Add RTCAudioSession proxy class.

webrtc/modules/audio_device/ios/objc/RTCAudioSession.mm

+/*
+ *  Copyright 2016 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#import "webrtc/modules/audio_device/ios/objc/RTCAudioSession.h"
+
+#include "webrtc/base/checks.h"
+
+#import "webrtc/base/objc/RTCLogging.h"
+#import "webrtc/modules/audio_device/ios/objc/RTCAudioSession+Private.h"
+
+NSString * const kRTCAudioSessionErrorDomain = @"org.webrtc.RTCAudioSession";
+NSInteger const kRTCAudioSessionErrorLockRequired = -1;
+
+// This class needs to be thread-safe because it is accessed from many threads.
+// TODO(tkchin): Consider more granular locking. We're not expecting a lot of
+// lock contention so coarse locks should be fine for now.
+@implementation RTCAudioSession {
+  AVAudioSession *_session;
+  NSHashTable *_delegates;
+  NSInteger _activationCount;
+  BOOL _isActive;
+  BOOL _isLocked;
+}
+
+@synthesize session = _session;
+@synthesize lock = _lock;
+
++ (instancetype)sharedInstance {
+  static dispatch_once_t onceToken;
+  static RTCAudioSession *sharedInstance = nil;
+  dispatch_once(&onceToken, ^{
+    sharedInstance = [[RTCAudioSession alloc] init];
+  });
+  return sharedInstance;
+}
+
+- (instancetype)init {
+  if (self = [super init]) {
+    _session = [AVAudioSession sharedInstance];
+    _delegates = [NSHashTable weakObjectsHashTable];
+    _lock = [[NSRecursiveLock alloc] init];
+    NSNotificationCenter *center = [NSNotificationCenter defaultCenter];
+    [center addObserver:self
+               selector:@selector(handleInterruptionNotification:)
+                   name:AVAudioSessionInterruptionNotification
+                 object:nil];
+    [center addObserver:self
+               selector:@selector(handleRouteChangeNotification:)
+                   name:AVAudioSessionRouteChangeNotification
+                 object:nil];
+    // TODO(tkchin): Maybe listen to SilenceSecondaryAudioHintNotification.
+    [center addObserver:self
+               selector:@selector(handleMediaServicesWereLost:)
+                   name:AVAudioSessionMediaServicesWereLostNotification
+                 object:nil];
+    [center addObserver:self
+               selector:@selector(handleMediaServicesWereReset:)
+                   name:AVAudioSessionMediaServicesWereResetNotification
+                 object:nil];
+  }
+  return self;
+}
+
+- (void)dealloc {
+  [[NSNotificationCenter defaultCenter] removeObserver:self];
+}
+
+- (void)setIsActive:(BOOL)isActive {
+  @synchronized(self) {
+    _isActive = isActive;
+  }
+}
+
+- (BOOL)isActive {
+  @synchronized(self) {
+    return _isActive;
+  }
+}
+
+- (BOOL)isLocked {
+  @synchronized(self) {
+    return _isLocked;
+  }
+}
+
+- (void)addDelegate:(id<RTCAudioSessionDelegate>)delegate {
+  @synchronized(self) {
+    [_delegates addObject:delegate];
+  }
+}
+
+- (void)removeDelegate:(id<RTCAudioSessionDelegate>)delegate {
+  @synchronized(self) {
+    [_delegates removeObject:delegate];
+  }
+}
+
+- (void)lockForConfiguration {
+  [_lock lock];
+  @synchronized(self) {
+    _isLocked = YES;
+  }
+}
+
+- (void)unlockForConfiguration {
+  // Don't let threads other than the one that called lockForConfiguration
+  // unlock.
+  if ([_lock tryLock]) {
+    @synchronized(self) {
+      _isLocked = NO;
+    }
+    // One unlock for the tryLock, and another one to actually unlock. If this
+    // was called without anyone calling lock, the underlying NSRecursiveLock
+    // should spit out an error.
