bwase.c

#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->strand = p->a;
				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, z = 0;
        uint64_t n_occ = 0;
		for (k = 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;
					s->multi[z++].strand = q->a;
				}
				rest -= q->l - q->k + 1;
			} else { // Random sampling (http://code.activestate.com/recipes/272884/). In fact, we never come here. 
				int j, i;
				for (j = rest, i = q->l - q->k + 1; 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;
					s->multi[z++].strand = q->a;
				}
				rest = 0;
				break;
			}
		}
		s->n_multi = z;
		for (k = z = 0; k < s->n_multi; ++k)
			if (s->multi[k].pos != s->sa)
				s->multi[z++] = s->multi[k];
		s->n_multi = z < n_multi? z : n_multi;
	}
}

//	uint32_t strand:1,              filled
//	         type:2,                filled
//	uint32_t n_mm:8;                filled
//	        n_gapo:8,               filled
//	        n_gape:8,               filled
//	int score;                      filled
//	int n_aln;                      needed
//	bwt_aln1_t *aln;                needed
//	bwtint_t sa,                    filled
//	uint64_t c1:28,                 filled
//	         c2:28,                 filled
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];
}

/**
 * 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.
 */

//	uint32_t len:20,                    needed
//	         strand:1,                  needed
//	         type:2,                    needed
//	uint32_t mapQ:8;                    filled
//	bwtint_t sa,                        needed
//	         pos;                       filled
//	uint64_t seQ:8;                     filled

void bwa_cal_pac_pos_core(const bwt_t *forward_bwt, const bwt_t *reverse_bwt, bwa_seq_t *seq, const int max_mm, const float fnr)
{
	int max_diff;
	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;
	if (seq->strand) { // reverse strand only
		seq->pos = bwt_sa(forward_bwt, seq->sa);
	} else { // forward strand only
		/* NB: For gapped alignment, p->pos may not be correct, which
		 *     will be fixed in refine_gapped_core(). This line also
		 *     determines the way "x" is calculated in
		 *     refine_gapped_core() when (ext < 0 && is_end == 0). */
		seq->pos = reverse_bwt->seq_len - (bwt_sa(reverse_bwt, seq->sa) + seq->len);
	}
    seq->seQ = seq->mapQ = bwa_approx_mapQ(seq, max_diff);
}

void bwa_cal_pac_pos(const char *prefix, int n_seqs, bwa_seq_t *seqs, int max_mm, float fnr)
{
	int i, j;
	char str[1024];
	bwt_t *bwt;
	// load forward SA
	strcpy(str, prefix); strcat(str, ".bwt");  bwt = bwt_restore_bwt(str,0);
	strcpy(str, prefix); strcat(str, ".sa"); bwt_restore_sa(str,bwt,0);
	for (i = 0; i != n_seqs; ++i) {
		if (seqs[i].strand) bwa_cal_pac_pos_core(bwt, 0, &seqs[i], max_mm, fnr);
		for (j = 0; j < seqs[i].n_multi; ++j) {
			bwt_multi1_t *p = seqs[i].multi + j;
			if (p->strand) p->pos = bwt_sa(bwt, p->pos);
		}
	}
	bwt_destroy(bwt);
	// load reverse BWT and SA
	strcpy(str, prefix); strcat(str, ".rbwt"); bwt = bwt_restore_bwt(str,0);
	strcpy(str, prefix); strcat(str, ".rsa"); bwt_restore_sa(str,bwt,0);
	for (i = 0; i != n_seqs; ++i) {
		if (!seqs[i].strand) bwa_cal_pac_pos_core(0, bwt, &seqs[i], max_mm, fnr);
		for (j = 0; j < seqs[i].n_multi; ++j) {
			bwt_multi1_t *p = seqs[i].multi + j;
			if (!p->strand) p->pos = bwt->seq_len - (bwt_sa(bwt, p->pos) + seqs[i].len);
		}
	}
	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. */
static bwa_cigar_t *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 > l_pac? (int64_t)((int32_t)*_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 on 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;
}

// To access pacseq: test against ambs and l_pac; else decode as below.
// We need to find an initial position in ambs, afterwards we only need
// to incrment, and then the ambs position can be updated easily.

