--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/sources/huffman/huffcodec.cpp Thu Dec 11 07:18:11 2014 +0200
@@ -0,0 +1,329 @@
+/*
+ * skulltag::HuffmanCodec class - Huffman encoder and decoder.
+ *
+ * Copyright 2009 Timothy Landers
+ * email: code.vortexcortex@gmail.com
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "huffcodec.h"
+
+/** Prevents naming convention problems via encapsulation. */
+namespace skulltag {
+
+// HuffmanCodec Implementation
+
+ /** Reverses the order of bits in a byte.
+ * EG: The statement <code>reverseMap[0xAF] == 0xF5</code> is <code>true</code>. <br>
+ * The index <code>10101111</code> stores the reverse value: <code>11110101</code>. <br>
+ * Note: One array lookup is much faster than Eight bit manipulating loop iterations. */
+ unsigned char const HuffmanCodec::reverseMap[] = {
+ 0,128, 64,192, 32,160, 96,224, 16,144, 80,208, 48,176,112,240,
+ 8,136, 72,200, 40,168,104,232, 24,152, 88,216, 56,184,120,248,
+ 4,132, 68,196, 36,164,100,228, 20,148, 84,212, 52,180,116,244,
+ 12,140, 76,204, 44,172,108,236, 28,156, 92,220, 60,188,124,252,
+ 2,130, 66,194, 34,162, 98,226, 18,146, 82,210, 50,178,114,242,
+ 10,138, 74,202, 42,170,106,234, 26,154, 90,218, 58,186,122,250,
+ 6,134, 70,198, 38,166,102,230, 22,150, 86,214, 54,182,118,246,
+ 14,142, 78,206, 46,174,110,238, 30,158, 94,222, 62,190,126,254,
+ 1,129, 65,193, 33,161, 97,225, 17,145, 81,209, 49,177,113,241,
+ 9,137, 73,201, 41,169,105,233, 25,153, 89,217, 57,185,121,249,
+ 5,133, 69,197, 37,165,101,229, 21,149, 85,213, 53,181,117,245,
+ 13,141, 77,205, 45,173,109,237, 29,157, 93,221, 61,189,125,253,
+ 3,131, 67,195, 35,163, 99,227, 19,147, 83,211, 51,179,115,243,
+ 11,139, 75,203, 43,171,107,235, 27,155, 91,219, 59,187,123,251,
+ 7,135, 71,199, 39,167,103,231, 23,151, 87,215, 55,183,119,247,
+ 15,143, 79,207, 47,175,111,239, 31,159, 95,223, 63,191,127,255
+ };
+
+ /** Creates a new HuffmanCodec
+ * @param treeData char array containing the tree data to use.
+ * @param dataLength number of chars in treeData. */
+ HuffmanCodec::HuffmanCodec(
+ unsigned char const * const treeData,
+ int dataLength
+ ) : Codec() {
+ init();
+ // init code table (256 pointers to Huffman Leaf Nodes.)
+ codeTable = new HuffmanNode*[256];
+ for (int i = 0; i < 256; i++) codeTable[i] = 0;
+ // build root node
+ root = new HuffmanNode;
+ root->bitCount = 0;
+ root->code = 0;
+ root->value = -1;
+ // recursive Huffman tree builder.
+ buildTree( root, treeData, 0, dataLength, codeTable, 256 );
+ huffResourceOwner = true;
+ }
+
+
+ /** Creates a new HuffmanCodec that uses the specified Huffman resources.
+ * @param treeRootNode The root node of a valid huffman tree.
+ * @param leafCodeTable A code lookup table where references to HuffmanNodes are stored with their array index equal to their value.
+ * Note: The tree nodes will not be released upon destruction of this HuffmanCodec. */
+ HuffmanCodec::HuffmanCodec(
+ HuffmanNode * treeRootNode,
+ HuffmanNode ** leafCodeTable
+ ){
+ init();
+ // assign values -- no table building or allocations.
+ root = treeRootNode;
+ codeTable = leafCodeTable;
+ huffResourceOwner = false;
+ }
+
+ /** Checks the ownership state of this HuffmanCodec's resources.
+ * @return true if the tree & code table will be released upon destruction of this HuffmanCodec. <br>
+ * A false return value means this HuffmanCodec is not responsible for deleting its resources. */
+ bool HuffmanCodec::huffmanResourceOwner(){
+ return huffResourceOwner;
+ }
+
+ /** Perform initialization procedures common to all constructors. */
+ void HuffmanCodec::init(){
+ writer = new BitWriter();
+ reverseBits = false;
+ expandable = true;
+ huffResourceOwner = false;
+ }
+
+ /** Increases a codeLength up to the longest Huffman code bit length found in the node or any of its children. <br>
+ * Set to Zero before calling to determine maximum code bit length.
+ * @param node in: The node to begin searching at.
