page@swan.ulowell.edu (Bob Page) (12/06/88)
Submitted-by: grwalter@watcgl.waterloo.edu
Posting-number: Volume 2, Issue 86
Archive-name: unix/regexp.2
# This is a shell archive.
# Remove everything above and including the cut line.
# Then run the rest of the file through sh.
#----cut here-----cut here-----cut here-----cut here----#
#!/bin/sh
# shar: Shell Archiver
# Run the following text with /bin/sh to create:
# regerror.c
# regexp.3
# regexp.c
# regexp.h
# regexp.lib.uue
# regmagic.h
# regsub.c
# This archive created: Mon Nov 28 19:50:58 1988
cat << \SHAR_EOF > regerror.c
#include <stdio.h>
void
regerror(s)
char *s;
{
#ifdef ERRAVAIL
error("regexp: %s", s);
#else
fprintf(stderr, "regexp(3): %s", s);
exit(1);
#endif
/* NOTREACHED */
}
SHAR_EOF
cat << \SHAR_EOF > regexp.3
.TH REGEXP 3 local
.DA 2 April 1986
.SH NAME
regcomp, regexec, regsub, regerror \- regular expression handler
.SH SYNOPSIS
.ft B
.nf
#include <regexp.h>
regexp *regcomp(exp)
char *exp;
int regexec(prog, string)
regexp *prog;
char *string;
regsub(prog, source, dest)
regexp *prog;
char *source;
char *dest;
regerror(msg)
char *msg;
.SH DESCRIPTION
These functions implement
.IR egrep (1)-style
regular expressions and supporting facilities.
.PP
.I Regcomp
compiles a regular expression into a structure of type
.IR regexp ,
and returns a pointer to it.
The space has been allocated using
.IR malloc (3)
and may be released by
.IR free .
.PP
.I Regexec
matches a NUL-terminated \fIstring\fR against the compiled regular expression
in \fIprog\fR.
It returns 1 for success and 0 for failure, and adjusts the contents of
\fIprog\fR's \fIstartp\fR and \fIendp\fR (see below) accordingly.
.PP
The members of a
.I regexp
structure include at least the following (not necessarily in order):
.PP
.RS
char *startp[NSUBEXP];
.br
char *endp[NSUBEXP];
.RE
.PP
where
.I NSUBEXP
is defined (as 10) in the header file.
Once a successful \fIregexec\fR has been done using the \fIregexp\fR,
each \fIstartp\fR-\fIendp\fR pair describes one substring
within the \fIstring\fR,
with the \fIstartp\fR pointing to the first character of the substring and
the \fIendp\fR pointing to the first character following the substring.
The 0th substring is the substring of \fIstring\fR that matched the whole
regular expression.
The others are those substrings that matched parenthesized expressions
within the regular expression, with parenthesized expressions numbered
in left-to-right order of their opening parentheses.
.PP
.I Regsub
copies \fIsource\fR to \fIdest\fR, making substitutions according to the
most recent \fIregexec\fR performed using \fIprog\fR.
Each instance of `&' in \fIsource\fR is replaced by the substring
indicated by \fIstartp\fR[\fI0\fR] and
\fIendp\fR[\fI0\fR].
Each instance of `\e\fIn\fR', where \fIn\fR is a digit, is replaced by
the substring indicated by
\fIstartp\fR[\fIn\fR] and
\fIendp\fR[\fIn\fR].
To get a literal `&' or `\e\fIn\fR' into \fIdest\fR, prefix it with `\e';
to get a literal `\e' preceding `&' or `\e\fIn\fR', prefix it with
another `\e'.
.PP
.I Regerror
is called whenever an error is detected in \fIregcomp\fR, \fIregexec\fR,
or \fIregsub\fR.
The default \fIregerror\fR writes the string \fImsg\fR,
with a suitable indicator of origin,
on the standard
error output
and invokes \fIexit\fR(2).
.I Regerror
can be replaced by the user if other actions are desirable.
.SH "REGULAR EXPRESSION SYNTAX"
A regular expression is zero or more \fIbranches\fR, separated by `|'.
It matches anything that matches one of the branches.
.PP
A branch is zero or more \fIpieces\fR, concatenated.
It matches a match for the first, followed by a match for the second, etc.
.PP
A piece is an \fIatom\fR possibly followed by `*', `+', or `?'.
An atom followed by `*' matches a sequence of 0 or more matches of the atom.
An atom followed by `+' matches a sequence of 1 or more matches of the atom.
An atom followed by `?' matches a match of the atom, or the null string.
.PP
An atom is a regular expression in parentheses (matching a match for the
regular expression), a \fIrange\fR (see below), `.'
(matching any single character), `^' (matching the null string at the
beginning of the input string), `$' (matching the null string at the
end of the input string), a `\e' followed by a single character (matching
that character), or a single character with no other significance
(matching that character).
.PP
A \fIrange\fR is a sequence of characters enclosed in `[]'.
It normally matches any single character from the sequence.
If the sequence begins with `^',
it matches any single character \fInot\fR from the rest of the sequence.
