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-rw-r--r--thirdparty/libwebp/utils/random_utils.h63
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diff --git a/thirdparty/libwebp/utils/random_utils.h b/thirdparty/libwebp/utils/random_utils.h
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--- a/thirdparty/libwebp/utils/random_utils.h
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-// Copyright 2013 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.
-// -----------------------------------------------------------------------------
-//
-// Pseudo-random utilities
-//
-// Author: Skal (pascal.massimino@gmail.com)
-
-#ifndef WEBP_UTILS_RANDOM_H_
-#define WEBP_UTILS_RANDOM_H_
-
-#include <assert.h>
-#include "../webp/types.h"
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-#define VP8_RANDOM_DITHER_FIX 8 // fixed-point precision for dithering
-#define VP8_RANDOM_TABLE_SIZE 55
-
-typedef struct {
- int index1_, index2_;
- uint32_t tab_[VP8_RANDOM_TABLE_SIZE];
- int amp_;
-} VP8Random;
-
-// Initializes random generator with an amplitude 'dithering' in range [0..1].
-void VP8InitRandom(VP8Random* const rg, float dithering);
-
-// Returns a centered pseudo-random number with 'num_bits' amplitude.
-// (uses D.Knuth's Difference-based random generator).
-// 'amp' is in VP8_RANDOM_DITHER_FIX fixed-point precision.
-static WEBP_INLINE int VP8RandomBits2(VP8Random* const rg, int num_bits,
- int amp) {
- int diff;
- assert(num_bits + VP8_RANDOM_DITHER_FIX <= 31);
- diff = rg->tab_[rg->index1_] - rg->tab_[rg->index2_];
- if (diff < 0) diff += (1u << 31);
- rg->tab_[rg->index1_] = diff;
- if (++rg->index1_ == VP8_RANDOM_TABLE_SIZE) rg->index1_ = 0;
- if (++rg->index2_ == VP8_RANDOM_TABLE_SIZE) rg->index2_ = 0;
- // sign-extend, 0-center
- diff = (int)((uint32_t)diff << 1) >> (32 - num_bits);
- diff = (diff * amp) >> VP8_RANDOM_DITHER_FIX; // restrict range
- diff += 1 << (num_bits - 1); // shift back to 0.5-center
- return diff;
-}
-
-static WEBP_INLINE int VP8RandomBits(VP8Random* const rg, int num_bits) {
- return VP8RandomBits2(rg, num_bits, rg->amp_);
-}
-
-#ifdef __cplusplus
-} // extern "C"
-#endif
-
-#endif /* WEBP_UTILS_RANDOM_H_ */