+ * @param codeLength out: Variable to hold the longest code bit length found. */
+ void HuffmanCodec::maxCodeLength( HuffmanNode const * const node, int &codeLength ){
+ // [TL] We must walk each tree node since the codeTable may not contain the set of all leaf nodes.
+ // bail on NULL node (tree is corrupt).
+ if ( node == 0) return;
+ // Recurse across children if they exist.
+ if ( node->branch != 0 ){
+ maxCodeLength( &(node->branch[0]), codeLength );
+ maxCodeLength( &(node->branch[1]), codeLength );
+ } else if ( codeLength < node->bitCount ){
+ // set codeLength if it's smaller than current node's bitCount.
+ codeLength = node->bitCount;
+ }
+ }
+
+ /** Decreases a codeLength to the shortest Huffman code bit length found in the node or any of its children. <br>
+ * Set to Zero before calling to determine minimum code bit length.
+ * @param node in: The node to begin searching at.
+ * @param codeLength out: Variable to hold the longest code bit length found. */
+ void HuffmanCodec::minCodeLength( HuffmanNode const * const node, int &codeLength ){
+ /* [TL] Do not optimize under the assumption child nodes will have longer code Lengths!
+ * Future subclasses may have trees that diverge from Huffman specs. */
+ // bail on NULL node (tree is corrupt).
+ if ( node == 0 ) return;
+ // Recurse across children if they exist.
+ if ( node->branch != 0 ){
+ minCodeLength( &(node->branch[0]), codeLength );
+ minCodeLength( &(node->branch[1]), codeLength );
+ } else if ( (codeLength > node->bitCount) || (codeLength == 0) ) {
+ // set codeLength if it's Zero or larger than current node's bitCount.
+ codeLength = node->bitCount;
+ }
+ }
+
+ /** Recursively builds a Huffman Tree. <br>
+ * The initial root node should have the following field values: <br>
+ * <pre>
+ * bitCount : 0
+ * code : 0
+ * value : -1
+ * branch : 0 (NULL)
+ * </pre>
+ * @param node in/out: branch node of the Huffman Tree.
+ * @param treeData in: char array containing the Huffman Tree's byte representation.
+ * @param index in: Current array element to read the next tree node from.
+ * @param dataLength in: Length of treeData
+ * @param codeTable in/out: array of pointers to HuffmanNode structs.
+ * @param tableLength in: maximum index allowed in the codeTable.
+ * @return the next index to read from or -1 if an error occurs.
+ * */
+ int HuffmanCodec::buildTree(
+ HuffmanNode * node,
+ unsigned char const * const treeData,
+ int index,
+ int dataLength,
+ HuffmanNode ** const &codeTable,
+ int tableLength
+ ){
+ if ( index >= dataLength ) return -1;
+ // Read the branch description bit field
+ int desc = treeData[index];
+ index++;
+
+ // Create the array that will hold L/R child nodes of this branch.
+ node->branch = new HuffmanNode[2];
+
+ // Read the child Nodes for this branch.
+ for ( int i = 0; i < 2; i++ ){
+ // Increase bit count, and update huffman code to match the node's tree position.
+ node->branch[i].bitCount = node->bitCount + 1;
+ node->branch[i].code = (node->code << 1) | i; // appends a 0 or 1 depending on L/R branch.
+ node->branch[i].value = -1; // default value.
+
+ // Test a bit from the branch description (least significant bit == left)
+ if ( (desc & (1 << i)) == 0 ){
+ // Child node is a branch; Recurse.
+ if ( (index = buildTree( &(node->branch[i]), treeData, index, dataLength, codeTable, tableLength )) < 0 ) return -1;
+ // This means the entire left sub tree will be read before the right sub tree gets read.
+ } else {
+ // Read leaf value and map its value/index in the nodes array.
+ if ( index >= dataLength ) return -1;
+ // set the nodes huffman code values.
+ node->branch[i].code = (node->code << 1) | i;
+ node->branch[i].bitCount = node->bitCount+1;
+ node->branch[i].value = treeData[index] & 0xff;
+ // NULL the child node's branch to mark it as a leaf.
+ node->branch[i].branch = 0;
+ // buffer overflow check.
+ if ( (node->branch[i].value >= 0) && (node->branch[i].value <= tableLength ) )
+ // store a pointer to the leaf node into the code table at the location of its byte value.
+ codeTable[ node->branch[i].value ] = &node->branch[i];
+ index++;
+ }
+ }
+
+ return index;
+ }
+
+ /** Decodes data read from an input buffer and stores the result in the output buffer.
+ * @return number of bytes stored in the output buffer or -1 if an error occurs while encoding. */
+ int HuffmanCodec::encode(
+ unsigned char const * const input, /**< in: pointer to the first byte to encode. */
+ unsigned char * const output, /**< out: pointer to an output buffer to store data. */
+ int const &inLength, /**< in: number of bytes of input buffer to encoded. */
+ int const &outLength /**< in: maximum length of data to output. */
+ ) const {
+ // setup the bit buffer to output. if not expandable Limit output to input length.
