1 files changed, 63 insertions, 0 deletions
diff --git a/modules/brotli/enc/bit_cost.h b/modules/brotli/enc/bit_cost.h
new file mode 100644
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+++ b/modules/brotli/enc/bit_cost.h
@@ -0,0 +1,63 @@
+/* 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_ */