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Fix an unsigned integer overflow error in enc/cost.h

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Change-Id: I9774b59c417c185f09a61a115364b9642976a100
(cherry picked from commit 0b2c58a91c)
This commit is contained in:
hui su 2016-07-26 13:55:09 -07:00 committed by James Zern
parent 13cf1d2e41
commit 7416280d75
1 changed files with 3 additions and 1 deletions
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src/enc/cost.h
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@ -44,7 +44,9 @@ int VP8RecordCoeffs(int ctx, const VP8Residual* const res);
// Record proba context used.
static WEBP_INLINE int VP8RecordStats(int bit, proba_t* const stats) {
proba_t p = *stats;
if (p >= 0xffff0000u) { // an overflow is inbound.
// An overflow is inbound. Note we handle this at 0xfffe0000u instead of
// 0xffff0000u to make sure p + 1u does not overflow.
if (p >= 0xfffe0000u) {
p = ((p + 1u) >> 1) & 0x7fff7fffu; // -> divide the stats by 2.
}
// record bit count (lower 16 bits) and increment total count (upper 16 bits).