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/* $Source: /u/mark/src/pax/RCS/regexp.c,v $
*
* $Revision: 1.2 $
*
* regexp.c - regular expression matching
*
* DESCRIPTION
*
* Underneath the reformatting and comment blocks which were added to
* make it consistent with the rest of the code, you will find a
* modified version of Henry Specer's regular expression library.
* Henry's functions were modified to provide the minimal regular
* expression matching, as required by P1003. Henry's code was
* copyrighted, and copy of the copyright message and restrictions
* are provided, verbatim, below:
*
* 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.
*
* AUTHORS
*
* Mark H. Colburn, NAPS International (mark@jhereg.mn.org)
* Henry Spencer, University of Torronto (henry@utzoo.edu)
*
* Sponsored by The USENIX Association for public distribution.
*
* $Log: regexp.c,v $
* Revision 1.2 89/02/12 10:05:39 mark
* 1.2 release fixes
*
* Revision 1.1 88/12/23 18:02:32 mark
* Initial revision
*
*/
/* Headers */
#include "pax.h"
#ifndef lint
static char *Ident = "$Id: regexp.c,v 1.2 89/02/12 10:05:39 mark Exp $";
#endif
/*
* 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 "nxt" pointer, possibly plus an operand. "Nxt" pointers of
* all nodes except BRANCH implement concatenation; a "nxt" 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
* nxt... */
#define BACK 7 /* no Match "", "nxt" 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 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 "nxt" pointers, since precedence prevents
* anything being concatenated to any individual branch. The
* "nxt" pointer of the last BRANCH in a choice points to the
* thing following the whole choice. This is also where the
* final "nxt" pointer of each individual branch points; each
* branch starts with the operand node of a BRANCH node.
*
* BACK Normal "nxt" pointers all implicitly point forward; BACK
* exists to make loop structures possible.
*
* STAR complex '*', are implemented as circular BRANCH structures
* using BACK. Simple cases (one character per match) are
* implemented with STAR 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 "nxt" pointer.
* "Nxt" 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 "nxt" 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)
/*
* Utility definitions.
*/
#define FAIL(m) { regerror(m); return(NULL); }
#define ISMULT(c) ((c) == '*')
#define META "^$.[()|*\\"
#ifndef CHARBITS
#define UCHARAT(p) ((int)*(unsigned char *)(p))
#else
#define UCHARAT(p) ((int)*(p)&CHARBITS)
#endif
/*
* Flags to be passed up and down.
*/
#define HASWIDTH 01 /* Known never to match null string. */
#define SIMPLE 02 /* Simple enough to be STAR operand. */
#define SPSTART 04 /* Starts with * */
#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; &regdummy = don't. */
static long regsize; /* Code size. */
/*
* Forward declarations for regcomp()'s friends.
