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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_UTILS_H_
     16 #define WEBP_UTILS_COLOR_CACHE_UTILS_H_
     17 
     18 #include <assert.h>
     19 
     20 #include "src/webp/types.h"
     21 
     22 #ifdef __cplusplus
     23 extern "C" {
     24 #endif
     25 
     26 // Main color cache struct.
     27 typedef struct {
     28   uint32_t *colors_;  // color entries
     29   int hash_shift_;    // Hash shift: 32 - hash_bits_.
     30   int hash_bits_;
     31 } VP8LColorCache;
     32 
     33 static const uint64_t kHashMul = 0x1e35a7bdull;
     34 
     35 static WEBP_INLINE int VP8LHashPix(uint32_t argb, int shift) {
     36   return (int)(((argb * kHashMul) & 0xffffffffu) >> shift);
     37 }
     38 
     39 static WEBP_INLINE uint32_t VP8LColorCacheLookup(
     40     const VP8LColorCache* const cc, uint32_t key) {
     41   assert((key >> cc->hash_bits_) == 0u);
     42   return cc->colors_[key];
     43 }
     44 
     45 static WEBP_INLINE void VP8LColorCacheSet(const VP8LColorCache* const cc,
     46                                           uint32_t key, uint32_t argb) {
     47   assert((key >> cc->hash_bits_) == 0u);
     48   cc->colors_[key] = argb;
     49 }
     50 
     51 static WEBP_INLINE void VP8LColorCacheInsert(const VP8LColorCache* const cc,
     52                                              uint32_t argb) {
     53   const int key = VP8LHashPix(argb, cc->hash_shift_);
     54   cc->colors_[key] = argb;
     55 }
     56 
     57 static WEBP_INLINE int VP8LColorCacheGetIndex(const VP8LColorCache* const cc,
     58                                               uint32_t argb) {
     59   return VP8LHashPix(argb, cc->hash_shift_);
     60 }
     61 
     62 // Return the key if cc contains argb, and -1 otherwise.
     63 static WEBP_INLINE int VP8LColorCacheContains(const VP8LColorCache* const cc,
     64                                               uint32_t argb) {
     65   const int key = VP8LHashPix(argb, cc->hash_shift_);
     66   return (cc->colors_[key] == argb) ? key : -1;
     67 }
     68 
     69 //------------------------------------------------------------------------------
     70 
     71 // Initializes the color cache with 'hash_bits' bits for the keys.
     72 // Returns false in case of memory error.
     73 int VP8LColorCacheInit(VP8LColorCache* const color_cache, int hash_bits);
     74 
     75 void VP8LColorCacheCopy(const VP8LColorCache* const src,
     76                         VP8LColorCache* const dst);
     77 
     78 // Delete the memory associated to color cache.
     79 void VP8LColorCacheClear(VP8LColorCache* const color_cache);
     80 
     81 //------------------------------------------------------------------------------
     82 
     83 #ifdef __cplusplus
     84 }
     85 #endif
     86 
     87 #endif  // WEBP_UTILS_COLOR_CACHE_UTILS_H_
     88