talk/sound/alsasoundsystem.cc - vendor/opensource/libjingle - Git at Google

 /*
  * libjingle
  * Copyright 2004--2010, Google Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *
  *  1. Redistributions of source code must retain the above copyright notice,
  *     this list of conditions and the following disclaimer.
  *  2. Redistributions in binary form must reproduce the above copyright notice,
  *     this list of conditions and the following disclaimer in the documentation
  *     and/or other materials provided with the distribution.
  *  3. The name of the author may not be used to endorse or promote products
  *     derived from this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
  * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
  * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #include "talk/sound/alsasoundsystem.h"

 #include "talk/base/common.h"
 #include "talk/base/logging.h"
 #include "talk/base/scoped_ptr.h"
 #include "talk/base/stringutils.h"
 #include "talk/base/timeutils.h"
 #include "talk/base/worker.h"
 #include "talk/sound/sounddevicelocator.h"
 #include "talk/sound/soundinputstreaminterface.h"
 #include "talk/sound/soundoutputstreaminterface.h"

 namespace cricket {

 // Lookup table from the cricket format enum in soundsysteminterface.h to
 // ALSA's enums.
 static const snd_pcm_format_t kCricketFormatToAlsaFormatTable[] = {
   // The order here must match the order in soundsysteminterface.h
   SND_PCM_FORMAT_S16_LE,
 };

 // Lookup table for the size of a single sample of a given format.
 static const size_t kCricketFormatToSampleSizeTable[] = {
   // The order here must match the order in soundsysteminterface.h
   sizeof(int16_t),  // 2
 };

 // Minimum latency we allow, in microseconds. This is more or less arbitrary,
 // but it has to be at least large enough to be able to buffer data during a
 // missed context switch, and the typical Linux scheduling quantum is 10ms.
 static const int kMinimumLatencyUsecs = 20 * 1000;

 // The latency we'll use for kNoLatencyRequirements (chosen arbitrarily).
 static const int kDefaultLatencyUsecs = kMinimumLatencyUsecs * 2;

 // We translate newlines in ALSA device descriptions to hyphens.
 static const char kAlsaDescriptionSearch[] = "\n";
 static const char kAlsaDescriptionReplace[] = " - ";

 class AlsaDeviceLocator : public SoundDeviceLocator {
  public:
   AlsaDeviceLocator(const std::string &name,
                     const std::string &device_name)
       : SoundDeviceLocator(name, device_name) {
     // The ALSA descriptions have newlines in them, which won't show up in
     // a drop-down box. Replace them with hyphens.
     talk_base::replace_substrs(kAlsaDescriptionSearch,
                                sizeof(kAlsaDescriptionSearch) - 1,
                                kAlsaDescriptionReplace,
                                sizeof(kAlsaDescriptionReplace) - 1,
                                &name_);
   }

   virtual SoundDeviceLocator *Copy() const {
     return new AlsaDeviceLocator(*this);
   }
 };

 // Accesses ALSA functions through our late-binding symbol table instead of
 // directly. This way we don't have to link to libasound, which means our binary
 // will load faster and we can run on strange systems that may not have
 // libasound
 #define LATE(sym) \
   LATESYM_GET(AlsaSymbolTable, &alsa_->symbol_table_, sym)

 // Functionality that is common to both AlsaInputStream and AlsaOutputStream.
 class AlsaStream {
  public:
   AlsaStream(AlsaSoundSystem *alsa,
              snd_pcm_t *handle,
              size_t frame_size,
              int wait_timeout_ms,
              int flags,
              int freq)
       : alsa_(alsa),
         handle_(handle),
         frame_size_(frame_size),
         wait_timeout_ms_(wait_timeout_ms),
         flags_(flags),
         freq_(freq) {
   }

   ~AlsaStream() {
     Close();
   }

   // Waits for the stream to be ready to accept/return more data, and returns
   // how much can be written/read, or 0 if we need to Wait() again.
   snd_pcm_uframes_t Wait() {
     snd_pcm_sframes_t frames;
     // Ideally we would not use snd_pcm_wait() and instead hook snd_pcm_poll_*
     // into PhysicalSocketServer, but PhysicalSocketServer is nasty enough
     // already and the current clients of SoundSystemInterface do not run
     // anything else on their worker threads, so snd_pcm_wait() is good enough.
     frames = LATE(snd_pcm_avail_update)(handle_);
     if (frames < 0) {
       LOG(LS_ERROR) << "snd_pcm_avail_update(): " << GetError(frames);
       Recover(frames);
       return 0;
     } else if (frames > 0) {
       // Already ready, so no need to wait.
       return frames;
     }
     // Else no space/data available, so must wait.
     int ready = LATE(snd_pcm_wait)(handle_, wait_timeout_ms_);
     if (ready < 0) {
       LOG(LS_ERROR) << "snd_pcm_wait(): " << GetError(ready);
       Recover(ready);
       return 0;
     } else if (ready == 0) {
       // Timeout, so nothing can be written/read right now.
       // We set the timeout to twice the requested latency, so continuous
       // timeouts are indicative of a problem, so log as a warning.
       LOG(LS_WARNING) << "Timeout while waiting on stream";
       return 0;
     }
     // Else ready > 0 (i.e., 1), so it's ready. Get count.
     frames = LATE(snd_pcm_avail_update)(handle_);
     if (frames < 0) {
       LOG(LS_ERROR) << "snd_pcm_avail_update(): " << GetError(frames);
       Recover(frames);
       return 0;
     } else if (frames == 0) {
       // wait() said we were ready, so this ought to have been positive. Has
       // been observed to happen in practice though.
       LOG(LS_WARNING) << "Spurious wake-up";
     }
     return frames;
   }

   int CurrentDelayUsecs() {
     if (!(flags_ & SoundSystemInterface::FLAG_REPORT_LATENCY)) {
       return 0;
     }

     snd_pcm_sframes_t delay;
     int err = LATE(snd_pcm_delay)(handle_, &delay);
     if (err != 0) {
       LOG(LS_ERROR) << "snd_pcm_delay(): " << GetError(err);
       Recover(err);
       // We'd rather continue playout/capture with an incorrect delay than stop
       // it altogether, so return a valid value.
       return 0;
     }
     // The delay is in frames. Convert to microseconds.
     return delay * talk_base::kNumMicrosecsPerSec / freq_;
   }

