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      1 // Copyright 2012 Google Inc. All Rights Reserved.
      2 //
      3 // Use of this source code is governed by a BSD-style license
      4 // that can be found in the COPYING file in the root of the source
      5 // tree. An additional intellectual property rights grant can be found
      6 // in the file PATENTS. All contributing project authors may
      7 // be found in the AUTHORS file in the root of the source tree.
      8 // -----------------------------------------------------------------------------
      9 //
     10 // Color Cache for WebP Lossless
     11 //
     12 // Authors: Jyrki Alakuijala (jyrki (at) google.com)
     13 //          Urvang Joshi (urvang (at) google.com)
     14 
     15 #ifndef WEBP_UTILS_COLOR_CACHE_H_
     16 #define WEBP_UTILS_COLOR_CACHE_H_
     17 
     18 #include "../webp/types.h"
     19 
     20 #ifdef __cplusplus
     21 extern "C" {
     22 #endif
     23 
     24 // Main color cache struct.
     25 typedef struct {
     26   uint32_t *colors_;  // color entries
     27   int hash_shift_;    // Hash shift: 32 - hash_bits_.
     28   int hash_bits_;
     29 } VP8LColorCache;
     30 
     31 static const uint32_t kHashMul = 0x1e35a7bd;
     32 
     33 static WEBP_INLINE uint32_t VP8LColorCacheLookup(
     34     const VP8LColorCache* const cc, uint32_t key) {
     35   assert((key >> cc->hash_bits_) == 0u);
     36   return cc->colors_[key];
     37 }
     38 
     39 static WEBP_INLINE void VP8LColorCacheSet(const VP8LColorCache* const cc,
     40                                           uint32_t key, uint32_t argb) {
     41   assert((key >> cc->hash_bits_) == 0u);
     42   cc->colors_[key] = argb;
     43 }
     44 
     45 static WEBP_INLINE void VP8LColorCacheInsert(const VP8LColorCache* const cc,
     46                                              uint32_t argb) {
     47   const uint32_t key = (kHashMul * argb) >> cc->hash_shift_;
     48   cc->colors_[key] = argb;
     49 }
     50 
     51 static WEBP_INLINE int VP8LColorCacheGetIndex(const VP8LColorCache* const cc,
     52                                               uint32_t argb) {
     53   return (kHashMul * argb) >> cc->hash_shift_;
     54 }
     55 
     56 static WEBP_INLINE int VP8LColorCacheContains(const VP8LColorCache* const cc,
     57                                               uint32_t argb) {
     58   const uint32_t key = (kHashMul * argb) >> cc->hash_shift_;
     59   return (cc->colors_[key] == argb);
     60 }
     61 
     62 //------------------------------------------------------------------------------
     63 
     64 // Initializes the color cache with 'hash_bits' bits for the keys.
     65 // Returns false in case of memory error.
     66 int VP8LColorCacheInit(VP8LColorCache* const color_cache, int hash_bits);
     67 
     68 void VP8LColorCacheCopy(const VP8LColorCache* const src,
     69                         VP8LColorCache* const dst);
     70 
     71 // Delete the memory associated to color cache.
     72 void VP8LColorCacheClear(VP8LColorCache* const color_cache);
     73 
     74 //------------------------------------------------------------------------------
     75 
     76 #ifdef __cplusplus
     77 }
     78 #endif
     79 
     80 #endif  // WEBP_UTILS_COLOR_CACHE_H_
     81