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wtv: Seek by sector properly

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Use an helper function to seek by sector to avoid possible mistakes
due shifting by WTV_SECTOR_BITS a 32bit integer.

Contrary to common intuition, a 32 bit integer left shifted
by a 64 bit integer does not promote the 32 bit integer to
64 bit before shifting.
This commit is contained in:
Luca Barbato 2013-10-18 13:45:13 +02:00
parent a27f1116cd
commit 2b72f8ac32
1 changed files with 16 additions and 9 deletions
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25
libavformat/wtv.c
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@ -48,10 +48,12 @@
*
*/
#define WTV_SECTOR_BITS INT64_C(12)
#define WTV_SECTOR_BITS 12
#define WTV_SECTOR_SIZE (1 << WTV_SECTOR_BITS)
#define WTV_BIGSECTOR_BITS 18
#define SHIFT_SECTOR_BITS(a) ((int64_t)(a) << WTV_SECTOR_BITS)
typedef struct {
AVIOContext *pb_filesystem; /** file system (AVFormatContext->pb) */
@ -64,6 +66,11 @@ typedef struct {
int64_t length;
} WtvFile;
static int64_t seek_by_sector(AVIOContext *pb, int64_t sector, int64_t offset)
{
return avio_seek(pb, SHIFT_SECTOR_BITS(sector) + offset, SEEK_SET);
}
/**
* @return bytes read, 0 on end of file, or <0 on error
*/
@ -94,7 +101,7 @@ static int wtvfile_read_packet(void *opaque, uint8_t *buf, int buf_size)
int i = wf->position >> wf->sector_bits;
if (i >= wf->nb_sectors ||
(wf->sectors[i] != wf->sectors[i - 1] + (1 << (wf->sector_bits - WTV_SECTOR_BITS)) &&
avio_seek(pb, wf->sectors[i] << WTV_SECTOR_BITS, SEEK_SET) < 0)) {
seek_by_sector(pb, wf->sectors[i], 0) < 0)) {
wf->error = 1;
break;
}
@ -119,8 +126,8 @@ static int64_t wtvfile_seek(void *opaque, int64_t offset, int whence)
offset = wf->length;
wf->error = offset < 0 || offset >= wf->length ||
avio_seek(pb, (wf->sectors[offset >> wf->sector_bits] << WTV_SECTOR_BITS)
+ (offset & ((1 << wf->sector_bits) - 1)), SEEK_SET) < 0;
seek_by_sector(pb, wf->sectors[offset >> wf->sector_bits],
offset & ((1 << wf->sector_bits) - 1)) < 0;
wf->position = offset;
return offset;
}
@ -155,7 +162,7 @@ static AVIOContext * wtvfile_open_sector(int first_sector, uint64_t length, int
WtvFile *wf;
uint8_t *buffer;
if (avio_seek(s->pb, first_sector << WTV_SECTOR_BITS, SEEK_SET) < 0)
if (seek_by_sector(s->pb, first_sector, 0) < 0)
return NULL;
wf = av_mallocz(sizeof(WtvFile));
@ -184,14 +191,14 @@ static AVIOContext * wtvfile_open_sector(int first_sector, uint64_t length, int
int nb_sectors1 = read_ints(s->pb, sectors1, WTV_SECTOR_SIZE / 4);
int i;
wf->sectors = av_malloc(nb_sectors1 << WTV_SECTOR_BITS);
wf->sectors = av_malloc(SHIFT_SECTOR_BITS(nb_sectors1));
if (!wf->sectors) {
av_free(wf);
return NULL;
}
wf->nb_sectors = 0;
for (i = 0; i < nb_sectors1; i++) {
if (avio_seek(s->pb, sectors1[i] << WTV_SECTOR_BITS, SEEK_SET) < 0)
if (seek_by_sector(s->pb, sectors1[i], 0) < 0)
break;
wf->nb_sectors += read_ints(s->pb, wf->sectors + i * WTV_SECTOR_SIZE / 4, WTV_SECTOR_SIZE / 4);
}
@ -218,7 +225,7 @@ static AVIOContext * wtvfile_open_sector(int first_sector, uint64_t length, int
/* seek to initial sector */
wf->position = 0;
if (avio_seek(s->pb, wf->sectors[0] << WTV_SECTOR_BITS, SEEK_SET) < 0) {
if (seek_by_sector(s->pb, wf->sectors[0], 0) < 0) {
av_free(wf->sectors);
av_free(wf);
return NULL;
@ -963,7 +970,7 @@ static int read_header(AVFormatContext *s)
avio_skip(s->pb, 4);
root_sector = avio_rl32(s->pb);
avio_seek(s->pb, root_sector << WTV_SECTOR_BITS, SEEK_SET);
seek_by_sector(s->pb, root_sector, 0);
root_size = avio_read(s->pb, root, root_size);
if (root_size < 0)
return AVERROR_INVALIDDATA;