Initial import of the CDE 2.1.30 sources from the Open Group.

cde/programs/dtdocbook/lib/tptregexp/README

@@ -0,0 +1,101 @@
+/* $XConsortium: README /main/2 1996/07/15 14:09:54 drk $ */
+#
+# Copyright (c) 1994  
+# Open Software Foundation, Inc. 
+#  
+# Permission is hereby granted to use, copy, modify and freely distribute 
+# the software in this file and its documentation for any purpose without 
+# fee, provided that the above copyright notice appears in all copies and 
+# that both the copyright notice and this permission notice appear in 
+# supporting documentation.  Further, provided that the name of Open 
+# Software Foundation, Inc. ("OSF") not be used in advertising or 
+# publicity pertaining to distribution of the software without prior 
+# written permission from OSF.  OSF makes no representations about the 
+# suitability of this software for any purpose.  It is provided "as is" 
+# without express or implied warranty. 
+#
+
+This is a nearly-public-domain reimplementation of the V8 regexp(3) package.
+It gives C programs the ability to use egrep-style regular expressions, and
+does it in a much cleaner fashion than the analogous routines in SysV.
+
+	Copyright (c) 1986 by University of Toronto.
+	Written by Henry Spencer.  Not derived from licensed software.
+
+	Permission is granted to anyone to use this software for any
+	purpose on any computer system, and to redistribute it freely,
+	subject to the following restrictions:
+
+	1. The author is not responsible for the consequences of use of
+		this software, no matter how awful, even if they arise
+		from defects in it.
+
+	2. The origin of this software must not be misrepresented, either
+		by explicit claim or by omission.
+
+	3. Altered versions must be plainly marked as such, and must not
+		be misrepresented as being the original software.
+
+Barring a couple of small items in the BUGS list, this implementation is
+believed 100% compatible with V8.  It should even be binary-compatible,
+sort of, since the only fields in a "struct regexp" that other people have
+any business touching are declared in exactly the same way at the same
+location in the struct (the beginning).
+
+This implementation is *NOT* AT&T/Bell code, and is not derived from licensed
+software.  Even though U of T is a V8 licensee.  This software is based on
+a V8 manual page sent to me by Dennis Ritchie (the manual page enclosed
+here is a complete rewrite and hence is not covered by AT&T copyright).
+The software was nearly complete at the time of arrival of our V8 tape.
+I haven't even looked at V8 yet, although a friend elsewhere at U of T has
+been kind enough to run a few test programs using the V8 regexp(3) to resolve
+a few fine points.  I admit to some familiarity with regular-expression
+implementations of the past, but the only one that this code traces any
+ancestry to is the one published in Kernighan & Plauger (from which this
+one draws ideas but not code).
+
+Simplistically:  put this stuff into a source directory, copy regexp.h into
+/usr/include, inspect Makefile for compilation options that need changing
+to suit your local environment, and then do "make r".  This compiles the
+regexp(3) functions, compiles a test program, and runs a large set of
+regression tests.  If there are no complaints, then put regexp.o, regsub.o,
+and regerror.o into your C library, and regexp.3 into your manual-pages
+directory.
+
+Note that if you don't put regexp.h into /usr/include *before* compiling,
+you'll have to add "-I." to CFLAGS before compiling.
+
+The files are:
+
+Makefile	instructions to make everything
+regexp.3	manual page
+regexp.h	header file, for /usr/include
+regexp.c	source for regcomp() and regexec()
+regsub.c	source for regsub()
+regerror.c	source for default regerror()
+regmagic.h	internal header file
+try.c		source for test program
+timer.c		source for timing program
+tests		test list for try and timer
+
+This implementation uses nondeterministic automata rather than the
+deterministic ones found in some other implementations, which makes it
+simpler, smaller, and faster at compiling regular expressions, but slower
+at executing them.  In theory, anyway.  This implementation does employ
+some special-case optimizations to make the simpler cases (which do make
+up the bulk of regular expressions actually used) run quickly.  In general,
+if you want blazing speed you're in the wrong place.  Replacing the insides
+of egrep with this stuff is probably a mistake; if you want your own egrep
+you're going to have to do a lot more work.  But if you want to use regular
+expressions a little bit in something else, you're in luck.  Note that many
+existing text editors use nondeterministic regular-expression implementations,
+so you're in good company.
+
+This stuff should be pretty portable, given appropriate option settings.
+If your chars have less than 8 bits, you're going to have to change the
+internal representation of the automaton, although knowledge of the details
+of this is fairly localized.  There are no "reserved" char values except for
+NUL, and no special significance is attached to the top bit of chars.
+The string(3) functions are used a fair bit, on the grounds that they are
+probably faster than coding the operations in line.  Some attempts at code
+tuning have been made, but this is invariably a bit machine-specific.