If two characters in the sequence are separated by `\-', this is shorthand
for the full list of ASCII characters between them
(e.g. `[0-9]' matches any decimal digit).
To include a literal `]' in the sequence, make it the first character
(following a possible `^').
To include a literal `\-', make it the first or last character.
.SH AMBIGUITY
If a regular expression could match two different parts of the input string,
it will match the one which begins earliest.
If both begin in the same place but match different lengths, or match
the same length in different ways, life gets messier, as follows.
.PP
In general, the possibilities in a list of branches are considered in
left-to-right order, the possibilities for `*', `+', and `?' are
considered longest-first, nested constructs are considered from the
outermost in, and concatenated constructs are considered leftmost-first.
The match that will be chosen is the one that uses the earliest
possibility in the first choice that has to be made.
If there is more than one choice, the next will be made in the same manner
(earliest possibility) subject to the decision on the first choice.
And so forth.
.PP
For example, `(ab|a)b*c' could match `abc' in one of two ways.
The first choice is between `ab' and `a'; since `ab' is earlier, and does
lead to a successful overall match, it is chosen.
Since the `b' is already spoken for,
the `b*' must match its last possibility\(emthe empty string\(emsince
it must respect the earlier choice.
.PP
In the particular case where no `|'s are present and there is only one
`*', `+', or `?', the net effect is that the longest possible
match will be chosen.
So `ab*', presented with `xabbbby', will match `abbbb'.
Note that if `ab*' is tried against `xabyabbbz', it
will match `ab' just after `x', due to the begins-earliest rule.
(In effect, the decision on where to start the match is the first choice
to be made, hence subsequent choices must respect it even if this leads them
to less-preferred alternatives.)
.SH SEE ALSO
egrep(1), expr(1)
.SH DIAGNOSTICS
\fIRegcomp\fR returns NULL for a failure
(\fIregerror\fR permitting),
where failures are syntax errors, exceeding implementation limits,
or applying `+' or `*' to a possibly-null operand.
.SH HISTORY
Both code and manual page were
written at U of T.
They are intended to be compatible with the Bell V8 \fIregexp\fR(3),
but are not derived from Bell code.
.SH BUGS
Empty branches and empty regular expressions are not portable to V8.
.PP
The restriction against
applying `*' or `+' to a possibly-null operand is an artifact of the
simplistic implementation.
.PP
Does not support \fIegrep\fR's newline-separated branches;
neither does the V8 \fIregexp\fR(3), though.
.PP
Due to emphasis on
compactness and simplicity,
it's not strikingly fast.
It does give special attention to handling simple cases quickly.
SHAR_EOF
cat << \SHAR_EOF > regexp.c
/*
* regcomp and regexec -- regsub and regerror are elsewhere @(#)regexp.c 1.3
* of 18 April 87
*
* 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.
*
* Beware that some of this code is subtly aware of the way operator precedence
* is structured in regular expressions. Serious changes in
* regular-expression syntax might require a total rethink.
*/
#include <stdio.h>
#ifdef AMIGA
#undef min
#include "regexp.h"
#else
#include <regexp.h>
#endif
#include "regmagic.h"
/*
* The "internal use only" fields in regexp.h are present to pass info from
* compile to execute that permits the execute phase to run lots faster on
* simple cases. They are:
*
* regstart char that must begin a match; '\0' if none obvious reganch
* is the match anchored (at beginning-of-line only)? regmust string
* (pointer into program) that match must include, or NULL regmlen
* length of regmust string
*
* Regstart and reganch permit very fast decisions on suitable starting points
* for a match, cutting down the work a lot. Regmust permits fast rejection
* of lines that cannot possibly match. The regmust tests are costly enough
* that regcomp() supplies a regmust only if the r.e. contains something
* potentially expensive (at present, the only such thing detected is * or +
* at the start of the r.e., which can involve a lot of backup). Regmlen is
* supplied because the test in regexec() needs it and regcomp() is computing
* it anyway.
*/
/*
* Structure for regexp "program". This is essentially a linear encoding of
* a nondeterministic finite-state machine (aka syntax charts or "railroad
* normal form" in parsing technology). Each node is an opcode plus a "next"
* pointer, possibly plus an operand. "Next" pointers of all nodes except
* BRANCH implement concatenation; a "next" pointer with a BRANCH on both
* ends of it is connecting two alternatives. (Here we have one of the
* subtle syntax dependencies: an individual BRANCH (as opposed to a
* collection of them) is never concatenated with anything because of
* operator precedence.) The operand of some types of node is a literal
* string; for others, it is a node leading into a sub-FSM. In particular,
* the operand of a BRANCH node is the first node of the branch. (NB this is
* *not* a tree structure: the tail of the branch connects to the thing
* following the set of BRANCHes.) The opcodes are:
*/
/* definition number opnd? meaning */
#define END 0 /* no End of program. */
#define BOL 1 /* no Match "" at beginning of line. */
#define EOL 2 /* no Match "" at end of line. */
#define ANY 3 /* no Match any one character. */
#define ANYOF 4 /* str Match any character in this string. */
#define ANYBUT 5 /* str Match any character not in this
* string. */
#define BRANCH 6 /* node Match this alternative, or the
* next... */
#define BACK 7 /* no Match "", "next" ptr points backward. */
#define EXACTLY 8 /* str Match this string. */
#define NOTHING 9 /* no Match empty string. */
#define STAR 10 /* node Match this (simple) thing 0 or more
* times. */
#define PLUS 11 /* node Match this (simple) thing 1 or more
* times. */
#define OPEN 20 /* no Mark this point in input as start of
* #n. */
/* OPEN+1 is number 1, etc. */
#define CLOSE 30 /* no Analogous to OPEN. */
/*
* Opcode notes:
*
* BRANCH The set of branches constituting a single choice are hooked together
* with their "next" pointers, since precedence prevents anything being
* concatenated to any individual branch. The "next" pointer of the last
* BRANCH in a choice points to the thing following the whole choice. This
* is also where the final "next" pointer of each individual branch points;
* each branch starts with the operand node of a BRANCH node.
