Fix: prevent crash and ensure output buffer size in SoxResampler::flush()

Author: samwell

livekit-ffi/src/server/resampler.rs

@@ -110,6 +110,22 @@ impl SoxResampler {
     }
 
     pub fn flush(&mut self) -> Result<&[i16], String> {
+        let delay = unsafe { soxr_sys::soxr_delay(self.soxr_ptr) };
+        let delay_samples = delay.ceil() as usize;
+        if delay_samples == 0 {
+            let error = unsafe { soxr_sys::soxr_clear(self.soxr_ptr) };
+            if !error.is_null() {
+                let msg = unsafe { std::ffi::CStr::from_ptr(error) };
+                return Err(msg.to_string_lossy().to_string());
+            }
+            return Ok(&[]);
+        }
+
+        let required_output_size = delay_samples * self.num_channels as usize;
+        if self.out_buf.len() < required_output_size {
+            self.out_buf.resize(required_output_size, 0);
+        }
+
         let mut odone: usize = 0;
         let error = unsafe {
             soxr_sys::soxr_process(
@@ -118,7 +134,7 @@ impl SoxResampler {
                 0,
                 std::ptr::null_mut(),
                 self.out_buf.as_mut_ptr() as *mut c_void,
-                self.out_buf.len(),
+                delay_samples,
                 &mut odone,
             )
         };
@@ -134,7 +150,8 @@ impl SoxResampler {
             return Err(error_msg.to_string_lossy().to_string());
         }
 
-        Ok(&self.out_buf[..odone])
+        let output_samples = odone * self.num_channels as usize;
+        Ok(&self.out_buf[..output_samples])
     }
 }