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REGEXP.C
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1995-12-17
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/*
* regcomp, regexec, regsub, and regerror
*
* 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.
*/
/* This is an altered version - Bob Withers - bwit@delphi.com */
/* #define REGERROR /**/
#include <stdio.h>
#include <string.h>
#ifdef UNIX
extern char * malloc();
#define USE_PROTO 0
#define PROTO(x) ()
#else
#include <stdlib.h>
#define USE_PROTO 1
#define PROTO(x) x
#endif
#include "regexp.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) ((short) *(unsigned char *) (p))
#else
#define UCHARAT(p) ((short) *(p) & CHARBITS)
#endif
#define FAIL(m) { regerror(m); return(NULL); }
#define ISMULT(c) ((c) == '*' || (c) == '+' || (c) == '?')
#define META "^$.[()|?+*\\"
#define NUL '\0'
/*
* 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 short 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 PROTO((short paren, short *flagp));
STATIC char * regbranch PROTO((short *flagp));
STATIC char * regpiece PROTO((short *flagp));
STATIC char * regatom PROTO((short *flagp));
STATIC char * regnode PROTO((char op));
STATIC char * regnext PROTO((char *p));
STATIC void regc PROTO((char b));
STATIC void reginsert PROTO((char op, char *opnd));
STATIC void regtail PROTO((char *p, char *val));
STATIC void regoptail PROTO((char *p, char *val));
#ifdef STRCSPN
STATIC short strcspn PROTO((char *s1, char *s2));
#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.
*/
#if USE_PROTO
regexp *regcomp(char *exp)
#else
regexp *regcomp(exp)
char *exp;
#endif
{
register regexp * r;
register char * scan;
register char * longest;
register short len;
auto short flags;
if (NULL == exp)
FAIL("NULL argument");
/* First pass: determine size, legality. */
regparse = exp;
regnpar = 1;
regsize = 0L;
regcode = ®dummy;
regc((char) 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((char) MAGIC);
if (reg(0, &flags) == NULL)
return(NULL);
/* Dig out information for optimizations. */
r->regstart = NUL; /* 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. */
#if USE_PROTO
STATIC char * reg(short paren, short *flagp)
#else
STATIC char * reg(paren, flagp)
short paren;
short *flagp;
#endif
{
register char *ret;
register char *br;
register char *ender;
register short parno;
auto short flags;
*flagp = HASWIDTH; /* Tentatively. */
/* Make an OPEN node, if parenthesized. */
if (paren)
{
if (regnpar >= NSUBEXP)
FAIL("too many ()");
parno = regnpar;
regnpar++;
ret = regnode((char) (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((char) ((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 ()");
}
if (!paren && *regparse != NUL)
{
if (*regparse == ')')
{
FAIL("unmatched ()");
}
FAIL("junk on end"); /* "Can't happen". */
}
return(ret);
}
/* regbranch - one alternative of an | operator */
/* */
/* Implements the concatenation operator. */
#if USE_PROTO
STATIC char * regbranch(short *flagp)
#else
STATIC char * regbranch(flagp)
short *flagp;
#endif
{
register char *ret;
register char *chain;
register char *latest;
auto short flags;
*flagp = WORST; /* Tentatively. */
ret = regnode(BRANCH);
chain = NULL;
while (*regparse != NUL && *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. */
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. */
#if USE_PROTO
STATIC char * regpiece(short *flagp)
#else
STATIC char * regpiece(flagp)
short *flagp;
#endif
{
register char *ret;
register char op;
register char *next;
auto short 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. */
#if USE_PROTO
STATIC char * regatom(short *flagp)
#else
STATIC char * regatom(flagp)
short *flagp;
#endif
{
register char *ret;
auto short 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 short class;
register short classend;
if (*regparse == '^')
{ /* Complement of range. */
