AudioFrameReader consumes the file of WaveReader

src/audio_frame_reader.rs

@@ -1,5 +1,5 @@
 use std::io::{Read, Seek};
-use std::io::SeekFrom::{Start,};
+use std::io::SeekFrom::{Start,Current,};
 
 use byteorder::LittleEndian;
 use byteorder::ReadBytesExt;
@@ -7,7 +7,6 @@ use byteorder::ReadBytesExt;
 use super::fmt::{WaveFmt};
 use super::errors::Error;
 use super::CommonFormat;
-use super::raw_chunk_reader::RawChunkReader;
 
 /// Read audio frames
 /// 
@@ -15,12 +14,14 @@ use super::raw_chunk_reader::RawChunkReader;
 /// bitstream having a format specified by `format`.
 /// 
 #[derive(Debug)]
-pub struct AudioFrameReader<'a, R: Read + Seek> {
-    inner : RawChunkReader<'a,R>,
-    format: WaveFmt
+pub struct AudioFrameReader<R: Read + Seek> {
+    inner : R,
+    format: WaveFmt,
+    start: u64,
+    length: u64
 }
 
-impl<'a, R: Read + Seek> AudioFrameReader<'a, R> {
+impl<R: Read + Seek> AudioFrameReader<R> {
 
     /// Create a new `AudioFrameReader`
     /// 
@@ -30,16 +31,21 @@ impl<'a, R: Read + Seek> AudioFrameReader<'a, R> {
     /// parameter to confirm the `block_alignment` law is fulfilled
     /// and the format tag is readable by this implementation (only
     /// format 0x01 is supported at this time.) 
-    pub fn new(inner: RawChunkReader<'a, R>, format: WaveFmt) -> Self {
+    pub fn new(mut inner: R, format: WaveFmt, start: u64, length: u64) -> Result<Self, Error> {
         assert!(format.block_alignment * 8 == format.bits_per_sample * format.channel_count, 
             "Unable to read audio frames from packed formats: block alignment is {}, should be {}",
             format.block_alignment, (format.bits_per_sample / 8 ) * format.channel_count);
         
-
         assert!(format.common_format() == CommonFormat::IntegerPCM , 
                 "Unsupported format tag {:?}", format.tag);
-                
-        AudioFrameReader { inner , format }
+        
+        inner.seek(Start(start))?;
+        Ok( AudioFrameReader { inner , format , start, length} )
+    }
+
+    /// Unwrap the inner reader.
+    pub fn into_inner(self) -> R {
+        self.inner
     }
 
     /// Locate the read position to a different frame
@@ -47,10 +53,13 @@ impl<'a, R: Read + Seek> AudioFrameReader<'a, R> {
     /// Seeks within the audio stream.
     /// 
     /// Returns the new location of the read position.
+    /// 
+    /// locate() behaves similarly to Read methods in that
+    /// seeking after the end of the audio data is not an error.
     pub fn locate(&mut self, to :u64) -> Result<u64,Error> {
         let position = to * self.format.block_alignment as u64;
-        let seek_result = self.inner.seek(Start(position))?;
-        Ok( seek_result / self.format.block_alignment as u64 )
+        let seek_result = self.inner.seek(Start(self.start + position))?;
+        Ok( (seek_result - self.start) / self.format.block_alignment as u64 )
     }
 
     /// Create a frame buffer sized to hold frames of the reader
@@ -69,7 +78,7 @@ impl<'a, R: Read + Seek> AudioFrameReader<'a, R> {
     /// Regardless of the number of bits in the audio sample, this method
     /// always writes `i32` samples back to the buffer. These samples are 
     /// written back "right-aligned" so samples that are shorter than i32
-    /// will leave the MSB bits empty. 
+    /// will leave the MSB bits empty.
     /// 
     /// For example: A full-code sample in 16 bit (0xFFFF) will be written 
     /// back to the buffer as 0x0000FFFF.
@@ -86,17 +95,22 @@ impl<'a, R: Read + Seek> AudioFrameReader<'a, R> {
 
         let framed_bits_per_sample = self.format.block_alignment * 8 / self.format.channel_count;
 
-        for n in 0..(self.format.channel_count as usize) {
-            buffer[n] = match (self.format.bits_per_sample, framed_bits_per_sample) {
-                (0..=8,8) => self.inner.read_u8()? as i32 - 0x80_i32, // EBU 3285 §A2.2
-                (9..=16,16) => self.inner.read_i16::<LittleEndian>()? as i32,
-                (10..=24,24) => self.inner.read_i24::<LittleEndian>()?,
-                (25..=32,32) => self.inner.read_i32::<LittleEndian>()?,
-                (b,_)=> panic!("Unrecognized integer format, bits per sample {}, channels {}, block_alignment {}", 
-                    b, self.format.channel_count, self.format.block_alignment)
-            }
-        }
+        let tell = self.inner.seek(Current(0))?;
 
-        Ok( 1 )
+        if (tell - self.start) < self.length {
+            for n in 0..(self.format.channel_count as usize) {
+                buffer[n] = match (self.format.bits_per_sample, framed_bits_per_sample) {
+                    (0..=8,8) => self.inner.read_u8()? as i32 - 0x80_i32, // EBU 3285 §A2.2
+                    (9..=16,16) => self.inner.read_i16::<LittleEndian>()? as i32,
+                    (10..=24,24) => self.inner.read_i24::<LittleEndian>()?,
+                    (25..=32,32) => self.inner.read_i32::<LittleEndian>()?,
+                    (b,_)=> panic!("Unrecognized integer format, bits per sample {}, channels {}, block_alignment {}", 
+                        b, self.format.channel_count, self.format.block_alignment)
+                }
+            }
+            Ok( 1 )
+        } else {
+            Ok( 0 )
+        }
     }
 }