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-rw-r--r--modules/brotli/enc/bit_cost.h63
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diff --git a/modules/brotli/enc/bit_cost.h b/modules/brotli/enc/bit_cost.h
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+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+ Distributed under MIT license.
+ See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Functions to estimate the bit cost of Huffman trees. */
+
+#ifndef BROTLI_ENC_BIT_COST_H_
+#define BROTLI_ENC_BIT_COST_H_
+
+#include "../common/platform.h"
+#include <brotli/types.h>
+#include "./fast_log.h"
+#include "./histogram.h"
+
+#if defined(__cplusplus) || defined(c_plusplus)
+extern "C" {
+#endif
+
+static BROTLI_INLINE double ShannonEntropy(
+ const uint32_t* population, size_t size, size_t* total) {
+ size_t sum = 0;
+ double retval = 0;
+ const uint32_t* population_end = population + size;
+ size_t p;
+ if (size & 1) {
+ goto odd_number_of_elements_left;
+ }
+ while (population < population_end) {
+ p = *population++;
+ sum += p;
+ retval -= (double)p * FastLog2(p);
+ odd_number_of_elements_left:
+ p = *population++;
+ sum += p;
+ retval -= (double)p * FastLog2(p);
+ }
+ if (sum) retval += (double)sum * FastLog2(sum);
+ *total = sum;
+ return retval;
+}
+
+static BROTLI_INLINE double BitsEntropy(
+ const uint32_t* population, size_t size) {
+ size_t sum;
+ double retval = ShannonEntropy(population, size, &sum);
+ if (retval < sum) {
+ /* At least one bit per literal is needed. */
+ retval = (double)sum;
+ }
+ return retval;
+}
+
+BROTLI_INTERNAL double BrotliPopulationCostLiteral(const HistogramLiteral*);
+BROTLI_INTERNAL double BrotliPopulationCostCommand(const HistogramCommand*);
+BROTLI_INTERNAL double BrotliPopulationCostDistance(const HistogramDistance*);
+
+#if defined(__cplusplus) || defined(c_plusplus)
+} /* extern "C" */
+#endif
+
+#endif /* BROTLI_ENC_BIT_COST_H_ */