libwebp-0.5.2-rc2

third_party/libwebp/enc/cost.h

Index: third_party/libwebp/enc/cost.h
diff --git a/third_party/libwebp/enc/cost.h b/third_party/libwebp/enc/cost.h
index 20960d6d74c0283688eefde24b3dae7dd62f57b1..ad7959feb41b4c084ed9e54d2f230b283be3c970 100644
--- a/third_party/libwebp/enc/cost.h
+++ b/third_party/libwebp/enc/cost.h
@@ -41,6 +41,20 @@ void VP8InitResidual(int first, int coeff_type,
 
 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;
+  // 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).
+  p += 0x00010000u + bit;
+  *stats = p;
+  return bit;
+}
+
 // Cost of coding one event with probability 'proba'.
 static WEBP_INLINE int VP8BitCost(int bit, uint8_t proba) {
   return !bit ? VP8EntropyCost[proba] : VP8EntropyCost[255 - proba];