ret = regnode(ANYBUT);
regparse++;
}
else
ret = regnode(ANYOF);
if (*regparse == ']' || *regparse == '-')
regc(*regparse++);
while (*regparse != NUL && *regparse != ']')
{
if (*regparse == '-')
{
regparse++;
if (*regparse == ']' || *regparse == NUL)
regc('-');
else
{
class = UCHARAT(regparse-2) + 1;
classend = UCHARAT(regparse);
if (class > classend + 1)
FAIL("invalid [] range");
for (; class <= classend; class++)
regc((char) class);
regparse++;
}
}
else
regc(*regparse++);
}
regc(NUL);
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 NUL:
case '|':
case ')':
FAIL("internal urp"); /* Supposed to be caught earlier. */
case '?':
case '+':
case '*':
FAIL("?+* follows nothing");
case '\\':
if (*regparse == NUL)
FAIL("trailing \\");
ret = regnode(EXACTLY);
regc(*regparse++);
regc(NUL);
*flagp |= HASWIDTH|SIMPLE;
break;
default:
{
register short 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(NUL);
}
break;
}
return(ret);
}
/* regnode - emit a node */
#if USE_PROTO
STATIC char * regnode(char op)
#else
STATIC char * regnode(op)
char op;
#endif
{
register char *ret;
register char *ptr;
ret = regcode;
if (ret == ®dummy)
{
regsize += 3;
return(ret);
}
ptr = ret;
*ptr++ = op;
*ptr++ = NUL; /* Null "next" pointer. */
*ptr++ = NUL;
regcode = ptr;
return(ret);
}
/* regc - emit (if appropriate) a byte of code */
#if USE_PROTO
STATIC void regc(char b)
#else
STATIC void regc(b)
char b;
#endif
{
if (regcode != ®dummy)
*regcode++ = b;
else
++regsize;
return;
}
/* reginsert - insert an operator in front of already-emitted operand */
/* */
/* Means relocating the operand. */
#if USE_PROTO
STATIC void reginsert(char op, char *opnd)
#else
STATIC void reginsert(op, opnd)
char op;
char *opnd;
#endif
{
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++ = NUL;
*place++ = NUL;
return;
}
/* regtail - set the next-pointer at the end of a node chain */
#if USE_PROTO
STATIC void regtail(char *p, char *val)
#else
STATIC void regtail(p, val)
char *p;
char *val;
#endif
{
register char *scan;
register char *temp;
register short 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;
return;
}
/* regoptail - regtail on operand of first argument; nop if operandless */
#if USE_PROTO
STATIC void regoptail(char *p, char *val)
#else
STATIC void regoptail(p, val)
char *p;
char *val;
#endif
{
/* "Operandless" and "op != BRANCH" are synonymous in practice. */
if (p == NULL || p == ®dummy || OP(p) != BRANCH)
return;
regtail(OPERAND(p), val);
return;
}
/* 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 short regtry PROTO((regexp *prog, char *string));
STATIC short regmatch PROTO((char *prog));
STATIC short regrepeat PROTO((char *p));
#ifdef DEBUG
short regnarrate = 0;
void regdump PROTO((regexp *r));
STATIC char * regprop PROTO((char *op));
#endif
/* regexec - match a regexp against a string */
#if USE_PROTO
short regexec(register regexp *prog, register char *string)
#else
short regexec(prog, string)
register regexp *prog;
register char *string;
#endif
{
register char *s;
/* Be paranoid... */
if (NULL == prog || NULL == string)
{
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 (NULL == s) /* 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 != NUL)
{
/* 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++ != NUL);
}
/* Failure. */
return(0);
}
/* regtry - try match at specific point */
#if USE_PROTO
STATIC short regtry(regexp *prog, char *string)
#else
STATIC short regtry(prog, string)
regexp *prog;
char *string;
#endif
{
register short 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);
}
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. */
#if USE_PROTO
STATIC short regmatch(char *prog)
#else
STATIC short regmatch(prog)
char *prog;
#endif
{
register char *scan; /* Current node. */
auto char *next; /* Next node. */
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 != NUL)
return(0);
break;
case ANY:
if (*reginput == NUL)
return(0);
++reginput;
break;
case EXACTLY:
{
register short 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 (NUL == *reginput
||
NULL == strchr(OPERAND(scan), *reginput))
return(0);
++reginput;
break;
case ANYBUT:
if (NUL == *reginput
||
NULL != strchr(OPERAND(scan), *reginput))
return(0);
++reginput;
break;
case NOTHING:
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 short 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);
}
}
return(0);
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 short 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);
}
}
return(0);
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);
}
}
break;
case STAR:
case PLUS:
{
register char nextch;
register short no;
register char *save;
register short min;
/* Lookahead to avoid useless match attempts when we */
/* know what character comes next. */
nextch = NUL;
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 == NUL || *reginput == nextch)
{
if (regmatch(next))
return(1);
}
/* Couldn't or didn't -- back up. */
no--;
reginput = save + no;
}
}
return(0);
case END:
return(1); /* Success! */
default:
regerror("memory corruption");
return(0);
}
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 */
#if USE_PROTO
STATIC short regrepeat(char *p)
#else
STATIC short regrepeat(p)
char *p;
#endif
{
register short 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 != NUL && strchr(opnd, *scan) != NULL)
{
++count;
++scan;
}
break;
case ANYBUT:
while (*scan != NUL && 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 */
#if USE_PROTO
STATIC char * regnext(register char *p)
#else
STATIC char * regnext(p)
register char *p;
#endif
{
register short offset;
if (p == ®dummy)
return(NULL);
offset = NEXT(p);
if (offset == 0)
return(NULL);
if (OP(p) == BACK)
return(p - offset);
return(p + offset);
}
/* regsub */
/* */
/* 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. */
#if USE_PROTO
void regsub(regexp *prog, char *source, char *dest)
#else
void regsub(prog, source, dest)
regexp *prog;
char *source;
char *dest;
#endif
{
register char *src;
register char *dst;
register char c;
register short no;
register short len;
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++) != NUL)
{
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];
strncpy(dst, prog->startp[no], len);
dst += len;
if (len != 0 && *(dst - 1) == NUL)
{ /* strncpy hit NUL. */
regerror("damaged match string");
return;
}
}
}
}
*dst++ = NUL;
return;
}
#ifdef DEBUG
/* regdump - dump a regexp onto stdout in vaguely comprehensible form */
#if USE_PROTO
void regdump(regexp *r)
#else
void regdump(r)
regexp *r;
#endif
{
register char *s;
register char op = EXACTLY; /* Arbitrary non-END op. */
register char *next;
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 != NUL)
{
putchar(*s);
s++;
}
++s;
}
putchar('\n');
}
/* Header fields of interest. */
if (r->regstart != NUL)
printf("start `%c' ", r->regstart);
if (r->reganch)
printf("anchored ");
if (r->regmust != NULL)
printf("must have \"%s\"", r->regmust);
printf("\n");
return;
}
/* regprop - printable representation of opcode */
#if USE_PROTO
STATIC char *regprop(char *op)
#else
STATIC char *regprop(op)
char *op;
#endif
{
register char *p;
static char buf[50];
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)
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 */
#if USE_PROTO
STATIC short strcspn(char *s1, char *s2)
#else
STATIC short strcspn(s1, s2)
char *s1;
char *s2;
#endif
{
register char *scan1;
register char *scan2;
register short count;
count = 0;
for (scan1 = s1; *scan1 != NUL; scan1++)
{
for (scan2 = s2; *scan2 != NUL;) /* ++ moved down. */
{
if (*scan1 == *scan2++)
return(count);
}
++count;
}
return(count);
}
#endif
#ifndef REGERROR
#if USE_PROTO
void regerror(char *msg)
#else
void regerror(msg)
char *msg;
#endif
{
fprintf(stderr, "%s", msg);
return;
}
#endif