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#ifdef __cplusplus
21extern "C" {
22#endif
23
24// Main color cache struct.
25typedef struct {
26  uint32_t *colors_;  // color entries
27  int hash_shift_;    // Hash shift: 32 - hash_bits.
28} VP8LColorCache;
29
30static const uint32_t kHashMul = 0x1e35a7bd;
31
32static 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
38static 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
44static WEBP_INLINE int VP8LColorCacheGetIndex(const VP8LColorCache* const cc,
45                                              uint32_t argb) {
46  return (kHashMul * argb) >> cc->hash_shift_;
47}
48
49static 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.
59int VP8LColorCacheInit(VP8LColorCache* const color_cache, int hash_bits);
60
61// Delete the memory associated to color cache.
62void VP8LColorCacheClear(VP8LColorCache* const color_cache);
63
64//------------------------------------------------------------------------------
65
66#ifdef __cplusplus
67}
68#endif
69
70#endif  // WEBP_UTILS_COLOR_CACHE_H_
71