io.rs.html -- source
Description: Source to the Rust file `src/libstd/sys_common/io.rs`.
Keywords: rust, rustlang, rust-lang

      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

    // 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.
    use io;
    use io::ErrorKind;
    use io::Read;
    use slice::from_raw_parts_mut;

    pub const DEFAULT_BUF_SIZE: usize = 8 * 1024;

    // Provides read_to_end functionality over an uninitialized buffer.
    // This function is unsafe because it calls the underlying
    // read function with a slice into uninitialized memory. The default
    // implementation of read_to_end for readers will zero out new memory in
    // the buf before passing it to read, but avoiding this zero can often
    // lead to a fairly significant performance win.
    //
    // Implementations using this method have to adhere to two guarantees:
    //  *  The implementation of read never reads the buffer provided.
    //  *  The implementation of read correctly reports how many bytes were written.
    pub unsafe fn read_to_end_uninitialized(r: &mut Read, buf: &mut Vec<u8>) -> io::Result<usize> {

        let start_len = buf.len();
        buf.reserve(16);

        // Always try to read into the empty space of the vector (from the length to the capacity).
        // If the vector ever fills up then we reserve an extra byte which should trigger the normal
        // reallocation routines for the vector, which will likely double the size.
        //
        // This function is similar to the read_to_end function in std::io, but the logic about
        // reservations and slicing is different enough that this is duplicated here.
        loop {
            if buf.len() == buf.capacity() {
                buf.reserve(1);
            }

            let buf_slice = from_raw_parts_mut(buf.as_mut_ptr().offset(buf.len() as isize),
                                               buf.capacity() - buf.len());

            match r.read(buf_slice) {
                Ok(0) => { return Ok(buf.len() - start_len); }
                Ok(n) => { let len = buf.len() + n; buf.set_len(len); },
                Err(ref e) if e.kind() == ErrorKind::Interrupted => { }
                Err(e) => { return Err(e); }
            }
        }
    }

    #[cfg(test)]
    #[allow(dead_code)] // not used on emscripten
    pub mod test {
        use path::{Path, PathBuf};
        use env;
        use rand::{self, Rng};
        use fs;

        pub struct TempDir(PathBuf);

        impl TempDir {
            pub fn join(&self, path: &str) -> PathBuf {
                let TempDir(ref p) = *self;
                p.join(path)
            }

            pub fn path<'a>(&'a self) -> &'a Path {
                let TempDir(ref p) = *self;
                p
            }
        }

        impl Drop for TempDir {
            fn drop(&mut self) {
                // Gee, seeing how we're testing the fs module I sure hope that we
                // at least implement this correctly!
                let TempDir(ref p) = *self;
                fs::remove_dir_all(p).unwrap();
            }
        }

        pub fn tmpdir() -> TempDir {
            let p = env::temp_dir();
            let mut r = rand::thread_rng();
            let ret = p.join(&format!("rust-{}", r.next_u32()));
            fs::create_dir(&ret).unwrap();
            TempDir(ret)
        }
    }

    #[cfg(test)]
    mod tests {
        use io::prelude::*;
        use super::*;
        use io;
        use io::{ErrorKind, Take, Repeat, repeat};
        use slice::from_raw_parts;

        struct ErrorRepeat {
            lr: Take<Repeat>
        }

        fn error_repeat(byte: u8, limit: u64) -> ErrorRepeat {
            ErrorRepeat { lr: repeat(byte).take(limit) }
        }

        impl Read for ErrorRepeat {
            fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
                let ret = self.lr.read(buf);
                if let Ok(0) = ret {
                    return Err(io::Error::new(ErrorKind::Other, ""))
                }
                ret
            }
        }

        fn init_vec_data() -> Vec<u8> {
            let mut vec = vec![10u8; 200];
            unsafe { vec.set_len(0); }
            vec
        }

        fn assert_all_eq(buf: &[u8], value: u8) {
            for n in buf {
                assert_eq!(*n, value);
            }
        }

        fn validate(buf: &Vec<u8>, good_read_len: usize) {
            assert_all_eq(buf, 1u8);
            let cap = buf.capacity();
            let end_slice = unsafe { from_raw_parts(buf.as_ptr().offset(good_read_len as isize),
                                                        cap - good_read_len) };
            assert_all_eq(end_slice, 10u8);
        }

        #[test]
        fn read_to_end_uninit_error() {
            let mut er = error_repeat(1,100);
            let mut vec = init_vec_data();
            if let Err(_) = unsafe { read_to_end_uninitialized(&mut er, &mut vec) } {
                validate(&vec, 100);
            } else {
                assert!(false);
            }
        }

        #[test]
        fn read_to_end_uninit_zero_len_vec() {
            let mut er = repeat(1).take(100);
            let mut vec = Vec::new();
            let n = unsafe{ read_to_end_uninitialized(&mut er, &mut vec).unwrap() };
            assert_all_eq(&vec, 1u8);
            assert_eq!(vec.len(), n);
        }

        #[test]
        fn read_to_end_uninit_good() {
            let mut er = repeat(1).take(100);
            let mut vec = init_vec_data();
            let n = unsafe{ read_to_end_uninitialized(&mut er, &mut vec).unwrap() };
            validate(&vec, 100);
            assert_eq!(vec.len(), n);
        }

        #[bench]
        #[cfg_attr(target_os = "emscripten", ignore)]
        fn bench_uninitialized(b: &mut ::test::Bencher) {
            b.iter(|| {
                let mut lr = repeat(1).take(10000000);
                let mut vec = Vec::with_capacity(1024);
                unsafe { read_to_end_uninitialized(&mut lr, &mut vec) }
            });
        }
    }

# Help

## Keyboard Shortcuts

?
  Show this help dialog
S
  Focus the search field
⇤
  Move up in search results
⇥
  Move down in search results
⏎
  Go to active search result
+
  Collapse/expand 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`)