--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/huffman/bitreader.cpp Fri May 15 20:13:36 2015 +0300
@@ -0,0 +1,144 @@
+/*
+ * skulltag::BitReader class - Allows reading arbitrary bit lengths of data.
+ * Version 1 - Revsion 0
+ *
+ * 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 "bitreader.h"
+/** Prevents naming convention problems via encapsulation. */
+namespace skulltag {
+ // BitReader class implementation
+
+ int BitReader::intBitSize = 0;
+ int BitReader::intSize = 0;
+ int BitReader::mask[32] = {0};
+
+ /** Creates a new BitReader. */
+ BitReader::BitReader(){
+ init();
+ }
+
+ /** Creates a new BitReader.
+ * @param input Source of data that bits will be read from.
+ * @param max Maximum number of chars to read. */
+ BitReader::BitReader( unsigned char const * input, int const &max ){
+ inputBuffer( input, max );
+ }
+
+ /** Sets the input buffer that bytes will be read from.
+ * @param input Source of data that bits will be read from.
+ * @param max Maximum number of chars to input.
+ * @return true if successful, false if an error occurs. */
+ bool BitReader::inputBuffer( unsigned char const * input, int const &max ){
+ init(); // zero the vars.
+ currentByte = input;
+ if ( input == 0 ) return false;
+ if ( max < 1 ) return false;
+ bytesAvailable = max;
+ bitsAvailable = max << 3;
+ maximumBytes = max;
+ return true;
+ }
+
+ /** Initializes this BitReader */
+ void BitReader::init(){
+ // initialize static variables if not initialized yet.
+ if ( intSize == 0 ){
+ intSize = sizeof maximumBytes;
+ mask[0] = 0;
+
+ // fill mask such that m = { 0, 1, 3, 7, 15, etc. }
+ for ( int i = 1; i < 32; i++ ) mask[i] = (mask[i-1] << 1) | 1;
+
+ intBitSize = intSize << 3;
+ }
+
+ // initialize member variables.
+ bitsAvailable = 0;
+ bytesAvailable = 0;
+ bufferBits = 0;
+ currentByte = 0;
+ maximumBytes = 0;
+ bitsUsed = 0;
+ }
+
+ /** Fills the internal bit buffer.
+ * @return true if successful, false if an error occurs. */
+ bool BitReader::fill(){
+ if ( (currentByte == 0) || (bytesAvailable <= 0) ) return false;
+
+ // while there's at least one octet free in the buffer, and one byte to read.
+ while ( (bitsUsed < (intBitSize - 8)) && (bytesAvailable > 0) ){
+
+ // put a byte into the bottom end of the buffer.
+ bufferBits |= (*currentByte & mask[8]) << (intBitSize - bitsUsed - 8);
+
+ // Set variables to reflect the change.
+ currentByte++;
+ bytesAvailable--;
+ bitsUsed += 8;
+ }
+ return true;
+ }
+
+ /** Fetches a specified number of bits and stores them in an int.
+ * @param bits destination of the retrieved bits. <br>
+ * The bits will be stored in the least significant portion of the int.
+ * @param count the number of bits to fetch.
+ * @return the number of bits read -- may not be equal to the amount requested. */
+ int BitReader::get( int &bits, int const &count ){
+ bits = 0;
+ // Requesting more bits than are available.
+ if ( count > bitsAvailable ) return 0;
+ if ( (count > bitsUsed) && (!fill()) ) return 0;
+ bits = (bufferBits >> (intBitSize - count)) & mask[count];
+ // lesser of bits in buffer or requested bits.
+ int got = (bitsUsed < count) ? bitsUsed : count;
+ // get as many bits from the buffer as we can.
+ if ( got > 0 ){
+ bufferBits <<= got;
+ bitsUsed -= got;
+ bitsAvailable -= got;
+ }
+ // if more bits are requested.
+ if ( count > got ){
+ if (!fill()) {
+ bits = (bits >> (count - got)) & mask[count - got];
+ return got;
+ }
+ got = count - got;
+ // avoid reading more bits than available.
+ if ( got <= bitsAvailable ){
+ bits |= (bufferBits >> (intBitSize - got)) & mask[got];
+ bufferBits <<= got;
+ bitsUsed -= got;
+ bitsAvailable -= got;
+ }
+ }
+ return count;
+ }
+
+ /** @return Amount of bits that can be read from this BitReader. */
+ int BitReader::availableBits(){ return bitsAvailable; }
+
+} // end namespace skulltag