Added AVFoundation Glue and Device Monitoring for Mac.

media/video/capture/mac/avfoundation_glue.mm

+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#import "media/video/capture/mac/avfoundation_glue.h"
+
+#include <dlfcn.h>
+
+#include "base/mac/mac_util.h"
+
+@implementation AVFoundationGlue

[Mark Mentovai, 2013/10/09 16:05:12]

I’m not sure that there’s any benefit to this class being an Objective-C class.
It has no instances or data other than static data, and has only class methods.
There’s a slight runtime penalty to it being Objective-C. Would you consider
turning it into a C++ namespace enclosing like functions, or a C++ class that
contains only static methods and prevents instantiation via
DISALLOW_IMPLICIT_CONSTRUCTORS?

[mcasas, 2013/10/12 09:59:27]

Done --second option: Class with static methods and no constructors.

+
++ (BOOL)isAVFoundationSupported {
+  return (base::mac::IsOSLionOrLater() &&
+     [[AVFoundationGlue avFoundationBundle] load]);
+}
+
++ (NSBundle const*)avFoundationBundle {
+  static NSBundle* bundle = [NSBundle
+      bundleWithPath:@"/System/Library/Frameworks/AVFoundation.framework"];
+  return bundle;
+}
+
++ (void*)avFoundationLibraryHandle {
+  static void* library_handle = dlopen([[[AVFoundationGlue avFoundationBundle]
+      executablePath] fileSystemRepresentation], RTLD_LAZY | RTLD_LOCAL);

[Mark Mentovai, 2013/10/09 16:05:12]

Not cool to pass NULL to dlopen in case any of the operations in that sequence
fail and wind up returning nil. That’ll give you an RTLD_DEFAULT handle, which
is not what you want. You should build up the first argument to dlopen
separately and then test it for NULLness before calling dlopen.

[mcasas, 2013/10/12 09:59:27]

Separated, if NULL then DCHECK(FALSE) and return NULL, otherwise sunny-side path
as is now.

+  DCHECK(library_handle) << dlerror();
+  return library_handle;
+}
+
++ (NSString* const)avCaptureDeviceWasConnectedNotification{
+  return [AVFoundationGlue readNSStringPtr:
+                               "AVCaptureDeviceWasConnectedNotification"
+                               fromLibrary:[AVFoundationGlue
+                                   avFoundationLibraryHandle]];
+}
+
++ (NSString* const)avCaptureDeviceWasDisconnectedNotification{
+  return [AVFoundationGlue readNSStringPtr:
+                               "AVCaptureDeviceWasDisconnectedNotification"
+                               fromLibrary:[AVFoundationGlue
+                               avFoundationLibraryHandle]];
+}
+
++ (NSString* const)avMediaTypeVideo{
+  return [AVFoundationGlue readNSStringPtr:"AVMediaTypeVideo"
+                               fromLibrary:[AVFoundationGlue
+                                   avFoundationLibraryHandle]];
+}
+
++ (NSString* const)avMediaTypeAudio{
+  return [AVFoundationGlue readNSStringPtr:"AVMediaTypeAudio"
+                               fromLibrary:[AVFoundationGlue
+                                   avFoundationLibraryHandle]];
+}
+
++ (NSString* const)avMediaTypeMuxed{
+  return [AVFoundationGlue readNSStringPtr:"AVMediaTypeMuxed"
+                               fromLibrary:[AVFoundationGlue
+                                   avFoundationLibraryHandle]];
+}
+
++(NSString* const)readNSStringPtr:(char const* const)symbol

[Mark Mentovai, 2013/10/09 16:05:12]

Space after +.

[mcasas, 2013/10/12 09:59:27]

Done.

+                      fromLibrary:(void* const)handle {
+  NSString** stringPointer = (NSString**) dlsym(handle, symbol);
+  DCHECK(stringPointer) << dlerror();
+  return *stringPointer;
+}
+
+@end  // @implementation AVFoundationGlue
+
+
+@implementation AVCaptureDeviceGlue

[Mark Mentovai, 2013/10/09 16:05:12]

On the other hand, this “glue” class makes perfect sense as an Objective-C class
because of its direct wrapping of AVCaptureDevice.

[mcasas, 2013/10/12 09:59:27]

Ack!

+
++ (NSArray*)devices {
+  Class avcClass = [[AVFoundationGlue avFoundationBundle]
+      classNamed:@"AVCaptureDevice"];
+  SEL selectorDevices = NSSelectorFromString(@"devices");
+  if ([avcClass respondsToSelector:selectorDevices]){
+    return [avcClass performSelector:selectorDevices];
+  }
+  return nil;
+}
+
++ (BOOL)hasMediaType:(NSString*)mediaType
+    forCaptureDevice:(CrAVCaptureDevice const*)device {
+  SEL selectorHasMediaType = NSSelectorFromString(@"hasMediaType:");
+  if ([device respondsToSelector:selectorHasMediaType]) {
+    return [device hasMediaType:mediaType];
+  }
+  return NO;
+}
+
++ (NSString*)uniqueID:(CrAVCaptureDevice const*)device {
+  SEL selectorUniqueID = NSSelectorFromString(@"uniqueID");
+  if ([device respondsToSelector:selectorUniqueID]) {
+    return [device uniqueID];
+  }
+  return nil;
+}
+
+@end  // @implementation AVCaptureDevice