   // Used to recover from certain recoverable errors, principally buffer overrun
   // or underrun (identified as EPIPE). Without calling this the stream stays
   // in the error state forever.
   bool Recover(int error) {
     int err;
     err = LATE(snd_pcm_recover)(handle_,
                                 error,
                                 // Silent; i.e., no logging on stderr.
                                 1);
     if (err != 0) {
       // Docs say snd_pcm_recover returns the original error if it is not one
       // of the recoverable ones, so this log message will probably contain the
       // same error twice.
       LOG(LS_ERROR) << "Unable to recover from \"" << GetError(error) << "\": "
                     << GetError(err);
       return false;
     }
     if (error == -EPIPE &&  // Buffer underrun/overrun.
         LATE(snd_pcm_stream)(handle_) == SND_PCM_STREAM_CAPTURE) {
       // For capture streams we also have to repeat the explicit start() to get
       // data flowing again.
       err = LATE(snd_pcm_start)(handle_);
       if (err != 0) {
         LOG(LS_ERROR) << "snd_pcm_start(): " << GetError(err);
         return false;
       }
     }
     return true;
   }

   bool Close() {
     if (handle_) {
       int err;
       err = LATE(snd_pcm_drop)(handle_);
       if (err != 0) {
         LOG(LS_ERROR) << "snd_pcm_drop(): " << GetError(err);
         // Continue anyways.
       }
       err = LATE(snd_pcm_close)(handle_);
       if (err != 0) {
         LOG(LS_ERROR) << "snd_pcm_close(): " << GetError(err);
         // Continue anyways.
       }
       handle_ = NULL;
     }
     return true;
   }

   AlsaSoundSystem *alsa() {
     return alsa_;
   }

   snd_pcm_t *handle() {
     return handle_;
   }

   const char *GetError(int err) {
     return alsa_->GetError(err);
   }

   size_t frame_size() {
     return frame_size_;
   }

  private:
   AlsaSoundSystem *alsa_;
   snd_pcm_t *handle_;
   size_t frame_size_;
   int wait_timeout_ms_;
   int flags_;
   int freq_;

   DISALLOW_COPY_AND_ASSIGN(AlsaStream);
 };

 // Redefine for the next two classes.
 #undef LATE
 #define LATE(sym) \
   LATESYM_GET(AlsaSymbolTable, &stream_.alsa()->symbol_table_, sym)

 // Implementation of an input stream. See soundinputstreaminterface.h regarding
 // thread-safety.
 class AlsaInputStream :
     public SoundInputStreamInterface,
     private talk_base::Worker {
  public:
   AlsaInputStream(AlsaSoundSystem *alsa,
                   snd_pcm_t *handle,
                   size_t frame_size,
                   int wait_timeout_ms,
                   int flags,
                   int freq)
       : stream_(alsa, handle, frame_size, wait_timeout_ms, flags, freq),
         buffer_size_(0) {
   }

   virtual ~AlsaInputStream() {
     bool success = StopReading();
     // We need that to live.
     VERIFY(success);
   }

   virtual bool StartReading() {
     return StartWork();
   }

   virtual bool StopReading() {
     return StopWork();
   }

   virtual bool GetVolume(int *volume) {
     // TODO: Implement this.
     return false;
   }

   virtual bool SetVolume(int volume) {
     // TODO: Implement this.
     return false;
   }

   virtual bool Close() {
     return StopReading() && stream_.Close();
   }

   virtual int LatencyUsecs() {
     return stream_.CurrentDelayUsecs();
   }

  private:
   // Inherited from Worker.
   virtual void OnStart() {
     HaveWork();
   }

   // Inherited from Worker.
   virtual void OnHaveWork() {
     // Block waiting for data.
     snd_pcm_uframes_t avail = stream_.Wait();
     if (avail > 0) {
       // Data is available.
       size_t size = avail * stream_.frame_size();
       if (size > buffer_size_) {
         // Must increase buffer size.
         buffer_.reset(new char[size]);
         buffer_size_ = size;
       }
       // Read all the data.
       snd_pcm_sframes_t read = LATE(snd_pcm_readi)(stream_.handle(),
                                                    buffer_.get(),
                                                    avail);
       if (read < 0) {
         LOG(LS_ERROR) << "snd_pcm_readi(): " << GetError(read);
         stream_.Recover(read);
       } else if (read == 0) {
         // Docs say this shouldn't happen.
         ASSERT(false);
         LOG(LS_ERROR) << "No data?";
       } else {
         // Got data. Pass it off to the app.
         SignalSamplesRead(buffer_.get(),
                           read * stream_.frame_size(),
                           this);
       }
     }
     // Check for more data with no delay, after any pending messages are
     // dispatched.
     HaveWork();
   }

   // Inherited from Worker.
   virtual void OnStop() {
     // Nothing to do.
   }

   const char *GetError(int err) {
     return stream_.GetError(err);
   }

   AlsaStream stream_;
   talk_base::scoped_array<char> buffer_;
   size_t buffer_size_;

   DISALLOW_COPY_AND_ASSIGN(AlsaInputStream);
 };

