blob: ca547709fec7bdebcea2d14541de0b615e3f5204
| 1 | /* ***** BEGIN LICENSE BLOCK ***** |
| 2 | * Source last modified: $Id: huffman.c,v 1.6 2005/04/27 19:20:50 hubbe Exp $ |
| 3 | * |
| 4 | * REALNETWORKS CONFIDENTIAL--NOT FOR DISTRIBUTION IN SOURCE CODE FORM |
| 5 | * Portions Copyright (c) 1995-2002 RealNetworks, Inc. |
| 6 | * All Rights Reserved. |
| 7 | * |
| 8 | * The contents of this file, and the files included with this file, |
| 9 | * are subject to the current version of the Real Format Source Code |
| 10 | * Porting and Optimization License, available at |
| 11 | * https://helixcommunity.org/2005/license/realformatsource (unless |
| 12 | * RealNetworks otherwise expressly agrees in writing that you are |
| 13 | * subject to a different license). You may also obtain the license |
| 14 | * terms directly from RealNetworks. You may not use this file except |
| 15 | * in compliance with the Real Format Source Code Porting and |
| 16 | * Optimization License. There are no redistribution rights for the |
| 17 | * source code of this file. Please see the Real Format Source Code |
| 18 | * Porting and Optimization License for the rights, obligations and |
| 19 | * limitations governing use of the contents of the file. |
| 20 | * |
| 21 | * RealNetworks is the developer of the Original Code and owns the |
| 22 | * copyrights in the portions it created. |
| 23 | * |
| 24 | * This file, and the files included with this file, is distributed and |
| 25 | * made available on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, |
| 26 | * EITHER EXPRESS OR IMPLIED, AND REALNETWORKS HEREBY DISCLAIMS ALL |
| 27 | * SUCH WARRANTIES, INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF |
| 28 | * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT |
| 29 | * OR NON-INFRINGEMENT. |
| 30 | * |
| 31 | * Technology Compatibility Kit Test Suite(s) Location: |
| 32 | * https://rarvcode-tck.helixcommunity.org |
| 33 | * |
| 34 | * Contributor(s): |
| 35 | * |
| 36 | * ***** END LICENSE BLOCK ***** */ |
| 37 | |
| 38 | /************************************************************************************** |
| 39 | * Fixed-point RealAudio 8 decoder |
| 40 | * Jon Recker (jrecker@real.com), Ken Cooke (kenc@real.com) |
| 41 | * October 2003 |
| 42 | * |
| 43 | * huffman.c - Wolfgang's implementation of Moffat-Turpin style Huffman decoder |
| 44 | **************************************************************************************/ |
| 45 | |
| 46 | #include "coder.h" |
| 47 | |
| 48 | /************************************************************************************** |
| 49 | * Function: DecodeHuffmanScalar |
| 50 | * |
| 51 | * Description: decode one Huffman symbol from bitstream |
| 52 | * |
| 53 | * Inputs: pointers to table and info |
| 54 | * right-aligned bit buffer with MAX_HUFF_BITS bits |
| 55 | * pointer to receive decoded symbol |
| 56 | * |
| 57 | * Outputs: decoded symbol |
| 58 | * |
| 59 | * Return: number of bits in symbol |
| 60 | **************************************************************************************/ |
| 61 | int DecodeHuffmanScalar(const unsigned short *huffTab, const HuffInfo *huffTabInfo, int bitBuf, int *val) |
| 62 | { |
| 63 | const unsigned char *countPtr; |
| 64 | unsigned int cache, total, count, t; |
| 65 | const unsigned short *map; |
| 66 | |
| 67 | map = huffTab + huffTabInfo->offset; |
| 68 | countPtr = huffTabInfo->count; |
| 69 | cache = (unsigned int)(bitBuf << (17 - MAX_HUFF_BITS)); |
| 70 | |
| 71 | total = 0; |
| 72 | count = *countPtr++; |
| 73 | t = count << 16; |
| 74 | |
| 75 | while (cache >= t) { |
| 76 | cache -= t; |
| 77 | cache <<= 1; |
| 78 | total += count; |
| 79 | count = *countPtr++; |
| 80 | t = count << 16; |
| 81 | } |
| 82 | *val = map[total + (cache >> 16)]; |
| 83 | |
| 84 | /* return number of bits in symbol */ |
| 85 | return (countPtr - huffTabInfo->count); |
| 86 | } |
| 87 |