320 lines
9.6 KiB
C
320 lines
9.6 KiB
C
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// Copyright 2012 Google Inc. All Rights Reserved.
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//
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// Use of this source code is governed by a BSD-style license
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// that can be found in the COPYING file in the root of the source
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// tree. An additional intellectual property rights grant can be found
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// in the file PATENTS. All contributing project authors may
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// be found in the AUTHORS file in the root of the source tree.
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// -----------------------------------------------------------------------------
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//
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// Utilities for building and looking up Huffman trees.
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//
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// Author: Urvang Joshi (urvang@google.com)
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#include <assert.h>
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#include <stdlib.h>
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#include <string.h>
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#include "./huffman.h"
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#include "../utils/utils.h"
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#include "../webp/format_constants.h"
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// Uncomment the following to use look-up table for ReverseBits()
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// (might be faster on some platform)
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// #define USE_LUT_REVERSE_BITS
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// Huffman data read via DecodeImageStream is represented in two (red and green)
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// bytes.
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#define MAX_HTREE_GROUPS 0x10000
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#define NON_EXISTENT_SYMBOL (-1)
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static void TreeNodeInit(HuffmanTreeNode* const node) {
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node->children_ = -1; // means: 'unassigned so far'
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}
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static int NodeIsEmpty(const HuffmanTreeNode* const node) {
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return (node->children_ < 0);
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}
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static int IsFull(const HuffmanTree* const tree) {
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return (tree->num_nodes_ == tree->max_nodes_);
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}
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static void AssignChildren(HuffmanTree* const tree,
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HuffmanTreeNode* const node) {
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HuffmanTreeNode* const children = tree->root_ + tree->num_nodes_;
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node->children_ = (int)(children - node);
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assert(children - node == (int)(children - node));
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tree->num_nodes_ += 2;
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TreeNodeInit(children + 0);
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TreeNodeInit(children + 1);
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}
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// A Huffman tree is a full binary tree; and in a full binary tree with L
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// leaves, the total number of nodes N = 2 * L - 1.
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static int HuffmanTreeMaxNodes(int num_leaves) {
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return (2 * num_leaves - 1);
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}
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static int HuffmanTreeAllocate(HuffmanTree* const tree, int num_nodes) {
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assert(tree != NULL);
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tree->root_ =
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(HuffmanTreeNode*)WebPSafeMalloc(num_nodes, sizeof(*tree->root_));
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return (tree->root_ != NULL);
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}
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static int TreeInit(HuffmanTree* const tree, int num_leaves) {
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assert(tree != NULL);
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if (num_leaves == 0) return 0;
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tree->max_nodes_ = HuffmanTreeMaxNodes(num_leaves);
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assert(tree->max_nodes_ < (1 << 16)); // limit for the lut_jump_ table
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if (!HuffmanTreeAllocate(tree, tree->max_nodes_)) return 0;
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TreeNodeInit(tree->root_); // Initialize root.
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tree->num_nodes_ = 1;
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memset(tree->lut_bits_, 255, sizeof(tree->lut_bits_));
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memset(tree->lut_jump_, 0, sizeof(tree->lut_jump_));
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return 1;
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}
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void VP8LHuffmanTreeFree(HuffmanTree* const tree) {
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if (tree != NULL) {
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WebPSafeFree(tree->root_);
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tree->root_ = NULL;
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tree->max_nodes_ = 0;
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tree->num_nodes_ = 0;
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}
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}
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HTreeGroup* VP8LHtreeGroupsNew(int num_htree_groups) {
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HTreeGroup* const htree_groups =
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(HTreeGroup*)WebPSafeCalloc(num_htree_groups, sizeof(*htree_groups));
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assert(num_htree_groups <= MAX_HTREE_GROUPS);
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if (htree_groups == NULL) {
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return NULL;
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}
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return htree_groups;
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}
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void VP8LHtreeGroupsFree(HTreeGroup* htree_groups, int num_htree_groups) {
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if (htree_groups != NULL) {
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int i, j;
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for (i = 0; i < num_htree_groups; ++i) {
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HuffmanTree* const htrees = htree_groups[i].htrees_;
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for (j = 0; j < HUFFMAN_CODES_PER_META_CODE; ++j) {
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VP8LHuffmanTreeFree(&htrees[j]);
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}
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}
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WebPSafeFree(htree_groups);
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}
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}
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int VP8LHuffmanCodeLengthsToCodes(
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const int* const code_lengths, int code_lengths_size,
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int* const huff_codes) {
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int symbol;
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int code_len;
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int code_length_hist[MAX_ALLOWED_CODE_LENGTH + 1] = { 0 };
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int curr_code;
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int next_codes[MAX_ALLOWED_CODE_LENGTH + 1] = { 0 };
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int max_code_length = 0;
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assert(code_lengths != NULL);
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assert(code_lengths_size > 0);
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assert(huff_codes != NULL);
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// Calculate max code length.
