Efficiently insert line endings.

If you have a buffer full of data and want to insert any sort of regularly-spaced separator, this will do it with a minimum of data copying. Commonly, this is to insert \n (see lf()) or \r\n (crlf()), but any byte sequence can be used.

1. Pick a line ending. For single byte separators, see ByteLineEnding, or for two bytes, TwoByteLineEnding. For arbitrary byte slices, use SliceLineEnding.
2. Call line_wrap.
3. Your data has been rearranged in place with the specified line ending inserted.

Examples

use line_wrap::*;
// suppose we have 80 bytes of data in a buffer and we want to wrap as per MIME.
// Buffer is large enough to hold line endings.
let mut data = vec![0; 82];

assert_eq!(2, line_wrap(&mut data, 80, 76, &crlf()));

// first line of zeroes
let mut expected_data = vec![0; 76];
// line ending
expected_data.extend_from_slice(b"\r\n");
// next line
expected_data.extend_from_slice(&[0, 0, 0, 0]);
assert_eq!(expected_data, data);

Performance

On an i7 6850k:

• 10 byte input, 1 byte line length takes ~60ns (~160MiB/s)
• 100 byte input, 10 byte lines takes ~60ns (~1.6GiB/s)
  • Startup costs dominate at these small lengths
• 1,000 byte input, 100 byte lines takes ~65ns (~15GiB/s)
• 10,000 byte input, 100 byte lines takes ~550ns (~17GiB/s)
• In general, SliceLineEncoding is about 75% the speed of the fixed-length impls.

Naturally, try cargo +nightly bench on your hardware to get more representative data.