag |= SAM_FMR;
+			} else flag |= SAM_FMU;
+		}
+		err_printf("%s\t%d\t%s\t", p->name, flag, bns->anns[seqid].name);
+		err_printf("%d\t%d\t", (int)(p->pos - bns->anns[seqid].offset + 1), p->mapQ);
+
+		// print CIGAR
+		if (p->cigar) {
+			for (j = 0; j != p->n_cigar; ++j)
+				err_printf("%d%c", __cigar_len(p->cigar[j]), "MIDS"[__cigar_op(p->cigar[j])]);
+		} else if (p->type == BWA_TYPE_NO_MATCH) err_printf("*");
+		else err_printf("%dM", p->len);
+
+		// print mate coordinate
+		if (mate && mate->type != BWA_TYPE_NO_MATCH) {
+			int m_seqid, m_is_N;
+			long long isize;
+			am = mate->seQ < p->seQ? mate->seQ : p->seQ; // smaller single-end mapping quality
+			// redundant calculation here, but should not matter too much
+			m_is_N = bns_cnt_ambi(bns, mate->pos, mate->len, &m_seqid);
+			err_printf("\t%s\t", (seqid == m_seqid)? "=" : bns->anns[m_seqid].name);
+			isize = (seqid == m_seqid)? pos_5(mate) - pos_5(p) : 0;
+			if (p->type == BWA_TYPE_NO_MATCH) isize = 0;
+			err_printf("%d\t%lld\t", (int)(mate->pos - bns->anns[m_seqid].offset + 1), isize);
+		} else if (mate) err_printf("\t=\t%d\t0\t", (int)(p->pos - bns->anns[seqid].offset + 1));
+		else err_printf("\t*\t0\t0\t");
+
+		// print sequence and quality
+		if (p->strand == 0)
+			for (j = 0; j != p->full_len; ++j) putchar("ACGTN"[(int)p->seq[j]]);
+		else for (j = 0; j != p->full_len; ++j) putchar("TGCAN"[p->seq[p->full_len - 1 - j]]);
+		putchar('\t');
+		if (p->qual) {
+			if (p->strand) seq_reverse(p->len, p->qual, 0); // reverse quality
+			err_printf("%s", p->qual);
+		} else err_printf("*");
+
+		if (bwa_rg_id) err_printf("\tRG:Z:%s", bwa_rg_id);
+		if (p->bc[0]) err_printf("\tBC:Z:%s", p->bc);
+		if (p->clip_len < p->full_len) err_printf("\tXC:i:%d", p->clip_len);
+		if (p->type != BWA_TYPE_NO_MATCH) {
+			int i;
+			// calculate XT tag
+			XT = "NURM"[p->type];
+			if (nn > 10) XT = 'N';
+			// print tags
+			err_printf("\tXT:A:%c\t%s:i:%d", XT, (mode & BWA_MODE_COMPREAD)? "NM" : "CM", p->nm);
+			if (nn) err_printf("\tXN:i:%d", nn);
+			if (mate) err_printf("\tSM:i:%d\tAM:i:%d", p->seQ, am);
+			if (p->type != BWA_TYPE_MATESW) { // X0 and X1 are not available for this type of alignment
+				err_printf("\tX0:i:%d", p->c1);
+				if (p->c1 <= max_top2) err_printf("\tX1:i:%d", p->c2);
+			}
+			err_printf("\tXM:i:%d\tXO:i:%d\tXG:i:%d", p->n_mm, p->n_gapo, p->n_gapo+p->n_gape);
+			if (p->md) err_printf("\tMD:Z:%s", p->md);
+			// print multiple hits
+			if (p->n_multi) {
+				err_printf("\tXA:Z:");
+				for (i = 0; i < p->n_multi; ++i) {
+					bwt_multi1_t *q = p->multi + i;
+					int k;
+					j = pos_end_multi(q, p->len) - q->pos;
+					nn = bns_cnt_ambi(bns, q->pos, j, &seqid);
+					err_printf("%s,%c%d,", bns->anns[seqid].name, q->strand? '-' : '+',
