1 files changed, 78 insertions, 0 deletions
diff --git a/third_party/rust/audio-mixer/src/channel.rs b/third_party/rust/audio-mixer/src/channel.rs
new file mode 100644
index 0000000000..b32936895e
--- /dev/null
+++ b/third_party/rust/audio-mixer/src/channel.rs
@@ -0,0 +1,78 @@
+// The number of channels must be unique and start from 0. They will be treated as indice in the
+// mixing matrix and used to form unique bitflags in the channel map, which is a bitmap.
+#[derive(Copy, Clone, Debug, PartialEq)]
+pub enum Channel {
+    FrontLeft = 0,
+    FrontRight = 1,
+    FrontCenter = 2,
+    LowFrequency = 3,
+    BackLeft = 4,
+    BackRight = 5,
+    FrontLeftOfCenter = 6,
+    FrontRightOfCenter = 7,
+    BackCenter = 8,
+    SideLeft = 9,
+    SideRight = 10,
+    TopCenter = 11,
+    TopFrontLeft = 12,
+    TopFrontCenter = 13,
+    TopFrontRight = 14,
+    TopBackLeft = 15,
+    TopBackCenter = 16,
+    TopBackRight = 17,
+    Silence = 18,
+}
+
+impl Channel {
+    pub const fn number(self) -> usize {
+        self as usize
+    }
+
+    pub const fn count() -> usize {
+        Channel::Silence as usize + 1
+    }
+
+    pub const fn bitmask(self) -> u32 {
+        1 << self as usize
+    }
+}
+
+bitflags! {
+    pub struct ChannelMap: u32 {
+        const FRONT_LEFT = Channel::FrontLeft.bitmask();
+        const FRONT_RIGHT = Channel::FrontRight.bitmask();
+        const FRONT_CENTER = Channel::FrontCenter.bitmask();
+        const LOW_FREQUENCY = Channel::LowFrequency.bitmask();
+        const BACK_LEFT = Channel::BackLeft.bitmask();
+        const BACK_RIGHT = Channel::BackRight.bitmask();
+        const FRONT_LEFT_OF_CENTER = Channel::FrontLeftOfCenter.bitmask();
+        const FRONT_RIGHT_OF_CENTER = Channel::FrontRightOfCenter.bitmask();
+        const BACK_CENTER = Channel::BackCenter.bitmask();
+        const SIDE_LEFT = Channel::SideLeft.bitmask();
+        const SIDE_RIGHT = Channel::SideRight.bitmask();
+        const TOP_CENTER = Channel::TopCenter.bitmask();
+        const TOP_FRONT_LEFT = Channel::TopFrontLeft.bitmask();
+        const TOP_FRONT_CENTER = Channel::TopFrontCenter.bitmask();
+        const TOP_FRONT_RIGHT = Channel::TopFrontRight.bitmask();
+        const TOP_BACK_LEFT = Channel::TopBackLeft.bitmask();
+        const TOP_BACK_CENTER = Channel::TopBackCenter.bitmask();
+        const TOP_BACK_RIGHT = Channel::TopBackRight.bitmask();
+        const SILENCE = Channel::Silence.bitmask();
+    }
+}
+
+// Avoid printing the following types in debugging context {:?} by declaring them in impl
+// rather than bitflags! {} scope.
+impl ChannelMap {
+    pub const FRONT_2: Self = Self::union(Self::FRONT_LEFT, Self::FRONT_RIGHT);
+    pub const BACK_2: Self = Self::union(Self::BACK_LEFT, Self::BACK_RIGHT);
+    pub const FRONT_2_OF_CENTER: Self =
+        Self::union(Self::FRONT_LEFT_OF_CENTER, Self::FRONT_RIGHT_OF_CENTER);
+    pub const SIDE_2: Self = Self::union(Self::SIDE_LEFT, Self::SIDE_RIGHT);
+}
+
+impl From<Channel> for ChannelMap {
+    fn from(channel: Channel) -> Self {
+        ChannelMap::from_bits(channel.bitmask()).expect("convert an invalid channel")
+    }
+}