audio_core: Make g_sink_details internally linked

We can hide the direct array from external view and instead provide
functions to retrieve the necessary info. This has the benefit of
completely hiding the makeup of the SinkDetails structure from the rest
of the code.

Given that this makes the array hidden, we can also make the array
constexpr by altering the members slightly. This gets rid of several
static constructor calls related to std::vector and std::function.

Now we don't have heap allocations here that need to occur before the
program can even enter main(). It also has the benefit of saving a
little bit of heap space, but this doesn't matter too much, since the
savings in that regard are pretty tiny.

1 files changed, 45 insertions, 8 deletions

diff --git a/src/audio_core/sink_details.cpp b/src/audio_core/sink_details.cpp
index 67cf1f3b2..a848eb1c9 100644
--- a/src/audio_core/sink_details.cpp
+++ b/src/audio_core/sink_details.cpp
@@ -14,31 +14,68 @@
 #include "common/logging/log.h"
 
 namespace AudioCore {
+namespace {
+struct SinkDetails {
+    using FactoryFn = std::unique_ptr<Sink> (*)(std::string_view);
+    using ListDevicesFn = std::vector<std::string> (*)();
 
-// g_sink_details is ordered in terms of desirability, with the best choice at the top.
-const std::vector<SinkDetails> g_sink_details = {
+    /// Name for this sink.
+    const char* id;
+    /// A method to call to construct an instance of this type of sink.
+    FactoryFn factory;
+    /// A method to call to list available devices.
+    ListDevicesFn list_devices;
+};
+
+// sink_details is ordered in terms of desirability, with the best choice at the top.
+constexpr SinkDetails sink_details[] = {
 #ifdef HAVE_CUBEB
-    SinkDetails{"cubeb", &std::make_unique<CubebSink, std::string>, &ListCubebSinkDevices},
+    SinkDetails{"cubeb",
+                [](std::string_view device_id) -> std::unique_ptr<Sink> {
+                    return std::make_unique<CubebSink>(device_id);
+                },
+                &ListCubebSinkDevices},
 #endif
-    SinkDetails{"null", &std::make_unique<NullSink, std::string>,
+    SinkDetails{"null",
+                [](std::string_view device_id) -> std::unique_ptr<Sink> {
+                    return std::make_unique<NullSink>(device_id);
+                },
                 [] { return std::vector<std::string>{"null"}; }},
 };
 
 const SinkDetails& GetSinkDetails(std::string_view sink_id) {
     auto iter =
-        std::find_if(g_sink_details.begin(), g_sink_details.end(),
+        std::find_if(std::begin(sink_details), std::end(sink_details),
                      [sink_id](const auto& sink_detail) { return sink_detail.id == sink_id; });
 
-    if (sink_id == "auto" || iter == g_sink_details.end()) {
+    if (sink_id == "auto" || iter == std::end(sink_details)) {
         if (sink_id != "auto") {
             LOG_ERROR(Audio, "AudioCore::SelectSink given invalid sink_id {}", sink_id);
         }
         // Auto-select.
-        // g_sink_details is ordered in terms of desirability, with the best choice at the front.
-        iter = g_sink_details.begin();
+        // sink_details is ordered in terms of desirability, with the best choice at the front.
+        iter = std::begin(sink_details);
     }
 
     return *iter;
 }
+} // Anonymous namespace
+
+std::vector<const char*> GetSinkIDs() {
+    std::vector<const char*> sink_ids(std::size(sink_details));
+
+    std::transform(std::begin(sink_details), std::end(sink_details), std::begin(sink_ids),
+                   [](const auto& sink) { return sink.id; });
+
+    return sink_ids;
+}
+
+std::vector<std::string> GetDeviceListForSink(std::string_view sink_id) {
+    return GetSinkDetails(sink_id).list_devices();
+}
+
+std::unique_ptr<Sink> CreateSinkFromID(std::string_view sink_id, std::string_view device_id) {
+    return GetSinkDetails(sink_id).factory(device_id);
+}
 
 } // namespace AudioCore