What is pikevm?
==============

re1 (http://code.google.com/p/re1/) is "toy regular expression implementation"
by Russel Cox, featuring simplicity and minimal code size unheard of in other
implementations. re2 (http://code.google.com/p/re2/) is "an efficient,
principled regular expression library" by the same author. It is robust,
full-featured, and ... bloated, comparing to re1.

This is implementation of pikevm based on re1.5 which adds features required for
minimalistic real-world use, while sticking to the minimal code size and
memory use.
https://github.com/pfalcon/re1.5

Why?
====
Pikevm guarantees that any input regex will scale O(n) with the size of the
string, thus making it the fastest regex implementation. There is no backtracking
that usually expodes to O(n^2). My goals were to explore this code and try
to use in my text editor, but after closer analysis pike performs roughly
3 times slower on small strings than traditional well optimized backtrack
engine. The cost of addthread is not exactly O(1) so it results in many 
extra operations since every character is processed in lockstep. There is
also a problem of submatch tracking that grows memory usage.

Features
========

* UnLike re1.5, here is only pikevm, one file easy to use.
* Unlike re1.5, regexes is compiled to type sized code rather than bytecode,
eliviating the problem of byte overflow in splits/jmps on large regexes. 
Currently the type used is int, and every atom in compiled code is aligned
to that.
* Matcher does not take size of string as param, it checks for '\0' instead,
so that the user does not need to waste time taking strlen()
* Support for quoted chars in regex.
* Support for ^, $ assertions in regex.
* Support for "match" vs "search" operations, as common in other regex APIs.
* Support for named character classes: \d \D \s \S \w \W.
* Support for repetition operator {n} and {n,m}.

TODO
====

* Support for Unicode (UTF-8). (trivial to do, because of int type sized code)
* Support for matching flags like case-insensitive, dot matches all,
multiline, etc.
* Support for more assertions like \A, \Z.

Author and License
==================
licensed under BSD license, just as the original re1.