lib/rs/src/transport/buffered.rs - packaging/sources/thrift - Gitiles

 // Licensed to the Apache Software Foundation (ASF) under one
 // or more contributor license agreements. See the NOTICE file
 // distributed with this work for additional information
 // regarding copyright ownership. The ASF licenses this file
 // to you under the Apache License, Version 2.0 (the
 // "License"); you may not use this file except in compliance
 // with the License. You may obtain a copy of the License at
 //
 //   http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing,
 // software distributed under the License is distributed on an
 // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 // KIND, either express or implied. See the License for the
 // specific language governing permissions and limitations
 // under the License.

 use std::cell::RefCell;
 use std::cmp;
 use std::io;
 use std::io::{Read, Write};
 use std::rc::Rc;

 use super::{TTransport, TTransportFactory};

 /// Default capacity of the read buffer in bytes.
 const DEFAULT_RBUFFER_CAPACITY: usize = 4096;

 /// Default capacity of the write buffer in bytes..
 const DEFAULT_WBUFFER_CAPACITY: usize = 4096;

 /// Transport that communicates with endpoints using a byte stream.
 ///
 /// A `TBufferedTransport` maintains a fixed-size internal write buffer. All
 /// writes are made to this buffer and are sent to the wrapped transport only
 /// when `TTransport::flush()` is called. On a flush a fixed-length header with a
 /// count of the buffered bytes is written, followed by the bytes themselves.
 ///
 /// A `TBufferedTransport` also maintains a fixed-size internal read buffer.
 /// On a call to `TTransport::read(...)` one full message - both fixed-length
 /// header and bytes - is read from the wrapped transport and buffered.
 /// Subsequent read calls are serviced from the internal buffer until it is
 /// exhausted, at which point the next full message is read from the wrapped
 /// transport.
 ///
 /// # Examples
 ///
 /// Create and use a `TBufferedTransport`.
 ///
 /// ```no_run
 /// use std::cell::RefCell;
 /// use std::rc::Rc;
 /// use std::io::{Read, Write};
 /// use thrift::transport::{TBufferedTransport, TTcpTransport, TTransport};
 ///
 /// let mut t = TTcpTransport::new();
 /// t.open("localhost:9090").unwrap();
 ///
 /// let t = Rc::new(RefCell::new(Box::new(t) as Box<TTransport>));
 /// let mut t = TBufferedTransport::new(t);
 ///
 /// // read
 /// t.read(&mut vec![0u8; 1]).unwrap();
 ///
 /// // write
 /// t.write(&[0x00]).unwrap();
 /// t.flush().unwrap();
 /// ```
 pub struct TBufferedTransport {
     rbuf: Box<[u8]>,
     rpos: usize,
     rcap: usize,
     wbuf: Vec<u8>,
     inner: Rc<RefCell<Box<TTransport>>>,
 }

 impl TBufferedTransport {
     /// Create a `TBufferedTransport` with default-sized internal read and
     /// write buffers that wraps an `inner` `TTransport`.
     pub fn new(inner: Rc<RefCell<Box<TTransport>>>) -> TBufferedTransport {
         TBufferedTransport::with_capacity(DEFAULT_RBUFFER_CAPACITY, DEFAULT_WBUFFER_CAPACITY, inner)
     }

     /// Create a `TBufferedTransport` with an internal read buffer of size
     /// `read_buffer_capacity` and an internal write buffer of size
     /// `write_buffer_capacity` that wraps an `inner` `TTransport`.
     pub fn with_capacity(read_buffer_capacity: usize,
                          write_buffer_capacity: usize,
                          inner: Rc<RefCell<Box<TTransport>>>)
                          -> TBufferedTransport {
         TBufferedTransport {
             rbuf: vec![0; read_buffer_capacity].into_boxed_slice(),
             rpos: 0,
             rcap: 0,
             wbuf: Vec::with_capacity(write_buffer_capacity),
             inner: inner,
         }
     }

     fn get_bytes(&mut self) -> io::Result<&[u8]> {
         if self.rcap - self.rpos == 0 {
             self.rpos = 0;
             self.rcap = self.inner.borrow_mut().read(&mut self.rbuf)?;
         }