*/
#ifndef STATIC
#define STATIC static
#endif
STATIC char *reg(int, int *); /* Xn */
STATIC char *regbranch(int *); /* Xn */
STATIC char *regpiece(int *); /* Xn */
STATIC char *regatom(int *); /* Xn */
STATIC char *regnode(char); /* Xn */
STATIC char *regnext(register char *); /* Xn */
STATIC void regc(char); /* Xn */
STATIC void reginsert(char, char *); /* Xn */
STATIC void regtail(char *, char *); /* Xn */
STATIC void regoptail(char *, char *); /* Xn */
#ifdef STRCSPN
STATIC size_t strcspn(const char *, const char *); /* Xn */
#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(char *exp) /* Xn */
{
register regexp *r;
register char *scan;
register char *longest;
register size_t len;
int flags;
if (exp == (char *)NULL)
FAIL("NULL argument");
/* First pass: determine size, legality. */
regparse = exp;
regnpar = 1;
regsize = 0L;
regcode = &regdummy;
regc(MAGIC);
if (reg(0, &flags) == (char *)NULL)
return ((regexp *)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 == (regexp *) NULL)
FAIL("out of space");
/* Second pass: emit code. */
regparse = exp;
regnpar = 1;
regcode = r->program;
regc(MAGIC);
if (reg(0, &flags) == NULL)
return ((regexp *) 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(int paren, int *flagp) /* Xn */
{
register char *ret;
register char *br;
register char *ender;
register int parno;
int flags;
*flagp = HASWIDTH; /* Tentatively. */
/* Make an OPEN node, if parenthesized. */
#ifdef DF_TRACE_DEBUG
printf("DF_TRACE_DEBUG: static char *reg() in regexp.c\n");
#endif
if (paren) {
if (regnpar >= NSUBEXP)
FAIL("too many ()");
parno = regnpar;
regnpar++;
ret = regnode((char)(OPEN + parno));
} else
ret = (char *)NULL;
/* Pick up the branches, linking them together. */
br = regbranch(&flags);
if (br == (char *)NULL)
return ((char *)NULL);
if (ret != (char *)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 == (char *)NULL)
return ((char *)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 != (char *)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(int *flagp) /* Xn */
{
register char *ret;
register char *chain;
register char *latest;
int flags;
*flagp = WORST; /* Tentatively. */
#ifdef DF_TRACE_DEBUG
printf("DF_TRACE_DEBUG: static char *regbranch() in regexp.c\n");
#endif
ret = regnode(BRANCH);
chain = (char *)NULL;
while (*regparse != '\0' && *regparse != '|' && *regparse != ')') {
latest = regpiece(&flags);
if (latest == (char *)NULL)
return ((char *)NULL);
*flagp |= flags & HASWIDTH;
if (chain == (char *)NULL) /* First piece. */
*flagp |= flags & SPSTART;
else
regtail(chain, latest);
chain = latest;
}
if (chain == (char *)NULL) /* Loop ran zero times. */
regnode(NOTHING);
return (ret);
}
/*
- regpiece - something followed by possible [*]
*
* Note that the branching code sequence used for * is 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(int *flagp) /* Xn */
{
register char *ret;
register char op;
int flags;
ret = regatom(&flags);
if (ret == (char *)NULL)
return ((char *)NULL);
op = *regparse;
if (!ISMULT(op)) {
*flagp = flags;
return (ret);
}
if (!(flags & HASWIDTH))
FAIL("* operand could be empty");
*flagp = (WORST | SPSTART);
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. */
}
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(int *flagp) /* Xn */
{
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((char)class);
regparse++;
}
} else
regc(*regparse++);
}
regc('\0');
if (*regparse != ']')
FAIL("unmatched []");
regparse++;
*flagp |= HASWIDTH | SIMPLE;
}
break;
case '(':
ret = reg(1, &flags);
if (ret == (char *)NULL)
return ((char *)NULL);
*flagp |= flags & (HASWIDTH | SPSTART);
break;
case '\0':
case '|':
case ')':
FAIL("internal urp"); /* Supposed to be caught earlier. */
case '*':
FAIL("* follows nothing");
case '\\':
if (*regparse == '\0')
FAIL("trailing \\");
ret = regnode(EXACTLY);
regc(*regparse++);
regc('\0');
*flagp |= HASWIDTH | SIMPLE;
break;
default:{
register uint len; /* Xn */
register char ender;
regparse--;
len = strcspn(regparse, META);
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 *regnode(char op) /* Xn */
{
register char *ret;
register char *ptr;
ret = regcode;
#ifdef DF_TRACE_DEBUG
printf("DF_TRACE_DEBUG: static char *regnode() in regexp.c\n");
#endif
if (ret == &regdummy) {
regsize += 3;
return (ret);
}
ptr = ret;
*ptr++ = op;
*ptr++ = '\0'; /* Null "nxt" pointer. */
*ptr++ = '\0';
regcode = ptr;
return (ret);
}
/*
- regc - emit (if appropriate) a byte of code
*/
static void regc(char b) /* Xn */
{
#ifdef DF_TRACE_DEBUG
printf("DF_TRACE_DEBUG: static void regc() in regexp.c\n");
#endif
if (regcode != &regdummy)
*regcode++ = b;
else
regsize++;
}
/*
- reginsert - insert an operator in front of already-emitted operand
*
* Means relocating the operand.