*
* BACK Normal "next" pointers all implicitly point forward; BACK exists to
* make loop structures possible.
*
* STAR,PLUS '?', and complex '*' and '+', are implemented as circular
* BRANCH structures using BACK. Simple cases (one character per match) are
* implemented with STAR and PLUS for speed and to minimize recursive
* plunges.
*
* OPEN,CLOSE ...are numbered at compile time.
*/
/*
* A node is one char of opcode followed by two chars of "next" pointer.
* "Next" pointers are stored as two 8-bit pieces, high order first. The
* value is a positive offset from the opcode of the node containing it. An
* operand, if any, simply follows the node. (Note that much of the code
* generation knows about this implicit relationship.)
*
* Using two bytes for the "next" pointer is vast overkill for most things, but
* allows patterns to get big without disasters.
*/
#define OP(p) (*(p))
#define NEXT(p) (((*((p)+1)&0377)<<8) + (*((p)+2)&0377))
#define OPERAND(p) ((p) + 3)
/*
* See regmagic.h for one further detail of program structure.
*/
/*
* Utility definitions.
*/
#ifndef CHARBITS
#define UCHARAT(p) ((int)*(unsigned char *)(p))
#else
#define UCHARAT(p) ((int)*(p)&CHARBITS)
#endif
#define FAIL(m) { regerror(m); return(NULL); }
#define ISMULT(c) ((c) == '*' || (c) == '+' || (c) == '?')
#define META "^$.[()|?+*\\"
/*
* Flags to be passed up and down.
*/
#define HASWIDTH 01 /* Known never to match null string. */
#define SIMPLE 02 /* Simple enough to be STAR/PLUS operand. */
#define SPSTART 04 /* Starts with * or +. */
#define WORST 0 /* Worst case. */
/*
* Global work variables for regcomp().
*/
static char *regparse; /* Input-scan pointer. */
static int regnpar; /* () count. */
static char regdummy;
static char *regcode; /* Code-emit pointer; ®dummy = don't. */
static long regsize; /* Code size. */
/*
* Forward declarations for regcomp()'s friends.
*/
#ifndef STATIC
#define STATIC static
#endif
STATIC char *reg();
STATIC char *regbranch();
STATIC char *regpiece();
STATIC char *regatom();
STATIC char *regnode();
STATIC char *regnext();
STATIC void regc();
STATIC void reginsert();
STATIC void regtail();
STATIC void regoptail();
#ifdef STRCSPN
int strcspn();
#endif
/*
* - regcomp - compile a regular expression into internal code
*
* We can't allocate space until we know how big the compiled form will be, but
* we can't compile it (and thus know how big it is) until we've got a place
* to put the code. So we cheat: we compile it twice, once with code
* generation turned off and size counting turned on, and once "for real".
* This also means that we don't allocate space until we are sure that the
* thing really will compile successfully, and we never have to move the code
* and thus invalidate pointers into it. (Note that it has to be in one
* piece because free() must be able to free it all.)
*
* Beware that the optimization-preparation code in here knows about some of the
* structure of the compiled regexp.
*/
regexp *
regcomp(exp)
char *exp;
{
register regexp *r;
register char *scan;
register char *longest;
register int len;
int flags;
extern char *malloc();
if (exp == NULL)
FAIL("NULL argument");
/* First pass: determine size, legality. */
regparse = exp;
regnpar = 1;
regsize = 0L;
regcode = ®dummy;
regc(MAGIC);
if (reg(0, &flags) == NULL)
return (NULL);
/* Small enough for pointer-storage convention? */
if (regsize >= 32767L) /* Probably could be 65535L. */
FAIL("regexp too big");
/* Allocate space. */
r = (regexp *) malloc(sizeof(regexp) + (unsigned) regsize);
if (r == NULL)
FAIL("out of space");
/* Second pass: emit code. */
regparse = exp;
regnpar = 1;
regcode = r->program;
regc(MAGIC);
if (reg(0, &flags) == NULL)
return (NULL);
/* Dig out information for optimizations. */
r->regstart = '\0'; /* Worst-case defaults. */
r->reganch = 0;
r->regmust = NULL;
r->regmlen = 0;
scan = r->program + 1; /* First BRANCH. */
if (OP(regnext(scan)) == END) { /* Only one top-level choice. */
scan = OPERAND(scan);
/* Starting-point info. */
if (OP(scan) == EXACTLY)
r->regstart = *OPERAND(scan);
else if (OP(scan) == BOL)
r->reganch++;
/*
* If there's something expensive in the r.e., find the longest
* literal string that must appear and make it the regmust. Resolve
* ties in favor of later strings, since the regstart check works
* with the beginning of the r.e. and avoiding duplication
* strengthens checking. Not a strong reason, but sufficient in the
* absence of others.