         Ok(&self.rbuf[self.rpos..self.rcap])
     }

     fn consume(&mut self, consumed: usize) {
         // TODO: was a bug here += <-- test somehow
         self.rpos = cmp::min(self.rcap, self.rpos + consumed);
     }
 }

 impl Read for TBufferedTransport {
     fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
         let mut bytes_read = 0;

         loop {
             let nread = {
                 let avail_bytes = self.get_bytes()?;
                 let avail_space = buf.len() - bytes_read;
                 let nread = cmp::min(avail_space, avail_bytes.len());
                 buf[bytes_read..(bytes_read + nread)].copy_from_slice(&avail_bytes[..nread]);
                 nread
             };

             self.consume(nread);
             bytes_read += nread;

             if bytes_read == buf.len() || nread == 0 {
                 break;
             }
         }

         Ok(bytes_read)
     }
 }

 impl Write for TBufferedTransport {
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
         let avail_bytes = cmp::min(buf.len(), self.wbuf.capacity() - self.wbuf.len());
         self.wbuf.extend_from_slice(&buf[..avail_bytes]);
         assert!(self.wbuf.len() <= self.wbuf.capacity(),
                 "copy overflowed buffer");
         Ok(avail_bytes)
     }

     fn flush(&mut self) -> io::Result<()> {
         self.inner.borrow_mut().write_all(&self.wbuf)?;
         self.inner.borrow_mut().flush()?;
         self.wbuf.clear();
         Ok(())
     }
 }

 /// Factory for creating instances of `TBufferedTransport`
 #[derive(Default)]
 pub struct TBufferedTransportFactory;

 impl TBufferedTransportFactory {
     /// Create a `TBufferedTransportFactory`.
     pub fn new() -> TBufferedTransportFactory {
         TBufferedTransportFactory {}
     }
 }

 impl TTransportFactory for TBufferedTransportFactory {
     fn create(&self, inner: Rc<RefCell<Box<TTransport>>>) -> Box<TTransport> {
         Box::new(TBufferedTransport::new(inner)) as Box<TTransport>
     }
 }

 #[cfg(test)]
 mod tests {
     use std::cell::RefCell;
     use std::io::{Read, Write};
     use std::rc::Rc;

     use super::*;
     use ::transport::{TPassThruTransport, TTransport};
     use ::transport::mem::TBufferTransport;

     macro_rules! new_transports {
         ($wbc:expr, $rbc:expr) => (
             {
                 let mem = Rc::new(RefCell::new(Box::new(TBufferTransport::with_capacity($wbc, $rbc))));
                 let thru: Box<TTransport> = Box::new(TPassThruTransport { inner: mem.clone() });
                 let thru = Rc::new(RefCell::new(thru));
                 (mem, thru)
             }
         );
     }

     #[test]
     fn must_return_zero_if_read_buffer_is_empty() {
         let (_, thru) = new_transports!(10, 0);
         let mut t = TBufferedTransport::with_capacity(10, 0, thru);

         let mut b = vec![0; 10];
         let read_result = t.read(&mut b);

         assert_eq!(read_result.unwrap(), 0);
     }

     #[test]
     fn must_return_zero_if_caller_reads_into_zero_capacity_buffer() {
         let (_, thru) = new_transports!(10, 0);
         let mut t = TBufferedTransport::with_capacity(10, 0, thru);

         let read_result = t.read(&mut []);

         assert_eq!(read_result.unwrap(), 0);
     }

     #[test]
     fn must_return_zero_if_nothing_more_can_be_read() {
         let (mem, thru) = new_transports!(4, 0);
         let mut t = TBufferedTransport::with_capacity(4, 0, thru);

         mem.borrow_mut().set_readable_bytes(&[0, 1, 2, 3]);

         // read buffer is exactly the same size as bytes available
         let mut buf = vec![0u8; 4];
         let read_result = t.read(&mut buf);

