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1 /*
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2 * SDL_sound -- An abstract sound format decoding API.
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3 * Copyright (C) 2001 Ryan C. Gordon.
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4 *
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5 * This library is free software; you can redistribute it and/or
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6 * modify it under the terms of the GNU Lesser General Public
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7 * License as published by the Free Software Foundation; either
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8 * version 2.1 of the License, or (at your option) any later version.
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9 *
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10 * This library is distributed in the hope that it will be useful,
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11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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13 * Lesser General Public License for more details.
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14 *
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15 * You should have received a copy of the GNU Lesser General Public
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16 * License along with this library; if not, write to the Free Software
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17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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18 */
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19
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20 /*
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21 * Shorten decoder for SDL_sound.
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22 *
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23 * This driver handles Shorten-compressed waveforms. Despite the fact that
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24 * SHNs are generally used in online trading communities, they tend to be
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25 * much bigger than MP3s. If an MP3 crunches the waveform to 10-20 percent
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26 * of its original size, SHNs only go to about 50-60%. Why do the Phish fans
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27 * of the world use this format then? Rabid music traders appreciate the
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28 * sound quality; SHNs, unlike MP3s, do not throw away any part of the
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29 * waveform. Yes, there are people that notice this, and further more, they
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30 * demand it...and if they can't get a good transfer of those larger files
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31 * over the 'net, they haven't underestimated the bandwidth of CDs travelling
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32 * the world through the postal system.
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33 *
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34 * Shorten homepage: http://www.softsound.com/Shorten.html
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35 *
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36 * The Shorten format was gleaned from the shorten codebase, by Tony
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37 * Robinson and SoftSound Limited, but none of their code was used here.
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38 *
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39 * Please see the file LICENSE in the source's root directory.
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40 *
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41 * This file written by Ryan C. Gordon. (icculus@clutteredmind.org)
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42 */
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43
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44 #if (defined SOUND_SUPPORTS_SHN)
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45
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46 #include <stdio.h>
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47 #include <stdlib.h>
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48 #include <string.h>
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49 #include <assert.h>
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50 #include "SDL_sound.h"
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51
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52 #define __SDL_SOUND_INTERNAL__
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53 #include "SDL_sound_internal.h"
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54
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55 static int SHN_init(void);
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56 static void SHN_quit(void);
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57 static int SHN_open(Sound_Sample *sample, const char *ext);
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58 static void SHN_close(Sound_Sample *sample);
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59 static Uint32 SHN_read(Sound_Sample *sample);
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60
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61 const Sound_DecoderFunctions __Sound_DecoderFunctions_SHN =
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62 {
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63 {
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64 "SHN",
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65 "Shorten-compressed audio data",
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66 "Ryan C. Gordon <icculus@clutteredmind.org>",
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67 "http://www.icculus.org/SDL_sound/"
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68 },
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69
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70 SHN_init, /* init() method */
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71 SHN_quit, /* quit() method */
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72 SHN_open, /* open() method */
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73 SHN_close, /* close() method */
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74 SHN_read /* read() method */
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75 };
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76
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77
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78 static int SHN_init(void)
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79 {
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80 return(1); /* initialization always successful. */
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81 } /* SHN_init */
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82
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83
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84 static void SHN_quit(void)
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85 {
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86 /* it's a no-op. */
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87 } /* SHN_quit */
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88
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89
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90 static Uint32 mask_table[] =
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91 {
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92 0x00000000, 0x00000001, 0x00000003, 0x00000007, 0x0000000F, 0x0000001F,
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93 0x0000003F, 0x0000007F, 0x000000FF, 0x000001FF, 0x000003FF, 0x000007FF,
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94 0x00000FFF, 0x00001FFF, 0x00003FFF, 0x00007FFF, 0x0000FFFF, 0x0001FFFF,
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95 0x0003FFFF, 0x0007FFFF, 0x000FFFFF, 0x001FFFFF, 0x003FFFFF, 0x007FFFFF,
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96 0x00FFFFFF, 0x01FFFFFF, 0x03FFFFFF, 0x07FFFFFF, 0x0FFFFFFF, 0x1FFFFFFF,
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97 0x3FFFFFFF, 0x7FFFFFFF, 0xFFFFFFFF
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98 };
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99
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100
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101 #define MAGIC_NUM 0x676B6A61 /* looks like "ajkg" as chars. */
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102
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103 /*
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104 * Look through the whole file for a SHN magic number. This is costly, so
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105 * it should only be done if the user SWEARS they have a Shorten stream...
