1 /*
2   Simple DirectMedia Layer
3   Copyright (C) 1997-2016 Sam Lantinga <slouken@libsdl.org>
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 #ifndef _SDL_sysaudio_h
24 #define _SDL_sysaudio_h
25 
26 #include "SDL_mutex.h"
27 #include "SDL_thread.h"
28 
29 /* !!! FIXME: These are wordy and unlocalized... */
30 #define DEFAULT_OUTPUT_DEVNAME "System audio output device"
31 #define DEFAULT_INPUT_DEVNAME "System audio capture device"
32 
33 /* The SDL audio driver */
34 typedef struct SDL_AudioDevice SDL_AudioDevice;
35 #define _THIS   SDL_AudioDevice *_this
36 
37 /* Audio targets should call this as devices are added to the system (such as
38    a USB headset being plugged in), and should also be called for
39    for every device found during DetectDevices(). */
40 extern void SDL_AddAudioDevice(const int iscapture, const char *name, void *handle);
41 
42 /* Audio targets should call this as devices are removed, so SDL can update
43    its list of available devices. */
44 extern void SDL_RemoveAudioDevice(const int iscapture, void *handle);
45 
46 /* Audio targets should call this if an opened audio device is lost while
47    being used. This can happen due to i/o errors, or a device being unplugged,
48    etc. If the device is totally gone, please also call SDL_RemoveAudioDevice()
49    as appropriate so SDL's list of devices is accurate. */
50 extern void SDL_OpenedAudioDeviceDisconnected(SDL_AudioDevice *device);
51 
52 
53 /* This is the size of a packet when using SDL_QueueAudio(). We allocate
54    these as necessary and pool them, under the assumption that we'll
55    eventually end up with a handful that keep recycling, meeting whatever
56    the app needs. We keep packing data tightly as more arrives to avoid
57    wasting space, and if we get a giant block of data, we'll split them
58    into multiple packets behind the scenes. My expectation is that most
59    apps will have 2-3 of these in the pool. 8k should cover most needs, but
60    if this is crippling for some embedded system, we can #ifdef this.
61    The system preallocates enough packets for 2 callbacks' worth of data. */
62 #define SDL_AUDIOBUFFERQUEUE_PACKETLEN (8 * 1024)
63 
64 /* Used by apps that queue audio instead of using the callback. */
65 typedef struct SDL_AudioBufferQueue
66 {
67     Uint8 data[SDL_AUDIOBUFFERQUEUE_PACKETLEN];  /* packet data. */
68     Uint32 datalen;  /* bytes currently in use in this packet. */
69     Uint32 startpos;  /* bytes currently consumed in this packet. */
70     struct SDL_AudioBufferQueue *next;  /* next item in linked list. */
71 } SDL_AudioBufferQueue;
72 
73 typedef struct SDL_AudioDriverImpl
74 {
75     void (*DetectDevices) (void);
76     int (*OpenDevice) (_THIS, void *handle, const char *devname, int iscapture);
77     void (*ThreadInit) (_THIS); /* Called by audio thread at start */
78     void (*WaitDevice) (_THIS);
79     void (*PlayDevice) (_THIS);
80     int (*GetPendingBytes) (_THIS);
81     Uint8 *(*GetDeviceBuf) (_THIS);
82     int (*CaptureFromDevice) (_THIS, void *buffer, int buflen);
83     void (*FlushCapture) (_THIS);
84     void (*PrepareToClose) (_THIS);  /**< Called between run and draining wait for playback devices */
85     void (*CloseDevice) (_THIS);
86     void (*LockDevice) (_THIS);
87     void (*UnlockDevice) (_THIS);
88     void (*FreeDeviceHandle) (void *handle);  /**< SDL is done with handle from SDL_AddAudioDevice() */
89     void (*Deinitialize) (void);
90 
91     /* !!! FIXME: add pause(), so we can optimize instead of mixing silence. */
