Use the upstream version of libwebp, v0.4.3.

third_party/libwebp/utils/color_cache.h

+// Copyright 2012 Google Inc. All Rights Reserved.
+//
+// Use of this source code is governed by a BSD-style license
+// that can be found in the COPYING file in the root of the source
+// tree. An additional intellectual property rights grant can be found
+// in the file PATENTS. All contributing project authors may
+// be found in the AUTHORS file in the root of the source tree.
+// -----------------------------------------------------------------------------
+//
+// Color Cache for WebP Lossless
+//
+// Authors: Jyrki Alakuijala (jyrki@google.com)
+//          Urvang Joshi (urvang@google.com)
+
+#ifndef WEBP_UTILS_COLOR_CACHE_H_
+#define WEBP_UTILS_COLOR_CACHE_H_
+
+#include "../webp/types.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// Main color cache struct.
+typedef struct {
+  uint32_t *colors_;  // color entries
+  int hash_shift_;    // Hash shift: 32 - hash_bits.
+} VP8LColorCache;
+
+static const uint32_t kHashMul = 0x1e35a7bd;
+
+static WEBP_INLINE uint32_t VP8LColorCacheLookup(
+    const VP8LColorCache* const cc, uint32_t key) {
+  assert(key <= (~0U >> cc->hash_shift_));
+  return cc->colors_[key];
+}
+
+static WEBP_INLINE void VP8LColorCacheInsert(const VP8LColorCache* const cc,
+                                             uint32_t argb) {
+  const uint32_t key = (kHashMul * argb) >> cc->hash_shift_;
+  cc->colors_[key] = argb;
+}
+
+static WEBP_INLINE int VP8LColorCacheGetIndex(const VP8LColorCache* const cc,
+                                              uint32_t argb) {
+  return (kHashMul * argb) >> cc->hash_shift_;
+}
+
+static WEBP_INLINE int VP8LColorCacheContains(const VP8LColorCache* const cc,
+                                              uint32_t argb) {
+  const uint32_t key = (kHashMul * argb) >> cc->hash_shift_;
+  return cc->colors_[key] == argb;
+}
+
+//------------------------------------------------------------------------------
+
+// Initializes the color cache with 'hash_bits' bits for the keys.
+// Returns false in case of memory error.
+int VP8LColorCacheInit(VP8LColorCache* const color_cache, int hash_bits);
+
+// Delete the memory associated to color cache.
+void VP8LColorCacheClear(VP8LColorCache* const color_cache);
+
+//------------------------------------------------------------------------------
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif  // WEBP_UTILS_COLOR_CACHE_H_