What is re1.5?

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.

re1.5 is an attempt to start with re1 codebase and add features required for minimalistic real-world use, while sticking to the minimal code size and memory use.

Why?

re1.5 is intended for use in highly constrained, e.g. embedded, environments, where offering familiar high-level string matching functionality is still beneficial.

Features

• Like re1, re1.5 retains design where compiled expression can be executed (matched) by multiple backends, each with its own distinctive design and runtime properties (complexity and memory usage).
• Unlike re1, regexes are compiled to memory-efficient bytecode. Exact size of the bytecode can be found prior to compilation (for memory allocation).
• External API functions feature namespace prefix to improve clarity and avoid name clashes when integrating into other projects.
• Matchers are NUL-char clean and take size of the input string as a param.
• 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.

TODO

• Support for repetition operator {n} and {n,m}.
• Support for Unicode (UTF-8).
• Support for matching flags like case-insensitive, dot matches all, multiline, etc.
• Support for more assertions like \A, \Z.

Author and License

re1.5 is maintained by Paul Sokolovsky pfalcon at users.sourceforge.net and licensed under BSD license, just as the original re1.