third_party/libwebp/utils/color_cache.h

   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@google.com)
  13 //          Urvang Joshi (urvang@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 #if defined(__cplusplus) || defined(c_plusplus)
  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 } VP8LColorCache;
  29
  30 static const uint32_t kHashMul = 0x1e35a7bd;
  31
  32 static WEBP_INLINE uint32_t VP8LColorCacheLookup(
  33     const VP8LColorCache* const cc, uint32_t key) {
  34   assert(key <= (~0U >> cc->hash_shift_));
  35   return cc->colors_[key];
  36 }
  37
  38 static WEBP_INLINE void VP8LColorCacheInsert(const VP8LColorCache* const cc,
  39                                              uint32_t argb) {
  40   const uint32_t key = (kHashMul * argb) >> cc->hash_shift_;
  41   cc->colors_[key] = argb;
  42 }
  43
  44 static WEBP_INLINE int VP8LColorCacheGetIndex(const VP8LColorCache* const cc,
  45                                               uint32_t argb) {
  46   return (kHashMul * argb) >> cc->hash_shift_;
  47 }
  48
  49 static WEBP_INLINE int VP8LColorCacheContains(const VP8LColorCache* const cc,
  50                                               uint32_t argb) {
  51   const uint32_t key = (kHashMul * argb) >> cc->hash_shift_;
  52   return cc->colors_[key] == argb;
  53 }
  54
  55 //------------------------------------------------------------------------------
  56
  57 // Initializes the color cache with 'hash_bits' bits for the keys.
  58 // Returns false in case of memory error.
  59 int VP8LColorCacheInit(VP8LColorCache* const color_cache, int hash_bits);
  60
  61 // Delete the memory associated to color cache.
  62 void VP8LColorCacheClear(VP8LColorCache* const color_cache);
  63
  64 //------------------------------------------------------------------------------
  65
  66 #if defined(__cplusplus) || defined(c_plusplus)
  67 }
  68 #endif
  69
  70 #endif  // WEBP_UTILS_COLOR_CACHE_H_