[pulseaudio-discuss] [PATCH v4] module-coreaudio-device: get channel name as CFString and convert to plain C string.

[Mihai Moldovan]

The old code fetched the channel name via AudioObjectGetPropertyData()
and accessed the "returned" data as a plain char buffer.

This may or may not have worked at some point according to the Apple
CFString documentation, which warns that the actual data layout is an
implementation detail and subject to change at any time.

On recent OS X versions, this behavior led to "random data" channel
names like >H��{, H��{<.

We need to actually let AudioObjectGetPropertyData() populate a CFString
struct and convert this into a plain char buffer.

The conversion function will not free the CFString, so do that in the
caller.

Signed-off-by: Mihai Moldovan <ionic at ionic.de>
---
 src/modules/macosx/module-coreaudio-device.c | 46 ++++++++++++++++++++++++++--
 1 file changed, 44 insertions(+), 2 deletions(-)

diff --git a/src/modules/macosx/module-coreaudio-device.c b/src/modules/macosx/module-coreaudio-device.c
index cb62661..3224655 100644
--- a/src/modules/macosx/module-coreaudio-device.c
+++ b/src/modules/macosx/module-coreaudio-device.c
@@ -375,6 +375,30 @@ static int ca_sink_set_state(pa_sink *s, pa_sink_state_t state) {
     return 0;
 }
 
+/* Caveat: The caller is responsible to get rid of the CFString(Ref). */
+static bool CFString_to_cstr_n(CFStringRef cfstr, char *buf, long n) {
+    bool ret;
+
+    pa_assert (buf);
+
+    ret = false;
+
+    if (cfstr != NULL) {
+        const char *tmp = CFStringGetCStringPtr(cfstr, kCFStringEncodingUTF8);
+
+        if (tmp == NULL) {
+            if (CFStringGetCString(cfstr, buf, n, kCFStringEncodingUTF8))
+                ret = true;
+        } else {
+            strncpy(buf, tmp, n);
+            buf[n - 1] = 0;
+            ret = true;
+        }
+    }
+
+    return ret;
+}
+
 static int ca_device_create_sink(pa_module *m, AudioBuffer *buf, int channel_idx) {
     OSStatus err;
     UInt32 size;
@@ -387,6 +411,7 @@ static int ca_device_create_sink(pa_module *m, AudioBuffer *buf, int channel_idx
     char tmp[255];
     pa_strbuf *strbuf;
     AudioObjectPropertyAddress property_address;
+    CFStringRef tmp_cfstr = NULL;
 
     ca_sink = pa_xnew0(coreaudio_sink, 1);
     ca_sink->map.channels = buf->mNumberChannels;
@@ -401,7 +426,15 @@ static int ca_device_create_sink(pa_module *m, AudioBuffer *buf, int channel_idx
         property_address.mScope = kAudioDevicePropertyScopeOutput;
         property_address.mElement = channel_idx + i + 1;
         size = sizeof(tmp);
-        err = AudioObjectGetPropertyData(u->object_id, &property_address, 0, NULL, &size, tmp);
+        err = AudioObjectGetPropertyData(u->object_id, &property_address, 0, NULL, &size, &tmp_cfstr);
+        if (err == 0) {
+            err = !(CFString_to_cstr_n(tmp_cfstr, tmp, sizeof(tmp)));
+
+            if (tmp_cfstr) {
+                CFRelease(tmp_cfstr);
+            }
+        }
+
         if (err || !strlen(tmp))
             snprintf(tmp, sizeof(tmp), "Channel %d", (int) property_address.mElement);
 
@@ -505,6 +538,7 @@ static int ca_device_create_source(pa_module *m, AudioBuffer *buf, int channel_i
     char tmp[255];
     pa_strbuf *strbuf;
     AudioObjectPropertyAddress property_address;
+    CFStringRef tmp_cfstr = NULL;
 
     ca_source = pa_xnew0(coreaudio_source, 1);
     ca_source->map.channels = buf->mNumberChannels;
@@ -519,7 +553,15 @@ static int ca_device_create_source(pa_module *m, AudioBuffer *buf, int channel_i
         property_address.mScope = kAudioDevicePropertyScopeInput;
         property_address.mElement = channel_idx + i + 1;
         size = sizeof(tmp);
-        err = AudioObjectGetPropertyData(u->object_id, &property_address, 0, NULL, &size, tmp);
+        err = AudioObjectGetPropertyData(u->object_id, &property_address, 0, NULL, &size, &tmp_cfstr);
+        if (err == 0) {
+            err = !(CFString_to_cstr_n(tmp_cfstr, tmp, sizeof(tmp)));
+
+            if (tmp_cfstr) {
+                CFRelease(tmp_cfstr);
+            }
+        }
+
         if (err || !strlen(tmp))
             snprintf(tmp, sizeof(tmp), "Channel %d", (int) property_address.mElement);
 
-- 
2.3.5


-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 884 bytes
Desc: OpenPGP digital signature
URL: <http://lists.freedesktop.org/archives/pulseaudio-discuss/attachments/20150420/fffd4512/attachment.sig>