         // we've read exactly 4 bytes
         assert_eq!(read_result.unwrap(), 4);
         assert_eq!(&buf, &[0, 1, 2, 3]);

         // try read again
         let buf_again = vec![0u8; 4];
         let read_result = t.read(&mut buf);

         // this time, 0 bytes and we haven't changed the buffer
         assert_eq!(read_result.unwrap(), 0);
         assert_eq!(&buf_again, &[0, 0, 0, 0])
     }

     #[test]
     fn must_fill_user_buffer_with_only_as_many_bytes_as_available() {
         let (mem, thru) = new_transports!(4, 0);
         let mut t = TBufferedTransport::with_capacity(4, 0, thru);

         mem.borrow_mut().set_readable_bytes(&[0, 1, 2, 3]);

         // read buffer is much larger than the bytes available
         let mut buf = vec![0u8; 8];
         let read_result = t.read(&mut buf);

         // we've read exactly 4 bytes
         assert_eq!(read_result.unwrap(), 4);
         assert_eq!(&buf[..4], &[0, 1, 2, 3]);

         // try read again
         let read_result = t.read(&mut buf[4..]);

         // this time, 0 bytes and we haven't changed the buffer
         assert_eq!(read_result.unwrap(), 0);
         assert_eq!(&buf, &[0, 1, 2, 3, 0, 0, 0, 0])
     }

     #[test]
     fn must_read_successfully() {
         // this test involves a few loops within the buffered transport
         // itself where it has to drain the underlying transport in order
         // to service a read

         // we have a much smaller buffer than the
         // underlying transport has bytes available
         let (mem, thru) = new_transports!(10, 0);
         let mut t = TBufferedTransport::with_capacity(2, 0, thru);

         // fill the underlying transport's byte buffer
         let mut readable_bytes = [0u8; 10];
         for i in 0..10 {
             readable_bytes[i] = i as u8;
         }
         mem.borrow_mut().set_readable_bytes(&readable_bytes);

         // we ask to read into a buffer that's much larger
         // than the one the buffered transport has; as a result
         // it's going to have to keep asking the underlying
         // transport for more bytes
         let mut buf = [0u8; 8];
         let read_result = t.read(&mut buf);

         // we should have read 8 bytes
         assert_eq!(read_result.unwrap(), 8);
         assert_eq!(&buf, &[0, 1, 2, 3, 4, 5, 6, 7]);

         // let's clear out the buffer and try read again
         for i in 0..8 {
             buf[i] = 0;
         }
         let read_result = t.read(&mut buf);

         // this time we were only able to read 2 bytes
         // (all that's remaining from the underlying transport)
         // let's also check that the remaining bytes are untouched
         assert_eq!(read_result.unwrap(), 2);
         assert_eq!(&buf[0..2], &[8, 9]);
         assert_eq!(&buf[2..], &[0, 0, 0, 0, 0, 0]);

         // try read again (we should get 0)
         // and all the existing bytes were untouched
         let read_result = t.read(&mut buf);
         assert_eq!(read_result.unwrap(), 0);
         assert_eq!(&buf[0..2], &[8, 9]);
         assert_eq!(&buf[2..], &[0, 0, 0, 0, 0, 0]);
     }

     #[test]
     fn must_return_zero_if_nothing_can_be_written() {
         let (_, thru) = new_transports!(0, 0);
         let mut t = TBufferedTransport::with_capacity(0, 0, thru);

         let b = vec![0; 10];
         let r = t.write(&b);

         assert_eq!(r.unwrap(), 0);
     }

     #[test]
     fn must_return_zero_if_caller_calls_write_with_empty_buffer() {
         let (mem, thru) = new_transports!(0, 10);
         let mut t = TBufferedTransport::with_capacity(0, 10, thru);

         let r = t.write(&[]);

         assert_eq!(r.unwrap(), 0);
         assert_eq!(mem.borrow_mut().write_buffer_as_ref(), &[]);
     }

