Keep audio alive only when the built-in audio device is set to output

README.md

@@ -27,7 +27,7 @@ Build
 
 `antipopd` can be built in a terminal using the following command:
 
-    clang -framework AppKit -framework IOKit -arch i386 -arch x86_64 -o antipopd antipopd.m
+    clang -framework AppKit -framework IOKit -framework CoreAudio -arch i386 -arch x86_64 -o antipopd antipopd.m
 
 A built version (`i386` and `x86_64`) of `antipopd` is included in the repository.
 
@@ -42,6 +42,10 @@ at `/usr/local/share/antipop/ac_only`.
 If the first byte of the configuration file is a `1` the audio system will 
 only be kept alive when on AC power. 
 
+If you want to allow `antipopd` to work only when the default output device is set to built-in 
+you can create a configuration file at `/usr/local/share/antipop/built_in_only` as described above. 
+This may be helpful when you have a bluetooth headset connected and don't want to drain it's battery.
+
 The configuration file is only read once when `antipopd` launches. Changing 
 the configuration file will not take effect until `antipopd` is restarted.
 

antipopd.m

@@ -19,49 +19,99 @@
 #import <Foundation/Foundation.h>
 #import <AppKit/AppKit.h>
 #import <IOKit/ps/IOPowerSources.h>
+#import <AudioToolbox/AudioToolbox.h>
 
 #import <unistd.h>
 
-#define ANTIPOPD_CONFIG	"/usr/local/share/antipop/ac_only"
+#define ANTIPOPD_AC_ONLY_CONFIG	"/usr/local/share/antipop/ac_only"
+#define ANTIPOPD_BUILT_IN_ONLY_CONFIG "/usr/local/share/antipop/built_in_only"
+
 #define BATTERY_STATE	CFSTR("State:/IOKit/PowerSources/InternalBattery-0")
 #define POWER_SOURCE	CFSTR("Power Source State")
 #define	INTERVAL	10 // seconds
 
 static BOOL runOnACOnly = NO;
+static BOOL runOnBuiltInOnly = NO;
 
 void banner() {
 	printf("antipopd\n\n");
-	
-	printf("Copyright (c) Matthew Robinson 2010, 2018\n"); 
+
+	printf("Copyright (c) Matthew Robinson 2010, 2018\n");
 	printf("Email: matt@blendedcocoa.com\n\n");
-	
+
 	printf("antipopd is a drop in replacement for Robert Tomsick's antipopd 1.0.2 bash\n");
 	printf("script which is available at http://www.tomsick.net/projects/antipop\n\n");
-	
+
 	printf("antipopd is a utility program which keeps the audio system active to stop\n");
 	printf("the popping sound that can occur when OS X puts the audio system to sleep.\n");
 	printf("This is achieved by using the Speech Synthesizer system to speak a space,\n");
 	printf("which results in no audio output but keeps the audio system awake.\n\n");
-	
+
 	printf("The benefit of this compiled version over the bash script is a reduction\n");
 	printf("in resource overheads.  The bash script executes two expensive processes \n");
 	printf("(pmset and say) every ten seconds (one process if ac_only is set to 0).\n\n");
-	
+
 	printf("This version of antipopd is released, like Robert Tomsick's version, under\n");
 	printf("a Creative Commons Attribution Noncommercial Share Alike License 3.0,\n");
 	printf("http://creativecommons.org/licenses/by-nc-sa/3.0/us\n\n");
-	
+
 }
 
 
 NSSpeechSynthesizer *speech = nil;
 
