Module memchr

This module defines 256-bit vector implementations of memchr and friends.

The main types in this module are One, Two and Three. They are for searching for one, two or three distinct bytes, respectively, in a haystack. Each type also has corresponding double ended iterators. These searchers are typically much faster than scalar routines accomplishing the same task.

The One searcher also provides a One::count routine for efficiently counting the number of times a single byte occurs in a haystack. This is useful, for example, for counting the number of lines in a haystack. This routine exists because it is usually faster, especially with a high match count, then using One::find repeatedly. (OneIter specializes its Iterator::count implementation to use this routine.)

Only one, two and three bytes are supported because three bytes is about the point where one sees diminishing returns. Beyond this point and it’s probably (but not necessarily) better to just use a simple [bool; 256] array or similar. However, it depends mightily on the specific work-load and the expected match frequency.

Structs

• One
  Finds all occurrences of a single byte in a haystack.
• OneIter
  An iterator over all occurrences of a single byte in a haystack.
• Three
  Finds all occurrences of three bytes in a haystack.
• ThreeIter
  An iterator over all occurrences of three possible bytes in a haystack.
• Two
  Finds all occurrences of two bytes in a haystack.
• TwoIter
  An iterator over all occurrences of two possible bytes in a haystack.