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106 */
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107 static inline int extended_shn_magic_search(Sound_Sample *sample)
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108 {
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109 SDL_RWops *rw = ((Sound_SampleInternal *) sample->opaque)->rw;
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110 Uint32 word = 0;
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111 Uint8 ch;
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112
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113 while (1)
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114 {
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115 BAIL_IF_MACRO(SDL_RWread(rw, &ch, sizeof (ch), 1) != 1, NULL, -1);
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116 word = ((word << 8) & 0xFFFFFF00) | ch;
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117 if (SDL_SwapLE32(word) == MAGIC_NUM)
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118 {
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119 BAIL_IF_MACRO(SDL_RWread(rw, &ch, sizeof (ch), 1) != 1, NULL, -1);
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120 return((int) ch);
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121 } /* if */
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122 } /* while */
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123
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124 return((int) ch);
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125 } /* extended_shn_magic_search */
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126
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127
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128 /* look for the magic number in the RWops and see what kind of file this is. */
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129 static inline int determine_shn_version(Sound_Sample *sample)
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130 {
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131 SDL_RWops *rw = ((Sound_SampleInternal *) sample->opaque)->rw;
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132 Uint32 magic;
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133 Uint8 ch;
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134
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135 /*
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136 * Apparently the magic number can start at any byte offset in the file,
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137 * and we should just discard prior data, but I'm going to restrict it
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138 * to offset zero for now, so we don't chug down every file that might
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139 * happen to pass through here. If the extension is explicitly "SHN", we
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140 * check the whole stream, though.
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141 */
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142
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143 if (__Sound_strcasecmp(ext, "shn") == 0)
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144 return(extended_shn_magic_search(sample);
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145
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146 BAIL_IF_MACRO(SDL_RWread(rw, &magic, sizeof (magic), 1) != 1, NULL, -1);
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147 BAIL_IF_MACRO(SDL_SwapLE32(magic) != MAGIC_NUM, "SHN: Not a SHN file", -1);
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148 BAIL_IF_MACRO(SDL_RWread(rw, &ch, sizeof (ch), 1) != 1, NULL, -1);
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149 BAIL_IF_MACRO(ch > 3, "SHN: Unsupported file version", -1);
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150
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151 return((int) ch);
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152 } /* determine_shn_version */
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153
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154
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155 static int SHN_open(Sound_Sample *sample, const char *ext)
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156 {
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157 Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque;
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158 SDL_RWops *rw = internal->rw;
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159 int shn_version = determine_shn_version(sample, ext);
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160 int mean = MEAN_VERSION2;
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161
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162 BAIL_IF_MACRO(shn_version == -1, NULL, 0);
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163 if (shn_version < 2) /* downgrade? */
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164 mean = MEAN_VERSION0;
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165
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166
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167
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168 SNDDBG(("SHN: Accepting data stream.\n"));
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169 set up sample->actual;
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170 sample->flags = SOUND_SAMPLEFLAG_NONE;
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171 return(1); /* we'll handle this data. */
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172 } /* SHN_open */
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173
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174
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175 static void SHN_close(Sound_Sample *sample)
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176 {
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177 Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque;
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178 clean up anything you put into internal->decoder_private;
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179 } /* SHN_close */
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180
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181
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182 static Uint32 SHN_read(Sound_Sample *sample)
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183 {
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184 Uint32 retval;
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185 Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque;
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186
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187 /*
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188 * We don't actually do any decoding, so we read the fmt data
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189 * directly into the internal buffer...
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190 */
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191 retval = SDL_RWread(internal->rw, internal->buffer,
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192 1, internal->buffer_size);
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193
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194 (or whatever. Do some decoding here...)
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195
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196 /* Make sure the read went smoothly... */
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197 if (retval == 0)
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198 sample->flags |= SOUND_SAMPLEFLAG_EOF;
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199
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200 else if (retval == -1)
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201 sample->flags |= SOUND_SAMPLEFLAG_ERROR;
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202
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203 /* (next call this EAGAIN may turn into an EOF or error.) */
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204 else if (retval < internal->buffer_size)
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205 sample->flags |= SOUND_SAMPLEFLAG_EAGAIN;
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206
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207 (or whatever. retval == number of bytes you put in internal->buffer).
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208
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209 return(retval);
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210 } /* SHN_read */
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211
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212 #endif /* defined SOUND_SUPPORTS_SHN */
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213
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214 /* end of shn.c ... */
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215
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