libwebp-0.5.2-rc2

third_party/libwebp/enc/cost.h

 // Copyright 2011 Google Inc. All Rights Reserved.
 //
 // Use of this source code is governed by a BSD-style license
 // that can be found in the COPYING file in the root of the source
 // tree. An additional intellectual property rights grant can be found
 // in the file PATENTS. All contributing project authors may
 // be found in the AUTHORS file in the root of the source tree.
 // -----------------------------------------------------------------------------
 //
 // Cost tables for level and modes.
@@ skipping 23 matching lines @@
   ProbaArray*   prob;
   StatsArray*   stats;
   CostArrayPtr  costs;
 };
 
 void VP8InitResidual(int first, int coeff_type,
                      VP8Encoder* const enc, VP8Residual* const res);
 
 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];
 }
 
 // Level cost calculations
 extern const uint16_t VP8LevelCodes[MAX_VARIABLE_LEVEL][2];
 void VP8CalculateLevelCosts(VP8EncProba* const proba);
 static WEBP_INLINE int VP8LevelCost(const uint16_t* const table, int level) {
   return VP8LevelFixedCosts[level]
        + table[(level > MAX_VARIABLE_LEVEL) ? MAX_VARIABLE_LEVEL : level];
 }
 
 // Mode costs
 extern const uint16_t VP8FixedCostsUV[4];
 extern const uint16_t VP8FixedCostsI16[4];
 extern const uint16_t VP8FixedCostsI4[NUM_BMODES][NUM_BMODES][NUM_BMODES];
 
 //------------------------------------------------------------------------------
 
 #ifdef __cplusplus
 }    // extern "C"
 #endif
 
 #endif  /* WEBP_ENC_COST_H_ */