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fix for issue #275: don't compare to out-of-bound pointers

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the original change triggered several internal API modifs.
This is to ensure that we're never computing pointer that can
possibly wrap around, or differences between pointers that can
overflow.

no observed speed difference

Change-Id: I9c94dda38d94fecc010305e4ad12f13b8fda5380
This commit is contained in:
Pascal Massimino
2015-11-20 09:12:48 +00:00
committed by James Zern
parent 21735e06f7
commit b37b0179c5
5 changed files with 40 additions and 21 deletions
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11
src/dec/idec.c
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@ -130,8 +130,12 @@ static void DoRemap(WebPIDecoder* const idec, ptrdiff_t offset) {
VP8RemapBitReader(&dec->br_, offset);
}
}
assert(last_part >= 0);
dec->parts_[last_part].buf_end_ = mem->buf_ + mem->end_;
{
const uint8_t* const last_start = dec->parts_[last_part].buf_;
assert(last_part >= 0);
VP8BitReaderSetBuffer(&dec->parts_[last_part], last_start,
mem->buf_ + mem->end_ - last_start);
}
if (NeedCompressedAlpha(idec)) {
ALPHDecoder* const alph_dec = dec->alph_dec_;
dec->alpha_data_ += offset;
@ -375,8 +379,7 @@ static VP8StatusCode CopyParts0Data(WebPIDecoder* const idec) {
}
memcpy(part0_buf, br->buf_, part_size);
mem->part0_buf_ = part0_buf;
br->buf_ = part0_buf;
br->buf_end_ = part0_buf + part_size;
VP8BitReaderSetBuffer(br, part0_buf, part_size);
} else {
// Else: just keep pointers to the partition #0's data in dec_->br_.
}