+    [_lock unlock];
+    [_lock unlock];
+  }
+}
+
+#pragma mark - AVAudioSession proxy methods
+
+- (NSString *)category {
+  return self.session.category;
+}
+
+- (AVAudioSessionCategoryOptions)categoryOptions {
+  return self.session.categoryOptions;
+}
+
+- (NSString *)mode {
+  return self.session.mode;
+}
+
+- (BOOL)secondaryAudioShouldBeSilencedHint {
+  return self.session.secondaryAudioShouldBeSilencedHint;
+}
+
+- (AVAudioSessionRouteDescription *)currentRoute {
+  return self.session.currentRoute;
+}
+
+- (NSInteger)maximumInputNumberOfChannels {
+  return self.session.maximumInputNumberOfChannels;
+}
+
+- (NSInteger)maximumOutputNumberOfChannels {
+  return self.session.maximumOutputNumberOfChannels;
+}
+
+- (float)inputGain {
+  return self.session.inputGain;
+}
+
+- (BOOL)inputGainSettable {
+  return self.session.inputGainSettable;
+}
+
+- (BOOL)inputAvailable {
+  return self.session.inputAvailable;
+}
+
+- (NSArray<AVAudioSessionDataSourceDescription *> *)inputDataSources {
+  return self.session.inputDataSources;
+}
+
+- (AVAudioSessionDataSourceDescription *)inputDataSource {
+  return self.session.inputDataSource;
+}
+
+- (NSArray<AVAudioSessionDataSourceDescription *> *)outputDataSources {
+  return self.session.outputDataSources;
+}
+
+- (AVAudioSessionDataSourceDescription *)outputDataSource {
+  return self.session.outputDataSource;
+}
+
+- (double)sampleRate {
+  return self.session.sampleRate;
+}
+
+- (NSInteger)inputNumberOfChannels {
+  return self.session.inputNumberOfChannels;
+}
+
+- (NSInteger)outputNumberOfChannels {
+  return self.session.outputNumberOfChannels;
+}
+
+- (float)outputVolume {
+  return self.session.outputVolume;
+}
+
+- (NSTimeInterval)inputLatency {
+  return self.session.inputLatency;
+}
+
+- (NSTimeInterval)outputLatency {
+  return self.session.outputLatency;
+}
+
+- (NSTimeInterval)IOBufferDuration {
+  return self.session.IOBufferDuration;
+}
+
+- (BOOL)setActive:(BOOL)active
+            error:(NSError **)outError {
+  if (![self checkLock:outError]) {
+    return NO;
+  }
+  NSInteger activationCount = self.activationCount;
+  if (!active && activationCount == 0) {
+    RTCLogWarning(@"Attempting to deactivate without prior activation.");
+  }
+  BOOL success = YES;
+  BOOL isActive = self.isActive;
+  // Keep a local error so we can log it.
+  NSError *error = nil;
+  BOOL shouldSetActive =
+      (active && !isActive) || (!active && isActive && activationCount == 1);
+  // Attempt to activate if we're not active.
+  // Attempt to deactivate if we're active and it's the last unbalanced call.
+  if (shouldSetActive) {
+    AVAudioSession *session = self.session;
+    // AVAudioSessionSetActiveOptionNotifyOthersOnDeactivation is used to ensure
+    // that other audio sessions that were interrupted by our session can return
+    // to their active state. It is recommended for VoIP apps to use this
+    // option.
+    AVAudioSessionSetActiveOptions options =
+        active ? 0 : AVAudioSessionSetActiveOptionNotifyOthersOnDeactivation;
+    success = [session setActive:active
+                     withOptions:options
+                           error:&error];
+    if (outError) {
+      *outError = error;
+    }
+  }
+  if (success) {
+    if (shouldSetActive) {
+      self.isActive = active;
+    }
+    if (active) {
+      [self incrementActivationCount];
+    }
+  } else {
+    RTCLogError(@"Failed to setActive:%d. Error: %@", active, error);
+  }
+  // Decrement activation count on deactivation whether or not it succeeded.
