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parallels: use pread 

Use pread instead of lseek + read in preparation of using the qemu
block API.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Christoph Hellwig 2010-05-06 22:04:34 +02:00 committed by Kevin Wolf
parent b76b6e95b8
commit 9d8b88f68c
1 changed files with 11 additions and 22 deletions
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33
block/parallels.c
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@ -83,7 +83,7 @@ static int parallels_open(BlockDriverState *bs, const char *filename, int flags)
s->fd = fd;
if (read(fd, &ph, sizeof(ph)) != sizeof(ph))
if (pread(fd, &ph, sizeof(ph), 0) != sizeof(ph))
goto fail;
if (memcmp(ph.magic, HEADER_MAGIC, 16) ||
@ -93,14 +93,11 @@ static int parallels_open(BlockDriverState *bs, const char *filename, int flags)
bs->total_sectors = le32_to_cpu(ph.nb_sectors);
if (lseek(s->fd, 64, SEEK_SET) != 64)
goto fail;
s->tracks = le32_to_cpu(ph.tracks);
s->catalog_size = le32_to_cpu(ph.catalog_entries);
s->catalog_bitmap = qemu_malloc(s->catalog_size * 4);
if (read(s->fd, s->catalog_bitmap, s->catalog_size * 4) !=
if (pread(s->fd, s->catalog_bitmap, s->catalog_size * 4, 64) !=
s->catalog_size * 4)
goto fail;
for (i = 0; i < s->catalog_size; i++)
@ -114,28 +111,18 @@ fail:
return -1;
}
static inline int seek_to_sector(BlockDriverState *bs, int64_t sector_num)
static int64_t seek_to_sector(BlockDriverState *bs, int64_t sector_num)
{
BDRVParallelsState *s = bs->opaque;
uint32_t index, offset;
uint64_t position;
index = sector_num / s->tracks;
offset = sector_num % s->tracks;
// not allocated
/* not allocated */
if ((index > s->catalog_size) || (s->catalog_bitmap[index] == 0))
return -1;
position = (uint64_t)(s->catalog_bitmap[index] + offset) * 512;
// fprintf(stderr, "sector: %llx index=%x offset=%x pointer=%x position=%x\n",
// sector_num, index, offset, s->catalog_bitmap[index], position);
if (lseek(s->fd, position, SEEK_SET) != position)
return -1;
return 0;
return (uint64_t)(s->catalog_bitmap[index] + offset) * 512;
}
static int parallels_read(BlockDriverState *bs, int64_t sector_num,
@ -144,11 +131,13 @@ static int parallels_read(BlockDriverState *bs, int64_t sector_num,
BDRVParallelsState *s = bs->opaque;
while (nb_sectors > 0) {
if (!seek_to_sector(bs, sector_num)) {
if (read(s->fd, buf, 512) != 512)
return -1;
} else
int64_t position = seek_to_sector(bs, sector_num);
if (position >= 0) {
if (pread(s->fd, buf, 512, position) != 512)
return -1;
} else {
memset(buf, 0, 512);
}
nb_sectors--;
sector_num++;
buf += 512;