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for (symbol = 0; symbol < code_lengths_size; ++symbol) {
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if (code_lengths[symbol] > max_code_length) {
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max_code_length = code_lengths[symbol];
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}
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}
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if (max_code_length > MAX_ALLOWED_CODE_LENGTH) return 0;
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// Calculate code length histogram.
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for (symbol = 0; symbol < code_lengths_size; ++symbol) {
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++code_length_hist[code_lengths[symbol]];
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}
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code_length_hist[0] = 0;
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// Calculate the initial values of 'next_codes' for each code length.
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// next_codes[code_len] denotes the code to be assigned to the next symbol
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// of code length 'code_len'.
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curr_code = 0;
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next_codes[0] = -1; // Unused, as code length = 0 implies code doesn't exist.
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for (code_len = 1; code_len <= max_code_length; ++code_len) {
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curr_code = (curr_code + code_length_hist[code_len - 1]) << 1;
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next_codes[code_len] = curr_code;
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}
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// Get symbols.
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for (symbol = 0; symbol < code_lengths_size; ++symbol) {
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if (code_lengths[symbol] > 0) {
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huff_codes[symbol] = next_codes[code_lengths[symbol]]++;
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} else {
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huff_codes[symbol] = NON_EXISTENT_SYMBOL;
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}
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}
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return 1;
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}
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#ifndef USE_LUT_REVERSE_BITS
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static int ReverseBitsShort(int bits, int num_bits) {
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int retval = 0;
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int i;
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assert(num_bits <= 8); // Not a hard requirement, just for coherency.
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for (i = 0; i < num_bits; ++i) {
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retval <<= 1;
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retval |= bits & 1;
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bits >>= 1;
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}
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return retval;
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}
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#else
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static const uint8_t kReversedBits[16] = { // Pre-reversed 4-bit values.
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0x0, 0x8, 0x4, 0xc, 0x2, 0xa, 0x6, 0xe,
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0x1, 0x9, 0x5, 0xd, 0x3, 0xb, 0x7, 0xf
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};
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static int ReverseBitsShort(int bits, int num_bits) {
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const uint8_t v = (kReversedBits[bits & 0xf] << 4) | kReversedBits[bits >> 4];
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assert(num_bits <= 8);
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return v >> (8 - num_bits);
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}
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#endif
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static int TreeAddSymbol(HuffmanTree* const tree,
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int symbol, int code, int code_length) {
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int step = HUFF_LUT_BITS;
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int base_code;
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HuffmanTreeNode* node = tree->root_;
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const HuffmanTreeNode* const max_node = tree->root_ + tree->max_nodes_;
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assert(symbol == (int16_t)symbol);
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if (code_length <= HUFF_LUT_BITS) {
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int i;
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base_code = ReverseBitsShort(code, code_length);
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for (i = 0; i < (1 << (HUFF_LUT_BITS - code_length)); ++i) {
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const int idx = base_code | (i << code_length);
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tree->lut_symbol_[idx] = (int16_t)symbol;
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tree->lut_bits_[idx] = code_length;
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}
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} else {
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base_code = ReverseBitsShort((code >> (code_length - HUFF_LUT_BITS)),
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HUFF_LUT_BITS);
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}
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while (code_length-- > 0) {
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if (node >= max_node) {
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return 0;
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}
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if (NodeIsEmpty(node)) {
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if (IsFull(tree)) return 0; // error: too many symbols.