*/
if (flags & SPSTART) {
longest = NULL;
len = 0;
for (; scan != NULL; scan = regnext(scan))
if (OP(scan) == EXACTLY && strlen(OPERAND(scan)) >= len) {
longest = OPERAND(scan);
len = strlen(OPERAND(scan));
}
r->regmust = longest;
r->regmlen = len;
}
}
return (r);
}
/*
* - reg - regular expression, i.e. main body or parenthesized thing
*
* Caller must absorb opening parenthesis.
*
* Combining parenthesis handling with the base level of regular expression is a
* trifle forced, but the need to tie the tails of the branches to what
* follows makes it hard to avoid.
*/
static char *
reg(paren, flagp)
int paren; /* Parenthesized? */
int *flagp;
{
register char *ret;
register char *br;
register char *ender;
register int parno;
int flags;
*flagp = HASWIDTH; /* Tentatively. */
/* Make an OPEN node, if parenthesized. */
if (paren) {
if (regnpar >= NSUBEXP)
FAIL("too many ()");
parno = regnpar;
regnpar++;
ret = regnode(OPEN + parno);
} else
ret = NULL;
/* Pick up the branches, linking them together. */
br = regbranch(&flags);
if (br == NULL)
return (NULL);
if (ret != NULL)
regtail(ret, br); /* OPEN -> first. */
else
ret = br;
if (!(flags & HASWIDTH))
*flagp &= ~HASWIDTH;
*flagp |= flags & SPSTART;
while (*regparse == '|') {
regparse++;
br = regbranch(&flags);
if (br == NULL)
return (NULL);
regtail(ret, br); /* BRANCH -> BRANCH. */
if (!(flags & HASWIDTH))
*flagp &= ~HASWIDTH;
*flagp |= flags & SPSTART;
}
/* Make a closing node, and hook it on the end. */
ender = regnode((paren) ? CLOSE + parno : END);
regtail(ret, ender);
/* Hook the tails of the branches to the closing node. */
for (br = ret; br != NULL; br = regnext(br))
regoptail(br, ender);
/* Check for proper termination. */
if (paren && *regparse++ != ')') {
FAIL("unmatched ()");
} else if (!paren && *regparse != '\0') {
if (*regparse == ')') {
FAIL("unmatched ()");
} else
FAIL("junk on end");/* "Can't happen". */
/* NOTREACHED */
}
return (ret);
}
/*
* - regbranch - one alternative of an | operator
*
* Implements the concatenation operator.
*/
static char *
regbranch(flagp)
int *flagp;
{
register char *ret;
register char *chain;
register char *latest;
int flags;
*flagp = WORST; /* Tentatively. */
ret = regnode(BRANCH);
chain = NULL;
while (*regparse != '\0' && *regparse != '|' && *regparse != ')') {
latest = regpiece(&flags);
if (latest == NULL)
return (NULL);
*flagp |= flags & HASWIDTH;
if (chain == NULL) /* First piece. */
*flagp |= flags & SPSTART;
else
regtail(chain, latest);
chain = latest;
}
if (chain == NULL) /* Loop ran zero times. */
(void) regnode(NOTHING);
return (ret);
}
/*
* - regpiece - something followed by possible [*+?]
*
* Note that the branching code sequences used for ? and the general cases of *
* and + are somewhat optimized: they use the same NOTHING node as both the
* endmarker for their branch list and the body of the last branch. It might
* seem that this node could be dispensed with entirely, but the endmarker
* role is not redundant.
*/
static char *
regpiece(flagp)
int *flagp;
{
register char *ret;
register char op;
register char *next;
int flags;
ret = regatom(&flags);
if (ret == NULL)
return (NULL);
op = *regparse;
if (!ISMULT(op)) {
*flagp = flags;
return (ret);
}
if (!(flags & HASWIDTH) && op != '?')
