// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

#[cfg(feature="alloc")] use alloc::boxed::Box;
use core::cmp;
use io::{self, SeekFrom, Read, Initializer, Write, Seek, Error, ErrorKind};
#[cfg(feature="alloc")] use io::BufRead;
use core::fmt;
use core::mem;
#[cfg(feature="alloc")] use alloc::string::String;
#[cfg(feature="alloc")] use alloc::vec::Vec;

// =============================================================================
// Forwarding implementations

impl<'a, R: Read + ?Sized> Read for &'a mut R {
    #[inline]
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        (**self).read(buf)
    }

    #[inline]
    unsafe fn initializer(&self) -> Initializer {
        (**self).initializer()
    }

    #[cfg(feature="alloc")]
    #[inline]
    fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
        (**self).read_to_end(buf)
    }

    #[cfg(feature="alloc")]
    #[inline]
    fn read_to_string(&mut self, buf: &mut String) -> io::Result<usize> {
        (**self).read_to_string(buf)
    }

    #[inline]
    fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> {
        (**self).read_exact(buf)
    }
}
impl<'a, W: Write + ?Sized> Write for &'a mut W {
    #[inline]
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> { (**self).write(buf) }

    #[inline]
    fn flush(&mut self) -> io::Result<()> { (**self).flush() }

    #[inline]
    fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
        (**self).write_all(buf)
    }

    #[inline]
    fn write_fmt(&mut self, fmt: fmt::Arguments) -> io::Result<()> {
        (**self).write_fmt(fmt)
    }
}
impl<'a, S: Seek + ?Sized> Seek for &'a mut S {
    #[inline]
    fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> { (**self).seek(pos) }
}
#[cfg(feature="alloc")]
impl<'a, B: BufRead + ?Sized> BufRead for &'a mut B {
    #[inline]
    fn fill_buf(&mut self) -> io::Result<&[u8]> { (**self).fill_buf() }

    #[inline]
    fn consume(&mut self, amt: usize) { (**self).consume(amt) }

    #[inline]
    fn read_until(&mut self, byte: u8, buf: &mut Vec<u8>) -> io::Result<usize> {
        (**self).read_until(byte, buf)
    }

    #[inline]
    fn read_line(&mut self, buf: &mut String) -> io::Result<usize> {
        (**self).read_line(buf)
    }
}

#[cfg(feature="alloc")]
impl<R: Read + ?Sized> Read for Box<R> {
    #[inline]
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        (**self).read(buf)
    }

    #[inline]
    unsafe fn initializer(&self) -> Initializer {
        (**self).initializer()
    }

    #[cfg(feature="alloc")]
    #[inline]
    fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
        (**self).read_to_end(buf)
    }

    #[cfg(feature="alloc")]
    #[inline]
    fn read_to_string(&mut self, buf: &mut String) -> io::Result<usize> {
        (**self).read_to_string(buf)
    }

    #[inline]
    fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> {
        (**self).read_exact(buf)
    }
}
#[cfg(feature="alloc")]
impl<W: Write + ?Sized> Write for Box<W> {
    #[inline]
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> { (**self).write(buf) }

    #[inline]
    fn flush(&mut self) -> io::Result<()> { (**self).flush() }

    #[inline]
    fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
        (**self).write_all(buf)
    }

    #[inline]
    fn write_fmt(&mut self, fmt: fmt::Arguments) -> io::Result<()> {
        (**self).write_fmt(fmt)
    }
}
#[cfg(feature="alloc")]
impl<S: Seek + ?Sized> Seek for Box<S> {
    #[inline]
    fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> { (**self).seek(pos) }
}
#[cfg(feature="alloc")]
impl<B: BufRead + ?Sized> BufRead for Box<B> {
    #[inline]
    fn fill_buf(&mut self) -> io::Result<&[u8]> { (**self).fill_buf() }

    #[inline]
    fn consume(&mut self, amt: usize) { (**self).consume(amt) }

    #[inline]
    fn read_until(&mut self, byte: u8, buf: &mut Vec<u8>) -> io::Result<usize> {
        (**self).read_until(byte, buf)
    }

    #[inline]
    fn read_line(&mut self, buf: &mut String) -> io::Result<usize> {
        (**self).read_line(buf)
    }
}

// =============================================================================
// In-memory buffer implementations

/// Read is implemented for `&[u8]` by copying from the slice.
///
/// Note that reading updates the slice to point to the yet unread part.
/// The slice will be empty when EOF is reached.
impl<'a> Read for &'a [u8] {
    #[inline]
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        let amt = cmp::min(buf.len(), self.len());
        let (a, b) = self.split_at(amt);

        // First check if the amount of bytes we want to read is small:
        // `copy_from_slice` will generally expand to a call to `memcpy`, and
        // for a single byte the overhead is significant.
        if amt == 1 {
            buf[0] = a[0];
        } else {
            buf[..amt].copy_from_slice(a);
        }

        *self = b;
        Ok(amt)
    }

    #[inline]
    unsafe fn initializer(&self) -> Initializer {
        Initializer::nop()
    }

    #[inline]
    fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> {
        if buf.len() > self.len() {
            return Err(Error::new(ErrorKind::UnexpectedEof,
                                  "failed to fill whole buffer"));
        }
        let (a, b) = self.split_at(buf.len());

        // First check if the amount of bytes we want to read is small:
        // `copy_from_slice` will generally expand to a call to `memcpy`, and
        // for a single byte the overhead is significant.
        if buf.len() == 1 {
            buf[0] = a[0];
        } else {
            buf.copy_from_slice(a);
        }

        *self = b;
        Ok(())
    }

    #[cfg(feature="alloc")]
    #[inline]
    fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
        buf.extend_from_slice(*self);
        let len = self.len();
        *self = &self[len..];
        Ok(len)
    }
}

#[cfg(feature="alloc")]
impl<'a> BufRead for &'a [u8] {
    #[inline]
    fn fill_buf(&mut self) -> io::Result<&[u8]> { Ok(*self) }

    #[inline]
    fn consume(&mut self, amt: usize) { *self = &self[amt..]; }
}

/// Write is implemented for `&mut [u8]` by copying into the slice, overwriting
/// its data.
///
/// Note that writing updates the slice to point to the yet unwritten part.
/// The slice will be empty when it has been completely overwritten.
impl<'a> Write for &'a mut [u8] {
    #[inline]
    fn write(&mut self, data: &[u8]) -> io::Result<usize> {
        let amt = cmp::min(data.len(), self.len());
        let (a, b) = mem::replace(self, &mut []).split_at_mut(amt);
        a.copy_from_slice(&data[..amt]);
        *self = b;
        Ok(amt)
    }

    #[inline]
    fn write_all(&mut self, data: &[u8]) -> io::Result<()> {
        if self.write(data)? == data.len() {
            Ok(())
        } else {
            Err(Error::new(ErrorKind::WriteZero, "failed to write whole buffer"))
        }
    }

    #[inline]
    fn flush(&mut self) -> io::Result<()> { Ok(()) }
}

/// Write is implemented for `Vec<u8>` by appending to the vector.
/// The vector will grow as needed.
#[cfg(feature="alloc")]
impl Write for Vec<u8> {
    #[inline]
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        self.extend_from_slice(buf);
        Ok(buf.len())
    }

    #[inline]
    fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
        self.extend_from_slice(buf);
        Ok(())
    }

    #[inline]
    fn flush(&mut self) -> io::Result<()> { Ok(()) }
}