92 
93     /* Some flags to push duplicate code into the core and reduce #ifdefs. */
94     /* !!! FIXME: these should be SDL_bool */
95     int ProvidesOwnCallbackThread;
96     int SkipMixerLock;
97     int HasCaptureSupport;
98     int OnlyHasDefaultOutputDevice;
99     int OnlyHasDefaultCaptureDevice;
100     int AllowsArbitraryDeviceNames;
101 } SDL_AudioDriverImpl;
102 
103 
104 typedef struct SDL_AudioDeviceItem
105 {
106     void *handle;
107     struct SDL_AudioDeviceItem *next;
108     #if (defined(__GNUC__) && (__GNUC__ <= 2))
109     char name[1];  /* actually variable length. */
110     #else
111     char name[];
112     #endif
113 } SDL_AudioDeviceItem;
114 
115 
116 typedef struct SDL_AudioDriver
117 {
118     /* * * */
119     /* The name of this audio driver */
120     const char *name;
121 
122     /* * * */
123     /* The description of this audio driver */
124     const char *desc;
125 
126     SDL_AudioDriverImpl impl;
127 
128     /* A mutex for device detection */
129     SDL_mutex *detectionLock;
130     SDL_bool captureDevicesRemoved;
131     SDL_bool outputDevicesRemoved;
132     int outputDeviceCount;
133     int inputDeviceCount;
134     SDL_AudioDeviceItem *outputDevices;
135     SDL_AudioDeviceItem *inputDevices;
136 } SDL_AudioDriver;
137 
138 
139 /* Streamer */
140 typedef struct
141 {
142     Uint8 *buffer;
143     int max_len;                /* the maximum length in bytes */
144     int read_pos, write_pos;    /* the position of the write and read heads in bytes */
145 } SDL_AudioStreamer;
146 
147 
148 /* Define the SDL audio driver structure */
149 struct SDL_AudioDevice
150 {
151     /* * * */
152     /* Data common to all devices */
153     SDL_AudioDeviceID id;
154 
155     /* The current audio specification (shared with audio thread) */
156     SDL_AudioSpec spec;
157 
158     /* An audio conversion block for audio format emulation */
159     SDL_AudioCVT convert;
160 
161     /* The streamer, if sample rate conversion necessitates it */
162     int use_streamer;
163     SDL_AudioStreamer streamer;
164 
165     /* Current state flags */
166     SDL_atomic_t shutdown; /* true if we are signaling the play thread to end. */
167     SDL_atomic_t enabled;  /* true if device is functioning and connected. */
168     SDL_atomic_t paused;
169     SDL_bool iscapture;
170 
171     /* Fake audio buffer for when the audio hardware is busy */
172     Uint8 *fake_stream;
173 
174     /* A mutex for locking the mixing buffers */
175     SDL_mutex *mixer_lock;
176 
177     /* A thread to feed the audio device */
178     SDL_Thread *thread;
179     SDL_threadID threadid;
180 
181     /* Queued buffers (if app not using callback). */
182     SDL_AudioBufferQueue *buffer_queue_head; /* device fed from here. */
183     SDL_AudioBufferQueue *buffer_queue_tail; /* queue fills to here. */
184     SDL_AudioBufferQueue *buffer_queue_pool; /* these are unused packets. */
185     Uint32 queued_bytes;  /* number of bytes of audio data in the queue. */
186 
187     /* * * */
188     /* Data private to this driver */
189     struct SDL_PrivateAudioData *hidden;
190 
191     void *handle;
192 };
193 #undef _THIS
194 
195 typedef struct AudioBootStrap
196 {
197     const char *name;
198     const char *desc;
199     int (*init) (SDL_AudioDriverImpl * impl);
200     int demand_only;  /* 1==request explicitly, or it won't be available. */
201 } AudioBootStrap;
202 
203 #endif /* _SDL_sysaudio_h */
204 
205 /* vi: set ts=4 sw=4 expandtab: */
206