FAIL("*+ operand could be empty");
*flagp = (op != '+') ? (WORST | SPSTART) : (WORST | HASWIDTH);
if (op == '*' && (flags & SIMPLE))
reginsert(STAR, ret);
else if (op == '*') {
/* Emit x* as (x&|), where & means "self". */
reginsert(BRANCH, ret); /* Either x */
regoptail(ret, regnode(BACK)); /* and loop */
regoptail(ret, ret); /* back */
regtail(ret, regnode(BRANCH)); /* or */
regtail(ret, regnode(NOTHING)); /* null. */
} else if (op == '+' && (flags & SIMPLE))
reginsert(PLUS, ret);
else if (op == '+') {
/* Emit x+ as x(&|), where & means "self". */
next = regnode(BRANCH); /* Either */
regtail(ret, next);
regtail(regnode(BACK), ret); /* loop back */
regtail(next, regnode(BRANCH)); /* or */
regtail(ret, regnode(NOTHING)); /* null. */
} else if (op == '?') {
/* Emit x? as (x|) */
reginsert(BRANCH, ret); /* Either x */
regtail(ret, regnode(BRANCH)); /* or */
next = regnode(NOTHING);/* null. */
regtail(ret, next);
regoptail(ret, next);
}
regparse++;
if (ISMULT(*regparse))
FAIL("nested *?+");
return (ret);
}
/*
* - regatom - the lowest level
*
* Optimization: gobbles an entire sequence of ordinary characters so that it
* can turn them into a single node, which is smaller to store and faster to
* run. Backslashed characters are exceptions, each becoming a separate
* node; the code is simpler that way and it's not worth fixing.
*/
static char *
regatom(flagp)
int *flagp;
{
register char *ret;
int flags;
*flagp = WORST; /* Tentatively. */
switch (*regparse++) {
case '^':
ret = regnode(BOL);
break;
case '$':
ret = regnode(EOL);
break;
case '.':
ret = regnode(ANY);
*flagp |= HASWIDTH | SIMPLE;
break;
case '[':{
register int class;
register int classend;
if (*regparse == '^') { /* Complement of range. */
ret = regnode(ANYBUT);
regparse++;
} else
ret = regnode(ANYOF);
if (*regparse == ']' || *regparse == '-')
regc(*regparse++);
while (*regparse != '\0' && *regparse != ']') {
if (*regparse == '-') {
regparse++;
if (*regparse == ']' || *regparse == '\0')
regc('-');
else {
class = UCHARAT(regparse - 2) + 1;
classend = UCHARAT(regparse);
if (class > classend + 1)
FAIL("invalid [] range");
for (; class <= classend; class++)
regc(class);
regparse++;
}
} else
regc(*regparse++);
}
regc('\0');
if (*regparse != ']')
FAIL("unmatched []");
regparse++;
*flagp |= HASWIDTH | SIMPLE;
}
break;
case '(':
ret = reg(1, &flags);
if (ret == NULL)
return (NULL);
*flagp |= flags & (HASWIDTH | SPSTART);
break;
case '\0':
case '|':
case ')':
FAIL("internal urp"); /* Supposed to be caught earlier. */
break;
case '?':
case '+':
case '*':
FAIL("?+* follows nothing");
break;
case '\\':
if (*regparse == '\0')
FAIL("trailing \\");
ret = regnode(EXACTLY);
regc(*regparse++);
regc('\0');
*flagp |= HASWIDTH | SIMPLE;
break;
default:{
register int len;
register char ender;
regparse--;
len = strcspn(regparse, META);
if (len <= 0)
FAIL("internal disaster");
ender = *(regparse + len);
if (len > 1 && ISMULT(ender))
len--; /* Back off clear of ?+* operand. */
*flagp |= HASWIDTH;
if (len == 1)
*flagp |= SIMPLE;
ret = regnode(EXACTLY);
while (len > 0) {
regc(*regparse++);
len--;
}
regc('\0');
}
break;
}
return (ret);
}
/*
* - regnode - emit a node
*/
static char * /* Location. */
regnode(op)
char op;
{
register char *ret;
register char *ptr;
ret = regcode;
if (ret == ®dummy) {
regsize += 3;
return (ret);
}
ptr = ret;
*ptr++ = op;
*ptr++ = '\0'; /* Null "next" pointer. */
*ptr++ = '\0';
regcode = ptr;
return (ret);
}
/*
* - regc - emit (if appropriate) a byte of code
*/
static void
regc(b)
char b;
{
if (regcode != ®dummy)
*regcode++ = b;
else
regsize++;
}
/*
* - reginsert - insert an operator in front of already-emitted operand
*
* Means relocating the operand.
*/
static void
reginsert(op, opnd)
char op;
char *opnd;
{
register char *src;
register char *dst;
register char *place;
if (regcode == ®dummy) {
regsize += 3;
return;
}
src = regcode;
regcode += 3;
dst = regcode;
while (src > opnd)
*--dst = *--src;
place = opnd; /* Op node, where operand used to be. */
*place++ = op;
*place++ = '\0';
*place++ = '\0';
}
/*
* - regtail - set the next-pointer at the end of a node chain
*/
static void
regtail(p, val)
char *p;
char *val;
{
register char *scan;
register char *temp;
register int offset;
if (p == ®dummy)
return;
/* Find last node. */
scan = p;
for (;;) {
temp = regnext(scan);
if (temp == NULL)
break;
scan = temp;
}
if (OP(scan) == BACK)
offset = scan - val;
else
offset = val - scan;
*(scan + 1) = (offset >> 8) & 0377;
*(scan + 2) = offset & 0377;
}
/*
* - regoptail - regtail on operand of first argument; nop if operandless
*/
static void
regoptail(p, val)
char *p;
char *val;
{
/* "Operandless" and "op != BRANCH" are synonymous in practice. */
if (p == NULL || p == ®dummy || OP(p) != BRANCH)
return;
regtail(OPERAND(p), val);
}
/*
* regexec and friends
*/
/*
* Global work variables for regexec().