+						   (int)(q->pos - bns->anns[seqid].offset + 1));
+					if (q->cigar) {
+						for (k = 0; k < q->n_cigar; ++k)
+							err_printf("%d%c", __cigar_len(q->cigar[k]), "MIDS"[__cigar_op(q->cigar[k])]);
+					} else err_printf("%dM", p->len);
+					err_printf(",%d;", q->gap + q->mm);
+				}
+			}
+		}
+		putchar('\n');
+	} else { // this read has no match
+		ubyte_t *s = p->strand? p->rseq : p->seq;
+		int flag = p->extra_flag | SAM_FSU;
+		if (mate && mate->type == BWA_TYPE_NO_MATCH) flag |= SAM_FMU;
+		err_printf("%s\t%d\t*\t0\t0\t*\t*\t0\t0\t", p->name, flag);
+		for (j = 0; j != p->len; ++j) putchar("ACGTN"[(int)s[j]]);
+		putchar('\t');
+		if (p->qual) {
+			if (p->strand) seq_reverse(p->len, p->qual, 0); // reverse quality
+			err_printf("%s", p->qual);
+		} else err_printf("*");
+		if (bwa_rg_id) err_printf("\tRG:Z:%s", bwa_rg_id);
+		if (p->bc[0]) err_printf("\tBC:Z:%s", p->bc);
+		if (p->clip_len < p->full_len) err_printf("\tXC:i:%d", p->clip_len);
+		putchar('\n');
+	}
+}
+
+bntseq_t *bwa_open_nt(const char *prefix)
+{
+	bntseq_t *ntbns;
+	char *str;
+	str = (char*)calloc(strlen(prefix) + 10, 1);
+	strcat(strcpy(str, prefix), ".nt");
+	ntbns = bns_restore(str);
+	free(str);
+	return ntbns;
+}
+
+void bwa_print_sam_SQ(const bntseq_t *bns)
+{
+	int i;
+	for (i = 0; i < bns->n_seqs; ++i)
+		err_printf("@SQ\tSN:%s\tLN:%d\n", bns->anns[i].name, bns->anns[i].len);
+	if (bwa_rg_line) err_printf("%s\n", bwa_rg_line);
+}
+
+void bwase_initialize() 
+{
+	int i;
+	for (i = 1; i != 256; ++i) g_log_n[i] = (int)(4.343 * log(i) + 0.5);
+}
+
+char *bwa_escape(char *s)
+{
+	char *p, *q;
+	for (p = q = s; *p; ++p) {
+		if (*p == '\\') {
+			++p;
+			if (*p == 't') *q++ = '\t';
+			else if (*p == 'n') *q++ = '\n';
+			else if (*p == 'r') *q++ = '\r';
+			else if (*p == '\\') *q++ = '\\';
+		} else *q++ = *p;
+	}
+	*q = '\0';
+	return s;
+}
+
+int bwa_set_rg(const char *s)
+{
+	char *p, *q, *r;
+	if (strstr(s, "@RG") != s) return -1;
+	if (bwa_rg_line) free(bwa_rg_line);
+	if (bwa_rg_id) free(bwa_rg_id);
+	bwa_rg_line = strdup(s);
+	bwa_rg_id = 0;
+	bwa_escape(bwa_rg_line);
+	p = strstr(bwa_rg_line, "\tID:");
+	if (p == 0) return -1;
+	p += 4;
+	for (q = p; *q && *q != '\t' && *q != '\n'; ++q);
+	bwa_rg_id = calloc(q - p + 1, 1);
+	for (q = p, r = bwa_rg_id; *q && *q != '\t' && *q != '\n'; ++q)
+		*r++ = *q;
+	return 0;
+}
+
+void bwa_sai2sam_se_core(const char *prefix, const char *fn_sa, const char *fn_fa, int n_occ)
+{
+	extern bwa_seqio_t *bwa_open_reads(int mode, const char *fn_fa);
+	int i, n_seqs, tot_seqs = 0, m_aln;
+	bwt_aln1_t *aln = 0;
+	bwa_seq_t *seqs;
+	bwa_seqio_t *ks;
+	clock_t t;
+	bntseq_t *bns, *ntbns = 0;
+	FILE *fp_sa;
+	gap_opt_t opt;
+
+	// initialization
+	bwase_initialize();