*/
static void reginsert(char op, char *opnd) /* Xn */
{
register char *src;
register char *dst;
register char *place;
#ifdef DF_TRACE_DEBUG
printf("DF_TRACE_DEBUG: static void reginsert() in regexp.c\n");
#endif
if (regcode == &regdummy) {
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(char *p, char *val) /* Xn */
{
register char *scan;
register char *temp;
register int offset;
if (p == &regdummy)
return;
/* Find last node. */
scan = p;
for (;;) {
temp = regnext(scan);
if (temp == (char *)NULL)
break;
scan = temp;
}
if (OP(scan) == BACK)
offset = (int)(scan - val);
else
offset = (int)(val - scan);
*(scan + 1) = (offset >> 8) & 0377;
*(scan + 2) = offset & 0377;
}
/*
- regoptail - regtail on operand of first argument; nop if operandless
*/
static void regoptail(char *p, char *val) /* Xn */
{
/* "Operandless" and "op != BRANCH" are synonymous in practice. */
if (p == (char *)NULL || p == &regdummy || 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(regexp *, char *); /* Xn */
STATIC int regmatch(char *); /* Xn */
STATIC int regrepeat(char *); /* Xn */
/* Xn */
#ifdef DEBUG /* Xn */
int regnarrate = 0; /* Xn */
void regdump(regexp *); /* Xn */
STATIC char *regprop(char *); /* Xn */
#endif /* Xn */
/*
- regexec - match a regexp against a string
*/
int regexec(register regexp *prog, register char *string) /* Xn */
{
register char *s;
/* Be paranoid... */
#ifdef DF_TRACE_DEBUG
printf("DF_TRACE_DEBUG: int regexec() in regexp.c\n");
#endif
if (prog == (regexp *)NULL || string == (char *)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 != (char *)NULL) {
s = string;
while ((s = strchr(s, prog->regmust[0])) != (char *)NULL) {
if (strncmp(s, prog->regmust, prog->regmlen) == 0)
break; /* Found it. */
s++;
}
if (s == (char *)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)) != (char *)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 regtry(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++ = (char *)NULL;
*ep++ = (char *)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 regmatch(char *prog)
{
register char *scan; /* Current node. */
char *nxt; /* nxt node. */
scan = prog;
#ifdef DEBUG
#ifdef DF_TRACE_DEBUG
printf("DF_TRACE_DEBUG: static int regmatch() in regexp.c\n");
#endif
if (scan != (char *)NULL && regnarrate)
fprintf(stderr, "%s(\n", regprop(scan));
#endif
while (scan != (char *)NULL) {
#ifdef DEBUG
if (regnarrate)
fprintf(stderr, "%s...\n", regprop(scan));
#endif
nxt = 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) == (char *)NULL)
return (0);
reginput++;
break;
case ANYBUT:
if (*reginput == '\0' ||
strchr(OPERAND(scan), *reginput) != (char *)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(nxt)) {
/*
* Don't set startp if some later invocation of the same
* parentheses already has.
*/
if (regstartp[no] == (char *)NULL)
regstartp[no] = save;
return (1);
} else
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 int no;
register char *save;
no = OP(scan) - CLOSE;
save = reginput;
if (regmatch(nxt)) {
/*
* Don't set endp if some later invocation of the same
* parentheses already has.
