| 1 | /* |
| 2 | SDL - Simple DirectMedia Layer |
| 3 | Copyright (C) 1997-2009 Sam Lantinga |
| 4 | |
| 5 | This library is free software; you can redistribute it and/or |
| 6 | modify it under the terms of the GNU Lesser General Public |
| 7 | License as published by the Free Software Foundation; either |
| 8 | version 2.1 of the License, or (at your option) any later version. |
| 9 | |
| 10 | This library is distributed in the hope that it will be useful, |
| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 13 | Lesser General Public License for more details. |
| 14 | |
| 15 | You should have received a copy of the GNU Lesser General Public |
| 16 | License along with this library; if not, write to the Free Software |
| 17 | Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA |
| 18 | |
| 19 | Sam Lantinga |
| 20 | slouken@libsdl.org |
| 21 | |
| 22 | This file written by Ryan C. Gordon (icculus@icculus.org) |
| 23 | */ |
| 24 | #include "SDL_config.h" |
| 25 | |
| 26 | /* Output audio to nowhere... */ |
| 27 | |
| 28 | #include "SDL_rwops.h" |
| 29 | #include "SDL_timer.h" |
| 30 | #include "SDL_audio.h" |
| 31 | #include "../SDL_audiomem.h" |
| 32 | #include "../SDL_audio_c.h" |
| 33 | #include "../SDL_audiodev_c.h" |
| 34 | #include "SDL_dummyaudio.h" |
| 35 | |
| 36 | /* The tag name used by DUMMY audio */ |
| 37 | #define DUMMYAUD_DRIVER_NAME "dummy" |
| 38 | |
| 39 | /* Audio driver functions */ |
| 40 | static int DUMMYAUD_OpenAudio(_THIS, SDL_AudioSpec *spec); |
| 41 | static void DUMMYAUD_WaitAudio(_THIS); |
| 42 | static void DUMMYAUD_PlayAudio(_THIS); |
| 43 | static Uint8 *DUMMYAUD_GetAudioBuf(_THIS); |
| 44 | static void DUMMYAUD_CloseAudio(_THIS); |
| 45 | |
| 46 | /* Audio driver bootstrap functions */ |
| 47 | static int DUMMYAUD_Available(void) |
| 48 | { |
| 49 | const char *envr = SDL_getenv("SDL_AUDIODRIVER"); |
| 50 | if (envr && (SDL_strcmp(envr, DUMMYAUD_DRIVER_NAME) == 0)) { |
| 51 | return(1); |
| 52 | } |
| 53 | return(0); |
| 54 | } |
| 55 | |
| 56 | static void DUMMYAUD_DeleteDevice(SDL_AudioDevice *device) |
| 57 | { |
| 58 | SDL_free(device->hidden); |
| 59 | SDL_free(device); |
| 60 | } |
| 61 | |
| 62 | static SDL_AudioDevice *DUMMYAUD_CreateDevice(int devindex) |
| 63 | { |
| 64 | SDL_AudioDevice *this; |
| 65 | |
| 66 | /* Initialize all variables that we clean on shutdown */ |
| 67 | this = (SDL_AudioDevice *)SDL_malloc(sizeof(SDL_AudioDevice)); |
| 68 | if ( this ) { |
| 69 | SDL_memset(this, 0, (sizeof *this)); |
| 70 | this->hidden = (struct SDL_PrivateAudioData *) |
| 71 | SDL_malloc((sizeof *this->hidden)); |
| 72 | } |
| 73 | if ( (this == NULL) || (this->hidden == NULL) ) { |
| 74 | SDL_OutOfMemory(); |
| 75 | if ( this ) { |
| 76 | SDL_free(this); |
| 77 | } |
| 78 | return(0); |
| 79 | } |
| 80 | SDL_memset(this->hidden, 0, (sizeof *this->hidden)); |
| 81 | |
| 82 | /* Set the function pointers */ |
| 83 | this->OpenAudio = DUMMYAUD_OpenAudio; |
| 84 | this->WaitAudio = DUMMYAUD_WaitAudio; |
| 85 | this->PlayAudio = DUMMYAUD_PlayAudio; |
| 86 | this->GetAudioBuf = DUMMYAUD_GetAudioBuf; |
| 87 | this->CloseAudio = DUMMYAUD_CloseAudio; |
| 88 | |
| 89 | this->free = DUMMYAUD_DeleteDevice; |
| 90 | |
| 91 | return this; |
| 92 | } |
| 93 | |
| 94 | AudioBootStrap DUMMYAUD_bootstrap = { |
| 95 | DUMMYAUD_DRIVER_NAME, "SDL dummy audio driver", |
| 96 | DUMMYAUD_Available, DUMMYAUD_CreateDevice |
| 97 | }; |
| 98 | |
| 99 | /* This function waits until it is possible to write a full sound buffer */ |
| 100 | static void DUMMYAUD_WaitAudio(_THIS) |
| 101 | { |
| 102 | /* Don't block on first calls to simulate initial fragment filling. */ |
| 103 | if (this->hidden->initial_calls) |
| 104 | this->hidden->initial_calls--; |
| 105 | else |
| 106 | SDL_Delay(this->hidden->write_delay); |
| 107 | } |
| 108 | |
| 109 | static void DUMMYAUD_PlayAudio(_THIS) |
| 110 | { |
| 111 | /* no-op...this is a null driver. */ |
| 112 | } |
| 113 | |
| 114 | static Uint8 *DUMMYAUD_GetAudioBuf(_THIS) |
| 115 | { |
| 116 | return(this->hidden->mixbuf); |
| 117 | } |
| 118 | |
| 119 | static void DUMMYAUD_CloseAudio(_THIS) |
| 120 | { |
| 121 | if ( this->hidden->mixbuf != NULL ) { |
| 122 | SDL_FreeAudioMem(this->hidden->mixbuf); |
| 123 | this->hidden->mixbuf = NULL; |
| 124 | } |
| 125 | } |
| 126 | |
| 127 | static int DUMMYAUD_OpenAudio(_THIS, SDL_AudioSpec *spec) |
| 128 | { |
| 129 | float bytes_per_sec = 0.0f; |
| 130 | |
| 131 | /* Allocate mixing buffer */ |
| 132 | this->hidden->mixlen = spec->size; |
| 133 | this->hidden->mixbuf = (Uint8 *) SDL_AllocAudioMem(this->hidden->mixlen); |
| 134 | if ( this->hidden->mixbuf == NULL ) { |
| 135 | return(-1); |
| 136 | } |
| 137 | SDL_memset(this->hidden->mixbuf, spec->silence, spec->size); |
| 138 | |
| 139 | bytes_per_sec = (float) (((spec->format & 0xFF) / 8) * |
| 140 | spec->channels * spec->freq); |
| 141 | |
| 142 | /* |
| 143 | * We try to make this request more audio at the correct rate for |
| 144 | * a given audio spec, so timing stays fairly faithful. |
| 145 | * Also, we have it not block at all for the first two calls, so |
| 146 | * it seems like we're filling two audio fragments right out of the |
| 147 | * gate, like other SDL drivers tend to do. |
| 148 | */ |
| 149 | this->hidden->initial_calls = 2; |
| 150 | this->hidden->write_delay = |
| 151 | (Uint32) ((((float) spec->size) / bytes_per_sec) * 1000.0f); |
| 152 | |
| 153 | /* We're ready to rock and roll. :-) */ |
| 154 | return(0); |
| 155 | } |
| 156 | |