     #[test]
     fn must_return_zero_if_write_buffer_full() {
         let (_, thru) = new_transports!(0, 0);
         let mut t = TBufferedTransport::with_capacity(0, 4, thru);

         let b = [0x00, 0x01, 0x02, 0x03];

         // we've now filled the write buffer
         let r = t.write(&b);
         assert_eq!(r.unwrap(), 4);

         // try write the same bytes again - nothing should be writable
         let r = t.write(&b);
         assert_eq!(r.unwrap(), 0);
     }

     #[test]
     fn must_only_write_to_inner_transport_on_flush() {
         let (mem, thru) = new_transports!(10, 10);
         let mut t = TBufferedTransport::new(thru);

         let b: [u8; 5] = [0, 1, 2, 3, 4];
         assert_eq!(t.write(&b).unwrap(), 5);
         assert_eq!(mem.borrow_mut().write_buffer_as_ref().len(), 0);

         assert!(t.flush().is_ok());

         {
             let inner = mem.borrow_mut();
             let underlying_buffer = inner.write_buffer_as_ref();
             assert_eq!(b, underlying_buffer);
         }
     }

     #[test]
     fn must_write_successfully_after_flush() {
         let (mem, thru) = new_transports!(0, 5);
         let mut t = TBufferedTransport::with_capacity(0, 5, thru);

         // write and flush
         let b: [u8; 5] = [0, 1, 2, 3, 4];
         assert_eq!(t.write(&b).unwrap(), 5);
         assert!(t.flush().is_ok());

         // check the flushed bytes
         {
             let inner = mem.borrow_mut();
             let underlying_buffer = inner.write_buffer_as_ref();
             assert_eq!(b, underlying_buffer);
         }

         // reset our underlying transport
         mem.borrow_mut().empty_write_buffer();

         // write and flush again
         assert_eq!(t.write(&b).unwrap(), 5);
         assert!(t.flush().is_ok());

         // check the flushed bytes
         {
             let inner = mem.borrow_mut();
             let underlying_buffer = inner.write_buffer_as_ref();
             assert_eq!(b, underlying_buffer);
         }
     }
 }
	// Licensed to the Apache Software Foundation (ASF) under one
	// or more contributor license agreements. See the NOTICE file
	// distributed with this work for additional information
	// regarding copyright ownership. The ASF licenses this file
	// to you under the Apache License, Version 2.0 (the
	// "License"); you may not use this file except in compliance
	// with the License. You may obtain a copy of the License at
	//
	// http://www.apache.org/licenses/LICENSE-2.0
	//
	// Unless required by applicable law or agreed to in writing,
	// software distributed under the License is distributed on an
	// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
	// KIND, either express or implied. See the License for the
	// specific language governing permissions and limitations
	// under the License.

	use std::cell::RefCell;
	use std::cmp;
	use std::io;
	use std::io::{Read, Write};
	use std::rc::Rc;

	use super::{TTransport, TTransportFactory};

	/// Default capacity of the read buffer in bytes.
	const DEFAULT_RBUFFER_CAPACITY: usize = 4096;

	/// Default capacity of the write buffer in bytes..
	const DEFAULT_WBUFFER_CAPACITY: usize = 4096;

	/// Transport that communicates with endpoints using a byte stream.
	///
	/// A `TBufferedTransport` maintains a fixed-size internal write buffer. All
	/// writes are made to this buffer and are sent to the wrapped transport only
	/// when `TTransport::flush()` is called. On a flush a fixed-length header with a
	/// count of the buffered bytes is written, followed by the bytes themselves.
	///
	/// A `TBufferedTransport` also maintains a fixed-size internal read buffer.
	/// On a call to `TTransport::read(...)` one full message - both fixed-length
	/// header and bytes - is read from the wrapped transport and buffered.
	/// Subsequent read calls are serviced from the internal buffer until it is
	/// exhausted, at which point the next full message is read from the wrapped
	/// transport.
	///
	/// # Examples
	///
	/// Create and use a `TBufferedTransport`.
	///
	/// ```no_run
	/// use std::cell::RefCell;
	/// use std::rc::Rc;
	/// use std::io::{Read, Write};
	/// use thrift::transport::{TBufferedTransport, TTcpTransport, TTransport};
	///
	/// let mut t = TTcpTransport::new();
	/// t.open("localhost:9090").unwrap();
	///
	/// let t = Rc::new(RefCell::new(Box::new(t) as Box<TTransport>));
	/// let mut t = TBufferedTransport::new(t);
	///
	/// // read
	/// t.read(&mut vec![0u8; 1]).unwrap();
	///
	/// // write
	/// t.write(&[0x00]).unwrap();
	/// t.flush().unwrap();
	/// ```
	pub struct TBufferedTransport {
	rbuf: Box<[u8]>,
	rpos: usize,
	rcap: usize,
	wbuf: Vec<u8>,
	inner: Rc<RefCell<Box<TTransport>>>,
	}