*/
static char *reginput; /* String-input pointer. */
static char *regbol; /* Beginning of input, for ^ check. */
static char **regstartp; /* Pointer to startp array. */
static char **regendp; /* Ditto for endp. */
/*
* Forwards.
*/
STATIC int regtry();
STATIC int regmatch();
STATIC int regrepeat();
#ifdef DEBUG
int regnarrate = 0;
void regdump();
STATIC char *regprop();
#endif
/*
* - regexec - match a regexp against a string
*/
int
regexec(prog, string)
register regexp *prog;
register char *string;
{
register char *s;
extern char *strchr();
/* Be paranoid... */
if (prog == NULL || string == NULL) {
regerror("NULL parameter");
return (0);
}
/* Check validity of program. */
if (UCHARAT(prog->program) != MAGIC) {
regerror("corrupted program");
return (0);
}
/* If there is a "must appear" string, look for it. */
if (prog->regmust != NULL) {
s = string;
while ((s = strchr(s, prog->regmust[0])) != NULL) {
if (strncmp(s, prog->regmust, prog->regmlen) == 0)
break; /* Found it. */
s++;
}
if (s == NULL) /* Not present. */
return (0);
}
/* Mark beginning of line for ^ . */
regbol = string;
/* Simplest case: anchored match need be tried only once. */
if (prog->reganch)
return (regtry(prog, string));
/* Messy cases: unanchored match. */
s = string;
if (prog->regstart != '\0')
/* We know what char it must start with. */
while ((s = strchr(s, prog->regstart)) != NULL) {
if (regtry(prog, s))
return (1);
s++;
}
else
/* We don't -- general case. */
do {
if (regtry(prog, s))
return (1);
} while (*s++ != '\0');
/* Failure. */
return (0);
}
/*
* - regtry - try match at specific point
*/
static int /* 0 failure, 1 success */
regtry(prog, string)
regexp *prog;
char *string;
{
register int i;
register char **sp;
register char **ep;
reginput = string;
regstartp = prog->startp;
regendp = prog->endp;
sp = prog->startp;
ep = prog->endp;
for (i = NSUBEXP; i > 0; i--) {
*sp++ = NULL;
*ep++ = NULL;
}
if (regmatch(prog->program + 1)) {
prog->startp[0] = string;
prog->endp[0] = reginput;
return (1);
} else
return (0);
}
/*
* - regmatch - main matching routine
*
* Conceptually the strategy is simple: check to see whether the current node
* matches, call self recursively to see whether the rest matches, and then
* act accordingly. In practice we make some effort to avoid recursion, in
* particular by going through "ordinary" nodes (that don't need to know
* whether the rest of the match failed) by a loop instead of by recursion.
*/
static int /* 0 failure, 1 success */
regmatch(prog)
char *prog;
{
register char *scan; /* Current node. */
char *next; /* Next node. */
extern char *strchr();
scan = prog;
#ifdef DEBUG
if (scan != NULL && regnarrate)
fprintf(stderr, "%s(\n", regprop(scan));
#endif
while (scan != NULL) {
#ifdef DEBUG
if (regnarrate)
fprintf(stderr, "%s...\n", regprop(scan));
#endif
next = regnext(scan);
switch (OP(scan)) {
case BOL:
if (reginput != regbol)
return (0);
break;
case EOL:
if (*reginput != '\0')
return (0);
break;
case ANY:
if (*reginput == '\0')
return (0);
reginput++;
break;
case EXACTLY:{
register int len;
register char *opnd;
opnd = OPERAND(scan);
/* Inline the first character, for speed. */
if (*opnd != *reginput)
return (0);
len = strlen(opnd);
if (len > 1 && strncmp(opnd, reginput, len) != 0)
return (0);
reginput += len;
}
break;
case ANYOF:
if (*reginput == '\0' || strchr(OPERAND(scan), *reginput) == NULL)
return (0);
reginput++;
break;
case ANYBUT:
if (*reginput == '\0' || strchr(OPERAND(scan), *reginput) != NULL)
return (0);
reginput++;
break;
case NOTHING:
break;
case BACK:
break;
case OPEN + 1:
case OPEN + 2:
case OPEN + 3:
case OPEN + 4:
case OPEN + 5:
case OPEN + 6:
case OPEN + 7:
case OPEN + 8:
case OPEN + 9:{
register int no;
register char *save;
no = OP(scan) - OPEN;
save = reginput;
if (regmatch(next)) {
/*
* Don't set startp if some later invocation of the same
* parentheses already has.