*/
if (regendp[no] == (char *)NULL)
regendp[no] = save;
return (1);
} else
return (0);
}
case BRANCH:{
register char *save;
if (OP(nxt) != BRANCH) /* No choice. */
nxt = OPERAND(scan); /* Avoid recursion. */
else {
do {
save = reginput;
if (regmatch(OPERAND(scan)))
return (1);
reginput = save;
scan = regnext(scan);
} while (scan != (char *)NULL && OP(scan) == BRANCH);
return (0);
/* NOTREACHED */
}
break; /* Xn */
} /* Xn */
case STAR:{
register char nextch;
register int no;
register char *save;
register int minimum;
/*
* Lookahead to avoid useless match attempts when we know
* what character comes next.
*/
nextch = '\0';
if (OP(nxt) == EXACTLY)
nextch = *OPERAND(nxt);
minimum = (OP(scan) == STAR) ? 0 : 1;
save = reginput;
no = regrepeat(OPERAND(scan));
while (no >= minimum) {
/* If it could work, try it. */
if (nextch == '\0' || *reginput == nextch)
if (regmatch(nxt))
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 = nxt;
}
/*
* 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(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) != (char *)NULL) {
count++;
scan++;
}
break;
case ANYBUT:
while (*scan != '\0' && strchr(opnd, *scan) == (char *)NULL) {
count++;
scan++;
}
break;
default: /* Oh dear. Called inappropriately. */
regerror("internal foulup");
count = 0; /* Best compromise. */
break;
}
reginput = scan;
return (count);
}
/*
- regnext - dig the "nxt" pointer out of a node
*/
static char *regnext(register char *p)
{
register int offset;
if (p == &regdummy)
return ((char *)NULL);
offset = NEXT(p);
if (offset == 0)
return ((char *)NULL);
if (OP(p) == BACK)
return (p - offset);
else
return (p + offset);
}
#ifdef DEBUG
#if 0 /* Xn */
STATIC char *regprop();
#endif /* Xn */
/*
- regdump - dump a regexp onto stdout in vaguely comprehensible form
*/
void regdump(regexp *r)
{
register char *s;
register char op = EXACTLY; /* Arbitrary non-END op. */
register char *nxt;
#if 0 /* Xn */
extern char *strchr();
#endif /* Xn */
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. */
nxt = regnext(s);
if (nxt == (char *)NULL) /* nxt ptr. */
printf("(0)");
else
printf("(%d)", (s - r->program) + (nxt - 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 != (char *)NULL)
printf("must have \"%s\"", r->regmust);
printf("\n");
}
/*
- regprop - printable representation of opcode
*/
static char *regprop(char *op)
{
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 = (char *)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 = (char *)NULL;
break;
case STAR:
p = "STAR";
break;
default:
regerror("corrupted opcode");
break;
}
if (p != (char *)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
*/
static size_t strcspn(const char *s1, const char *s2) /* Xn */
{
#ifdef __STDC__ /* Xn */
register const char *scan1; /* Xn */
register const char *scan2; /* Xn */
register size_t count; /* Xn */
#else /* Xn */
register char *scan1;
register char *scan2;
register uint count; /* Xn */
#endif /* Xn */
count = 0;
for (scan1 = s1; *scan1 != '\0'; scan1++) {
for (scan2 = s2; *scan2 != '\0';) /* ++ moved down. */
if (*scan1 == *scan2++)
return (count);
count++;
}
return (count);
}
#endif
/*
- regsub - perform substitutions after a regexp match
*/
void regsub(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 == (regexp *)NULL ||
source == (char *)NULL || dest == (char *)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] != (char *)NULL &&
prog->endp[no] != (char *)NULL) {
len = (int)(prog->endp[no] - prog->startp[no]);
strncpy(dst, prog->startp[no], len);
dst += len;
if (len != 0 && *(dst - 1) == '\0') { /* strncpy hit NUL. */
regerror("damaged match string");
return;
}
}
}
*dst++ = '\0';
}
void regerror(char *s)
{
fprintf(stderr, "regexp(3): %s", s);
exit(1);
}
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