	impl TBufferedTransport {
	/// Create a `TBufferedTransport` with default-sized internal read and
	/// write buffers that wraps an `inner` `TTransport`.
	pub fn new(inner: Rc<RefCell<Box<TTransport>>>) -> TBufferedTransport {
	TBufferedTransport::with_capacity(DEFAULT_RBUFFER_CAPACITY, DEFAULT_WBUFFER_CAPACITY, inner)
	}

	/// Create a `TBufferedTransport` with an internal read buffer of size
	/// `read_buffer_capacity` and an internal write buffer of size
	/// `write_buffer_capacity` that wraps an `inner` `TTransport`.
	pub fn with_capacity(read_buffer_capacity: usize,
	write_buffer_capacity: usize,
	inner: Rc<RefCell<Box<TTransport>>>)
	-> TBufferedTransport {
	TBufferedTransport {
	rbuf: vec![0; read_buffer_capacity].into_boxed_slice(),
	rpos: 0,
	rcap: 0,
	wbuf: Vec::with_capacity(write_buffer_capacity),
	inner: inner,
	}
	}

	fn get_bytes(&mut self) -> io::Result<&[u8]> {
	if self.rcap - self.rpos == 0 {
	self.rpos = 0;
	self.rcap = self.inner.borrow_mut().read(&mut self.rbuf)?;
	}

	Ok(&self.rbuf[self.rpos..self.rcap])
	}

	fn consume(&mut self, consumed: usize) {
	// TODO: was a bug here += <-- test somehow
	self.rpos = cmp::min(self.rcap, self.rpos + consumed);
	}
	}

	impl Read for TBufferedTransport {
	fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
	let mut bytes_read = 0;

	loop {
	let nread = {
	let avail_bytes = self.get_bytes()?;
	let avail_space = buf.len() - bytes_read;
	let nread = cmp::min(avail_space, avail_bytes.len());
	buf[bytes_read..(bytes_read + nread)].copy_from_slice(&avail_bytes[..nread]);
	nread
	};

	self.consume(nread);
	bytes_read += nread;

	if bytes_read == buf.len() \|\| nread == 0 {
	break;
	}
	}

	Ok(bytes_read)
	}
	}

	impl Write for TBufferedTransport {
	fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
	let avail_bytes = cmp::min(buf.len(), self.wbuf.capacity() - self.wbuf.len());
	self.wbuf.extend_from_slice(&buf[..avail_bytes]);
	assert!(self.wbuf.len() <= self.wbuf.capacity(),
	"copy overflowed buffer");
	Ok(avail_bytes)
	}

	fn flush(&mut self) -> io::Result<()> {
	self.inner.borrow_mut().write_all(&self.wbuf)?;
	self.inner.borrow_mut().flush()?;
	self.wbuf.clear();
	Ok(())
	}
	}

	/// Factory for creating instances of `TBufferedTransport`
	#[derive(Default)]
	pub struct TBufferedTransportFactory;

	impl TBufferedTransportFactory {
	/// Create a `TBufferedTransportFactory`.
	pub fn new() -> TBufferedTransportFactory {
	TBufferedTransportFactory {}
	}
	}

	impl TTransportFactory for TBufferedTransportFactory {
	fn create(&self, inner: Rc<RefCell<Box<TTransport>>>) -> Box<TTransport> {
	Box::new(TBufferedTransport::new(inner)) as Box<TTransport>
	}
	}

