[FFmpeg-cvslog] wtv: Seek by sector properly
Luca Barbato
git at videolan.org
Sat Oct 19 11:13:45 CEST 2013
ffmpeg | branch: master | Luca Barbato <lu_zero at gentoo.org> | Fri Oct 18 13:45:13 2013 +0200| [2b72f8ac320c8c5087b1bd0589fc3df132eb42bc] | committer: Luca Barbato
wtv: Seek by sector properly
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.
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=2b72f8ac320c8c5087b1bd0589fc3df132eb42bc
---
libavformat/wtv.c | 25 ++++++++++++++++---------
1 file changed, 16 insertions(+), 9 deletions(-)
diff --git a/libavformat/wtv.c b/libavformat/wtv.c
index 5099739..b144eb6 100644
--- a/libavformat/wtv.c
+++ b/libavformat/wtv.c
@@ -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;
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