Refactor AVAudioSession intialization code.

webrtc/modules/audio_device/ios/objc/RTCAudioSession+Configuration.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"
+
+#import "webrtc/base/objc/RTCLogging.h"
+#import "webrtc/modules/audio_device/ios/objc/RTCAudioSession+Private.h"
+#import "webrtc/modules/audio_device/ios/objc/RTCAudioSessionConfiguration.h"
+
+@implementation RTCAudioSession (Configuration)
+
+- (BOOL)isConfiguredForWebRTC {
+  // Ensure that the device currently supports audio input.
+  if (!self.inputAvailable) {
+    RTCLogError(@"No audio input path is available!");
+    return NO;
+  }
+
+  // Only check a minimal list of requirements for whether we have
+  // what we want.
+  RTCAudioSessionConfiguration *currentConfig =
+      [RTCAudioSessionConfiguration currentConfiguration];
+  RTCAudioSessionConfiguration *webRTCConfig =
+      [RTCAudioSessionConfiguration webRTCConfiguration];
+
+  if (![currentConfig.category isEqualToString:webRTCConfig.category]) {
+    RTCLog(@"Current category %@ does not match %@",
+           currentConfig.category,
+           webRTCConfig.category);
+    return NO;
+  }
+
+  if (![currentConfig.mode isEqualToString:webRTCConfig.mode]) {
+    RTCLog(@"Current mode %@ does not match %@",
+           currentConfig.mode,
+           webRTCConfig.mode);
+    return NO;
+  }
+
+  return YES;
+}
+
+- (BOOL)setConfiguration:(RTCAudioSessionConfiguration *)configuration
+                  active:(BOOL)active
+                   error:(NSError **)outError {
+  if (![self checkLock:outError]) {
+    return NO;
+  }
+  // Provide an error even if there isn't one so we can log it. We will not

[henrika_webrtc, 2016/03/10 14:42:12]

Nit, you have space above comment on lines 25 and 26.

[tkchin_webrtc, 2016/03/10 23:07:09]

Done.

+  // return immediately on error in this function and instead try to set
+  // everything we can.
+  NSError *error = nil;
+  if (outError) {
+    error = *outError;

[Chuck, 2016/03/10 21:16:37]

I might be reasoning about this incorrectly, but will this actually return an
error object to the caller?

if (outError) {
  *outError = nil;
}

and

if (outError) {
  *outError = error;
}

at the end before return YES is what I would expect.

[tkchin_webrtc, 2016/03/10 23:07:09]

Done.

+  }
+
+  if (self.category != configuration.category ||
+      self.categoryOptions != configuration.categoryOptions) {
+    error = nil;
+    if (![self setCategory:configuration.category
+               withOptions:configuration.categoryOptions
+                     error:&error]) {
+      RTCLogError(@"Failed to set category: %@", error.localizedDescription);
+    }
+  }
+
+  if (self.mode != configuration.mode) {
+    error = nil;
+    if (![self setMode:configuration.mode error:&error]) {
+      RTCLogError(@"Failed to set mode: %@", error.localizedDescription);
+    }
+  }
+
+  if (self.sampleRate != configuration.sampleRate) {
+    error = nil;
+    if (![self setPreferredSampleRate:configuration.sampleRate
+                                error:&error]) {
+      RTCLogError(@"Failed to set preferred sample rate: %@",
+                  error.localizedDescription);
+    }
+  }
+
+  if (self.IOBufferDuration != configuration.ioBufferDuration) {
+    error = nil;
+    if (![self setPreferredIOBufferDuration:configuration.ioBufferDuration
+                                      error:&error]) {
+      RTCLogError(@"Failed to set preferred IO buffer duration: %@",
+                  error.localizedDescription);
+    }
+  }
+
+  error = nil;

[Chuck, 2016/03/10 21:16:37]

This pattern is different than the other blocks of if() { error = nil;
Is that intentional?

[tkchin_webrtc, 2016/03/10 23:07:09]

Yup. Always forcing the active.

+  if (![self setActive:active error:&error]) {
+    RTCLogError(@"Failed to setActive to %d: %@",
+                active, error.localizedDescription);
+  }
+
+  if (self.isActive) {
+    // Try to set the preferred number of hardware audio channels. These calls
+    // must be done after setting the audio session’s category and mode and
+    // activating the session.
+    NSInteger inputNumberOfChannels = configuration.inputNumberOfChannels;
+    if (self.inputNumberOfChannels != inputNumberOfChannels) {
+      error = nil;
+      if (![self setPreferredInputNumberOfChannels:inputNumberOfChannels
+                                             error:&error]) {
+       RTCLogError(@"Failed to set preferred input number of channels: %@",
+                   error.localizedDescription);
+      }
+    }
+    NSInteger outputNumberOfChannels = configuration.outputNumberOfChannels;
+    if (self.outputNumberOfChannels != outputNumberOfChannels) {
+      error = nil;
+      if (![self setPreferredOutputNumberOfChannels:outputNumberOfChannels
+                                              error:&error]) {
+        RTCLogError(@"Failed to set preferred output number of channels: %@",
+                    error.localizedDescription);
+      }
+    }
+  }
+
+  return YES;
+}
+
+- (BOOL)configureWebRTCSession:(NSError **)outError {
+  if (![self checkLock:outError]) {
+    return NO;
+  }
+  RTCLog(@"Configuring audio session for WebRTC.");
+
+  // Provide an error even if there isn't one so we can log it.
+  NSError *error = nil;
+  if (outError) {
+    error = *outError;
+  }
+
+  RTCAudioSessionConfiguration *currentConfig =
+      [RTCAudioSessionConfiguration currentConfiguration];
+  RTCAudioSessionConfiguration *webRTCConfig =
+      [RTCAudioSessionConfiguration webRTCConfiguration];
+  if (![self setConfiguration:webRTCConfig active:YES error:&error]) {
+    RTCLogError(@"Failed to set WebRTC audio configuration: %@",
+                error.localizedDescription);
+    // Attempt to restore previous state.
+    [self setConfiguration:currentConfig active:NO error:nil];
+    return NO;
+  }
+
+  // Ensure that the active audio session has the correct category and mode.
+  if (![self isConfiguredForWebRTC]) {
+    // This should never happen - this means that we succeeded earlier but
+    // somehow the settings didn't apply.
+    RTCLogError(@"Failed to configure audio session.");
+    // Attempt to restore previous state.
+    [self setConfiguration:currentConfig active:NO error:nil];
+    return NO;
+  }
+
+  return YES;
+}
+
+@end