util.rs.html -- source
Description: Source to the Rust file `/usr/obj/ports/rust-1.20.0/rustc-1.20.0-src/src/libstd/io/util.rs`.
Keywords: rust, rustlang, rust-lang

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    // Copyright 2014 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.

    #![allow(missing_copy_implementations)]

    use fmt;
    use io::{self, Read, Initializer, Write, ErrorKind, BufRead};
    use mem;

    /// Copies the entire contents of a reader into a writer.
    ///
    /// This function will continuously read data from `reader` and then
    /// write it into `writer` in a streaming fashion until `reader`
    /// returns EOF.
    ///
    /// On success, the total number of bytes that were copied from
    /// `reader` to `writer` is returned.
    ///
    /// # Errors
    ///
    /// This function will return an error immediately if any call to `read` or
    /// `write` returns an error. All instances of `ErrorKind::Interrupted` are
    /// handled by this function and the underlying operation is retried.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::io;
    ///
    /// # fn foo() -> io::Result<()> {
    /// let mut reader: &[u8] = b"hello";
    /// let mut writer: Vec<u8> = vec![];
    ///
    /// io::copy(&mut reader, &mut writer)?;
    ///
    /// assert_eq!(reader, &writer[..]);
    /// # Ok(())
    /// # }
    /// ```
    #[stable(feature = "rust1", since = "1.0.0")]
    pub fn copy<R: ?Sized, W: ?Sized>(reader: &mut R, writer: &mut W) -> io::Result<u64>
        where R: Read, W: Write
    {
        let mut buf = unsafe {
            let mut buf: [u8; super::DEFAULT_BUF_SIZE] = mem::uninitialized();
            reader.initializer().initialize(&mut buf);
            buf
        };

        let mut written = 0;
        loop {
            let len = match reader.read(&mut buf) {
                Ok(0) => return Ok(written),
                Ok(len) => len,
                Err(ref e) if e.kind() == ErrorKind::Interrupted => continue,
                Err(e) => return Err(e),
            };
            writer.write_all(&buf[..len])?;
            written += len as u64;
        }
    }

    /// A reader which is always at EOF.
    ///
    /// This struct is generally created by calling [`empty`][empty]. Please see
    /// the documentation of `empty()` for more details.
    ///
    /// [empty]: fn.empty.html
    #[stable(feature = "rust1", since = "1.0.0")]
    pub struct Empty { _priv: () }

    /// Constructs a new handle to an empty reader.
    ///
    /// All reads from the returned reader will return `Ok(0)`.
    ///
    /// # Examples
    ///
    /// A slightly sad example of not reading anything into a buffer:
    ///
    /// ```
    /// use std::io::{self, Read};
    ///
    /// let mut buffer = String::new();
    /// io::empty().read_to_string(&mut buffer).unwrap();
    /// assert!(buffer.is_empty());
    /// ```
    #[stable(feature = "rust1", since = "1.0.0")]
    pub fn empty() -> Empty { Empty { _priv: () } }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl Read for Empty {
        #[inline]
        fn read(&mut self, _buf: &mut [u8]) -> io::Result<usize> { Ok(0) }

        #[inline]
        unsafe fn initializer(&self) -> Initializer {
            Initializer::nop()
        }
    }
    #[stable(feature = "rust1", since = "1.0.0")]
    impl BufRead for Empty {
        #[inline]
        fn fill_buf(&mut self) -> io::Result<&[u8]> { Ok(&[]) }
        #[inline]
        fn consume(&mut self, _n: usize) {}
    }

    #[stable(feature = "std_debug", since = "1.16.0")]
    impl fmt::Debug for Empty {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            f.pad("Empty { .. }")
        }
    }

    /// A reader which yields one byte over and over and over and over and over and...
    ///
    /// This struct is generally created by calling [`repeat`][repeat]. Please
    /// see the documentation of `repeat()` for more details.
    ///
    /// [repeat]: fn.repeat.html
    #[stable(feature = "rust1", since = "1.0.0")]
    pub struct Repeat { byte: u8 }

