device/client: make device_get_list() allocate the result buffer itself

Using device_get_count() and device_get_list() separately can return different
device counts in case there are devices added to the list inbetween these two
function calls. To prevent this, device_get_list() will allocate the buffer by
itself.

src/client.c

@@ -267,23 +267,21 @@ static int send_device_list(struct mux_client *client, uint32_t tag)
 	plist_t dict = plist_new_dict();
 	plist_t devices = plist_new_array();
 
-	int count = device_get_count(0);
-	if (count > 0) {
-		struct device_info *devs;
-		struct device_info *dev;
-		int i;
-
-		devs = malloc(sizeof(struct device_info) * count);
-		count = device_get_list(0, devs);
-		dev = devs;
-		for (i = 0; i < count; i++) {
-			plist_t device = create_device_attached_plist(dev++);
-			if (device) {
-				plist_array_append_item(devices, device);
-			}
+	struct device_info *devs = NULL;
+	struct device_info *dev;
+	int i;
+
+	int count = device_get_list(0, &devs);
+	dev = devs;
+	for (i = 0; devs && i < count; i++) {
+		plist_t device = create_device_attached_plist(dev++);
+		if (device) {
+			plist_array_append_item(devices, device);
 		}
-		free(devs);
 	}
+	if (devs)
+		free(devs);
+
 	plist_dict_insert_item(dict, "DeviceList", devices);
 	res = send_plist_pkt(client, tag, dict);
 	plist_free(dict);
@@ -369,25 +367,23 @@ static int notify_device_remove(struct mux_client *client, uint32_t device_id)
 
 static int start_listen(struct mux_client *client)
 {
-	struct device_info *devs;
+	struct device_info *devs = NULL;
 	struct device_info *dev;
 	int count, i;
 
 	client->state = CLIENT_LISTEN;
-	count = device_get_count(0);
-	if(!count)
-		return 0;
-	devs = malloc(sizeof(struct device_info) * count);
-	count = device_get_list(0, devs);
 
+	count = device_get_list(0, &devs);
 	dev = devs;
-	for(i=0; i<count; i++) {
+	for(i=0; devs && i < count; i++) {
 		if(notify_device_add(client, dev++) < 0) {
 			free(devs);
 			return -1;
 		}
 	}
-	free(devs);
+	if (devs)
+		free(devs);
+
 	return count;
 }
 

src/device.c

@@ -746,10 +746,15 @@ int device_get_count(int include_hidden)
 	return count;
 }
 
-int device_get_list(int include_hidden, struct device_info *p)
+int device_get_list(int include_hidden, struct device_info **devices)
 {
 	int count = 0;
 	pthread_mutex_lock(&device_list_mutex);
+
+	int total_count = collection_count(&device_list);
+	*devices = malloc(sizeof(struct device_info) * total_count);
+	struct device_info *p = *devices;
+
 	FOREACH(struct mux_device *dev, &device_list) {
 		if((dev->state == MUXDEV_ACTIVE) && (include_hidden || dev->visible)) {
 			p->id = dev->id;

src/device.h

@@ -44,7 +44,7 @@ void device_set_visible(int device_id);
 void device_set_preflight_cb_data(int device_id, void* data);
 
 int device_get_count(int include_hidden);
-int device_get_list(int include_hidden, struct device_info *p);
+int device_get_list(int include_hidden, struct device_info **devices);
 
 int device_get_timeout(void);
 void device_check_timeouts(void);