should be it

external/duckdb/third_party/brotli/enc/bit_cost.h

@@ -0,0 +1,60 @@
+/* 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 <brotli/types.h>
+
+#include "../common/brotli_platform.h"
+#include "fast_log.h"
+#include "histogram.h"
+
+namespace duckdb_brotli {
+
+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 < (double)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*);
+
+}
+
+#endif  /* BROTLI_ENC_BIT_COST_H_ */