	#[cfg(test)]
	mod tests {
	use std::cell::RefCell;
	use std::io::{Read, Write};
	use std::rc::Rc;

	use super::*;
	use ::transport::{TPassThruTransport, TTransport};
	use ::transport::mem::TBufferTransport;

	macro_rules! new_transports {
	($wbc:expr, $rbc:expr) => (
	{
	let mem = Rc::new(RefCell::new(Box::new(TBufferTransport::with_capacity($wbc, $rbc))));
	let thru: Box<TTransport> = Box::new(TPassThruTransport { inner: mem.clone() });
	let thru = Rc::new(RefCell::new(thru));
	(mem, thru)
	}
	);
	}

	#[test]
	fn must_return_zero_if_read_buffer_is_empty() {
	let (_, thru) = new_transports!(10, 0);
	let mut t = TBufferedTransport::with_capacity(10, 0, thru);

	let mut b = vec![0; 10];
	let read_result = t.read(&mut b);

	assert_eq!(read_result.unwrap(), 0);
	}

	#[test]
	fn must_return_zero_if_caller_reads_into_zero_capacity_buffer() {
	let (_, thru) = new_transports!(10, 0);
	let mut t = TBufferedTransport::with_capacity(10, 0, thru);

	let read_result = t.read(&mut []);

	assert_eq!(read_result.unwrap(), 0);
	}

	#[test]
	fn must_return_zero_if_nothing_more_can_be_read() {
	let (mem, thru) = new_transports!(4, 0);
	let mut t = TBufferedTransport::with_capacity(4, 0, thru);

	mem.borrow_mut().set_readable_bytes(&[0, 1, 2, 3]);

	// read buffer is exactly the same size as bytes available
	let mut buf = vec![0u8; 4];
	let read_result = t.read(&mut buf);

	// we've read exactly 4 bytes
	assert_eq!(read_result.unwrap(), 4);
	assert_eq!(&buf, &[0, 1, 2, 3]);

	// try read again
	let buf_again = vec![0u8; 4];
	let read_result = t.read(&mut buf);

	// this time, 0 bytes and we haven't changed the buffer
	assert_eq!(read_result.unwrap(), 0);
	assert_eq!(&buf_again, &[0, 0, 0, 0])
	}

	#[test]
	fn must_fill_user_buffer_with_only_as_many_bytes_as_available() {
	let (mem, thru) = new_transports!(4, 0);
	let mut t = TBufferedTransport::with_capacity(4, 0, thru);

	mem.borrow_mut().set_readable_bytes(&[0, 1, 2, 3]);

	// read buffer is much larger than the bytes available
	let mut buf = vec![0u8; 8];
	let read_result = t.read(&mut buf);

	// we've read exactly 4 bytes
	assert_eq!(read_result.unwrap(), 4);
	assert_eq!(&buf[..4], &[0, 1, 2, 3]);

	// try read again
	let read_result = t.read(&mut buf[4..]);

	// this time, 0 bytes and we haven't changed the buffer
	assert_eq!(read_result.unwrap(), 0);
	assert_eq!(&buf, &[0, 1, 2, 3, 0, 0, 0, 0])
	}

	#[test]
	fn must_read_successfully() {
	// this test involves a few loops within the buffered transport
	// itself where it has to drain the underlying transport in order
	// to service a read

	// we have a much smaller buffer than the
	// underlying transport has bytes available
	let (mem, thru) = new_transports!(10, 0);
	let mut t = TBufferedTransport::with_capacity(2, 0, thru);

	// fill the underlying transport's byte buffer
	let mut readable_bytes = [0u8; 10];
	for i in 0..10 {
	readable_bytes[i] = i as u8;
	}
	mem.borrow_mut().set_readable_bytes(&readable_bytes);

