stream-util: Add pa_stream_get_volume_channel_map()

The new function isn't used yet, but it soon will.

src/Makefile.am

@@ -895,6 +895,7 @@ libpulsecore_@PA_MAJORMINOR@_la_SOURCES = \
 		pulsecore/remap_mmx.c pulsecore/remap_sse.c \
 		pulsecore/resampler.c pulsecore/resampler.h \
 		pulsecore/rtpoll.c pulsecore/rtpoll.h \
+		pulsecore/stream-util.c pulsecore/stream-util.h \
 		pulsecore/mix.c pulsecore/mix.h \
 		pulsecore/cpu.h \
 		pulsecore/cpu-arm.c pulsecore/cpu-arm.h \

src/pulsecore/stream-util.c

@@ -0,0 +1,86 @@
+/***
+  This file is part of PulseAudio.
+
+  Copyright 2013 Intel Corporation
+
+  PulseAudio is free software; you can redistribute it and/or modify
+  it under the terms of the GNU Lesser General Public License as published
+  by the Free Software Foundation; either version 2.1 of the License,
+  or (at your option) any later version.
+
+  PulseAudio is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with PulseAudio; if not, write to the Free Software
+  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+  USA.
+***/
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include "stream-util.h"
+
+#include <pulse/def.h>
+
+#include <pulsecore/core-format.h>
+#include <pulsecore/macro.h>
+
+int pa_stream_get_volume_channel_map(const pa_cvolume *volume, const pa_channel_map *original_map, const pa_format_info *format,
+                                     pa_channel_map *volume_map) {
+    int r;
+    pa_channel_map volume_map_local;
+
+    pa_assert(volume);
+    pa_assert(format);
+    pa_assert(volume_map);
+
+    if (original_map) {
+        if (volume->channels == original_map->channels) {
+            *volume_map = *original_map;
+            return 0;
+        }
+
+        if (volume->channels == 1) {
+            pa_channel_map_init_mono(volume_map);
+            return 0;
+        }
+
+        pa_log_info("Invalid stream parameters: the volume is incompatible with the channel map.");
+        return -PA_ERR_INVALID;
+    }
+
+    r = pa_format_info_get_channel_map(format, &volume_map_local);
+    if (r == -PA_ERR_NOENTITY) {
+        if (volume->channels == 1) {
+            pa_channel_map_init_mono(volume_map);
+            return 0;
+        }
+
+        pa_log_info("Invalid stream parameters: multi-channel volume is set, but channel map is not.");
+        return -PA_ERR_INVALID;
+    }
+
+    if (r < 0) {
+        pa_log_info("Invalid channel map.");
+        return -PA_ERR_INVALID;
+    }
+
+    if (volume->channels == volume_map_local.channels) {
+        *volume_map = volume_map_local;
+        return 0;
+    }
+
+    if (volume->channels == 1) {
+        pa_channel_map_init_mono(volume_map);
+        return 0;
+    }
+
+    pa_log_info("Invalid stream parameters: the volume is incompatible with the channel map.");
+
+    return -PA_ERR_INVALID;
+}

src/pulsecore/stream-util.h

@@ -0,0 +1,50 @@
+#ifndef foostreamutilhfoo
+#define foostreamutilhfoo
+
+/***
+  This file is part of PulseAudio.
+
+  Copyright 2013 Intel Corporation
+
+  PulseAudio is free software; you can redistribute it and/or modify
+  it under the terms of the GNU Lesser General Public License as published
+  by the Free Software Foundation; either version 2.1 of the License,
+  or (at your option) any later version.
+
+  PulseAudio is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with PulseAudio; if not, write to the Free Software
+  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+  USA.
+***/
+
+#include <pulse/format.h>
+#include <pulse/volume.h>
+
+/* This is a helper function that is called from pa_sink_input_new() and
+ * pa_source_output_new(). The job of this function is to figure out what
+ * channel map should be used for interpreting the volume that was set for the
+ * stream. The channel map that the client intended for the volume may be
+ * different than the final stream channel map, because the client may want the
+ * server to decide the stream channel map.
+ *
+ * volume is the volume for which the channel map should be figured out.
+ *
+ * original_map is the channel map that is set in the new data struct's
+ * channel_map field. If the channel map hasn't been set in the new data, then
+ * original_map should be NULL.
+ *
+ * format is the negotiated format for the stream. It's used as a fallback if
+ * original_map is not available.
+ *
+ * On success, the result is saved in volume_map. It's possible that this
+ * function fails to figure out the right channel map for the volume, in which
+ * case a negative error code is returned. */
+int pa_stream_get_volume_channel_map(const pa_cvolume *volume, const pa_channel_map *original_map, const pa_format_info *format,
+                                     pa_channel_map *volume_map);
+
+#endif