 // Implementation of an output stream. See soundoutputstreaminterface.h
 // regarding thread-safety.
 class AlsaOutputStream :
     public SoundOutputStreamInterface,
     private talk_base::Worker {
  public:
   AlsaOutputStream(AlsaSoundSystem *alsa,
                    snd_pcm_t *handle,
                    size_t frame_size,
                    int wait_timeout_ms,
                    int flags,
                    int freq)
       : stream_(alsa, handle, frame_size, wait_timeout_ms, flags, freq) {
   }

   virtual ~AlsaOutputStream() {
     bool success = DisableBufferMonitoring();
     // We need that to live.
     VERIFY(success);
   }

   virtual bool EnableBufferMonitoring() {
     return StartWork();
   }

   virtual bool DisableBufferMonitoring() {
     return StopWork();
   }

   virtual bool WriteSamples(const void *sample_data,
                             size_t size) {
     if (size % stream_.frame_size() != 0) {
       // No client of SoundSystemInterface does this, so let's not support it.
       // (If we wanted to support it, we'd basically just buffer the fractional
       // frame until we get more data.)
       ASSERT(false);
       LOG(LS_ERROR) << "Writes with fractional frames are not supported";
       return false;
     }
     snd_pcm_uframes_t frames = size / stream_.frame_size();
     snd_pcm_sframes_t written = LATE(snd_pcm_writei)(stream_.handle(),
                                                      sample_data,
                                                      frames);
     if (written < 0) {
       LOG(LS_ERROR) << "snd_pcm_writei(): " << GetError(written);
       stream_.Recover(written);
       return false;
     } else if (static_cast<snd_pcm_uframes_t>(written) < frames) {
       // Shouldn't happen. Drop the rest of the data.
       LOG(LS_ERROR) << "Stream wrote only " << written << " of " << frames
                     << " frames!";
       return false;
     }
     return true;
   }

   virtual bool GetVolume(int *volume) {
     // TODO: Implement this.
     return false;
   }

   virtual bool SetVolume(int volume) {
     // TODO: Implement this.
     return false;
   }

   virtual bool Close() {
     return DisableBufferMonitoring() && stream_.Close();
   }

   virtual int LatencyUsecs() {
     return stream_.CurrentDelayUsecs();
   }

  private:
   // Inherited from Worker.
   virtual void OnStart() {
     HaveWork();
   }

   // Inherited from Worker.
   virtual void OnHaveWork() {
     snd_pcm_uframes_t avail = stream_.Wait();
     if (avail > 0) {
       size_t space = avail * stream_.frame_size();
       SignalBufferSpace(space, this);
     }
     HaveWork();
   }

   // Inherited from Worker.
   virtual void OnStop() {
     // Nothing to do.
   }

   const char *GetError(int err) {
     return stream_.GetError(err);
   }

   AlsaStream stream_;

   DISALLOW_COPY_AND_ASSIGN(AlsaOutputStream);
 };

 // Redefine for the main class.
 #undef LATE
 #define LATE(sym) LATESYM_GET(AlsaSymbolTable, &symbol_table_, sym)

 AlsaSoundSystem::AlsaSoundSystem() : initialized_(false) {}

 AlsaSoundSystem::~AlsaSoundSystem() {
   // Not really necessary, because Terminate() doesn't really do anything.
   Terminate();
 }

 bool AlsaSoundSystem::Init() {
   if (IsInitialized()) {
     return true;
   }

   // Load libasound.
   if (!symbol_table_.Load()) {
     // Very odd for a Linux machine to not have a working libasound ...
     LOG(LS_ERROR) << "Failed to load symbol table";
     return false;
   }

   initialized_ = true;

   return true;
 }

 void AlsaSoundSystem::Terminate() {
   if (!IsInitialized()) {
     return;
   }

   initialized_ = false;

   // We do not unload the symbol table because we may need it again soon if
   // Init() is called again.
 }

 bool AlsaSoundSystem::EnumeratePlaybackDevices(
     SoundDeviceLocatorList *devices) {
   return EnumerateDevices(devices, false);
 }

 bool AlsaSoundSystem::EnumerateCaptureDevices(
     SoundDeviceLocatorList *devices) {
   return EnumerateDevices(devices, true);
 }

 bool AlsaSoundSystem::GetDefaultPlaybackDevice(SoundDeviceLocator **device) {
   return GetDefaultDevice(device);
 }

 bool AlsaSoundSystem::GetDefaultCaptureDevice(SoundDeviceLocator **device) {
   return GetDefaultDevice(device);
 }

 SoundOutputStreamInterface *AlsaSoundSystem::OpenPlaybackDevice(
     const SoundDeviceLocator *device,
     const OpenParams &params) {
   return OpenDevice<SoundOutputStreamInterface>(
       device,
       params,
       SND_PCM_STREAM_PLAYBACK,
       &AlsaSoundSystem::StartOutputStream);
 }

 SoundInputStreamInterface *AlsaSoundSystem::OpenCaptureDevice(
     const SoundDeviceLocator *device,
     const OpenParams &params) {
   return OpenDevice<SoundInputStreamInterface>(
       device,
       params,
       SND_PCM_STREAM_CAPTURE,
       &AlsaSoundSystem::StartInputStream);
 }

 const char *AlsaSoundSystem::GetName() const {
   return "ALSA";
 }

 bool AlsaSoundSystem::EnumerateDevices(
     SoundDeviceLocatorList *devices,
     bool capture_not_playback) {
   ClearSoundDeviceLocatorList(devices);

   if (!IsInitialized()) {
     return false;
   }

   const char *type = capture_not_playback ? "Input" : "Output";
   // dmix and dsnoop are only for playback and capture, respectively, but ALSA
   // stupidly includes them in both lists.
   const char *ignore_prefix = capture_not_playback ? "dmix:" : "dsnoop:";
   // (ALSA lists many more "devices" of questionable interest, but we show them
   // just in case the weird devices may actually be desirable for some
   // users/systems.)
   const char *ignore_default = "default";
   const char *ignore_null = "null";
   const char *ignore_pulse = "pulse";
   // The 'pulse' entry has a habit of mysteriously disappearing when you query
   // a second time. Remove it from our list. (GIPS lib did the same thing.)
   int err;

   void **hints;
   err = LATE(snd_device_name_hint)(-1,     // All cards
                                    "pcm",  // Only PCM devices
                                    &hints);
   if (err != 0) {
     LOG(LS_ERROR) << "snd_device_name_hint(): " << GetError(err);
     return false;
   }

   for (void **list = hints; *list != NULL; ++list) {
     char *actual_type = LATE(snd_device_name_get_hint)(*list, "IOID");
     if (actual_type) {  // NULL means it's both.
       bool wrong_type = (strcmp(actual_type, type) != 0);
       free(actual_type);
       if (wrong_type) {
         // Wrong type of device (i.e., input vs. output).
         continue;
       }
     }

     char *name = LATE(snd_device_name_get_hint)(*list, "NAME");
     if (!name) {
       LOG(LS_ERROR) << "Device has no name???";
       // Skip it.
       continue;
     }

