1/*
2    SDL - Simple DirectMedia Layer
3    Copyright (C) 1997-2012 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 */
40static int DUMMYAUD_OpenAudio(_THIS, SDL_AudioSpec *spec);
41static void DUMMYAUD_WaitAudio(_THIS);
42static void DUMMYAUD_PlayAudio(_THIS);
43static Uint8 *DUMMYAUD_GetAudioBuf(_THIS);
44static void DUMMYAUD_CloseAudio(_THIS);
45
46/* Audio driver bootstrap functions */
47static 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
56static void DUMMYAUD_DeleteDevice(SDL_AudioDevice *device)
57{
58	SDL_free(device->hidden);
59	SDL_free(device);
60}
61
62static 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
94AudioBootStrap 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 */
100static 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
109static void DUMMYAUD_PlayAudio(_THIS)
110{
111	/* no-op...this is a null driver. */
112}
113
114static Uint8 *DUMMYAUD_GetAudioBuf(_THIS)
115{
116	return(this->hidden->mixbuf);
117}
118
119static 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
127static 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
157