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1 /* |
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2 SDL - Simple DirectMedia Layer |
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3 Copyright (C) 1997-2006 Sam Lantinga |
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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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA |
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18 |
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19 Sam Lantinga |
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20 slouken@libsdl.org |
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21 |
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22 This file written by Ryan C. Gordon (icculus@icculus.org) |
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23 */ |
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24 #include "SDL_config.h" |
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25 |
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26 /* Output audio to nowhere... */ |
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27 |
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28 #include "SDL_rwops.h" |
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29 #include "SDL_timer.h" |
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30 #include "SDL_audio.h" |
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31 #include "../SDL_audiomem.h" |
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32 #include "../SDL_audio_c.h" |
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33 #include "../SDL_audiodev_c.h" |
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34 #include "SDL_dummyaudio.h" |
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35 |
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36 /* The tag name used by DUMMY audio */ |
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37 #define DUMMYAUD_DRIVER_NAME "dummy" |
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38 |
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39 /* Audio driver functions */ |
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40 static int DUMMYAUD_OpenAudio(_THIS, SDL_AudioSpec *spec); |
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41 static void DUMMYAUD_WaitAudio(_THIS); |
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42 static void DUMMYAUD_PlayAudio(_THIS); |
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43 static Uint8 *DUMMYAUD_GetAudioBuf(_THIS); |
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44 static void DUMMYAUD_CloseAudio(_THIS); |
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45 |
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46 /* Audio driver bootstrap functions */ |
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47 static int DUMMYAUD_Available(void) |
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48 { |
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49 const char *envr = SDL_getenv("SDL_AUDIODRIVER"); |
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50 if (envr && (SDL_strcmp(envr, DUMMYAUD_DRIVER_NAME) == 0)) { |
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51 return(1); |
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52 } |
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53 return(0); |
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54 } |
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55 |
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56 static void DUMMYAUD_DeleteDevice(SDL_AudioDevice *device) |
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57 { |
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58 SDL_free(device->hidden); |
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59 SDL_free(device); |
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60 } |
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61 |
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62 static SDL_AudioDevice *DUMMYAUD_CreateDevice(int devindex) |
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63 { |
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64 SDL_AudioDevice *this; |
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65 |
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66 /* Initialize all variables that we clean on shutdown */ |
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67 this = (SDL_AudioDevice *)SDL_malloc(sizeof(SDL_AudioDevice)); |
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68 if ( this ) { |
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69 SDL_memset(this, 0, (sizeof *this)); |
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70 this->hidden = (struct SDL_PrivateAudioData *) |
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71 SDL_malloc((sizeof *this->hidden)); |
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72 } |
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73 if ( (this == NULL) || (this->hidden == NULL) ) { |
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74 SDL_OutOfMemory(); |
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75 if ( this ) { |
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76 SDL_free(this); |
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77 } |
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78 return(0); |
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79 } |
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80 SDL_memset(this->hidden, 0, (sizeof *this->hidden)); |
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81 |
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82 /* Set the function pointers */ |
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83 this->OpenAudio = DUMMYAUD_OpenAudio; |
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84 this->WaitAudio = DUMMYAUD_WaitAudio; |
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85 this->PlayAudio = DUMMYAUD_PlayAudio; |
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86 this->GetAudioBuf = DUMMYAUD_GetAudioBuf; |
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87 this->CloseAudio = DUMMYAUD_CloseAudio; |
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88 |
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89 this->free = DUMMYAUD_DeleteDevice; |
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90 |
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91 return this; |
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92 } |
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93 |
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94 AudioBootStrap DUMMYAUD_bootstrap = { |
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95 DUMMYAUD_DRIVER_NAME, "SDL dummy audio driver", |
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96 DUMMYAUD_Available, DUMMYAUD_CreateDevice |
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97 }; |
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98 |
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99 /* This function waits until it is possible to write a full sound buffer */ |
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100 static void DUMMYAUD_WaitAudio(_THIS) |
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101 { |
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102 /* Don't block on first calls to simulate initial fragment filling. */ |
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103 if (this->hidden->initial_calls) |
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104 this->hidden->initial_calls--; |
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105 else |
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106 SDL_Delay(this->hidden->write_delay); |
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107 } |
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108 |
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109 static void DUMMYAUD_PlayAudio(_THIS) |
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110 { |
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111 /* no-op...this is a null driver. */ |
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112 } |
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113 |
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114 static Uint8 *DUMMYAUD_GetAudioBuf(_THIS) |
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115 { |
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116 return(this->hidden->mixbuf); |
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117 } |
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118 |
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119 static void DUMMYAUD_CloseAudio(_THIS) |
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120 { |
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121 if ( this->hidden->mixbuf != NULL ) { |
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122 SDL_FreeAudioMem(this->hidden->mixbuf); |
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123 this->hidden->mixbuf = NULL; |
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124 } |
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125 } |
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126 |
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127 static int DUMMYAUD_OpenAudio(_THIS, SDL_AudioSpec *spec) |
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128 { |
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129 float bytes_per_sec = 0.0f; |
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130 |
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131 /* Allocate mixing buffer */ |
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132 this->hidden->mixlen = spec->size; |
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133 this->hidden->mixbuf = (Uint8 *) SDL_AllocAudioMem(this->hidden->mixlen); |
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134 if ( this->hidden->mixbuf == NULL ) { |
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135 return(-1); |
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136 } |
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137 SDL_memset(this->hidden->mixbuf, spec->silence, spec->size); |
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138 |
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139 bytes_per_sec = (float) (((spec->format & 0xFF) / 8) * |
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140 spec->channels * spec->freq); |
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141 |
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142 /* |
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143 * We try to make this request more audio at the correct rate for |
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144 * a given audio spec, so timing stays fairly faithful. |
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145 * Also, we have it not block at all for the first two calls, so |
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146 * it seems like we're filling two audio fragments right out of the |
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147 * gate, like other SDL drivers tend to do. |
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148 */ |
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149 this->hidden->initial_calls = 2; |
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150 this->hidden->write_delay = |
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151 (Uint32) ((((float) spec->size) / bytes_per_sec) * 1000.0f); |
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152 |
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153 /* We're ready to rock and roll. :-) */ |
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154 return(0); |
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155 } |
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156 |