e14743d1 |
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 | |