+  if (!active) {
+    [self decrementActivationCount];
+  }
+  RTCLog(@"Number of current activations: %ld", (long)self.activationCount);
+  return success;
+}
+
+- (BOOL)setCategory:(NSString *)category
+        withOptions:(AVAudioSessionCategoryOptions)options
+              error:(NSError **)outError {
+  if (![self checkLock:outError]) {
+    return NO;
+  }
+  return [self.session setCategory:category withOptions:options error:outError];
+}
+
+- (BOOL)setMode:(NSString *)mode error:(NSError **)outError {
+  if (![self checkLock:outError]) {
+    return NO;
+  }
+  return [self.session setMode:mode error:outError];
+}
+
+- (BOOL)setInputGain:(float)gain error:(NSError **)outError {
+  if (![self checkLock:outError]) {
+    return NO;
+  }
+  return [self.session setInputGain:gain error:outError];
+}
+
+- (BOOL)setPreferredSampleRate:(double)sampleRate error:(NSError **)outError {
+  if (![self checkLock:outError]) {
+    return NO;
+  }
+  return [self.session setPreferredSampleRate:sampleRate error:outError];
+}
+
+- (BOOL)setPreferredIOBufferDuration:(NSTimeInterval)duration
+                               error:(NSError **)outError {
+  if (![self checkLock:outError]) {
+    return NO;
+  }
+  return [self.session setPreferredIOBufferDuration:duration error:outError];
+}
+
+- (BOOL)setPreferredInputNumberOfChannels:(NSInteger)count
+                                    error:(NSError **)outError {
+  if (![self checkLock:outError]) {
+    return NO;
+  }
+  return [self.session setPreferredInputNumberOfChannels:count error:outError];
+}
+- (BOOL)setPreferredOutputNumberOfChannels:(NSInteger)count
+                                     error:(NSError **)outError {
+  if (![self checkLock:outError]) {
+    return NO;
+  }
+  return [self.session setPreferredOutputNumberOfChannels:count error:outError];
+}
+
+- (BOOL)overrideOutputAudioPort:(AVAudioSessionPortOverride)portOverride
+                          error:(NSError **)outError {
+  if (![self checkLock:outError]) {
+    return NO;
+  }
+  return [self.session overrideOutputAudioPort:portOverride error:outError];
+}
+
+- (BOOL)setPreferredInput:(AVAudioSessionPortDescription *)inPort
+                    error:(NSError **)outError {
+  if (![self checkLock:outError]) {
+    return NO;
+  }
+  return [self.session setPreferredInput:inPort error:outError];
+}
+
+- (BOOL)setInputDataSource:(AVAudioSessionDataSourceDescription *)dataSource
+                     error:(NSError **)outError {
+  if (![self checkLock:outError]) {
+    return NO;
+  }
+  return [self.session setInputDataSource:dataSource error:outError];
+}
+
+- (BOOL)setOutputDataSource:(AVAudioSessionDataSourceDescription *)dataSource
+                      error:(NSError **)outError {
+  if (![self checkLock:outError]) {
+    return NO;
+  }
+  return [self.session setOutputDataSource:dataSource error:outError];
+}
+
+#pragma mark - Notifications
+
+- (void)handleInterruptionNotification:(NSNotification *)notification {
+  NSNumber* typeNumber =
+      notification.userInfo[AVAudioSessionInterruptionTypeKey];
+  AVAudioSessionInterruptionType type =
+      (AVAudioSessionInterruptionType)typeNumber.unsignedIntegerValue;
+  switch (type) {
+    case AVAudioSessionInterruptionTypeBegan:
+      RTCLog(@"Audio session interruption began.");
+      self.isActive = NO;
+      [self notifyDidBeginInterruption];
+      break;
+    case AVAudioSessionInterruptionTypeEnded: {
+      RTCLog(@"Audio session interruption ended.");
+      [self updateAudioSessionAfterEvent];
+      NSNumber *optionsNumber =
+          notification.userInfo[AVAudioSessionInterruptionOptionKey];
+      AVAudioSessionInterruptionOptions options =
+          optionsNumber.unsignedIntegerValue;
+      BOOL shouldResume =
+          options & AVAudioSessionInterruptionOptionShouldResume;
+      [self notifyDidEndInterruptionWithShouldResumeSession:shouldResume];
+      break;
+    }
+  }
+}
+
+- (void)handleRouteChangeNotification:(NSNotification *)notification {
+  // Get reason for current route change.
+  NSNumber* reasonNumber =
+      notification.userInfo[AVAudioSessionRouteChangeReasonKey];
+  AVAudioSessionRouteChangeReason reason =
+      (AVAudioSessionRouteChangeReason)reasonNumber.unsignedIntegerValue;
+  RTCLog(@"Audio route changed:");
+  switch (reason) {
+    case AVAudioSessionRouteChangeReasonUnknown:
+      RTCLog(@"Audio route changed: ReasonUnknown");
+      break;
+    case AVAudioSessionRouteChangeReasonNewDeviceAvailable:
+      RTCLog(@"Audio route changed: NewDeviceAvailable");
+      break;
+    case AVAudioSessionRouteChangeReasonOldDeviceUnavailable:
+      RTCLog(@"Audio route changed: OldDeviceUnavailable");
+      break;
+    case AVAudioSessionRouteChangeReasonCategoryChange:
+      RTCLog(@"Audio route changed: CategoryChange to :%@",
+             self.session.category);
+      break;
+    case AVAudioSessionRouteChangeReasonOverride:
+      RTCLog(@"Audio route changed: Override");
+      break;
+    case AVAudioSessionRouteChangeReasonWakeFromSleep:
+      RTCLog(@"Audio route changed: WakeFromSleep");
+      break;
+    case AVAudioSessionRouteChangeReasonNoSuitableRouteForCategory:
+      RTCLog(@"Audio route changed: NoSuitableRouteForCategory");
+      break;
+    case AVAudioSessionRouteChangeReasonRouteConfigurationChange:
+      RTCLog(@"Audio route changed: RouteConfigurationChange");
+      break;
+  }
+  AVAudioSessionRouteDescription* previousRoute =
+      notification.userInfo[AVAudioSessionRouteChangePreviousRouteKey];
+  // Log previous route configuration.
