Atlas - SDL_dummyaudio.c
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[FILE BEGIN]
1/*
2  Simple DirectMedia Layer
3  Copyright (C) 1997-2025 Sam Lantinga <[email protected]>
4
5  This software is provided 'as-is', without any express or implied
6  warranty.  In no event will the authors be held liable for any damages
7  arising from the use of this software.
8
9  Permission is granted to anyone to use this software for any purpose,
10  including commercial applications, and to alter it and redistribute it
11  freely, subject to the following restrictions:
12
13  1. The origin of this software must not be misrepresented; you must not
14     claim that you wrote the original software. If you use this software
15     in a product, an acknowledgment in the product documentation would be
16     appreciated but is not required.
17  2. Altered source versions must be plainly marked as such, and must not be
18     misrepresented as being the original software.
19  3. This notice may not be removed or altered from any source distribution.
20*/
21#include "SDL_internal.h"
22
23// Output audio to nowhere...
24
25#include "../SDL_sysaudio.h"
26#include "SDL_dummyaudio.h"
27
28#if defined(SDL_PLATFORM_EMSCRIPTEN) && !defined(__EMSCRIPTEN_PTHREADS__)
29#include <emscripten/emscripten.h>
30#endif
31
32static bool DUMMYAUDIO_WaitDevice(SDL_AudioDevice *device)
33{
34    SDL_Delay(device->hidden->io_delay);
35    return true;
36}
37
38static bool DUMMYAUDIO_OpenDevice(SDL_AudioDevice *device)
39{
40    device->hidden = (struct SDL_PrivateAudioData *) SDL_calloc(1, sizeof(*device->hidden));
41    if (!device->hidden) {
42        return false;
43    }
44
45    if (!device->recording) {
46        device->hidden->mixbuf = (Uint8 *) SDL_malloc(device->buffer_size);
47        if (!device->hidden->mixbuf) {
48            return false;
49        }
50    }
51
52    device->hidden->io_delay = ((device->sample_frames * 1000) / device->spec.freq);
53
54    const char *hint = SDL_GetHint(SDL_HINT_AUDIO_DUMMY_TIMESCALE);
55    if (hint) {
56        double scale = SDL_atof(hint);
57        if (scale >= 0.0) {
58            device->hidden->io_delay = (Uint32)SDL_round(device->hidden->io_delay * scale);
59        }
60    }
61
62    // on Emscripten without threads, we just fire a repeating timer to consume audio.
63    #if defined(SDL_PLATFORM_EMSCRIPTEN) && !defined(__EMSCRIPTEN_PTHREADS__)
64    MAIN_THREAD_EM_ASM({
65        var a = Module['SDL3'].dummy_audio;
66        if (a.timers[$0] !== undefined) { clearInterval(a.timers[$0]); }
67        a.timers[$0] = setInterval(function() { dynCall('vi', $3, [$4]); }, ($1 / $2) * 1000);
68    }, device->recording ? 1 : 0, device->sample_frames, device->spec.freq, device->recording ? SDL_RecordingAudioThreadIterate : SDL_PlaybackAudioThreadIterate, device);
69    #endif
70
71    return true; // we're good; don't change reported device format.
72}
73
74static void DUMMYAUDIO_CloseDevice(SDL_AudioDevice *device)
75{
76    if (device->hidden) {
77        // on Emscripten without threads, we just fire a repeating timer to consume audio.
78        #if defined(SDL_PLATFORM_EMSCRIPTEN) && !defined(__EMSCRIPTEN_PTHREADS__)
79        MAIN_THREAD_EM_ASM({
80            var a = Module['SDL3'].dummy_audio;
81            if (a.timers[$0] !== undefined) { clearInterval(a.timers[$0]); }
82            a.timers[$0] = undefined;
83        }, device->recording ? 1 : 0);
84        #endif
85        SDL_free(device->hidden->mixbuf);
86        SDL_free(device->hidden);
87        device->hidden = NULL;
88    }
89}
90
91static Uint8 *DUMMYAUDIO_GetDeviceBuf(SDL_AudioDevice *device, int *buffer_size)
92{
93    return device->hidden->mixbuf;
94}
95
96static int DUMMYAUDIO_RecordDevice(SDL_AudioDevice *device, void *buffer, int buflen)
97{
98    // always return a full buffer of silence.
99    SDL_memset(buffer, device->silence_value, buflen);
100    return buflen;
101}
102
103static bool DUMMYAUDIO_Init(SDL_AudioDriverImpl *impl)
104{
105    impl->OpenDevice = DUMMYAUDIO_OpenDevice;
106    impl->CloseDevice = DUMMYAUDIO_CloseDevice;
107    impl->WaitDevice = DUMMYAUDIO_WaitDevice;
108    impl->GetDeviceBuf = DUMMYAUDIO_GetDeviceBuf;
109    impl->WaitRecordingDevice = DUMMYAUDIO_WaitDevice;
110    impl->RecordDevice = DUMMYAUDIO_RecordDevice;
111
112    impl->OnlyHasDefaultPlaybackDevice = true;
113    impl->OnlyHasDefaultRecordingDevice = true;
114    impl->HasRecordingSupport = true;
115
116    // on Emscripten without threads, we just fire a repeating timer to consume audio.
117    #if defined(SDL_PLATFORM_EMSCRIPTEN) && !defined(__EMSCRIPTEN_PTHREADS__)
118    MAIN_THREAD_EM_ASM({
119        if (typeof(Module['SDL3']) === 'undefined') {
120            Module['SDL3'] = {};
121        }
122        Module['SDL3'].dummy_audio = {};
123        Module['SDL3'].dummy_audio.timers = [];
124        Module['SDL3'].dummy_audio.timers[0] = undefined;
125        Module['SDL3'].dummy_audio.timers[1] = undefined;
126    });
127    impl->ProvidesOwnCallbackThread = true;
128    #endif
129
130    return true;
131}
132
133AudioBootStrap DUMMYAUDIO_bootstrap = {
134    "dummy", "SDL dummy audio driver", DUMMYAUDIO_Init, true, false
135};
136
[FILE END]
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