+	bns = bns_restore(prefix);
+	srand48(bns->seed);
+	fp_sa = xopen(fn_sa, "r");
+
+	m_aln = 0;
+	fread(&opt, sizeof(gap_opt_t), 1, fp_sa);
+	if (!(opt.mode & BWA_MODE_COMPREAD)) // in color space; initialize ntpac
+		ntbns = bwa_open_nt(prefix);
+	bwa_print_sam_SQ(bns);
+	//bwa_print_sam_PG();
+	// set ks
+	ks = bwa_open_reads(opt.mode, fn_fa);
+	// core loop
+	while ((seqs = bwa_read_seq(ks, 0x40000, &n_seqs, opt.mode, opt.trim_qual)) != 0) {
+		tot_seqs += n_seqs;
+		t = clock();
+
+		// read alignment
+		for (i = 0; i < n_seqs; ++i) {
+			bwa_seq_t *p = seqs + i;
+			int n_aln;
+			fread(&n_aln, 4, 1, fp_sa);
+			if (n_aln > m_aln) {
+				m_aln = n_aln;
+				aln = (bwt_aln1_t*)realloc(aln, sizeof(bwt_aln1_t) * m_aln);
+			}
+			fread(aln, sizeof(bwt_aln1_t), n_aln, fp_sa);
+			bwa_aln2seq_core(n_aln, aln, p, 1, n_occ);
+		}
+
+		fprintf(stderr, "[bwa_aln_core] convert to sequence coordinate... ");
+		bwa_cal_pac_pos(bns, prefix, n_seqs, seqs, opt.max_diff, opt.fnr); // forward bwt will be destroyed here
+		fprintf(stderr, "%.2f sec\n", (float)(clock() - t) / CLOCKS_PER_SEC); t = clock();
+
+		fprintf(stderr, "[bwa_aln_core] refine gapped alignments... ");
+		bwa_refine_gapped(bns, n_seqs, seqs, 0, ntbns);
+		fprintf(stderr, "%.2f sec\n", (float)(clock() - t) / CLOCKS_PER_SEC); t = clock();
+
+		fprintf(stderr, "[bwa_aln_core] print alignments... ");
+		for (i = 0; i < n_seqs; ++i)
+			bwa_print_sam1(bns, seqs + i, 0, opt.mode, opt.max_top2);
+		fprintf(stderr, "%.2f sec\n", (float)(clock() - t) / CLOCKS_PER_SEC); t = clock();
+
+		bwa_free_read_seq(n_seqs, seqs);
+		fprintf(stderr, "[bwa_aln_core] %d sequences have been processed.\n", tot_seqs);
+	}
+
+	// destroy
+	bwa_seq_close(ks);
+	if (ntbns) bns_destroy(ntbns);
+	bns_destroy(bns);
+	fclose(fp_sa);
+	free(aln);
+}
+
+int bwa_sai2sam_se(int argc, char *argv[])
+{
+	extern char *bwa_infer_prefix(const char *hint);
+	int c, n_occ = 3;
+	char *prefix;
+	while ((c = getopt(argc, argv, "hn:f:r:")) >= 0) {
+		switch (c) {
+		case 'h': break;
+		case 'r':
+			if (bwa_set_rg(optarg) < 0) {
+				fprintf(stderr, "[%s] malformated @RG line\n", __func__);
+				return 1;
+			}
+			break;
+		case 'n': n_occ = atoi(optarg); break;
+		case 'f': xreopen(optarg, "w", stdout); break;
+		default: return 1;
+		}
+	}
+
+	if (optind + 3 > argc) {
+		fprintf(stderr, "Usage: bwa samse [-n max_occ] [-f out.sam] [-r RG_line] <prefix> <in.sai> <in.fq>\n");
+		return 1;
+	}
+	if ((prefix = bwa_infer_prefix(argv[optind])) == 0) {
+		fprintf(stderr, "[%s] fail to locate the index\n", __func__);
+		free(bwa_rg_line); free(bwa_rg_id);
+		return 0;
+	}
+	bwa_sai2sam_se_core(prefix, argv[optind+1], argv[optind+2], n_occ);
+	free(bwa_rg_line); free(bwa_rg_id);
+	return 0;
+}