+void *preparePropertyAddress(AudioObjectPropertyAddress *propertyAddress, UInt32 prop) {
+    propertyAddress->mSelector = prop;
+    propertyAddress->mScope = kAudioObjectPropertyScopeGlobal;
+    propertyAddress->mElement = kAudioObjectPropertyElementMaster;
+
+    return propertyAddress;
+}
+
+OSStatus getDeviceTransportType(AudioDeviceID deviceId, UInt32 *transportType) {
+    AudioObjectPropertyAddress propertyAddress;
+    preparePropertyAddress(&propertyAddress, kAudioDevicePropertyTransportType);
+    UInt32 dataSize = sizeof(UInt32);
+
+    return AudioObjectGetPropertyData(deviceId, &propertyAddress, 0, NULL, &dataSize, transportType);
+}
+
+OSStatus getDefaultOutputDevice(AudioDeviceID *deviceId) {
+    AudioObjectPropertyAddress propertyAddress;
+    preparePropertyAddress(&propertyAddress, kAudioHardwarePropertyDefaultOutputDevice);
+    UInt32 dataSize = sizeof(AudioDeviceID);
+
+    return AudioObjectGetPropertyData(kAudioObjectSystemObject, &propertyAddress, 0, NULL, &dataSize, deviceId);
+}
+
+OSStatus isDefaultOutputDeviceBuiltIn(BOOL *result) {
+    AudioDeviceID defaultOutputId;
+    OSStatus error = getDefaultOutputDevice(&defaultOutputId);
+
+    if (error) {
+        NSLog(@"Error getting default output device (code: %d)", (int) error);
+        return error;
+    }
+
+    UInt32 transportType;
+    error = getDeviceTransportType(defaultOutputId, &transportType);
+
+    if (error) {
+        NSLog(@"Error getting transport type for device ID: %d (code: %d)", (int) defaultOutputId, (int) error);
+        return error;
+    }
+
+    *result = transportType == kAudioDeviceTransportTypeBuiltIn;
+
+    return kAudioServicesNoError;
+}
+
 // Timer callback that actually speaks the space
 void speak(CFRunLoopTimerRef timer, void *info) {
     if (!speech) {
         speech = [[NSSpeechSynthesizer alloc] initWithVoice:nil];
     }
-    
+
     // If we are only supposed to run on AC power
     if (runOnACOnly) {
         // and we don't have unlimited power remaining
@@ -70,45 +120,60 @@ void speak(CFRunLoopTimerRef timer, void *info) {
             return;
         }
     }
-
+
+    if (runOnBuiltInOnly) {
+        BOOL defaultOutputIsBuiltIn;
+        OSStatus error = isDefaultOutputDeviceBuiltIn(&defaultOutputIsBuiltIn);
+
+        if (error) {
+            NSLog(@"Error while trying to determine default output device. Code: %d", (int) error);
+            exit(error);
+        }
+
+        if (!defaultOutputIsBuiltIn) {
+            return;
+        }
+    }
+
     [speech startSpeakingString:@" "];
 }
 
-// Check for the existance of the ac_only file, check the contents
-// and set runOnACOnly as appropriate
-void loadACOnlyConfig() {
-    // Try to open the ac_only config file
-	int fd = open(ANTIPOPD_CONFIG, O_RDONLY);
-	
-	// If succesful look inside, otherwise proceed with runOnACOnly default
+// Check for the existence of the config file, check the contents
+// and set parameter as appropriate
+void loadConfigAndSetParameter(BOOL *parameter, char *config) {
+    // Try to open the config file
+	int fd = open(config, O_RDONLY);
+
+	// If succesful look inside, otherwise proceed with default parameter
 	if (fd != -1) {
 		char    buffer;
-		
+
 		ssize_t result = read(fd, &buffer, 1);
-				
+
 		// ...the first byte of the file is 1
 		if (result == 1 && buffer == '1') {
-			runOnACOnly = YES;
+			*parameter = YES;
 		}
-		
+
 		close(fd);
   }
 }
 
 int main(int argc, char *argv[]) {
-    loadACOnlyConfig();
+    loadConfigAndSetParameter(&runOnACOnly, ANTIPOPD_AC_ONLY_CONFIG);
+    loadConfigAndSetParameter(&runOnBuiltInOnly, ANTIPOPD_BUILT_IN_ONLY_CONFIG);
 
     // Put an AutoreleasePool in place in case NSSpeechSynthesizer expects it
     @autoreleasepool {
         if (argc >= 2) { // if we have any parameter show the banner
             banner();
             exit(EXIT_SUCCESS);
         }
-        
+
         CFRunLoopTimerContext context = {
             0, NULL, NULL, NULL, NULL,
         };
-        
+
         CFRunLoopTimerRef timer = CFRunLoopTimerCreate(
                                                        NULL,
                                                        0,
@@ -118,9 +183,9 @@ int main(int argc, char *argv[]) {
                                                        speak,
                                                        &context
                                                        );
-        
+
         CFRunLoopAddTimer(CFRunLoopGetCurrent(), timer, kCFRunLoopDefaultMode);
-        
+
         CFRunLoopRun();
     }