     // Now check if we actually want to show this device.
     if (strcmp(name, ignore_default) != 0 &&
         strcmp(name, ignore_null) != 0 &&
         strcmp(name, ignore_pulse) != 0 &&
         !talk_base::starts_with(name, ignore_prefix)) {

       // Yes, we do.
       char *desc = LATE(snd_device_name_get_hint)(*list, "DESC");
       if (!desc) {
         // Virtual devices don't necessarily have descriptions. Use their names
         // instead (not pretty!).
         desc = name;
       }

       AlsaDeviceLocator *device = new AlsaDeviceLocator(desc, name);

       devices->push_back(device);

       if (desc != name) {
         free(desc);
       }
     }

     free(name);
   }

   err = LATE(snd_device_name_free_hint)(hints);
   if (err != 0) {
     LOG(LS_ERROR) << "snd_device_name_free_hint(): " << GetError(err);
     // Continue and return true anyways, since we did get the whole list.
   }

   return true;
 }

 bool AlsaSoundSystem::GetDefaultDevice(SoundDeviceLocator **device) {
   if (!IsInitialized()) {
     return false;
   }
   *device = new AlsaDeviceLocator("Default device", "default");
   return true;
 }

 inline size_t AlsaSoundSystem::FrameSize(const OpenParams &params) {
   ASSERT(params.format < ARRAY_SIZE(kCricketFormatToSampleSizeTable));
   return kCricketFormatToSampleSizeTable[params.format] * params.channels;
 }

 template <typename StreamInterface>
 StreamInterface *AlsaSoundSystem::OpenDevice(
     const SoundDeviceLocator *device,
     const OpenParams &params,
     snd_pcm_stream_t type,
     StreamInterface *(AlsaSoundSystem::*start_fn)(
         snd_pcm_t *handle,
         size_t frame_size,
         int wait_timeout_ms,
         int flags,
         int freq)) {

   if (!IsInitialized()) {
     return NULL;
   }

   StreamInterface *stream;
   int err;

   const char *dev = static_cast<const AlsaDeviceLocator *>(device)->
       device_name().c_str();

   snd_pcm_t *handle = NULL;
   err = LATE(snd_pcm_open)(
       &handle,
       dev,
       type,
       // No flags.
       0);
   if (err != 0) {
     LOG(LS_ERROR) << "snd_pcm_open(" << dev << "): " << GetError(err);
     return NULL;
   }
   LOG(LS_VERBOSE) << "Opening " << dev;
   ASSERT(handle);  // If open succeeded, handle ought to be valid

   // Compute requested latency in microseconds.
   int latency;
   if (params.latency == kNoLatencyRequirements) {
     latency = kDefaultLatencyUsecs;
   } else {
     // kLowLatency is 0, so we treat it the same as a request for zero latency.
     // Compute what the user asked for.
     latency = talk_base::kNumMicrosecsPerSec *
         params.latency /
         params.freq /
         FrameSize(params);
     // And this is what we'll actually use.
     latency = talk_base::_max(latency, kMinimumLatencyUsecs);
   }

   ASSERT(params.format < ARRAY_SIZE(kCricketFormatToAlsaFormatTable));

   err = LATE(snd_pcm_set_params)(handle,
                                  kCricketFormatToAlsaFormatTable[params.format],
                                  // SoundSystemInterface only supports
                                  // interleaved audio.
                                  SND_PCM_ACCESS_RW_INTERLEAVED,
                                  params.channels,
                                  params.freq,
                                  1,  // Allow ALSA to resample.
                                  latency);
   if (err != 0) {
     LOG(LS_ERROR) << "snd_pcm_set_params(): " << GetError(err);
     goto fail;
   }

   err = LATE(snd_pcm_prepare)(handle);
   if (err != 0) {
     LOG(LS_ERROR) << "snd_pcm_prepare(): " << GetError(err);
     goto fail;
   }

   stream = (this->*start_fn)(
       handle,
       FrameSize(params),
       // We set the wait time to twice the requested latency, so that wait
       // timeouts should be rare.
       2 * latency / talk_base::kNumMicrosecsPerMillisec,
       params.flags,
       params.freq);
   if (stream) {
     return stream;
   }
   // Else fall through.

  fail:
   err = LATE(snd_pcm_close)(handle);
   if (err != 0) {
     LOG(LS_ERROR) << "snd_pcm_close(): " << GetError(err);
   }
   return NULL;
 }

 SoundOutputStreamInterface *AlsaSoundSystem::StartOutputStream(
     snd_pcm_t *handle,
     size_t frame_size,
     int wait_timeout_ms,
     int flags,
     int freq) {
   // Nothing to do here but instantiate the stream.
   return new AlsaOutputStream(
       this, handle, frame_size, wait_timeout_ms, flags, freq);
 }

 SoundInputStreamInterface *AlsaSoundSystem::StartInputStream(
     snd_pcm_t *handle,
     size_t frame_size,
     int wait_timeout_ms,
     int flags,
     int freq) {
   // Output streams start automatically once enough data has been written, but
   // input streams must be started manually or else snd_pcm_wait() will never
   // return true.
   int err;
   err = LATE(snd_pcm_start)(handle);
   if (err != 0) {
     LOG(LS_ERROR) << "snd_pcm_start(): " << GetError(err);
     return NULL;
   }
   return new AlsaInputStream(
       this, handle, frame_size, wait_timeout_ms, flags, freq);
 }

 inline const char *AlsaSoundSystem::GetError(int err) {
   return LATE(snd_strerror)(err);
 }

