Determine iPhoto library location with and without sandbox

iPhotoLibLocation.m

+ (NSString *)libraryPath {
#ifdef APPSTORE
	// Sandbox prevents us from accessing other apps' preferences.
	// So we get a r/o access to ~/Library/Preferences/ and read the files directly.
	//
	// Need the following entitlement:
	//
	// <key>com.apple.security.temporary-exception.files.home-relative-path.read-only</key>
	// <array>
	//   <string>/Library/Preferences/</string>
	// </array>
	// http://stackoverflow.com/a/10955994
	const char *home = getpwuid(getuid())->pw_dir;
	NSString *homePath = [[NSFileManager defaultManager] stringWithFileSystemRepresentation:home length:strlen(home)];
	NSString *plistPath = [homePath stringByAppendingPathComponent:@"Library/Preferences/com.apple.iPhoto.plist"];
	NSDictionary *iPhotoPrefs = [NSDictionary dictionaryWithContentsOfFile:plistPath];
	return [iPhotoPrefs objectForKey:@"LibraryPath"];
#else
	CFStringRef appId = (__bridge CFStringRef)iPhotoBundleID;
	return [(NSString *)CFBridgingRelease(CFPreferencesCopyAppValue(CFSTR("LibraryPath"), appId)) stringByExpandingTildeInPath];
#endif
}