apple/StringRef: new library wrapping CFStringRef

src/apple/StringRef.hxx

+/*
+ * Copyright 2020 Max Kellermann <max.kellermann@gmail.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef APPLE_STRING_REF_HXX
+#define APPLE_STRING_REF_HXX
+
+#include <CoreFoundation/CFString.h>
+
+#include <utility>
+
+namespace Apple {
+
+class StringRef {
+	CFStringRef ref = nullptr;
+
+public:
+	explicit StringRef(CFStringRef _ref) noexcept
+		:ref(_ref) {}
+
+	StringRef(StringRef &&src) noexcept
+		:ref(std::exchange(src.ref, nullptr)) {}
+
+	~StringRef() noexcept {
+		if (ref)
+			CFRelease(ref);
+	}
+
+	StringRef &operator=(StringRef &&src) noexcept {
+		using std::swap;
+		swap(ref, src.ref);
+		return *this;
+	}
+
+	operator bool() const noexcept {
+		return ref != nullptr;
+	}
+
+	bool GetCString(char *buffer, std::size_t size,
+			CFStringEncoding encoding=kCFStringEncodingUTF8) const noexcept
+	{
+		return CFStringGetCString(ref, buffer, size, encoding);
+	}
+};
+
+} // namespace Apple
+
+#endif

src/output/plugins/OSXOutputPlugin.cxx

@@ -17,11 +17,11 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
+#include "apple/StringRef.hxx"
 #include "config.h"
 #include "OSXOutputPlugin.hxx"
 #include "../OutputAPI.hxx"
 #include "mixer/MixerList.hxx"
-#include "util/ScopeExit.hxx"
 #include "util/RuntimeError.hxx"
 #include "util/Domain.hxx"
 #include "util/Manual.hxx"
@@ -111,15 +111,13 @@ static void
 osx_os_status_to_cstring(OSStatus status, char *str, size_t size)
 {
 	CFErrorRef cferr = CFErrorCreate(nullptr, kCFErrorDomainOSStatus, status, nullptr);
-	CFStringRef cfstr = CFErrorCopyDescription(cferr);
-	if (!CFStringGetCString(cfstr, str, size, kCFStringEncodingUTF8)) {
+	const Apple::StringRef cfstr(CFErrorCopyDescription(cferr));
+	if (!cfstr.GetCString(str, size)) {
 		/* conversion failed, return empty string */
 		*str = '\0';
 	}
 	if (cferr)
 		CFRelease(cferr);
-	if (cfstr)
-		CFRelease(cfstr);
 }
 
 static bool
@@ -629,12 +627,6 @@ osx_output_set_device(OSXOutput *oo)
 {
 	OSStatus status;
 	UInt32 size, numdevices;
-	CFStringRef cfname = nullptr;
-
-	AtScopeExit(&cfname) {
-		if (cfname)
-			CFRelease(cfname);
-	};
 
 	if (oo->component_subtype != kAudioUnitSubType_HALOutput)
 		return;
@@ -678,6 +670,7 @@ osx_output_set_device(OSXOutput *oo)
 	unsigned i;
 	size = sizeof(CFStringRef);
 	for (i = 0; i < numdevices; i++) {
+		CFStringRef cfname = nullptr;
 		status = AudioObjectGetPropertyData(deviceids[i], &aopa_name,
 						    0, nullptr,
 						    &size, &cfname);
@@ -690,9 +683,10 @@ osx_output_set_device(OSXOutput *oo)
 						 errormsg);
 		}
 
+		const Apple::StringRef cfname_(cfname);
+
 		char name[256];
-		if (!CFStringGetCString(cfname, name, sizeof(name),
-					kCFStringEncodingUTF8))
+		if (!cfname_.GetCString(name, sizeof(name)))
 			throw std::runtime_error("Unable to convert device name from CFStringRef to char*");
 
 		if (strcmp(oo->device_name, name) == 0) {