comparison: huffman/bitwriter.h
huffman/bitwriter.h
- changeset 76
- 6de6d9a64ebd
- parent 8
- 8b697d30c49f
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| 75:5f8a03274d75 | 76:6de6d9a64ebd |
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| 1 /* | |
| 2 * skulltag::BitWriter class - Enables writing arbitrary bit lengths of data. | |
| 3 * | |
| 4 * Copyright 2009 Timothy Landers | |
| 5 * email: code.vortexcortex@gmail.com | |
| 6 * | |
| 7 * Permission is hereby granted, free of charge, to any person obtaining a copy | |
| 8 * of this software and associated documentation files (the "Software"), to deal | |
| 9 * in the Software without restriction, including without limitation the rights | |
| 10 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | |
| 11 * copies of the Software, and to permit persons to whom the Software is | |
| 12 * furnished to do so, subject to the following conditions: | |
| 13 * | |
| 14 * The above copyright notice and this permission notice shall be included in | |
| 15 * all copies or substantial portions of the Software. | |
| 16 * | |
| 17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | |
| 18 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | |
| 19 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE | |
| 20 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | |
| 21 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | |
| 22 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN | |
| 23 * THE SOFTWARE. | |
| 24 */ | |
| 25 | |
| 26 #ifndef _BIT_WRITER_VERSION | |
| 27 #define _BIT_WRITER_VERSION 1 | |
| 28 | |
| 29 /** Prevents naming convention problems via encapsulation. */ | |
| 30 namespace skulltag { // scope limitation | |
| 31 | |
| 32 /** BitWriter - Allows writing of varying amounts of bits to a char buffer. <br> | |
| 33 * Very usefull for outputting variable bit length encodings such as Huffman. */ | |
| 34 | |
| 35 class BitWriter { | |
| 36 int bufferBits; /**< intermediary buffer of bits. */ | |
| 37 int bitsLeft; /**< number of bits left in the buffer. */ | |
| 38 unsigned char * currentByte; /**< position in memory the next char will be stored. */ | |
| 39 int bytesAvailable; /**< amount of available space left in the output buffer in bytes. Excludes the contents of bufferBits. */ | |
| 40 int bitsAvailable; /**< amount of available space left in the output buffer in bits. Includes the contents of bufferBits. */ | |
| 41 int maximumBytes; /**< total amount of bytes that can be written to the output buffer. */ | |
| 42 static int mask[]; /**< maps a number of bits to a bit mask containing as many bits. */ | |
| 43 static int intSize; /**< number of chars in an int. */ | |
| 44 public: | |
| 45 | |
| 46 /** Creates a new BitWriter. */ | |
| 47 BitWriter(); | |
| 48 | |
| 49 /** Creates a new BitWriter. | |
| 50 * @param output Destination that bits will be written to. | |
| 51 * @param max Maximum number of chars to output. */ | |
| 52 BitWriter( unsigned char * const output, int const &max ); | |
| 53 | |
| 54 /** Appends a char worth of bits to the buffer. | |
| 55 * @param bits the bits to append. | |
| 56 * @return true if successful, false if an error occurs. */ | |
| 57 bool put( unsigned char const &bits ); | |
| 58 | |
| 59 /** Appends a short worth of bits to the buffer. | |
| 60 * @param bits the bits to append. | |
| 61 * @return true if successful, false otherwise. | |
| 62 * @return true if successful, false if an error occurs. */ | |
| 63 bool put( short const &bits ); | |
| 64 | |
| 65 /** Appends an int worth of bits to the buffer. | |
| 66 * @param bits the bits to append. | |
| 67 * @return true if successful, false if an error occurs. */ | |
| 68 bool put( int const &bits ); | |
| 69 | |
| 70 /** Appends a specified number of bits from an int to the buffer. | |
| 71 * @param bits the bits to append. <br> | |
| 72 * The bits should be stored in the least significant portion of the int. | |
| 73 * @param count the number of bits to append. | |
| 74 * @return true if successful, false if an error occurs. */ | |
| 75 bool put( int const &bits, int count ); | |
| 76 | |
| 77 /** Appends multiple chars from a buffer to this BitWriter. | |
| 78 * @param inputBuffer pointer to char data | |
| 79 * @param count number of chars to read | |
| 80 * @return true if successful, false if an error occurs. */ | |
| 81 bool put( unsigned char const * const inputBuffer, int count ); | |
| 82 | |
| 83 /** Sets the output buffer that bytes will be written to. | |
| 84 * @param output Destination that bits will be written to. | |
| 85 * @param max Maximum number of chars to output. | |
| 86 * @return true if successful, false if an error occurs. */ | |
| 87 bool outputBuffer( unsigned char * const output, int const &max ); | |
| 88 | |
| 89 /** Writes any full chars of data stored in this BitWriter to the output char buffer. | |
| 90 * @return true if successful, false if an error occurs. */ | |
| 91 bool flush(); | |
| 92 | |
| 93 /** Flushes this BitWriter then outputs any partial chars by padding them with zeros. <br> | |
| 94 * After calling finish() all other calls to update the BitWriter will fail until a buffer is set via outputBuffer(). | |
| 95 * @param bytesWritten out: the number of bytes written to the output buffer. | |
| 96 * @param paddingBits out: the number of padding bits used in the final byte of output. | |
| 97 * @return true if successful, false if an error occurs. */ | |
| 98 bool finish( int &bytesWritten, int &paddingBits ); | |
| 99 | |
| 100 private: | |
| 101 | |
| 102 /** Initializes this BitWriter. */ | |
| 103 void init(); | |
| 104 | |
| 105 }; | |
| 106 | |
| 107 } | |
| 108 #endif | |
| 109 |
