diff -r 5f8a03274d75 -r 6de6d9a64ebd huffman/bitwriter.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/huffman/bitwriter.cpp	Fri May 15 20:13:36 2015 +0300
@@ -0,0 +1,271 @@
+/*
+ * skulltag::BitWriter class - Enables writing arbitrary bit lengths of data.
+ *
+ * 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 "bitwriter.h"
+
+/* The internal buffer of bits is an int which is initiallized to zero.
+ * The Bit Buffer: [00000000000000000000000000000000] - 0 bits stored.
+ *
+ * Bits stored in the bit buffer occupy the most significant bits available.
+ * When bits are stored their order is preserved.
+ * Storing the 5 bits 01011 into the bit buffer would result in:
+ * The Bit Buffer: [01011000000000000000000000000000] - 5 bits stored.
+ *
+ * Additionally storing 0x12f3 (13 bits) would result in:
+ * The Bit Buffer: [01011100101111001100000000000000] - 18 bits stored.
+ *
+ * Data is stored via any of the put(...) functions.
+ *
+ * To retrieve bytes (chars) of data from the bit buffer and empty the bit buffer: flush();
+ * Flushing the bit buffer takes groups of 8 bits (octets) and stores them in the
+ * output buffer at the current byte position. Calling flush() would cause output
+ * to receive 2 bytes (0x5c, 0xbc) == (01011100, 10111100) and the remaining bits would
+ * be moved to the most significant bit positions.
+ * The Bit Buffer: [11000000000000000000000000000000] - 2 bits stored.
+ * Note: The empty bits of the bit buffer must be zero to avoid additional masking operations.
+ * flush() is called automatically if the bit buffer is too full during a call to put(...)
+ *
+ * When the bit storage operation is complete call finish(...).  Finish will flush as many full
+ * bytes of data into the output buffer as possible, the remaining bits will be padded out
+ * to a full octet with zeros (on their less significant side), then written to the output
+ * buffer. finish( bytesStored, padding ) passes by reference the number of bytes stored
+ * and number of padding bits added (0 to 7) to the last stored byte.
+ *
+ * Bits are not added one at a time, they are masked, shifted and bitwise OR'ed into
+ * the buffer in as large a group as possible. This allows the BitWriter to add multiple bits in a single
+ * operation instead of calling a function for each 1 bit added.
+ *
+ * Normal usage:
+ *
+ * char * dataArray = new char[ max_output_size ];
+ * BitWriter * buffer = new BitWriter( dataArray, max_output_size );
+ * ...
+ * // various calls to put(...);
+ * ...
+ * int numBytesOutput, paddedBits;
+ * buffer->finish( numBytesOutput, paddedBits );
+ * ...
+ * // do something with dataArray
+ * ...
+ * delete buffer;
+ * delete dataArray;
+ *
+ * */
+
+/** Prevents naming convention problems via encapsulation. */
+namespace skulltag {
+
+	// Static variable initially set to zero as a signal for init()
+	int BitWriter::intSize = 0;
+	int BitWriter::mask[32];
+
+	/** Initializes this BitWriter. */
+	void BitWriter::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;
+		}
+
+		// initialize member variables.
+		bitsAvailable =		0;
+		bytesAvailable =	0;
+		bufferBits =		0;
+		currentByte =		0;
+		maximumBytes =		0;
+		bitsLeft =			intSize << 3;
+	}
+
+	/** Creates a new BitWriter. */
+	BitWriter::BitWriter(){
+		init();
+	}
+
+	/** Creates a new BitWriter.
+	 * @param output	Destination that bits will be written to.
+	 * @param max		Maximum number of chars to output. */
+	BitWriter::BitWriter( unsigned char * const output, int const &max ){
+		outputBuffer( output, max );
+	}
+
+	/** Sets the output buffer that bytes will be written to.
+	 * @param output	Destination that bits will be written to.
+	 * @param max		Maximum number of chars to output.
+	 * @return true if successful, false otherwise. */
+	bool BitWriter::outputBuffer( unsigned char * const output, int const &max ){
+		init(); // zero the vars.
+		currentByte = output;
+		if ( output == 0 ) return false;
+		if ( max < 1 ) return false;
+		bytesAvailable = max;
+		bitsAvailable = max << 3;
+		maximumBytes = max;
+		return true;
+	}
+
+	/** Appends a char worth of bits to the buffer.
+	 * @param bits 		the bits to append.
+	 * @return true if successful, false otherwise. */
+	bool BitWriter::put( unsigned char const &bits ){
+		return put( (int)bits, 8 );
+	}
+
+	/** Appends a short worth of bits to the buffer.
+	 * @param bits 		the bits to append.
+	 * @return true if successful, false otherwise. */
+	bool BitWriter::put( short const &bits ){
+		static int shortBitSize = (sizeof bits) << 3;
+		return put( (int)bits, shortBitSize );
+	}
+	/** Appends an int worth of bits to the buffer.
