implement device reservation scheme

src/modules/reserve.h

@@ -0,0 +1,68 @@
+#ifndef fooreservehfoo
+#define fooreservehfoo
+
+/***
+  Copyright 2009 Lennart Poettering
+
+  Permission is hereby granted, free of charge, to any person
+  obtaining a copy of this software and associated documentation files
+  (the "Software"), to deal in the Software without restriction,
+  including without limitation the rights to use, copy, modify, merge,
+  publish, distribute, sublicense, and/or sell copies of the Software,
+  and to permit persons to whom the Software is furnished to do so,
+  subject to the following conditions:
+
+  The above copyright notice and this permission notice shall be
+  included in all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+  BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+  ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+  CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+  SOFTWARE.
+***/
+
+#include <dbus/dbus.h>
+#include <inttypes.h>
+
+typedef struct rd_device rd_device;
+
+/* Prototype for a function that is called whenever someone else wants
+ * your app to release the device you having locked. A return value <=
+ * 0 denies the request, a positive return value agrees to it. Before
+ * returning your application should close the device in question
+ * completely to make sure the new application may acceess it. */
+typedef int (*rd_request_cb_t)(
+	rd_device *d,
+	int forced);                  /* Non-zero if an application forcibly took the lock away without asking. If this is the case then the return value of this call is ignored. */
+
+/* Try to lock the device. Returns 0 on success, a negative errno
+ * style return value on error. The DBus error might be set as well if
+ * the error was caused D-Bus. */
+int rd_acquire(
+	rd_device **d,                /* On success a pointer to the newly allocated rd_device object will be filled in here */
+	DBusConnection *connection,
+	const char *device_name,      /* The device to lock, e.g. "Audio0" */
+	const char *application_name, /* A human readable name of the application, e.g. "PulseAudio Sound Server" */
+	int32_t priority,             /* The priority for this application. If unsure use 0 */
+	rd_request_cb_t request_cb,   /* Will be called whenever someone asks that this device shall be released. May be NULL if priority is INT32_MAX */
+	DBusError *error);            /* If we fail due to a D-Bus related issue the error will be filled in here. May be NULL. */
+
+/* Unlock (if needed) and destroy a rd_device object again */
+void rd_release(rd_device *d);
+
+/* Set the application device name for a rd_device object Returns 0 on
+ * success, a negative errno style return value on error. */
+int rd_set_application_device_name(rd_device *d, const char *name);
+
+/* Attach a userdata pointer to a rd_device */
+void rd_set_userdata(rd_device *d, void *userdata);
+
+/* Query the userdata pointer from a rd_device. Returns NULL if no
+ * userdata was set. */
+void* rd_get_userdata(rd_device *d);
+
+#endif