+  RTCLog(@"Previous route: %@\nCurrent route:%@",
+         previousRoute, self.session.currentRoute);
+  [self notifyDidChangeRouteWithReason:reason previousRoute:previousRoute];
+}
+
+- (void)handleMediaServicesWereLost:(NSNotification *)notification {
+  RTCLog(@"Media services were lost.");
+  [self updateAudioSessionAfterEvent];
+  [self notifyMediaServicesWereLost];
+}
+
+- (void)handleMediaServicesWereReset:(NSNotification *)notification {
+  RTCLog(@"Media services were reset.");
+  [self updateAudioSessionAfterEvent];
+  [self notifyMediaServicesWereReset];
+}
+
+#pragma mark - Private
+
++ (NSError *)lockError {
+  NSDictionary *userInfo = @{
+    NSLocalizedDescriptionKey:
+        @"Must call lockForConfiguration before calling this method."
+  };
+  NSError *error =
+      [[NSError alloc] initWithDomain:kRTCAudioSessionErrorDomain
+                                 code:kRTCAudioSessionErrorLockRequired
+                             userInfo:userInfo];
+  return error;
+}
+
+- (BOOL)checkLock:(NSError **)outError {
+  // Check ivar instead of trying to acquire lock so that we won't accidentally
+  // acquire lock if it hasn't already been called.
+  if (!self.isLocked) {
+    if (outError) {
+      *outError = [RTCAudioSession lockError];
+    }
+    return NO;
+  }
+  return YES;
+}
+
+- (NSSet *)delegates {
+  @synchronized(self) {
+    return _delegates.setRepresentation;
+  }
+}
+
+- (NSInteger)activationCount {
+  @synchronized(self) {
+    return _activationCount;
+  }
+}
+
+- (NSInteger)incrementActivationCount {
+  RTCLog(@"Incrementing activation count.");
+  @synchronized(self) {
+    return ++_activationCount;
+  }
+}
+
+- (NSInteger)decrementActivationCount {
+  RTCLog(@"Decrementing activation count.");
+  @synchronized(self) {
+    return --_activationCount;
+  }
+}
+
+- (void)updateAudioSessionAfterEvent {
+  BOOL shouldActivate = self.activationCount > 0;
+  AVAudioSessionSetActiveOptions options = shouldActivate ?
+      0 : AVAudioSessionSetActiveOptionNotifyOthersOnDeactivation;
+  NSError *error = nil;
+  if ([self.session setActive:shouldActivate
+                  withOptions:options
+                        error:&error]) {
+    self.isActive = shouldActivate;
+  } else {
+    RTCLogError(@"Failed to set session active to %d. Error:%@",
+                shouldActivate, error.localizedDescription);
+  }
+}
+
+- (void)notifyDidBeginInterruption {
+  for (id<RTCAudioSessionDelegate> delegate in self.delegates) {
+    [delegate audioSessionDidBeginInterruption:self];
+  }
+}
+
+- (void)notifyDidEndInterruptionWithShouldResumeSession:
+    (BOOL)shouldResumeSession {
+  for (id<RTCAudioSessionDelegate> delegate in self.delegates) {
+    [delegate audioSessionDidEndInterruption:self
+                         shouldResumeSession:shouldResumeSession];
+  }
+
+}
+
+- (void)notifyDidChangeRouteWithReason:(AVAudioSessionRouteChangeReason)reason
+    previousRoute:(AVAudioSessionRouteDescription *)previousRoute {
+  for (id<RTCAudioSessionDelegate> delegate in self.delegates) {
+    [delegate audioSessionDidChangeRoute:self
+                                  reason:reason
+                           previousRoute:previousRoute];
+  }
+}
+
+- (void)notifyMediaServicesWereLost {
+  for (id<RTCAudioSessionDelegate> delegate in self.delegates) {
+    [delegate audioSessionMediaServicesWereLost:self];
+  }
+}
+
+- (void)notifyMediaServicesWereReset {
+  for (id<RTCAudioSessionDelegate> delegate in self.delegates) {
+    [delegate audioSessionMediaServicesWereReset:self];
+  }
+}
+
+@end