LineReader is a byte-delimiter-focused buffered reader for Rust, meant as a faster, less error-prone alternative to BufRead::read_until.

It provides three main functions:

Returns Option<io::Result<&[u8]>> - None on end-of-file, an IO error from the wrapped reader, or an immutable byte slice ending on and including any delimiter.

Line length is limited to the size of the internal buffer - longer lines will be spread across multiple reads.

In contrast with read_until, detecting end-of-file is more natural with the use of Option; line length is naturally limited to some sensible value without the use of by_ref().take(limit); copying is minimised by returning borrowed slices; you'll never forget to call buf.clear().

Behaves identically to next_line(), except it returns a slice of all the complete lines in the buffer.

Calls a closure on each line of the input, while the closure returns true and no IO errors are detected. Such errors terminate iteration and are returned from the function.

extern crate linereader;
use linereader::LineReader;

let mut file = File::open(myfile).expect("open");

// Defaults to a 64 KiB buffer and b'\n' delimiter; change with one of:
//  * LineReader::with_capacity(usize);
//  * LineReader::with_delimiter(u8);
//  * LineReader::with_delimiter_and_capacity(u8, usize)
let mut reader = LineReader::new(file);

while let Some(line) = reader.next_line() {
    let line = line.expect("read error");
    // line is a &[u8] owned by reader.
}

Tests performed using 'Dickens_Charles_Pickwick_Papers.xml', concatinated to itself 480 times. The resulting file is 976 MB and 10.3 million lines long.