 }  // namespace cricket
	/*
	* libjingle
	* Copyright 2004--2010, Google Inc.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions are met:
	*
	* 1. Redistributions of source code must retain the above copyright notice,
	* this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright notice,
	* this list of conditions and the following disclaimer in the documentation
	* and/or other materials provided with the distribution.
	* 3. The name of the author may not be used to endorse or promote products
	* derived from this software without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
	* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
	* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
	* EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
	* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
	* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
	* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
	* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
	* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#include "talk/sound/alsasoundsystem.h"

	#include "talk/base/common.h"
	#include "talk/base/logging.h"
	#include "talk/base/scoped_ptr.h"
	#include "talk/base/stringutils.h"
	#include "talk/base/timeutils.h"
	#include "talk/base/worker.h"
	#include "talk/sound/sounddevicelocator.h"
	#include "talk/sound/soundinputstreaminterface.h"
	#include "talk/sound/soundoutputstreaminterface.h"

	namespace cricket {

	// Lookup table from the cricket format enum in soundsysteminterface.h to
	// ALSA's enums.
	static const snd_pcm_format_t kCricketFormatToAlsaFormatTable[] = {
	// The order here must match the order in soundsysteminterface.h
	SND_PCM_FORMAT_S16_LE,
	};

	// Lookup table for the size of a single sample of a given format.
	static const size_t kCricketFormatToSampleSizeTable[] = {
	// The order here must match the order in soundsysteminterface.h
	sizeof(int16_t), // 2
	};

	// Minimum latency we allow, in microseconds. This is more or less arbitrary,
	// but it has to be at least large enough to be able to buffer data during a
	// missed context switch, and the typical Linux scheduling quantum is 10ms.
	static const int kMinimumLatencyUsecs = 20 * 1000;

	// The latency we'll use for kNoLatencyRequirements (chosen arbitrarily).
	static const int kDefaultLatencyUsecs = kMinimumLatencyUsecs * 2;

	// We translate newlines in ALSA device descriptions to hyphens.
	static const char kAlsaDescriptionSearch[] = "\n";
	static const char kAlsaDescriptionReplace[] = " - ";

	class AlsaDeviceLocator : public SoundDeviceLocator {
	public:
	AlsaDeviceLocator(const std::string &name,
	const std::string &device_name)
	: SoundDeviceLocator(name, device_name) {
	// The ALSA descriptions have newlines in them, which won't show up in
	// a drop-down box. Replace them with hyphens.
	talk_base::replace_substrs(kAlsaDescriptionSearch,
	sizeof(kAlsaDescriptionSearch) - 1,
	kAlsaDescriptionReplace,
	sizeof(kAlsaDescriptionReplace) - 1,
	&name_);
	}

	virtual SoundDeviceLocator *Copy() const {
	return new AlsaDeviceLocator(*this);
	}
	};

	// Accesses ALSA functions through our late-binding symbol table instead of
	// directly. This way we don't have to link to libasound, which means our binary
	// will load faster and we can run on strange systems that may not have
	// libasound
	#define LATE(sym) \
	LATESYM_GET(AlsaSymbolTable, &alsa_->symbol_table_, sym)

	// Functionality that is common to both AlsaInputStream and AlsaOutputStream.
	class AlsaStream {
	public:
	AlsaStream(AlsaSoundSystem *alsa,
	snd_pcm_t *handle,
	size_t frame_size,
	int wait_timeout_ms,
	int flags,
	int freq)
	: alsa_(alsa),
	handle_(handle),
	frame_size_(frame_size),
	wait_timeout_ms_(wait_timeout_ms),
	flags_(flags),
	freq_(freq) {
	}

	~AlsaStream() {
	Close();
	}

	// Waits for the stream to be ready to accept/return more data, and returns
	// how much can be written/read, or 0 if we need to Wait() again.
	snd_pcm_uframes_t Wait() {
	snd_pcm_sframes_t frames;
	// Ideally we would not use snd_pcm_wait() and instead hook snd_pcm_poll_*
	// into PhysicalSocketServer, but PhysicalSocketServer is nasty enough
	// already and the current clients of SoundSystemInterface do not run
	// anything else on their worker threads, so snd_pcm_wait() is good enough.
	frames = LATE(snd_pcm_avail_update)(handle_);
	if (frames < 0) {
	LOG(LS_ERROR) << "snd_pcm_avail_update(): " << GetError(frames);
	Recover(frames);
	return 0;
	} else if (frames > 0) {
	// Already ready, so no need to wait.
	return frames;
	}
	// Else no space/data available, so must wait.
	int ready = LATE(snd_pcm_wait)(handle_, wait_timeout_ms_);
	if (ready < 0) {
	LOG(LS_ERROR) << "snd_pcm_wait(): " << GetError(ready);
	Recover(ready);
	return 0;
	} else if (ready == 0) {
	// Timeout, so nothing can be written/read right now.
	// We set the timeout to twice the requested latency, so continuous
	// timeouts are indicative of a problem, so log as a warning.
	LOG(LS_WARNING) << "Timeout while waiting on stream";
	return 0;
	}
	// Else ready > 0 (i.e., 1), so it's ready. Get count.
	frames = LATE(snd_pcm_avail_update)(handle_);
	if (frames < 0) {
	LOG(LS_ERROR) << "snd_pcm_avail_update(): " << GetError(frames);
	Recover(frames);
	return 0;
	} else if (frames == 0) {
	// wait() said we were ready, so this ought to have been positive. Has
	// been observed to happen in practice though.
	LOG(LS_WARNING) << "Spurious wake-up";
	}
	return frames;
	}

	int CurrentDelayUsecs() {
	if (!(flags_ & SoundSystemInterface::FLAG_REPORT_LATENCY)) {
	return 0;
	}

	snd_pcm_sframes_t delay;
	int err = LATE(snd_pcm_delay)(handle_, &delay);
	if (err != 0) {
	LOG(LS_ERROR) << "snd_pcm_delay(): " << GetError(err);
	Recover(err);
	// We'd rather continue playout/capture with an incorrect delay than stop
	// it altogether, so return a valid value.
	return 0;
	}
	// The delay is in frames. Convert to microseconds.
	return delay * talk_base::kNumMicrosecsPerSec / freq_;
	}

