1This is a nearly-public-domain reimplementation of the V8 regexp(3) package. 2It gives C programs the ability to use egrep-style regular expressions, and 3does it in a much cleaner fashion than the analogous routines in SysV. 4 5 Copyright (c) 1986 by University of Toronto. 6 Written by Henry Spencer. Not derived from licensed software. 7 8 Permission is granted to anyone to use this software for any 9 purpose on any computer system, and to redistribute it freely, 10 subject to the following restrictions: 11 12 1. The author is not responsible for the consequences of use of 13 this software, no matter how awful, even if they arise 14 from defects in it. 15 16 2. The origin of this software must not be misrepresented, either 17 by explicit claim or by omission. 18 19 3. Altered versions must be plainly marked as such, and must not 20 be misrepresented as being the original software. 21 22Barring a couple of small items in the BUGS list, this implementation is 23believed 100% compatible with V8. It should even be binary-compatible, 24sort of, since the only fields in a "struct regexp" that other people have 25any business touching are declared in exactly the same way at the same 26location in the struct (the beginning). 27 28This implementation is *NOT* AT&T/Bell code, and is not derived from licensed 29software. Even though U of T is a V8 licensee. This software is based on 30a V8 manual page sent to me by Dennis Ritchie (the manual page enclosed 31here is a complete rewrite and hence is not covered by AT&T copyright). 32The software was nearly complete at the time of arrival of our V8 tape. 33I haven't even looked at V8 yet, although a friend elsewhere at U of T has 34been kind enough to run a few test programs using the V8 regexp(3) to resolve 35a few fine points. I admit to some familiarity with regular-expression 36implementations of the past, but the only one that this code traces any 37ancestry to is the one published in Kernighan & Plauger (from which this 38one draws ideas but not code). 39 40Simplistically: put this stuff into a source directory, copy regexp.h into 41/usr/include, inspect Makefile for compilation options that need changing 42to suit your local environment, and then do "make r". This compiles the 43regexp(3) functions, compiles a test program, and runs a large set of 44regression tests. If there are no complaints, then put regexp.o, regsub.o, 45and regerror.o into your C library, and regexp.3 into your manual-pages 46directory. 47 48Note that if you don't put regexp.h into /usr/include *before* compiling, 49you'll have to add "-I." to CFLAGS before compiling. 50 51The files are: 52 53Makefile instructions to make everything 54regexp.3 manual page 55regexp.h header file, for /usr/include 56regexp.c source for regcomp() and regexec() 57regsub.c source for regsub() 58regerror.c source for default regerror() 59regmagic.h internal header file 60try.c source for test program 61timer.c source for timing program 62tests test list for try and timer 63 64This implementation uses nondeterministic automata rather than the 65deterministic ones found in some other implementations, which makes it 66simpler, smaller, and faster at compiling regular expressions, but slower 67at executing them. In theory, anyway. This implementation does employ 68some special-case optimizations to make the simpler cases (which do make 69up the bulk of regular expressions actually used) run quickly. In general, 70if you want blazing speed you're in the wrong place. Replacing the insides 71of egrep with this stuff is probably a mistake; if you want your own egrep 72you're going to have to do a lot more work. But if you want to use regular 73expressions a little bit in something else, you're in luck. Note that many 74existing text editors use nondeterministic regular-expression implementations, 75so you're in good company. 76 77This stuff should be pretty portable, given appropriate option settings. 78If your chars have less than 8 bits, you're going to have to change the 79internal representation of the automaton, although knowledge of the details 80of this is fairly localized. There are no "reserved" char values except for 81NUL, and no special significance is attached to the top bit of chars. 82The string(3) functions are used a fair bit, on the grounds that they are 83probably faster than coding the operations in line. Some attempts at code 84tuning have been made, but this is invariably a bit machine-specific. 85