allow streaming decoder to also be used with a &mut FrameDecoder for …

…easier reusing of the decoder

src/streaming_decoder.rs

@@ -1,3 +1,5 @@
+use core::borrow::BorrowMut;
+
 use crate::frame_decoder::{BlockDecodingStrategy, FrameDecoder, FrameDecoderError};
 use crate::io::{Error, ErrorKind, Read};
 
@@ -6,22 +8,26 @@ use crate::io::{Error, ErrorKind, Read};
 ///
 /// The lower level FrameDecoder by comparison allows for finer grained control but need sto have it's decode_blocks method called continously
 /// to decode the zstd-frame.
-pub struct StreamingDecoder<READ: Read> {
-    pub decoder: FrameDecoder,
+pub struct StreamingDecoder<READ: Read, DEC: BorrowMut<FrameDecoder>> {
+    pub decoder: DEC,
     source: READ,
 }
 
-impl<READ: Read> StreamingDecoder<READ> {
-    pub fn new(mut source: READ) -> Result<StreamingDecoder<READ>, FrameDecoderError> {
-        let mut decoder = FrameDecoder::new();
-        decoder.init(&mut source)?;
+impl<READ: Read, DEC: BorrowMut<FrameDecoder>> StreamingDecoder<READ, DEC> {
+    pub fn new_with_decoder(
+        mut source: READ,
+        mut decoder: DEC,
+    ) -> Result<StreamingDecoder<READ, DEC>, FrameDecoderError> {
+        decoder.borrow_mut().init(&mut source)?;
         Ok(StreamingDecoder { decoder, source })
     }
+}
 
-    pub fn new_with_decoder(
+impl<READ: Read> StreamingDecoder<READ, FrameDecoder> {
+    pub fn new(
         mut source: READ,
-        mut decoder: FrameDecoder,
-    ) -> Result<StreamingDecoder<READ>, FrameDecoderError> {
+    ) -> Result<StreamingDecoder<READ, FrameDecoder>, FrameDecoderError> {
+        let mut decoder = FrameDecoder::new();
         decoder.init(&mut source)?;
         Ok(StreamingDecoder { decoder, source })
     }
@@ -31,9 +37,10 @@ impl<READ: Read> StreamingDecoder<READ> {
     }
 }
 
-impl<READ: Read> Read for StreamingDecoder<READ> {
+impl<READ: Read, DEC: BorrowMut<FrameDecoder>> Read for StreamingDecoder<READ, DEC> {
     fn read(&mut self, buf: &mut [u8]) -> Result<usize, Error> {
-        if self.decoder.is_finished() && self.decoder.can_collect() == 0 {
+        let decoder = self.decoder.borrow_mut();
+        if decoder.is_finished() && decoder.can_collect() == 0 {
             //No more bytes can ever be decoded
             return Ok(0);
         }
@@ -43,10 +50,10 @@ impl<READ: Read> Read for StreamingDecoder<READ> {
         // So we need to call this until we can actually collect enough bytes
 
         // TODO add BlockDecodingStrategy::UntilCollectable(usize) that pushes this logic into the decode_blocks function
-        while self.decoder.can_collect() < buf.len() && !self.decoder.is_finished() {
+        while decoder.can_collect() < buf.len() && !decoder.is_finished() {
             //More bytes can be decoded
-            let additional_bytes_needed = buf.len() - self.decoder.can_collect();
-            match self.decoder.decode_blocks(
+            let additional_bytes_needed = buf.len() - decoder.can_collect();
+            match decoder.decode_blocks(
                 &mut self.source,
                 BlockDecodingStrategy::UptoBytes(additional_bytes_needed),
             ) {
@@ -61,6 +68,6 @@ impl<READ: Read> Read for StreamingDecoder<READ> {
             }
         }
 
-        self.decoder.read(buf)
+        decoder.read(buf)
     }
 }