+	 * @param bits 		the bits to append.
+	 * @return true if successful, false otherwise. */
+	bool BitWriter::put( int const &bits ){
+		static int intBitSize = intSize << 3;
+		return put( bits, intBitSize);
+	}
+
+	/** Appends multiple chars from a buffer to this BitWriter.
+	 * @param inputBuffer 		pointer to char data
+	 * @param count				number of chars to read
+	 * @return true if successful, false otherwise. */
+	bool BitWriter::put( unsigned char const * const inputBuffer, int count ){
+		int i = 0;
+
+		// Read in 4 bytes at a time and send all at once to the bit buffer.
+		while ( (i + 3) < count ){
+			if ( !put(
+				((int)inputBuffer[ i ]	<<	24) |
+				((int)inputBuffer[i+1]	<<	16) |
+				((int)inputBuffer[i+2]	<<	 8) |
+				 (int)inputBuffer[i+3],		32
+			) ) return false;
+			i+=4;
+		}
+
+		// If any bytes remain, output them one at a time.
+		while ( i < count ){
+			if ( !put( (int)inputBuffer[ i ], 8 ) ) return false;
+			i++;
+		}
+
+		return true;
+	}
+
+	/** Appends a specified number of bits from an int to the buffer.
+	 * @param bits 		the bits to append. <br>
+	 *		The bits should be stored in the least significant portion of the int.
+	 * @param count		the number of bits to append.
+	 * @return true if successful, false otherwise. */
+	bool BitWriter::put( int const &bits, int count ){
+		if ( count > bitsAvailable ) return false;
+		if ( (bitsLeft < 1) && (!flush()) ) return false;
+		if ( count > bitsLeft ){
+			// not enough space in buffer, fill buffer with top end of input bits then flush.
+			bufferBits |= mask[bitsLeft] & (bits >> (count - bitsLeft));
+			count -= bitsLeft;
+			bitsAvailable -= bitsLeft;
+			bitsLeft = 0;
+
+			// Buffer's full, needs flushing.
+			if (!flush()) return false;
+		}
+
+		// if there are still bits of input...
+		if ( count > 0 ){
+
+			// shift the input bits up to the end of the bit buffer.
+			bufferBits |= (mask[count] & bits) << (bitsLeft - count);
+			bitsAvailable -= count;
+			bitsLeft -= count;
+		}
+		return true;
+	}
+
+	/** Writes any full chars of data stored in this BitWriter to the output char buffer.
+	 * @return true if successful, false if an error occurs. */
+	bool BitWriter::flush(){
+		// static var to hold how many bits are in an int.
+		static int intBitSize = intSize << 3;
+		if ( currentByte == 0 ) return false;
+		int numBits = intBitSize - bitsLeft;
+
+		// while there's at least one octet of data in the buffer.
+		while ( numBits > 7 ){
+
+			// fail if no bytes can be written.
+			if ( bytesAvailable <= 0 ) return false;
+
+			// get a byte off the top end of the buffer.
+			*currentByte = (bufferBits >> (intBitSize - 8)) & mask[8];
+
+			// Set variables to reflect the change.
+			currentByte++;
+			bytesAvailable--;
+			bufferBits = bufferBits << 8;
+			bitsLeft += 8;
+			numBits -= 8;
+		}
+		return true;
+	}
+
+	/** Flushes this BitWriter then outputs any partial chars by padding them with zeros. <br>
+	 * After calling finish() all other calls to update the BitWriter will fail until a buffer is set via outputBuffer().
+	 * @param bytesWritten 	out: the number of bytes written to the output buffer.
+	 * @param paddingBits	out: the number of padding bits used in the final byte of output.
+	 * @return true if successful, false if an error occurs. */
+	bool BitWriter::finish( int &bytesWritten, int &paddingBits ){
+		static int intBitSize = intSize << 3;
+		// set meaningful return values even if flush() fails.
+		bytesWritten = maximumBytes - bytesAvailable;
+		paddingBits = 0;
+		if ( flush() ){
+			// use a temp var to avoid setting paddingBits to invalid value on failure.
+			int pad = (8 - (intBitSize - bitsLeft)) & 7;
+			if ( pad > 0 ){
+				// all empty bits should be zero. Artificially extend by the number of bits needed.
+				bitsLeft -= pad;
+				if ( !flush() ){
+					// Prevent futher use even on failure.
+					init();
+					return false;
+				}
+				// return the temp bit padding value.
+				paddingBits = pad;
+			}
+			bytesWritten = maximumBytes - bytesAvailable;
+			init(); // set initial state -- no further writing can occur.
+			return true;
+		}
+		// Prevents futher use even on failure.
+		init();
+		return false;
+	}
+
+}