Index: third_party/libwebp/utils/huffman.h |
diff --git a/third_party/libwebp/utils/huffman.h b/third_party/libwebp/utils/huffman.h |
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+// Copyright 2012 Google Inc. All Rights Reserved. |
+// |
+// This code is licensed under the same terms as WebM: |
+// Software License Agreement: http://www.webmproject.org/license/software/ |
+// Additional IP Rights Grant: http://www.webmproject.org/license/additional/ |
+// ----------------------------------------------------------------------------- |
+// |
+// Utilities for building and looking up Huffman trees. |
+// |
+// Author: Urvang Joshi (urvang@google.com) |
+ |
+#ifndef WEBP_UTILS_HUFFMAN_H_ |
+#define WEBP_UTILS_HUFFMAN_H_ |
+ |
+#include <assert.h> |
+#include "../webp/types.h" |
+ |
+#if defined(__cplusplus) || defined(c_plusplus) |
+extern "C" { |
+#endif |
+ |
+// A node of a Huffman tree. |
+typedef struct { |
+ int symbol_; |
+ int children_; // delta offset to both children (contiguous) or 0 if leaf. |
+} HuffmanTreeNode; |
+ |
+// Huffman Tree. |
+typedef struct HuffmanTree HuffmanTree; |
+struct HuffmanTree { |
+ HuffmanTreeNode* root_; // all the nodes, starting at root. |
+ int max_nodes_; // max number of nodes |
+ int num_nodes_; // number of currently occupied nodes |
+}; |
+ |
+// Returns true if the given node is a leaf of the Huffman tree. |
+static WEBP_INLINE int HuffmanTreeNodeIsLeaf( |
+ const HuffmanTreeNode* const node) { |
+ return (node->children_ == 0); |
+} |
+ |
+// Go down one level. Most critical function. 'right_child' must be 0 or 1. |
+static WEBP_INLINE const HuffmanTreeNode* HuffmanTreeNextNode( |
+ const HuffmanTreeNode* node, int right_child) { |
+ return node + node->children_ + right_child; |
+} |
+ |
+// Releases the nodes of the Huffman tree. |
+// Note: It does NOT free 'tree' itself. |
+void HuffmanTreeRelease(HuffmanTree* const tree); |
+ |
+// Builds Huffman tree assuming code lengths are implicitly in symbol order. |
+// Returns false in case of error (invalid tree or memory error). |
+int HuffmanTreeBuildImplicit(HuffmanTree* const tree, |
+ const int* const code_lengths, |
+ int code_lengths_size); |
+ |
+// Build a Huffman tree with explicitly given lists of code lengths, codes |
+// and symbols. Verifies that all symbols added are smaller than max_symbol. |
+// Returns false in case of an invalid symbol, invalid tree or memory error. |
+int HuffmanTreeBuildExplicit(HuffmanTree* const tree, |
+ const int* const code_lengths, |
+ const int* const codes, |
+ const int* const symbols, int max_symbol, |
+ int num_symbols); |
+ |
+// Utility: converts Huffman code lengths to corresponding Huffman codes. |
+// 'huff_codes' should be pre-allocated. |
+// Returns false in case of error (memory allocation, invalid codes). |
+int HuffmanCodeLengthsToCodes(const int* const code_lengths, |
+ int code_lengths_size, int* const huff_codes); |
+ |
+ |
+#if defined(__cplusplus) || defined(c_plusplus) |
+} // extern "C" |
+#endif |
+ |
+#endif // WEBP_UTILS_HUFFMAN_H_ |