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make the bitreader preload at least 8bits, instead of post-load them

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(this makes initialization easier and will be helpful for incremental
decoding).
Modify ParsePartitions() to accommodate for truncated input.

Change-Id: I62f52078d6b7a2314a11880a20d9eac5b4714bd0
This commit is contained in:
Pascal Massimino
2011-03-10 15:05:59 -08:00
parent f4888f7702
commit 13e50da6f8
3 changed files with 65 additions and 52 deletions
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49
src/dec/vp8.c
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@ -111,33 +111,41 @@ static int ParseSegmentHeader(VP8BitReader* br,
}
// Paragraph 9.5
static int ParsePartitions(VP8Decoder* const dec,
const uint8_t* buf, uint32_t size) {
// This function returns VP8_STATUS_SUSPENDED if we don't have all the
// necessary data in 'buf'.
// This case is not necessarily an error (for incremental decoding).
// Still, no bitreader is ever initialized to make it possible to read
// unavailable memory.
// If we don't even have the partitions' sizes, than VP8_STATUS_NOT_ENOUGH_DATA
// is returned, and this is an unrecoverable error.
// If the partitions were positioned ok, VP8_STATUS_OK is returned.
static VP8StatusCode ParsePartitions(VP8Decoder* const dec,
const uint8_t* buf, uint32_t size) {
VP8BitReader* const br = &dec->br_;
const uint8_t* sz = buf;
const uint8_t* buf_end = buf + size;
const uint8_t* part_start;
int last_part;
uint32_t offset;
int p;
dec->num_parts_ = 1 << VP8GetValue(br, 2);
last_part = dec->num_parts_ - 1;
offset = last_part * 3;
if (size <= offset) {
return 0;
part_start = buf + last_part * 3;
if (buf_end < part_start) {
// we can't even read the sizes with sz[]! That's a failure.
return VP8_STATUS_NOT_ENOUGH_DATA;
}
for (p = 0; p < last_part; ++p) {
const uint32_t psize = sz[0] | (sz[1] << 8) | (sz[2] << 16);
if (offset + psize > size) {
return 0;
}
VP8Init(dec->parts_ + p, buf + offset, psize);
offset += psize;
const uint8_t* part_end = part_start + psize;
if (part_end > buf_end) part_end = buf_end;
VP8InitBitReader(dec->parts_ + p, part_start, part_end);
part_start = part_end;
sz += 3;
}
size -= offset;
VP8Init(dec->parts_ + last_part, buf + offset, size);
return 1;
VP8InitBitReader(dec->parts_ + last_part, part_start, buf_end);
return (part_start < buf_end) ? VP8_STATUS_OK :
VP8_STATUS_SUSPENDED; // Init is ok, but there's not enough data
}
// Paragraph 9.4
@ -284,14 +292,17 @@ int VP8GetHeaders(VP8Decoder* const dec, VP8Io* const io) {
dec->segment_ = 0; // default for intra
}
br = &dec->br_;
VP8Init(br, buf, buf_size);
// Check if we have all the partition #0 available, and initialize dec->br_
// to read this partition (and this partition only).
if (frm_hdr->partition_length_ > buf_size) {
return VP8SetError(dec, VP8_STATUS_NOT_ENOUGH_DATA,
"bad partition length");
}
}
br = &dec->br_;
VP8InitBitReader(br, buf, buf + frm_hdr->partition_length_);
buf += frm_hdr->partition_length_;
buf_size -= frm_hdr->partition_length_;
if (frm_hdr->key_frame_) {
pic_hdr->colorspace_ = VP8Get(br);
pic_hdr->clamp_type_ = VP8Get(br);
@ -305,7 +316,7 @@ int VP8GetHeaders(VP8Decoder* const dec, VP8Io* const io) {
return VP8SetError(dec, VP8_STATUS_BITSTREAM_ERROR,
"cannot parse filter header");
}
if (!ParsePartitions(dec, buf, buf_size)) {
if (ParsePartitions(dec, buf, buf_size) != VP8_STATUS_OK) {
return VP8SetError(dec, VP8_STATUS_BITSTREAM_ERROR,
"cannot parse partitions");
}