Add method to specify the output sample rate

src/lib.rs

@@ -68,6 +68,7 @@ pub use mp3lame_sys as ffi;
 
 use alloc::vec::Vec;
 use core::mem::{self, MaybeUninit};
+use core::num::NonZeroU32;
 use core::ptr::{self, NonNull};
 use core::{cmp, fmt};
 use core::ffi::c_int;
@@ -385,7 +386,42 @@ impl Builder {
     }
 
     #[inline]
-    ///Sets sample rate.
+    ///Sets output sample rate.
+    ///
+    ///The default `None` allows LAME to pick the best value.
+    ///The supported values are:
+    /// - MPEG1: `32_000`, `44_100` and `48_000`
+    /// - MPEG2: `16_000`, `22_050` and `24_000`
+    /// - MPEG2.5: `8_000`, `11_025` and `12_000`
+    ///
+    ///Returns `Ok(())` the requested value is supported and was set successfully.
+    pub fn set_output_sample_rate(&mut self, rate: Option<NonZeroU32>) -> Result<(), BuildError> {
+        let rate = rate.map_or(0, NonZeroU32::get).try_into().unwrap_or(libc::c_int::MAX);
+
+        let res = unsafe {
+             ffi::lame_set_out_samplerate(self.ptr(), rate)
+        };
+
+        BuildError::from_c_int(res)
+    }
+
+    #[inline]
+    ///Sets output sample rate using the builder pattern.
+    ///
+    ///The default `None` allows LAME to pick the best value.
+    ///The supported values are:
+    /// - MPEG1: `32_000`, `44_100` and `48_000`
+    /// - MPEG2: `16_000`, `22_050` and `24_000`
+    /// - MPEG2.5: `8_000`, `11_025` and `12_000`
+    ///
+    ///Returns `Ok(())` the requested value is supported and was set successfully.
+    pub fn with_output_sample_rate(mut self, rate: Option<NonZeroU32>) -> Result<Self, BuildError> {
+        self.set_output_sample_rate(rate)?;
+        Ok(self)
+    }
+
+    #[inline]
+    ///Sets input sample rate.
     ///
     ///Defaults to 44_100.
     ///
@@ -399,8 +435,8 @@ impl Builder {
     }
 
     #[inline]
-    ///Sets sample rate using the builder pattern.
-    ///
+    ///Sets input sample rate using the builder pattern.
+    /// 
     ///Defaults to 44_100.
     ///
     ///Returns an error if it is not supported.