    /// Creates an instance of a reader that infinitely repeats one byte.
    ///
    /// All reads from this reader will succeed by filling the specified buffer with
    /// the given byte.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::io::{self, Read};
    ///
    /// let mut buffer = [0; 3];
    /// io::repeat(0b101).read_exact(&mut buffer).unwrap();
    /// assert_eq!(buffer, [0b101, 0b101, 0b101]);
    /// ```
    #[stable(feature = "rust1", since = "1.0.0")]
    pub fn repeat(byte: u8) -> Repeat { Repeat { byte: byte } }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl Read for Repeat {
        #[inline]
        fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
            for slot in &mut *buf {
                *slot = self.byte;
            }
            Ok(buf.len())
        }

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

    #[stable(feature = "std_debug", since = "1.16.0")]
    impl fmt::Debug for Repeat {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            f.pad("Repeat { .. }")
        }
    }

    /// A writer which will move data into the void.
    ///
    /// This struct is generally created by calling [`sink`][sink]. Please
    /// see the documentation of `sink()` for more details.
    ///
    /// [sink]: fn.sink.html
    #[stable(feature = "rust1", since = "1.0.0")]
    pub struct Sink { _priv: () }

    /// Creates an instance of a writer which will successfully consume all data.
    ///
    /// All calls to `write` on the returned instance will return `Ok(buf.len())`
    /// and the contents of the buffer will not be inspected.
    ///
    /// # Examples
    ///
    /// ```rust
    /// use std::io::{self, Write};
    ///
    /// let buffer = vec![1, 2, 3, 5, 8];
    /// let num_bytes = io::sink().write(&buffer).unwrap();
    /// assert_eq!(num_bytes, 5);
    /// ```
    #[stable(feature = "rust1", since = "1.0.0")]
    pub fn sink() -> Sink { Sink { _priv: () } }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl Write for Sink {
        #[inline]
        fn write(&mut self, buf: &[u8]) -> io::Result<usize> { Ok(buf.len()) }
        #[inline]
        fn flush(&mut self) -> io::Result<()> { Ok(()) }
    }

    #[stable(feature = "std_debug", since = "1.16.0")]
    impl fmt::Debug for Sink {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            f.pad("Sink { .. }")
        }
    }

    #[cfg(test)]
    mod tests {
        use io::prelude::*;
        use io::{copy, sink, empty, repeat};

        #[test]
        fn copy_copies() {
            let mut r = repeat(0).take(4);
            let mut w = sink();
            assert_eq!(copy(&mut r, &mut w).unwrap(), 4);

            let mut r = repeat(0).take(1 << 17);
            assert_eq!(copy(&mut r as &mut Read, &mut w as &mut Write).unwrap(), 1 << 17);
        }

        #[test]
        fn sink_sinks() {
            let mut s = sink();
            assert_eq!(s.write(&[]).unwrap(), 0);
            assert_eq!(s.write(&[0]).unwrap(), 1);
            assert_eq!(s.write(&[0; 1024]).unwrap(), 1024);
            assert_eq!(s.by_ref().write(&[0; 1024]).unwrap(), 1024);
        }

        #[test]
        fn empty_reads() {
            let mut e = empty();
            assert_eq!(e.read(&mut []).unwrap(), 0);
            assert_eq!(e.read(&mut [0]).unwrap(), 0);
            assert_eq!(e.read(&mut [0; 1024]).unwrap(), 0);
            assert_eq!(e.by_ref().read(&mut [0; 1024]).unwrap(), 0);
        }

        #[test]
        fn repeat_repeats() {
            let mut r = repeat(4);
            let mut b = [0; 1024];
            assert_eq!(r.read(&mut b).unwrap(), 1024);
            assert!(b.iter().all(|b| *b == 4));
        }

        #[test]
        fn take_some_bytes() {
            assert_eq!(repeat(4).take(100).bytes().count(), 100);
            assert_eq!(repeat(4).take(100).bytes().next().unwrap().unwrap(), 4);
            assert_eq!(repeat(1).take(10).chain(repeat(2).take(10)).bytes().count(), 20);
        }
    }

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