Regular expression matching on Rust streams.

The regex crate implements regular expression matching on strings and byte arrays. However, in order to match the output of implementations of fmt::Debug and fmt::Display, or by any code which writes to an instance of fmt::Write or io::Write, it is necessary to first allocate a buffer, write to that buffer, and then match the buffer against a regex.

In cases where it is not necessary to extract substrings, but only to test whether or not output matches a regex, it is not strictly necessary to allocate and write this output to a buffer. This crate provides a simple interface on top of the lower-level regex-automata library that implements fmt::Write and io::Write for regex patterns. This may be used to test whether streaming output matches a pattern without buffering that output.

Users who need to extract substrings based on a pattern or who already have buffered data should probably use the regex crate instead.