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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 uint64_t kHashMul = 0x1e35a7bdull;
     32 
     33 static WEBP_INLINE int HashPix(uint32_t argb, int shift) {
     34   return (int)(((argb * kHashMul) & 0xffffffffu) >> shift);
     35 }
     36 
     37 static WEBP_INLINE uint32_t VP8LColorCacheLookup(
     38     const VP8LColorCache* const cc, uint32_t key) {
     39   assert((key >> cc->hash_bits_) == 0u);
     40   return cc->colors_[key];
     41 }
     42 
     43 static WEBP_INLINE void VP8LColorCacheSet(const VP8LColorCache* const cc,
     44                                           uint32_t key, uint32_t argb) {
     45   assert((key >> cc->hash_bits_) == 0u);
     46   cc->colors_[key] = argb;
     47 }
     48 
     49 static WEBP_INLINE void VP8LColorCacheInsert(const VP8LColorCache* const cc,
     50                                              uint32_t argb) {
     51   const int key = HashPix(argb, cc->hash_shift_);
     52   cc->colors_[key] = argb;
     53 }
     54 
     55 static WEBP_INLINE int VP8LColorCacheGetIndex(const VP8LColorCache* const cc,
     56                                               uint32_t argb) {
     57   return HashPix(argb, cc->hash_shift_);
     58 }
     59 
     60 // Return the key if cc contains argb, and -1 otherwise.
     61 static WEBP_INLINE int VP8LColorCacheContains(const VP8LColorCache* const cc,
     62                                               uint32_t argb) {
     63   const int key = HashPix(argb, cc->hash_shift_);
     64   return (cc->colors_[key] == argb) ? key : -1;
     65 }
     66 
     67 //------------------------------------------------------------------------------
     68 
     69 // Initializes the color cache with 'hash_bits' bits for the keys.
     70 // Returns false in case of memory error.
     71 int VP8LColorCacheInit(VP8LColorCache* const color_cache, int hash_bits);
     72 
     73 void VP8LColorCacheCopy(const VP8LColorCache* const src,
     74                         VP8LColorCache* const dst);
     75 
     76 // Delete the memory associated to color cache.
     77 void VP8LColorCacheClear(VP8LColorCache* const color_cache);
     78 
     79 //------------------------------------------------------------------------------
     80 
     81 #ifdef __cplusplus
     82 }
     83 #endif
     84 
     85 #endif  // WEBP_UTILS_COLOR_CACHE_H_
     86