	// Used to recover from certain recoverable errors, principally buffer overrun
	// or underrun (identified as EPIPE). Without calling this the stream stays
	// in the error state forever.
	bool Recover(int error) {
	int err;
	err = LATE(snd_pcm_recover)(handle_,
	error,
	// Silent; i.e., no logging on stderr.
	1);
	if (err != 0) {
	// Docs say snd_pcm_recover returns the original error if it is not one
	// of the recoverable ones, so this log message will probably contain the
	// same error twice.
	LOG(LS_ERROR) << "Unable to recover from \"" << GetError(error) << "\": "
	<< GetError(err);
	return false;
	}
	if (error == -EPIPE && // Buffer underrun/overrun.
	LATE(snd_pcm_stream)(handle_) == SND_PCM_STREAM_CAPTURE) {
	// For capture streams we also have to repeat the explicit start() to get
	// data flowing again.
	err = LATE(snd_pcm_start)(handle_);
	if (err != 0) {
	LOG(LS_ERROR) << "snd_pcm_start(): " << GetError(err);
	return false;
	}
	}
	return true;
	}

	bool Close() {
	if (handle_) {
	int err;
	err = LATE(snd_pcm_drop)(handle_);
	if (err != 0) {
	LOG(LS_ERROR) << "snd_pcm_drop(): " << GetError(err);
	// Continue anyways.
	}
	err = LATE(snd_pcm_close)(handle_);
	if (err != 0) {
	LOG(LS_ERROR) << "snd_pcm_close(): " << GetError(err);
	// Continue anyways.
	}
	handle_ = NULL;
	}
	return true;
	}

	AlsaSoundSystem *alsa() {
	return alsa_;
	}

	snd_pcm_t *handle() {
	return handle_;
	}

	const char *GetError(int err) {
	return alsa_->GetError(err);
	}

	size_t frame_size() {
	return frame_size_;
	}

	private:
	AlsaSoundSystem *alsa_;
	snd_pcm_t *handle_;
	size_t frame_size_;
	int wait_timeout_ms_;
	int flags_;
	int freq_;

	DISALLOW_COPY_AND_ASSIGN(AlsaStream);
	};

	// Redefine for the next two classes.
	#undef LATE
	#define LATE(sym) \
	LATESYM_GET(AlsaSymbolTable, &stream_.alsa()->symbol_table_, sym)

	// Implementation of an input stream. See soundinputstreaminterface.h regarding
	// thread-safety.
	class AlsaInputStream :
	public SoundInputStreamInterface,
	private talk_base::Worker {
	public:
	AlsaInputStream(AlsaSoundSystem *alsa,
	snd_pcm_t *handle,
	size_t frame_size,
	int wait_timeout_ms,
	int flags,
	int freq)
	: stream_(alsa, handle, frame_size, wait_timeout_ms, flags, freq),
	buffer_size_(0) {
	}

	virtual ~AlsaInputStream() {
	bool success = StopReading();
	// We need that to live.
	VERIFY(success);
	}

	virtual bool StartReading() {
	return StartWork();
	}

	virtual bool StopReading() {
	return StopWork();
	}

	virtual bool GetVolume(int *volume) {
	// TODO: Implement this.
	return false;
	}

	virtual bool SetVolume(int volume) {
	// TODO: Implement this.
	return false;
	}

	virtual bool Close() {
	return StopReading() && stream_.Close();
	}

	virtual int LatencyUsecs() {
	return stream_.CurrentDelayUsecs();
	}

	private:
	// Inherited from Worker.
	virtual void OnStart() {
	HaveWork();
	}

	// Inherited from Worker.
	virtual void OnHaveWork() {
	// Block waiting for data.
	snd_pcm_uframes_t avail = stream_.Wait();
	if (avail > 0) {
	// Data is available.
	size_t size = avail * stream_.frame_size();
	if (size > buffer_size_) {
	// Must increase buffer size.
	buffer_.reset(new char[size]);
	buffer_size_ = size;
	}
	// Read all the data.
	snd_pcm_sframes_t read = LATE(snd_pcm_readi)(stream_.handle(),
	buffer_.get(),
	avail);
	if (read < 0) {
	LOG(LS_ERROR) << "snd_pcm_readi(): " << GetError(read);
	stream_.Recover(read);
	} else if (read == 0) {
	// Docs say this shouldn't happen.
	ASSERT(false);
	LOG(LS_ERROR) << "No data?";
	} else {
	// Got data. Pass it off to the app.
	SignalSamplesRead(buffer_.get(),
	read * stream_.frame_size(),
	this);
	}
	}
	// Check for more data with no delay, after any pending messages are
	// dispatched.
	HaveWork();
	}

	// Inherited from Worker.
	virtual void OnStop() {
	// Nothing to do.
	}

	const char *GetError(int err) {
	return stream_.GetError(err);
	}

	AlsaStream stream_;
	talk_base::scoped_array<char> buffer_;
	size_t buffer_size_;

	DISALLOW_COPY_AND_ASSIGN(AlsaInputStream);
	};