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AssignChildren(tree, node);
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} else if (!HuffmanTreeNodeIsNotLeaf(node)) {
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return 0; // leaf is already occupied.
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}
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node += node->children_ + ((code >> code_length) & 1);
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if (--step == 0) {
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tree->lut_jump_[base_code] = (int16_t)(node - tree->root_);
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}
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}
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if (NodeIsEmpty(node)) {
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node->children_ = 0; // turn newly created node into a leaf.
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} else if (HuffmanTreeNodeIsNotLeaf(node)) {
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return 0; // trying to assign a symbol to already used code.
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}
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node->symbol_ = symbol; // Add symbol in this node.
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return 1;
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}
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int VP8LHuffmanTreeBuildImplicit(HuffmanTree* const tree,
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const int* const code_lengths,
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int* const codes,
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int code_lengths_size) {
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int symbol;
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int num_symbols = 0;
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int root_symbol = 0;
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assert(tree != NULL);
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assert(code_lengths != NULL);
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// Find out number of symbols and the root symbol.
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for (symbol = 0; symbol < code_lengths_size; ++symbol) {
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if (code_lengths[symbol] > 0) {
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// Note: code length = 0 indicates non-existent symbol.
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++num_symbols;
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root_symbol = symbol;
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}
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}
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// Initialize the tree. Will fail for num_symbols = 0
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if (!TreeInit(tree, num_symbols)) return 0;
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// Build tree.
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if (num_symbols == 1) { // Trivial case.
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const int max_symbol = code_lengths_size;
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if (root_symbol < 0 || root_symbol >= max_symbol) {
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VP8LHuffmanTreeFree(tree);
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return 0;
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}
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return TreeAddSymbol(tree, root_symbol, 0, 0);
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} else { // Normal case.
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int ok = 0;
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memset(codes, 0, code_lengths_size * sizeof(*codes));
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if (!VP8LHuffmanCodeLengthsToCodes(code_lengths, code_lengths_size,
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codes)) {
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goto End;
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}
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// Add symbols one-by-one.
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for (symbol = 0; symbol < code_lengths_size; ++symbol) {
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if (code_lengths[symbol] > 0) {
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if (!TreeAddSymbol(tree, symbol, codes[symbol],
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code_lengths[symbol])) {
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goto End;
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}
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}
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}
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ok = 1;
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End:
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ok = ok && IsFull(tree);
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if (!ok) VP8LHuffmanTreeFree(tree);
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return ok;
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}
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}
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int VP8LHuffmanTreeBuildExplicit(HuffmanTree* const tree,
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const int* const code_lengths,
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const int* const codes,
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const int* const symbols, int max_symbol,
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int num_symbols) {
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int ok = 0;
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int i;
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assert(tree != NULL);
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assert(code_lengths != NULL);
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assert(codes != NULL);
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assert(symbols != NULL);
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// Initialize the tree. Will fail if num_symbols = 0.
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if (!TreeInit(tree, num_symbols)) return 0;
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// Add symbols one-by-one.
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for (i = 0; i < num_symbols; ++i) {
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if (codes[i] != NON_EXISTENT_SYMBOL) {
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if (symbols[i] < 0 || symbols[i] >= max_symbol) {
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goto End;
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}
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if (!TreeAddSymbol(tree, symbols[i], codes[i], code_lengths[i])) {
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goto End;
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}
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}
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}
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ok = 1;
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End:
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ok = ok && IsFull(tree);
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if (!ok) VP8LHuffmanTreeFree(tree);
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return ok;
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}
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