    1
    2
    3
    4
    5
    6
    7
    8
    9
    10
    11
    12
    13
    14
    15
    16
    17
    18
    19
    20
    21
    22
    23
    24
    25
    26
    27
    28
    29
    30
    31
    32
    33
    34
    35
    36
    37
    38
    39
    40
    41
    42
    43
    44
    45
    46
    47
    48
    49
    50
    51
    52
    53
    54
    55
    56
    57
    58
    59
    60
    61
    62
    63
    64
    65
    66
    67
    68
    69
    70
    71
    72
    73
    74
    75
    76
    77
    78
    79
    80
    81
    82
    83
    84
    85
    86
    87
    88

    use crate::BufMut;

    use std::{cmp, io};

    /// A `BufMut` adapter which implements `io::Write` for the inner value.
    ///
    /// This struct is generally created by calling `writer()` on `BufMut`. See
    /// documentation of [`writer()`](BufMut::writer) for more
    /// details.
    #[derive(Debug)]
    pub struct Writer<B> {
        buf: B,
    }

    pub fn new<B>(buf: B) -> Writer<B> {
        Writer { buf }
    }

    impl<B: BufMut> Writer<B> {
        /// Gets a reference to the underlying `BufMut`.
        ///
        /// It is inadvisable to directly write to the underlying `BufMut`.
        ///
        /// # Examples
        ///
        /// ```rust
        /// use bytes::BufMut;
        ///
        /// let buf = Vec::with_capacity(1024).writer();
        ///
        /// assert_eq!(1024, buf.get_ref().capacity());
        /// ```
        pub fn get_ref(&self) -> &B {
            &self.buf
        }

        /// Gets a mutable reference to the underlying `BufMut`.
        ///
        /// It is inadvisable to directly write to the underlying `BufMut`.
        ///
        /// # Examples
        ///
        /// ```rust
        /// use bytes::BufMut;
        ///
        /// let mut buf = vec![].writer();
        ///
        /// buf.get_mut().reserve(1024);
        ///
        /// assert_eq!(1024, buf.get_ref().capacity());
        /// ```
        pub fn get_mut(&mut self) -> &mut B {
            &mut self.buf
        }

        /// Consumes this `Writer`, returning the underlying value.
        ///
        /// # Examples
        ///
        /// ```rust
        /// use bytes::BufMut;
        /// use std::io;
        ///
        /// let mut buf = vec![].writer();
        /// let mut src = &b"hello world"[..];
        ///
        /// io::copy(&mut src, &mut buf).unwrap();
        ///
        /// let buf = buf.into_inner();
        /// assert_eq!(*buf, b"hello world"[..]);
        /// ```
        pub fn into_inner(self) -> B {
            self.buf
        }
    }

    impl<B: BufMut + Sized> io::Write for Writer<B> {
        fn write(&mut self, src: &[u8]) -> io::Result<usize> {
            let n = cmp::min(self.buf.remaining_mut(), src.len());

            self.buf.put_slice(&src[..n]);
            Ok(n)
        }

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