	// Implementation of an output stream. See soundoutputstreaminterface.h
	// regarding thread-safety.
	class AlsaOutputStream :
	public SoundOutputStreamInterface,
	private talk_base::Worker {
	public:
	AlsaOutputStream(AlsaSoundSystem *alsa,
	snd_pcm_t *handle,
	size_t frame_size,
	int wait_timeout_ms,
	int flags,
	int freq)
	: stream_(alsa, handle, frame_size, wait_timeout_ms, flags, freq) {
	}

	virtual ~AlsaOutputStream() {
	bool success = DisableBufferMonitoring();
	// We need that to live.
	VERIFY(success);
	}

	virtual bool EnableBufferMonitoring() {
	return StartWork();
	}

	virtual bool DisableBufferMonitoring() {
	return StopWork();
	}

	virtual bool WriteSamples(const void *sample_data,
	size_t size) {
	if (size % stream_.frame_size() != 0) {
	// No client of SoundSystemInterface does this, so let's not support it.
	// (If we wanted to support it, we'd basically just buffer the fractional
	// frame until we get more data.)
	ASSERT(false);
	LOG(LS_ERROR) << "Writes with fractional frames are not supported";
	return false;
	}
	snd_pcm_uframes_t frames = size / stream_.frame_size();
	snd_pcm_sframes_t written = LATE(snd_pcm_writei)(stream_.handle(),
	sample_data,
	frames);
	if (written < 0) {
	LOG(LS_ERROR) << "snd_pcm_writei(): " << GetError(written);
	stream_.Recover(written);
	return false;
	} else if (static_cast<snd_pcm_uframes_t>(written) < frames) {
	// Shouldn't happen. Drop the rest of the data.
	LOG(LS_ERROR) << "Stream wrote only " << written << " of " << frames
	<< " frames!";
	return false;
	}
	return true;
	}

	virtual bool GetVolume(int *volume) {
	// TODO: Implement this.
	return false;
	}

	virtual bool SetVolume(int volume) {
	// TODO: Implement this.
	return false;
	}

	virtual bool Close() {
	return DisableBufferMonitoring() && stream_.Close();
	}

	virtual int LatencyUsecs() {
	return stream_.CurrentDelayUsecs();
	}

	private:
	// Inherited from Worker.
	virtual void OnStart() {
	HaveWork();
	}

	// Inherited from Worker.
	virtual void OnHaveWork() {
	snd_pcm_uframes_t avail = stream_.Wait();
	if (avail > 0) {
	size_t space = avail * stream_.frame_size();
	SignalBufferSpace(space, this);
	}
	HaveWork();
	}

	// Inherited from Worker.
	virtual void OnStop() {
	// Nothing to do.
	}

	const char *GetError(int err) {
	return stream_.GetError(err);
	}

	AlsaStream stream_;

	DISALLOW_COPY_AND_ASSIGN(AlsaOutputStream);
	};

	// Redefine for the main class.
	#undef LATE
	#define LATE(sym) LATESYM_GET(AlsaSymbolTable, &symbol_table_, sym)

	AlsaSoundSystem::AlsaSoundSystem() : initialized_(false) {}

	AlsaSoundSystem::~AlsaSoundSystem() {
	// Not really necessary, because Terminate() doesn't really do anything.
	Terminate();
	}

	bool AlsaSoundSystem::Init() {
	if (IsInitialized()) {
	return true;
	}

	// Load libasound.
	if (!symbol_table_.Load()) {
	// Very odd for a Linux machine to not have a working libasound ...
	LOG(LS_ERROR) << "Failed to load symbol table";
	return false;
	}

	initialized_ = true;

	return true;
	}

	void AlsaSoundSystem::Terminate() {
	if (!IsInitialized()) {
	return;
	}

	initialized_ = false;

	// We do not unload the symbol table because we may need it again soon if
	// Init() is called again.
	}

	bool AlsaSoundSystem::EnumeratePlaybackDevices(
	SoundDeviceLocatorList *devices) {
	return EnumerateDevices(devices, false);
	}

	bool AlsaSoundSystem::EnumerateCaptureDevices(
	SoundDeviceLocatorList *devices) {
	return EnumerateDevices(devices, true);
	}

	bool AlsaSoundSystem::GetDefaultPlaybackDevice(SoundDeviceLocator **device) {
	return GetDefaultDevice(device);
	}

	bool AlsaSoundSystem::GetDefaultCaptureDevice(SoundDeviceLocator **device) {
	return GetDefaultDevice(device);
	}

	SoundOutputStreamInterface *AlsaSoundSystem::OpenPlaybackDevice(
	const SoundDeviceLocator *device,
	const OpenParams &params) {
	return OpenDevice<SoundOutputStreamInterface>(
	device,
	params,
	SND_PCM_STREAM_PLAYBACK,
	&AlsaSoundSystem::StartOutputStream);
	}

	SoundInputStreamInterface *AlsaSoundSystem::OpenCaptureDevice(
	const SoundDeviceLocator *device,
	const OpenParams &params) {
	return OpenDevice<SoundInputStreamInterface>(
	device,
	params,
	SND_PCM_STREAM_CAPTURE,
	&AlsaSoundSystem::StartInputStream);
	}

	const char *AlsaSoundSystem::GetName() const {
	return "ALSA";
	}

	bool AlsaSoundSystem::EnumerateDevices(
	SoundDeviceLocatorList *devices,
	bool capture_not_playback) {
	ClearSoundDeviceLocatorList(devices);

	if (!IsInitialized()) {
	return false;
	}

	const char *type = capture_not_playback ? "Input" : "Output";
	// dmix and dsnoop are only for playback and capture, respectively, but ALSA
	// stupidly includes them in both lists.
	const char *ignore_prefix = capture_not_playback ? "dmix:" : "dsnoop:";
	// (ALSA lists many more "devices" of questionable interest, but we show them
	// just in case the weird devices may actually be desirable for some
	// users/systems.)
	const char *ignore_default = "default";
	const char *ignore_null = "null";
	const char *ignore_pulse = "pulse";
	// The 'pulse' entry has a habit of mysteriously disappearing when you query
	// a second time. Remove it from our list. (GIPS lib did the same thing.)
	int err;

	void **hints;
	err = LATE(snd_device_name_hint)(-1, // All cards
	"pcm", // Only PCM devices
	&hints);
	if (err != 0) {
	LOG(LS_ERROR) << "snd_device_name_hint(): " << GetError(err);
	return false;
	}

	for (void *list = hints; list != NULL; ++list) {
	char actual_type = LATE(snd_device_name_get_hint)(list, "IOID");
	if (actual_type) { // NULL means it's both.
	bool wrong_type = (strcmp(actual_type, type) != 0);
	free(actual_type);
	if (wrong_type) {
	// Wrong type of device (i.e., input vs. output).
	continue;
	}
	}

	char name = LATE(snd_device_name_get_hint)(list, "NAME");
	if (!name) {
	LOG(LS_ERROR) << "Device has no name???";
	// Skip it.
	continue;
	}