	// we ask to read into a buffer that's much larger
	// than the one the buffered transport has; as a result
	// it's going to have to keep asking the underlying
	// transport for more bytes
	let mut buf = [0u8; 8];
	let read_result = t.read(&mut buf);

	// we should have read 8 bytes
	assert_eq!(read_result.unwrap(), 8);
	assert_eq!(&buf, &[0, 1, 2, 3, 4, 5, 6, 7]);

	// let's clear out the buffer and try read again
	for i in 0..8 {
	buf[i] = 0;
	}
	let read_result = t.read(&mut buf);

	// this time we were only able to read 2 bytes
	// (all that's remaining from the underlying transport)
	// let's also check that the remaining bytes are untouched
	assert_eq!(read_result.unwrap(), 2);
	assert_eq!(&buf[0..2], &[8, 9]);
	assert_eq!(&buf[2..], &[0, 0, 0, 0, 0, 0]);

	// try read again (we should get 0)
	// and all the existing bytes were untouched
	let read_result = t.read(&mut buf);
	assert_eq!(read_result.unwrap(), 0);
	assert_eq!(&buf[0..2], &[8, 9]);
	assert_eq!(&buf[2..], &[0, 0, 0, 0, 0, 0]);
	}

	#[test]
	fn must_return_zero_if_nothing_can_be_written() {
	let (_, thru) = new_transports!(0, 0);
	let mut t = TBufferedTransport::with_capacity(0, 0, thru);

	let b = vec![0; 10];
	let r = t.write(&b);

	assert_eq!(r.unwrap(), 0);
	}

	#[test]
	fn must_return_zero_if_caller_calls_write_with_empty_buffer() {
	let (mem, thru) = new_transports!(0, 10);
	let mut t = TBufferedTransport::with_capacity(0, 10, thru);

	let r = t.write(&[]);

	assert_eq!(r.unwrap(), 0);
	assert_eq!(mem.borrow_mut().write_buffer_as_ref(), &[]);
	}

	#[test]
	fn must_return_zero_if_write_buffer_full() {
	let (_, thru) = new_transports!(0, 0);
	let mut t = TBufferedTransport::with_capacity(0, 4, thru);

	let b = [0x00, 0x01, 0x02, 0x03];

	// we've now filled the write buffer
	let r = t.write(&b);
	assert_eq!(r.unwrap(), 4);

	// try write the same bytes again - nothing should be writable
	let r = t.write(&b);
	assert_eq!(r.unwrap(), 0);
	}

	#[test]
	fn must_only_write_to_inner_transport_on_flush() {
	let (mem, thru) = new_transports!(10, 10);
	let mut t = TBufferedTransport::new(thru);

	let b: [u8; 5] = [0, 1, 2, 3, 4];
	assert_eq!(t.write(&b).unwrap(), 5);
	assert_eq!(mem.borrow_mut().write_buffer_as_ref().len(), 0);

	assert!(t.flush().is_ok());

	{
	let inner = mem.borrow_mut();
	let underlying_buffer = inner.write_buffer_as_ref();
	assert_eq!(b, underlying_buffer);
	}
	}

	#[test]
	fn must_write_successfully_after_flush() {
	let (mem, thru) = new_transports!(0, 5);
	let mut t = TBufferedTransport::with_capacity(0, 5, thru);

	// write and flush
	let b: [u8; 5] = [0, 1, 2, 3, 4];
	assert_eq!(t.write(&b).unwrap(), 5);
	assert!(t.flush().is_ok());

	// check the flushed bytes
	{
	let inner = mem.borrow_mut();
	let underlying_buffer = inner.write_buffer_as_ref();
	assert_eq!(b, underlying_buffer);
	}

	// reset our underlying transport
	mem.borrow_mut().empty_write_buffer();

	// write and flush again
	assert_eq!(t.write(&b).unwrap(), 5);
	assert!(t.flush().is_ok());

	// check the flushed bytes
	{
	let inner = mem.borrow_mut();
	let underlying_buffer = inner.write_buffer_as_ref();
	assert_eq!(b, underlying_buffer);
	}
	}
	}