+ if ( expandable ) writer->outputBuffer( output, outLength );
+ else writer->outputBuffer( output, ((inLength + 1) < outLength) ? inLength + 1 : outLength );
+
+ writer->put( (unsigned char)0 ); // reserve place for padding signal.
+
+ HuffmanNode * node; // temp ptr cache;
+ for ( int i = 0; i < inLength; i++ ){
+ node = codeTable[ 0xff & input[i] ]; //lookup node
+ // Put the huffman code into the bit buffer and bail if error occurs.
+ if ( !writer->put( node->code, node->bitCount ) ) return -1;
+ }
+ int bytesWritten, padding;
+ if ( writer->finish( bytesWritten, padding ) ){
+ // write padding signal byte to begining of stream.
+ output[0] = (unsigned char)padding;
+ } else return -1;
+
+ // Reverse the bit order of each byte (Old Huffman Compatibility Mode)
+ if ( reverseBits ) for ( int i = 1; i < bytesWritten; i++ ){
+ output[i] = reverseMap[ 0xff & output[i] ];
+ }
+
+ return bytesWritten;
+ } // end function encode
+
+ /** Decodes data read from an input buffer and stores the result in the output buffer.
+ * @return number of bytes stored in the output buffer or -1 if an error occurs while decoding. */
+ int HuffmanCodec::decode(
+ unsigned char const * const input, /**< in: pointer to data that needs decoding. */
+ unsigned char * const output, /**< out: pointer to output buffer to store decoded data. */
+ int const &inLength, /**< in: number of bytes of input buffer to read. */
+ int const &outLength /**< in: maximum length of data to output. */
+ ){
+ if ( inLength < 1 ) return 0;
+ int bitsAvailable = ((inLength-1) << 3) - (0xff & input[0]);
+ int rIndex = 1; // read index of input buffer.
+ int wIndex = 0; // write index of output buffer.
+ char byte = 0; // bits of the current byte.
+ int bitsLeft = 0; // bits left in byte;
+
+ HuffmanNode * node = root;
+
+ // Traverse the tree, output values.
+ while ( (bitsAvailable > 0) && (node != 0) ){
+
+ // Get the next byte if we've run out.
+ if ( bitsLeft <= 0 ){
+ byte = input[rIndex++];
+ if ( reverseBits ) byte = reverseMap[ 0xff & byte ];
+ bitsLeft = 8;
+ }
+
+ // Traverse the tree according to the most significant bit.
+ node = &(node->branch[ ((byte >> 7) & 0x01) ]);
+
+ // Is the node Non NULL, and a leaf?
+ if ( (node != 0) && (node->branch == 0) ){
+ // buffer overflow prevention
+ if ( wIndex >= outLength ) return wIndex;
+ // Output leaf node's value and restart traversal at root node.
+ output[ wIndex++ ] = (unsigned char)(node->value & 0xff);
+ node = root;
+ }
+
+ byte <<= 1; // cue up the next bit
+ bitsLeft--; // use up one bit of byte
+ bitsAvailable--; // decrement total bits left
+ }
+
+ return wIndex;
+ } // end function decode
+
+ /** Deletes all sub nodes of a HuffmanNode by traversing and deleting its child nodes.
+ * @param treeNode pointer to a HuffmanNode whos children will be deleted. */
+ void HuffmanCodec::deleteTree( HuffmanNode * treeNode ){
+ if ( treeNode == 0 ) return;
+ if ( treeNode->branch != 0 ){
+ deleteTree( &(treeNode->branch[0]) );
+ deleteTree( &(treeNode->branch[1]) );
+ delete treeNode->branch;
+ }
+ }
+
+ /** Destructor - frees resources. */
+ HuffmanCodec::~HuffmanCodec() {
+ delete writer;
+ //check for resource ownership before deletion
+ if ( huffmanResourceOwner() ){
+ delete codeTable;
+ deleteTree( root );
+ delete root;
+ }
+ }
+
+ /** Enables or Disables backwards bit ordering of bytes.
+ * @param backwards "true" enables reversed bit order bytes, "false" uses standard byte bit ordering. */
+ void HuffmanCodec::reversedBytes( bool backwards ){ reverseBits = backwards; }
+
+ /** Check the state of backwards bit ordering for bytes.
+ * @return true: bits within bytes are reversed. false: bits within bytes are normal. */
+ bool HuffmanCodec::reversedBytes(){ return reverseBits; }
+
+ /** Enable or Disable data expansion during encoding.
+ * @param expandingAllowed "true" allows encoding to expand data. "false" causes failure upon expansion. */
+ void HuffmanCodec::allowExpansion( bool expandingAllowed ){ expandable = expandingAllowed; }
+
+ /** Check the state of data expandability.
+ * @return true: data expansion is allowed. false: data is not allowed to expand. */
+ bool HuffmanCodec::allowExpansion(){ return expandable; }
+
+
+}; // end namespace skulltag