read

fn read(Stream s, Vec<byte> buf) -> Result<Option<int>, IoError>

use io::{read};

Reads bytes from s into the front of buf without waiting.

Reads at most buf.len() bytes (the buffer’s length, not its capacity), overwriting buf[0..n]. Returns Ok(Option::Some(n)) with the number of bytes read, Ok(Option::None) at end of file, and Err(IoError::WouldBlock) when no data is available yet; then call wait_readable(s) and retry. An empty buf returns Ok(Option::Some(0)). io::sync::read_exact and read_to_end do the waiting for you.

Parameters#

Returns#

Result<Option<int>, IoError>

Examples#

use io::{close, open, read};
use io::fs::{remove_file};
use io::sync::{write_all};
use string::{to_bytes};
use tests::assert;
let path = "/tmp/coil_doc_read.txt";
let w = match open(path, "w") {
    Result::Ok(s) => s,
    Result::Err(_) => panic "open failed",
};
let _ = write_all(w, to_bytes("hey"));
let _ = close(w);

let r = match open(path, "r") {
    Result::Ok(s) => s,
    Result::Err(_) => panic "open failed",
};
let buf = to_bytes("..........");
let first = match read(r, buf) {
    Result::Ok(Option::Some(n)) => n,
    default => 0,
};
let at_eof = match read(r, buf) {
    Result::Ok(Option::None) => true,
    default => false,
};
let _ = close(r);
let _ = remove_file(path);
assert!(first == 3);
assert!(buf[0] == 104 as byte);
assert!(at_eof);

See also#

• io::sync::read_exact
• stdin: Returns a new stream on the process’s standard input.
• stdout: Returns a new stream on the process’s standard output.
• stderr: Returns a new stream on the process’s standard error.
• capture_begin: Starts keeping this thread’s stdout and stderr writes in memory instead of writing them, until the matching capture_end().
• capture_end: Ends the innermost capture_begin() and returns what it kept, as (stdout, stderr).
• open: Opens the file at path with mode and returns a stream on it.
• close: Closes s.