*/
if (regstartp[no] == NULL)
regstartp[no] = save;
return (1);
} else
return (0);
}
break;
case CLOSE + 1:
case CLOSE + 2:
case CLOSE + 3:
case CLOSE + 4:
case CLOSE + 5:
case CLOSE + 6:
case CLOSE + 7:
case CLOSE + 8:
case CLOSE + 9:{
register int no;
register char *save;
no = OP(scan) - CLOSE;
save = reginput;
if (regmatch(next)) {
/*
* Don't set endp if some later invocation of the same
* parentheses already has.
*/
if (regendp[no] == NULL)
regendp[no] = save;
return (1);
} else
return (0);
}
break;
case BRANCH:{
register char *save;
if (OP(next) != BRANCH) /* No choice. */
next = OPERAND(scan); /* Avoid recursion. */
else {
do {
save = reginput;
if (regmatch(OPERAND(scan)))
return (1);
reginput = save;
scan = regnext(scan);
} while (scan != NULL && OP(scan) == BRANCH);
return (0);
/* NOTREACHED */
}
}
break;
case STAR:
case PLUS:{
register char nextch;
register int no;
register char *save;
register int min;
/*
* Lookahead to avoid useless match attempts when we know
* what character comes next.
*/
nextch = '\0';
if (OP(next) == EXACTLY)
nextch = *OPERAND(next);
min = (OP(scan) == STAR) ? 0 : 1;
save = reginput;
no = regrepeat(OPERAND(scan));
while (no >= min) {
/* If it could work, try it. */
if (nextch == '\0' || *reginput == nextch)
if (regmatch(next))
return (1);
/* Couldn't or didn't -- back up. */
no--;
reginput = save + no;
}
return (0);
}
break;
case END:
return (1); /* Success! */
break;
default:
regerror("memory corruption");
return (0);
break;
}
scan = next;
}
/*
* We get here only if there's trouble -- normally "case END" is the
* terminating point.
*/
regerror("corrupted pointers");
return (0);
}
/*
* - regrepeat - repeatedly match something simple, report how many
*/
static int
regrepeat(p)
char *p;
{
register int count = 0;
register char *scan;
register char *opnd;
scan = reginput;
opnd = OPERAND(p);
switch (OP(p)) {
case ANY:
count = strlen(scan);
scan += count;
break;
case EXACTLY:
while (*opnd == *scan) {
count++;
scan++;
}
break;
case ANYOF:
while (*scan != '\0' && strchr(opnd, *scan) != NULL) {
count++;
scan++;
}
break;
case ANYBUT:
while (*scan != '\0' && strchr(opnd, *scan) == NULL) {
count++;
scan++;
}
break;
default: /* Oh dear. Called inappropriately. */
regerror("internal foulup");
count = 0; /* Best compromise. */
break;
}
reginput = scan;
return (count);
}
/*
* - regnext - dig the "next" pointer out of a node
*/
static char *
regnext(p)
register char *p;
{
register int offset;
if (p == ®dummy)
return (NULL);
offset = NEXT(p);
if (offset == 0)
return (NULL);
if (OP(p) == BACK)
return (p - offset);
else
return (p + offset);
}
#ifdef DEBUG
STATIC char *regprop();
/*
* - regdump - dump a regexp onto stdout in vaguely comprehensible form
*/
void
regdump(r)
regexp *r;
{
register char *s;
register char op = EXACTLY; /* Arbitrary non-END op. */
register char *next;
extern char *strchr();
s = r->program + 1;
while (op != END) { /* While that wasn't END last time... */
op = OP(s);
printf("%2d%s", s - r->program, regprop(s)); /* Where, what. */
next = regnext(s);
if (next == NULL) /* Next ptr. */
printf("(0)");
else
printf("(%d)", (s - r->program) + (next - s));
s += 3;
if (op == ANYOF || op == ANYBUT || op == EXACTLY) {
/* Literal string, where present. */
while (*s != '\0') {
putchar(*s);
s++;
}
s++;
}
putchar('\n');
}
/* Header fields of interest. */
if (r->regstart != '\0')
printf("start `%c' ", r->regstart);
if (r->reganch)
printf("anchored ");
if (r->regmust != NULL)
printf("must have \"%s\"", r->regmust);
printf("\n");
}
/*
* - regprop - printable representation of opcode
*/
static char *
regprop(op)
char *op;
{
register char *p;
static char buf[50];
(void) strcpy(buf, ":");
switch (OP(op)) {
case BOL:
p = "BOL";
break;
case EOL:
p = "EOL";
break;
case ANY:
p = "ANY";
break;
case ANYOF:
p = "ANYOF";
break;
case ANYBUT:
p = "ANYBUT";
break;
case BRANCH:
p = "BRANCH";
break;
case EXACTLY:
p = "EXACTLY";
break;
case NOTHING:
p = "NOTHING";
break;
case BACK:
p = "BACK";
break;
case END:
p = "END";
break;
case OPEN + 1:
case OPEN + 2:
case OPEN + 3:
case OPEN + 4:
case OPEN + 5:
case OPEN + 6:
case OPEN + 7:
case OPEN + 8:
case OPEN + 9:
sprintf(buf + strlen(buf), "OPEN%d", OP(op) - OPEN);
p = NULL;
break;
case CLOSE + 1:
case CLOSE + 2:
case CLOSE + 3:
case CLOSE + 4:
case CLOSE + 5:
case CLOSE + 6:
case CLOSE + 7:
case CLOSE + 8:
case CLOSE + 9:
sprintf(buf + strlen(buf), "CLOSE%d", OP(op) - CLOSE);
p = NULL;
break;
case STAR:
p = "STAR";
break;
case PLUS:
p = "PLUS";
break;
default:
regerror("corrupted opcode");
break;
}
if (p != NULL)
(void) strcat(buf, p);
return (buf);
}
#endif
/*
* The following is provided for those people who do not have strcspn() in
* their C libraries. They should get off their butts and do something about
* it; at least one public-domain implementation of those (highly useful)
* string routines has been published on Usenet.
