Add a very basic gain plugin with some todos

plugins/gain/src/lib.rs

@@ -1,33 +1,95 @@
-use nih_plug::params::{FloatParam, IntParam, Params, Range};
+use nih_plug::{
+    params::{FloatParam, Params, Range},
+    plugin::{BufferConfig, BusConfig, Plugin},
+};
 use nih_plug_derive::Params;
+use std::pin::Pin;
 
-#[derive(Params)]
-struct FooParams {
-    #[id("pain")]
-    pub pain: FloatParam,
-    #[id("pain_stages")]
-    pub pain_stages: IntParam,
-
-    #[id("identifiers_are_stable")]
-    pub but_field_names_can_change: FloatParam,
+struct Gain {
+    params: Pin<Box<GainParams>>,
 }
 
-impl Default for FooParams {
+#[derive(Params)]
+struct GainParams {
+    #[id("gain")]
+    pub gain: FloatParam,
+}
+
+impl Default for Gain {
     fn default() -> Self {
         Self {
-            pain: FloatParam {
-                value: 69.0,
-                range: Range::Linear {
-                    min: -420.0,
-                    max: 420.0,
-                },
-                name: "Pain",
-                unit: " Hertz",
-                value_to_string: None,
-                string_to_value: None,
-            },
-            pain_stages: todo!(),
-            but_field_names_can_change: todo!(),
+            params: Pin::new(Box::default()),
+        }
+    }
+}
+
+impl Default for GainParams {
+    fn default() -> Self {
+        Self {
+            gain: FloatParam {
+                value: 0.00,
+                range: Range::Linear {
+                    min: -30.0,
+                    max: 300.0,
+                },
+                name: "Gain",
+                unit: " dB",
+                value_to_string: None,
+                string_to_value: None,
+            },
+        }
+    }
+}
+
+impl Plugin for Gain {
+    const DEFAULT_NUM_INPUTS: u32 = 2;
+    const DEFAULT_NUM_OUTPUTS: u32 = 2;
+
+    fn params(&self) -> Pin<&dyn Params> {
+        todo!()
+    }
+
+    fn accepts_bus_config(&self, config: &BusConfig) -> bool {
+        // This works with any symmetrical IO layout
+        config.num_input_channels == config.num_output_channels && config.num_input_channels > 0
+    }
+
+    fn initialize(&mut self, _bus_config: &BusConfig, _buffer_config: &BufferConfig) -> bool {
+        // This plugin doesn't need any special initialization, but if you need to do anything
+        // expensive then this would be the place. State is kept around while when the host
+        // reconfigures the plugin.
+        true
+    }
+
+    fn process(&mut self, samples: &mut [&mut [f32]]) {
+        if samples.is_empty() {
+            return;
+        }
+
+        // TODO: The wrapper should set FTZ if not yet enabled, mention ths in the process fuctnion
+        // TODO: Move this iterator to an adapter
+        let num_channels = samples.len();
+        let num_samples = samples[0].len();
+        for channel in &samples[1..] {
+            if channel.len() != num_samples {
+                // TODO: Debug assert
+                eprintln!("Mismatched channel lengths, aborting");
+                return;
+            }
+        }
+
+        for sample_idx in 0..num_samples {
+            for channel_idx in 0..num_channels {
+                let sample = unsafe {
+                    samples
+                        .get_unchecked_mut(channel_idx)
+                        .get_unchecked_mut(sample_idx)
+                };
+
+                // TODO: Smoothing
+                // TODO: Gain to decibel function in a separate module, add a minus infinity check when I do
+                *sample *= 10.0f32.powf(self.params.gain.value * 0.05);
+            }
         }
     }
 }