1 files changed, 51 insertions, 0 deletions
diff --git a/src/zopfli/tree.h b/src/zopfli/tree.h
new file mode 100644
index 0000000..4d6f469
--- /dev/null
+++ b/src/zopfli/tree.h
@@ -0,0 +1,51 @@
+/*
+Copyright 2011 Google Inc. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+
+Author: lode.vandevenne@gmail.com (Lode Vandevenne)
+Author: jyrki.alakuijala@gmail.com (Jyrki Alakuijala)
+*/
+
+/*
+Utilities for creating and using Huffman trees.
+*/
+
+#ifndef ZOPFLI_TREE_H_
+#define ZOPFLI_TREE_H_
+
+#include <string.h>
+
+/*
+Calculates the bitlengths for the Huffman tree, based on the counts of each
+symbol.
+*/
+void ZopfliCalculateBitLengths(const size_t* count, size_t n, int maxbits,
+                               unsigned *bitlengths);
+
+/*
+Converts a series of Huffman tree bitlengths, to the bit values of the symbols.
+*/
+void ZopfliLengthsToSymbols(const unsigned* lengths, size_t n, unsigned maxbits,
+                            unsigned* symbols);
+
+/*
+Calculates the entropy of each symbol, based on the counts of each symbol. The
+result is similar to the result of ZopfliCalculateBitLengths, but with the
+actual theoritical bit lengths according to the entropy. Since the resulting
+values are fractional, they cannot be used to encode the tree specified by
+DEFLATE.
+*/
+void ZopfliCalculateEntropy(const size_t* count, size_t n, double* bitlengths);
+
+#endif  /* ZOPFLI_TREE_H_ */