      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
     89
     90
     91
     92
     93
     94
     95
     96
     97
     98
     99
    100
    101
    102
    103
    104
    105
    106
    107
    108
    109
    110
    111
    112
    113
    114
    115
    116
    117
    118
    119
    120
    121
    122
    123
    124
    125
    126
    127
    128
    129
    130
    131
    132
    133
    134
    135
    136
    137
    138
    139
    140
    141
    142
    143
    144
    145
    146
    147
    148
    149
    150
    151
    152
    153
    154
    155
    156
    157
    158
    159
    160
    161
    162
    163
    164
    165
    166
    167
    168
    169
    170
    171
    172
    173
    174
    175
    176
    177
    178
    179
    180
    181
    182
    183
    184
    185
    186
    187
    188
    189
    190
    191
    192
    193
    194
    195
    196
    197
    198
    199
    200
    201
    202
    203
    204
    205
    206
    207
    208
    209
    210
    211
    212
    213
    214
    215
    216
    217
    218
    219
    220
    221
    222
    223
    224
    225
    226
    227
    228
    229
    230
    231
    232
    233
    234
    235
    236
    237
    238
    239
    240
    241
    242
    243
    244
    245
    246
    247
    248
    249
    250
    251
    252
    253
    254
    255
    256
    257
    258
    259
    260
    261
    262
    263
    264
    265
    266
    267
    268
    269
    270
    271
    272

    #![allow(missing_copy_implementations)]

    use crate::fmt;
    use crate::io::{self, Read, Initializer, Write, ErrorKind, BufRead, IoSlice, IoSliceMut};
    use crate::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.
    ///
    /// If you’re wanting to copy the contents of one file to another and you’re
    /// working with filesystem paths, see the [`fs::copy`] function.
    ///
    /// [`fs::copy`]: ../fs/fn.copy.html
    ///
    /// # 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 main() -> io::Result<()> {
    ///     let mut reader: &[u8] = b"hello";
    ///     let mut writer: Vec<u8> = vec![];
    ///
    ///     io::copy(&mut reader, &mut writer)?;
    ///
    ///     assert_eq!(&b"hello"[..], &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`]. Please see
    /// the documentation of [`empty()`][`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)`.
    ///
    /// [`Ok`]: ../result/enum.Result.html#variant.Ok
    ///
    /// # 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 } }

    #[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]
        fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
            let mut nwritten = 0;
            for buf in bufs {
                nwritten += self.read(buf)?;
            }
            Ok(nwritten)
        }

        #[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 write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
            let total_len = bufs.iter().map(|b| b.len()).sum();
            Ok(total_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 crate::io::prelude::*;
        use crate::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 dyn Read, &mut w as &mut dyn 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);
        }
    }

# Help

## Keyboard Shortcuts

`?`
  Show this help dialog
`S`
  Focus the search field
`↑`
  Move up in search results
`↓`
  Move down in search results
`↹`
  Switch tab
`⏎`
  Go to active search result
`+`
  Expand all sections
`-`
  Collapse all sections

## Search Tricks

Prefix searches with a type followed by a colon (e.g., `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g., `vec -> usize` or `* -> vec`)

Search multiple things at once by splitting your query with comma (e.g., `str,u8` or `String,struct:Vec,test`)