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      1 // Copyright 2012 Google Inc. All Rights Reserved.
      2 //
      3 // This code is licensed under the same terms as WebM:
      4 //  Software License Agreement:  http://www.webmproject.org/license/software/
      5 //  Additional IP Rights Grant:  http://www.webmproject.org/license/additional/
      6 // -----------------------------------------------------------------------------
      7 //
      8 // Color Cache for WebP Lossless
      9 //
     10 // Authors: Jyrki Alakuijala (jyrki (at) google.com)
     11 //          Urvang Joshi (urvang (at) google.com)
     12 
     13 #ifndef WEBP_UTILS_COLOR_CACHE_H_
     14 #define WEBP_UTILS_COLOR_CACHE_H_
     15 
     16 #include "webp/types.h"
     17 
     18 #if defined(__cplusplus) || defined(c_plusplus)
     19 extern "C" {
     20 #endif
     21 
     22 // Main color cache struct.
     23 typedef struct {
     24   uint32_t *colors_;  // color entries
     25   int hash_shift_;    // Hash shift: 32 - hash_bits.
     26 } VP8LColorCache;
     27 
     28 static const uint32_t kHashMul = 0x1e35a7bd;
     29 
     30 static WEBP_INLINE uint32_t VP8LColorCacheLookup(
     31     const VP8LColorCache* const cc, uint32_t key) {
     32   assert(key <= (~0U >> cc->hash_shift_));
     33   return cc->colors_[key];
     34 }
     35 
     36 static WEBP_INLINE void VP8LColorCacheInsert(const VP8LColorCache* const cc,
     37                                              uint32_t argb) {
     38   const uint32_t key = (kHashMul * argb) >> cc->hash_shift_;
     39   cc->colors_[key] = argb;
     40 }
     41 
     42 static WEBP_INLINE int VP8LColorCacheGetIndex(const VP8LColorCache* const cc,
     43                                               uint32_t argb) {
     44   return (kHashMul * argb) >> cc->hash_shift_;
     45 }
     46 
     47 static WEBP_INLINE int VP8LColorCacheContains(const VP8LColorCache* const cc,
     48                                               uint32_t argb) {
     49   const uint32_t key = (kHashMul * argb) >> cc->hash_shift_;
     50   return cc->colors_[key] == argb;
     51 }
     52 
     53 //------------------------------------------------------------------------------
     54 
     55 // Initializes the color cache with 'hash_bits' bits for the keys.
     56 // Returns false in case of memory error.
     57 int VP8LColorCacheInit(VP8LColorCache* const color_cache, int hash_bits);
     58 
     59 // Delete the memory associated to color cache.
     60 void VP8LColorCacheClear(VP8LColorCache* const color_cache);
     61 
     62 //------------------------------------------------------------------------------
     63 
     64 #if defined(__cplusplus) || defined(c_plusplus)
     65 }
     66 #endif
     67 
     68 #endif  // WEBP_UTILS_COLOR_CACHE_H_
     69