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use Buffer;
use BufferRef;
use std::fs;
use std::io::Read;
use std::io;
use std::net;
use std::process;
use with_buffer;

/// A utility function for unsafely implementing `ReadBufferRef` for readers
/// that don't read the buffer passed to `Read::read`.
pub unsafe fn read_buffer_ref<'d, 's, T: Read>(reader: &mut T, mut buf: BufferRef<'d, 's>)
    -> io::Result<&'d [u8]>
{
    let read = try!(reader.read(buf.uninitialized_mut()));
    buf.advance(read);
    Ok(buf.initialized())
}

/// An internal trait to be implemented by `T: Read` which do not access the
/// read buffer in `Read::read`.
pub unsafe trait ReadBufferMarker: Read { }

/// An internal trait to be implemented by `T: Read` which do not access the
/// read buffer in `Read::read`. Prefer implementing `ReadBufferMarker` over
/// this.
pub trait ReadBufferRef: Read {
    /// Reads (equivalently to `Read::read`) into the buffer ref and returns
    /// the newly written bytes.
    fn read_buffer_ref<'d, 's>(&mut self, buf: BufferRef<'d, 's>) -> io::Result<&'d [u8]>;
}

/// Trait to read to `T: Buffer`.
///
/// This trait should be imported to read into buffers.
pub trait ReadBuffer: ReadBufferRef {
    /// Reads (equivalently to `Read::read`) into the buffer and returns the
    /// newly read bytes.
    fn read_buffer<'d, B: Buffer<'d>>(&mut self, buf: B) -> io::Result<&'d [u8]> {
        with_buffer(buf, |buf| self.read_buffer_ref(buf))
    }
}

impl<T: ReadBufferRef> ReadBuffer for T { }
impl<T: ReadBufferMarker> ReadBufferRef for T {
    fn read_buffer_ref<'d, 's>(&mut self, buf: BufferRef<'d, 's>)
        -> io::Result<&'d [u8]>
    {
        unsafe {
            read_buffer_ref(self, buf)
        }
    }
}

unsafe impl ReadBufferMarker for fs::File { }
unsafe impl ReadBufferMarker for io::Empty { }
unsafe impl ReadBufferMarker for io::Repeat { }
unsafe impl ReadBufferMarker for io::Stdin { }
unsafe impl ReadBufferMarker for net::TcpStream { }
unsafe impl ReadBufferMarker for process::ChildStderr { }
unsafe impl ReadBufferMarker for process::ChildStdout { }
unsafe impl<'a> ReadBufferMarker for &'a [u8] { }
unsafe impl<'a> ReadBufferMarker for &'a fs::File { }
unsafe impl<'a> ReadBufferMarker for &'a net::TcpStream { }
unsafe impl<'a> ReadBufferMarker for io::StdinLock<'a> { }
unsafe impl<R> ReadBufferMarker for io::Take<R> where R: ReadBufferMarker { }
unsafe impl<R> ReadBufferMarker for io::BufReader<R> where R: ReadBufferMarker { }
unsafe impl<T, U> ReadBufferMarker for io::Chain<T, U> where T: ReadBufferMarker, U: ReadBufferMarker { }

unsafe impl<'a, R> ReadBufferMarker for &'a mut R where R: ReadBufferMarker { }
unsafe impl<R> ReadBufferMarker for Box<R> where R: ReadBufferMarker { }