#define advance_pos() {                                     \
    ++pos ;                                                 \
    if( right < bns->ambs + bns->n_holes &&                 \
            pos >= right->offset + right->len )             \
        right++ ;                                           \
} while(0)

#define get_pac ( right < bns->ambs + bns->n_holes && pos >= right->offset        \
                  ? right->amb : pacseq[(pos)>>2] >> ((~(pos)&3)<<1) & 3 )

char *bwa_cal_md1(int n_cigar, bwa_cigar_t *cigar, int len, bwtint_t pos, ubyte_t *seq,
				  const bntseq_t *bns, ubyte_t *pacseq, kstring_t *str, int *_nm)
{
	int z, u, c, nm = 0;
    bntamb1_t *left = bns->ambs, *right = bns->ambs + bns->n_holes;
	str->l = 0; // reset
	
	// Find smallest block in ambs that ends after @pos@.  One
    // past-the-end is valid but must not be accessed!  Correct interval
    // ends up in @right@.
	while (left < right) {
		bntamb1_t *mid = left + ((right - left) >> 1);
		if (pos >= mid->offset + mid->len) left = mid + 1;
		else if (pos < mid->offset) right = mid;
		else left = right = mid ;
	}

	if (cigar) {
		int k, l, y = 0;
		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 && pos < bns->l_pac; ++z, ++y) {
					c = get_pac ;
					if (c > 3 || seq[y] > 3 || c != seq[y]) {
						ksprintf(str, "%d", u);
						kputc(c>3?c:"ACGT"[c], str);
						++nm;
						u = 0;
					} else ++u;
                    advance_pos() ;
				}
            } 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 && pos < bns->l_pac; ++z) {
                    c = get_pac;
					kputc(c>3?c:"ACGT"[c], str);
                    advance_pos() ;
                }
				u = 0;
				nm += l;
			}
		}
	} else { // no gaps
		for (z = u = 0; z < (bwtint_t)len; ++z) {
			c = get_pac ;
			if (c > 3 || seq[z] > 3 || c != seq[z]) {
				ksprintf(str, "%d", u);
				kputc(c>3?c:"ACGT"[c], str);
				++nm;
				u = 0;
			} else ++u;
            advance_pos() ;
		}
	}
	ksprintf(str, "%d", u);
	*_nm = nm;
	return strdup(str->s);
}

#undef advance_pos
#undef get_pac

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;

    // in color space
	if (ntbns) ntpac = bwt_restore_pac(ntbns,0) ;

	if (!_pacseq) pacseq = bwt_restore_pac(bns,0); 
	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 = 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 = 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 (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 = 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 = 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);
			}
		}
	}

	// 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, 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) bwt_destroy_pac(pacseq,bns);
	bwt_destroy_pac(ntpac,ntbns);
}

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;
}

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, m_seqid = -1, flag = p->extra_flag;
		char XT;

		if (p->type == BWA_TYPE_NO_MATCH) {
			p->pos = mate->pos;
			p->strand = mate->strand;
			flag |= SAM_FSU;
            flag &= ~SAM_FPP ;
			j = 1;
		} else j = pos_end(p) - p->pos; // j is the length of the reference in the alignment

		// get seqid
		nn = bns_coor_pac2real(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
            flag &= ~SAM_FPP ;
            p->mapQ = 0;
        }

		// update flag and print it
		if (p->strand) flag |= SAM_FSR;
		if (mate) {
			if (mate->type != BWA_TYPE_NO_MATCH) {
                int m_j;
                // redundant calculation here, but should not matter too much
                nn += bns_coor_pac2real(bns, mate->pos, mate->len, &m_seqid);

                m_j = pos_end(mate) - mate->pos; // m_j is the length of the reference in the alignment
                if( mate->pos + m_j - bns->anns[m_seqid].offset > bns->anns[m_seqid].len ) {
                    flag |= SAM_FMU; // flag MUNMAP as the mate's alignment bridges two adjacent reference sequences
                    flag &= ~SAM_FPP ;
                }

				if (mate->strand) flag |= SAM_FMR;
            } else {
                flag |= SAM_FMU;
                flag &= ~SAM_FPP ;
            }
		}
		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) {
			long long isize;
			am = mate->seQ < p->seQ? mate->seQ : p->seQ; // smaller single-end mapping quality
			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_coor_pac2real(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);
		if (mate && mate->type != BWA_TYPE_NO_MATCH) {
            int m_seqid, nn;
            // reproduce XN field of the mate if it has any
            nn = bns_coor_pac2real(bns, mate->pos, mate->len, &m_seqid);
			if (nn) err_printf("\tXN:i:%d", nn);
        }
		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;
	err_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;
			err_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);
			}
			err_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(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[])
{
	int c, n_occ = 3;
    char *ofile = 0;
	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': ofile=optarg; 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;
	}
	bwa_sai2sam_se_core(argv[optind], argv[optind+1], argv[optind+2], n_occ);
	free(bwa_rg_line); free(bwa_rg_id);
    final_rename( "sai2sam_se", ofile );
	return 0;
}