*/
#ifdef STRCSPN
/*
* strcspn - find length of initial segment of s1 consisting entirely of
* characters not from s2
*/
static int
strcspn(s1, s2)
char *s1;
char *s2;
{
register char *scan1;
register char *scan2;
register int count;
count = 0;
for (scan1 = s1; *scan1 != '\0'; scan1++) {
for (scan2 = s2; *scan2 != '\0';) /* ++ moved down. */
if (*scan1 == *scan2++)
return (count);
count++;
}
return (count);
}
#endif
SHAR_EOF
cat << \SHAR_EOF > regexp.h
/*
* Definitions etc. for regexp(3) routines.
*
* Caveat: this is V8 regexp(3) [actually, a reimplementation thereof],
* not the System V one.
*/
#define NSUBEXP 10
typedef struct regexp {
char *startp[NSUBEXP];
char *endp[NSUBEXP];
char regstart; /* Internal use only. */
char reganch; /* Internal use only. */
char *regmust; /* Internal use only. */
int regmlen; /* Internal use only. */
char program[1]; /* Unwarranted chumminess with compiler. */
} regexp;
extern regexp *regcomp();
extern int regexec();
extern void regsub();
extern void regerror();
SHAR_EOF
cat << \SHAR_EOF > regexp.lib.uue
begin 644 regexp.lib
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M '*(&P $DH09QHB2R)+5HD0$$B 2, O "\)3KH %!/2H!F!G 8 !ME*L
M !)@ &:(&P $DH09QHB2R)+5HD0$$B 2, O "\)3KH %!/2H!G!G 8 !
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M $Y53$P@<&%R86UE=&5R !C;W)R=7!T960@<')O9W)A;0!M96UO<GD@8V]R
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M != +, P ! L#Z0 ( &4 ;@!V '\ AP O " * " ) *- ! )D !
6 #H 4P/J Z D#ZP '\
end
SHAR_EOF
cat << \SHAR_EOF > regmagic.h
/*
* The first byte of the regexp internal "program" is actually this magic
* number; the start node begins in the second byte.
*/
#define MAGIC 0234
SHAR_EOF
cat << \SHAR_EOF > regsub.c
/*
* regsub @(#)regsub.c 1.3 of 2 April 86
*
* 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.
*/
#include <stdio.h>
#ifdef AMIGA
#include "regexp.h"
#else
#include <regexp.h>
#endif
#include "regmagic.h"
#ifndef CHARBITS
#define UCHARAT(p) ((int)*(unsigned char *)(p))
#else
#define UCHARAT(p) ((int)*(p)&CHARBITS)
#endif
/*
* - regsub - perform substitutions after a regexp match
*/
void
regsub(prog, source, dest)
regexp *prog;
char *source;
char *dest;
{
register char *src;
register char *dst;
register char c;
register int no;
register int len;
extern char *strncpy();
if (prog == NULL || source == NULL || dest == NULL) {
regerror("NULL parm to regsub");
return;
}
if (UCHARAT(prog->program) != MAGIC) {
regerror("damaged regexp fed to regsub");
return;
}
src = source;
dst = dest;
while ((c = *src++) != '\0') {
if (c == '&')
no = 0;
else if (c == '\\' && '0' <= *src && *src <= '9')
no = *src++ - '0';
else
no = -1;
if (no < 0) { /* Ordinary character. */
if (c == '\\' && (*src == '\\' || *src == '&'))
c = *src++;
*dst++ = c;
} else if (prog->startp[no] != NULL && prog->endp[no] != NULL) {
len = prog->endp[no] - prog->startp[no];
(void) strncpy(dst, prog->startp[no], len);
dst += len;
if (len != 0 && *(dst - 1) == '\0') { /* strncpy hit NUL. */
regerror("damaged match string");
return;
}
}
}
*dst++ = '\0';
}
SHAR_EOF
# End of shell archive
exit 0
--
Bob Page, U of Lowell CS Dept. page@swan.ulowell.edu ulowell!page
Have five nice days.