Implementing fade-in as a wrapper

...around LinearRamp

src/source/fadein.rs

@@ -2,7 +2,7 @@ use std::time::Duration;
 
 use crate::{Sample, Source};
 
-use super::SeekError;
+use super::{linear_ramp::linear_gain_ramp, LinearGainRamp, SeekError};
 
 /// Internal function that builds a `FadeIn` object.
 pub fn fadein<I>(input: I, duration: Duration) -> FadeIn<I>
@@ -10,21 +10,15 @@ where
     I: Source,
     I::Item: Sample,
 {
-    let duration = duration.as_secs() * 1000000000 + duration.subsec_nanos() as u64;
-
     FadeIn {
-        input,
-        remaining_ns: duration as f32,
-        total_ns: duration as f32,
+        ramp: linear_gain_ramp(input, duration, 0.0f32, 1.0f32, false),
     }
 }
 
 /// Filter that modifies raises the volume from silence over a time period.
 #[derive(Clone, Debug)]
 pub struct FadeIn<I> {
-    input: I,
-    remaining_ns: f32,
-    total_ns: f32,
+    ramp: LinearGainRamp<I>
 }
 
 impl<I> FadeIn<I>
@@ -35,19 +29,19 @@ where
     /// Returns a reference to the inner source.
     #[inline]
     pub fn inner(&self) -> &I {
-        &self.input
+        self.ramp.inner()
     }
 
     /// Returns a mutable reference to the inner source.
     #[inline]
     pub fn inner_mut(&mut self) -> &mut I {
-        &mut self.input
+        self.ramp.inner_mut()
     }
 
     /// Returns the inner source.
     #[inline]
     pub fn into_inner(self) -> I {
-        self.input
+        self.ramp.into_inner()
     }
 }
 
@@ -60,19 +54,12 @@ where
 
     #[inline]
     fn next(&mut self) -> Option<I::Item> {
-        if self.remaining_ns <= 0.0 {
-            return self.input.next();
-        }
-
-        let factor = 1.0 - self.remaining_ns / self.total_ns;
-        self.remaining_ns -=
-            1000000000.0 / (self.input.sample_rate() as f32 * self.channels() as f32);
-        self.input.next().map(|value| value.amplify(factor))
+        self.inner_mut().next()
     }
 
     #[inline]
     fn size_hint(&self) -> (usize, Option<usize>) {
-        self.input.size_hint()
+        self.inner().size_hint()
     }
 }
 
@@ -90,26 +77,26 @@ where
 {
     #[inline]
     fn current_frame_len(&self) -> Option<usize> {
-        self.input.current_frame_len()
+        self.inner().current_frame_len()
     }
 
     #[inline]
     fn channels(&self) -> u16 {
-        self.input.channels()
+        self.inner().channels()
     }
 
     #[inline]
     fn sample_rate(&self) -> u32 {
-        self.input.sample_rate()
+        self.inner().sample_rate()
     }
 
     #[inline]
     fn total_duration(&self) -> Option<Duration> {
-        self.input.total_duration()
+        self.inner().total_duration()
     }
 
     #[inline]
     fn try_seek(&mut self, pos: Duration) -> Result<(), SeekError> {
-        self.input.try_seek(pos)
+        self.inner_mut().try_seek(pos)
     }
 }