Function write_sparse

fileio.c:78–123

Note that the offset is just the caller letting us know where * the current file position is in the file. The use_seek arg tells * us that we should seek over matching data instead of writing it. */

 * the current file position is in the file. The use_seek arg tells
 * us that we should seek over matching data instead of writing it. */
static int write_sparse(int f, int use_seek, OFF_T offset, const char *buf, int len)
{
	int l1 = 0, l2 = 0;
	int ret;

	for (l1 = 0; l1 < len && buf[l1] == 0; l1++) {}
	for (l2 = 0; l2 < len-l1 && buf[len-(l2+1)] == 0; l2++) {}

	sparse_seek += l1;

	if (l1 == len)
		return len;

	if (sparse_seek) {
		if (sparse_past_write >= preallocated_len) {
			if (do_lseek(f, sparse_seek, SEEK_CUR) < 0)
				return -1;
		} else if (do_punch_hole(f, sparse_past_write, sparse_seek) < 0) {
			sparse_seek = 0;
			return -1;
		}
	}
	sparse_seek = l2;
	sparse_past_write = offset + len - l2;

	if (use_seek) {
		/* The in-place data already matches. */
		if (do_lseek(f, len - (l1+l2), SEEK_CUR) < 0)
			return -1;
		return len;
	}

	while ((ret = write(f, buf + l1, len - (l1+l2))) <= 0) {
		if (ret < 0 && errno == EINTR)
			continue;
		sparse_seek = 0;
		return ret;
	}

	if (ret != (int)(len - (l1+l2))) {
		sparse_seek = 0;
		return l1+ret;
	}

	return len;
}

static char *wf_writeBuf;
static size_t wf_writeBufSize;