bamlite.c

#include <stdlib.h>
#include <ctype.h>
#include <string.h>
#include <stdio.h>
#include "bamlite.h"
#include "byteorder.h"

/**************
 * from bam.c *
 **************/

int bam_is_be;

bam_header_t *bam_header_init()
{
	bam_is_be = is_big_endian();
	return (bam_header_t*)calloc(1, sizeof(bam_header_t));
}

void bam_header_destroy(bam_header_t *header)
{
	int32_t i;
	if (header == 0) return;
	if (header->target_name) {
		for (i = 0; i < header->n_targets; ++i)
			free(header->target_name[i]);
		free(header->target_name);
		free(header->target_len);
	}
	free(header->text);
	free(header);
}

bam_header_t *bam_header_read(bamFile fp)
{
	bam_header_t *header;
	char buf[4];
	int magic_len;
	int32_t i = 1, name_len;
	// read "BAM1"
	magic_len = bam_read(fp, buf, 4);
	if (magic_len != 4 || strncmp(buf, "BAM\001", 4) != 0) {
		fprintf(stderr, "[bam_header_read] invalid BAM binary header (this is not a BAM file).\n");
		return 0;
	}
	header = bam_header_init();
	// read plain text and the number of reference sequences
	bam_read(fp, &header->l_text, 4);
	if (bam_is_be) swap_endian_4p(&header->l_text);
	header->text = (char*)calloc(header->l_text + 1, 1);
	bam_read(fp, header->text, header->l_text);
	bam_read(fp, &header->n_targets, 4);
	if (bam_is_be) swap_endian_4p(&header->n_targets);
	// read reference sequence names and lengths
	header->target_name = (char**)calloc(header->n_targets, sizeof(char*));
	header->target_len = (uint32_t*)calloc(header->n_targets, 4);
	for (i = 0; i != header->n_targets; ++i) {
		bam_read(fp, &name_len, 4);
		if (bam_is_be) swap_endian_4p(&name_len);
		header->target_name[i] = (char*)calloc(name_len, 1);
		bam_read(fp, header->target_name[i], name_len);
		bam_read(fp, &header->target_len[i], 4);
		if (bam_is_be) swap_endian_4p(&header->target_len[i]);
	}
	return header;
}

static void swap_endian_data(const bam1_core_t *c, int data_len, uint8_t *data)
{
	uint8_t *s;
	uint32_t i, *cigar = (uint32_t*)(data + c->l_qname);
	s = data + c->n_cigar*4 + c->l_qname + c->l_qseq + (c->l_qseq + 1)/2;
	for (i = 0; i < c->n_cigar; ++i) swap_endian_4p(&cigar[i]);
	while (s < data + data_len) {
		uint8_t type;
		s += 2; // skip key
		type = toupper(*s); ++s; // skip type
		if (type == 'C' || type == 'A') ++s;
		else if (type == 'S') { swap_endian_2p(s); s += 2; }
		else if (type == 'I' || type == 'F') { swap_endian_4p(s); s += 4; }
		else if (type == 'D') { swap_endian_8p(s); s += 8; }
		else if (type == 'Z' || type == 'H') { while (*s) ++s; ++s; }
	}
}

int bam_read1(bamFile fp, bam1_t *b)
{
	bam1_core_t *c = &b->core;
	int32_t block_len, ret, i;
	uint32_t x[8];

	if ((ret = bam_read(fp, &block_len, 4)) != 4) {
		if (ret == 0) return -1; // normal end-of-file
		else return -2; // truncated
	}
	if (bam_read(fp, x, sizeof(bam1_core_t)) != sizeof(bam1_core_t)) return -3;
	if (bam_is_be) {
		swap_endian_4p(&block_len);
		for (i = 0; i < 8; ++i) swap_endian_4p(x + i);
	}
	c->tid = x[0]; c->pos = x[1];
	c->bin = x[2]>>16; c->qual = x[2]>>8&0xff; c->l_qname = x[2]&0xff;
	c->flag = x[3]>>16; c->n_cigar = x[3]&0xffff;
	c->l_qseq = x[4];
	c->mtid = x[5]; c->mpos = x[6]; c->isize = x[7];
	b->data_len = block_len - sizeof(bam1_core_t);
	if (b->m_data < b->data_len) {
		b->m_data = b->data_len;
		kroundup32(b->m_data);
		b->data = (uint8_t*)realloc(b->data, b->m_data);
	}
	if (bam_read(fp, b->data, b->data_len) != b->data_len) return -4;
	b->l_aux = b->data_len - c->n_cigar * 4 - c->l_qname - c->l_qseq - (c->l_qseq+1)/2;
	if (bam_is_be) swap_endian_data(c, b->data_len, b->data);
	return 4 + block_len;
}