	// Now check if we actually want to show this device.
	if (strcmp(name, ignore_default) != 0 &&
	strcmp(name, ignore_null) != 0 &&
	strcmp(name, ignore_pulse) != 0 &&
	!talk_base::starts_with(name, ignore_prefix)) {

	// Yes, we do.
	char desc = LATE(snd_device_name_get_hint)(list, "DESC");
	if (!desc) {
	// Virtual devices don't necessarily have descriptions. Use their names
	// instead (not pretty!).
	desc = name;
	}

	AlsaDeviceLocator *device = new AlsaDeviceLocator(desc, name);

	devices->push_back(device);

	if (desc != name) {
	free(desc);
	}
	}

	free(name);
	}

	err = LATE(snd_device_name_free_hint)(hints);
	if (err != 0) {
	LOG(LS_ERROR) << "snd_device_name_free_hint(): " << GetError(err);
	// Continue and return true anyways, since we did get the whole list.
	}

	return true;
	}

	bool AlsaSoundSystem::GetDefaultDevice(SoundDeviceLocator **device) {
	if (!IsInitialized()) {
	return false;
	}
	*device = new AlsaDeviceLocator("Default device", "default");
	return true;
	}

	inline size_t AlsaSoundSystem::FrameSize(const OpenParams &params) {
	ASSERT(params.format < ARRAY_SIZE(kCricketFormatToSampleSizeTable));
	return kCricketFormatToSampleSizeTable[params.format] * params.channels;
	}

	template <typename StreamInterface>
	StreamInterface *AlsaSoundSystem::OpenDevice(
	const SoundDeviceLocator *device,
	const OpenParams &params,
	snd_pcm_stream_t type,
	StreamInterface (AlsaSoundSystem::start_fn)(
	snd_pcm_t *handle,
	size_t frame_size,
	int wait_timeout_ms,
	int flags,
	int freq)) {

	if (!IsInitialized()) {
	return NULL;
	}

	StreamInterface *stream;
	int err;

	const char dev = static_cast<const AlsaDeviceLocator >(device)->
	device_name().c_str();

	snd_pcm_t *handle = NULL;
	err = LATE(snd_pcm_open)(
	&handle,
	dev,
	type,
	// No flags.
	0);
	if (err != 0) {
	LOG(LS_ERROR) << "snd_pcm_open(" << dev << "): " << GetError(err);
	return NULL;
	}
	LOG(LS_VERBOSE) << "Opening " << dev;
	ASSERT(handle); // If open succeeded, handle ought to be valid

	// Compute requested latency in microseconds.
	int latency;
	if (params.latency == kNoLatencyRequirements) {
	latency = kDefaultLatencyUsecs;
	} else {
	// kLowLatency is 0, so we treat it the same as a request for zero latency.
	// Compute what the user asked for.
	latency = talk_base::kNumMicrosecsPerSec *
	params.latency /
	params.freq /
	FrameSize(params);
	// And this is what we'll actually use.
	latency = talk_base::_max(latency, kMinimumLatencyUsecs);
	}

	ASSERT(params.format < ARRAY_SIZE(kCricketFormatToAlsaFormatTable));

	err = LATE(snd_pcm_set_params)(handle,
	kCricketFormatToAlsaFormatTable[params.format],
	// SoundSystemInterface only supports
	// interleaved audio.
	SND_PCM_ACCESS_RW_INTERLEAVED,
	params.channels,
	params.freq,
	1, // Allow ALSA to resample.
	latency);
	if (err != 0) {
	LOG(LS_ERROR) << "snd_pcm_set_params(): " << GetError(err);
	goto fail;
	}

	err = LATE(snd_pcm_prepare)(handle);
	if (err != 0) {
	LOG(LS_ERROR) << "snd_pcm_prepare(): " << GetError(err);
	goto fail;
	}

	stream = (this->*start_fn)(
	handle,
	FrameSize(params),
	// We set the wait time to twice the requested latency, so that wait
	// timeouts should be rare.
	2 * latency / talk_base::kNumMicrosecsPerMillisec,
	params.flags,
	params.freq);
	if (stream) {
	return stream;
	}
	// Else fall through.

	fail:
	err = LATE(snd_pcm_close)(handle);
	if (err != 0) {
	LOG(LS_ERROR) << "snd_pcm_close(): " << GetError(err);
	}
	return NULL;
	}

	SoundOutputStreamInterface *AlsaSoundSystem::StartOutputStream(
	snd_pcm_t *handle,
	size_t frame_size,
	int wait_timeout_ms,
	int flags,
	int freq) {
	// Nothing to do here but instantiate the stream.
	return new AlsaOutputStream(
	this, handle, frame_size, wait_timeout_ms, flags, freq);
	}

	SoundInputStreamInterface *AlsaSoundSystem::StartInputStream(
	snd_pcm_t *handle,
	size_t frame_size,
	int wait_timeout_ms,
	int flags,
	int freq) {
	// Output streams start automatically once enough data has been written, but
	// input streams must be started manually or else snd_pcm_wait() will never
	// return true.
	int err;
	err = LATE(snd_pcm_start)(handle);
	if (err != 0) {
	LOG(LS_ERROR) << "snd_pcm_start(): " << GetError(err);
	return NULL;
	}
	return new AlsaInputStream(
	this, handle, frame_size, wait_timeout_ms, flags, freq);
	}

	inline const char *AlsaSoundSystem::GetError(int err) {
	return LATE(snd_strerror)(err);
	}

	} // namespace cricket