Ultrix-3.1/src/cmd/more/regex.c
/**********************************************************************
* Copyright (c) Digital Equipment Corporation 1984, 1985, 1986. *
* All Rights Reserved. *
* Reference "/usr/src/COPYRIGHT" for applicable restrictions. *
**********************************************************************/
static char Sccsid[] = "@(#)regex.c 3.0 4/21/86";
/* regex.c 4.1 (Berkeley) 12/21/80 */
#
/*
* routines to do regular expression matching
*
* Entry points:
*
* re_comp(s)
* char *s;
* ... returns 0 if the string s was compiled successfully,
* a pointer to an error message otherwise.
* If passed 0 or a null string returns without changing
* the currently compiled re (see note 11 below).
*
* re_exec(s)
* char *s;
* ... returns 1 if the string s matches the last compiled regular
* expression,
* 0 if the string s failed to match the last compiled
* regular expression, and
* -1 if the compiled regular expression was invalid
* (indicating an internal error).
*
* The strings passed to both re_comp and re_exec may have trailing or
* embedded newline characters; they are terminated by nulls.
*
* The identity of the author of these routines is lost in antiquity;
* this is essentially the same as the re code in the original V6 ed.
*
* The regular expressions recognized are described below. This description
* is essentially the same as that for ed.
*
* A regular expression specifies a set of strings of characters.
* A member of this set of strings is said to be matched by
* the regular expression. In the following specification for
* regular expressions the word `character' means any character but NUL.
*
* 1. Any character except a special character matches itself.
* Special characters are the regular expression delimiter plus
* \ [ . and sometimes ^ * $.
* 2. A . matches any character.
* 3. A \ followed by any character except a digit or ( )
* matches that character.
* 4. A nonempty string s bracketed [s] (or [^s]) matches any
* character in (or not in) s. In s, \ has no special meaning,
* and ] may only appear as the first letter. A substring
* a-b, with a and b in ascending ASCII order, stands for
* the inclusive range of ASCII characters.
* 5. A regular expression of form 1-4 followed by * matches a
* sequence of 0 or more matches of the regular expression.
* 6. A regular expression, x, of form 1-8, bracketed \(x\)
* matches what x matches.
* 7. A \ followed by a digit n matches a copy of the string that the
* bracketed regular expression beginning with the nth \( matched.
* 8. A regular expression of form 1-8, x, followed by a regular
* expression of form 1-7, y matches a match for x followed by
* a match for y, with the x match being as long as possible
* while still permitting a y match.
* 9. A regular expression of form 1-8 preceded by ^ (or followed
* by $), is constrained to matches that begin at the left
* (or end at the right) end of a line.
* 10. A regular expression of form 1-9 picks out the longest among
* the leftmost matches in a line.
* 11. An empty regular expression stands for a copy of the last
* regular expression encountered.
*/
/*
* constants for re's
*/
#define CBRA 1
#define CCHR 2
#define CDOT 4
#define CCL 6
#define NCCL 8
#define CDOL 10
#define CEOF 11
#define CKET 12
#define CBACK 18
#define CSTAR 01
#define ESIZE 512
#define NBRA 9
static char expbuf[ESIZE], *braslist[NBRA], *braelist[NBRA];
static char circf;
/*
* compile the regular expression argument into a dfa
*/
char *
re_comp(sp)
register char *sp;
{
register int c;
register char *ep = expbuf;
int cclcnt, numbra = 0;
char *lastep = 0;
char bracket[NBRA];
char *bracketp = &bracket[0];
static char *retoolong = "Regular expression too long";
#define comerr(msg) {expbuf[0] = 0; numbra = 0; return(msg); }
if (sp == 0 || *sp == '\0') {
if (*ep == 0)
return("No previous regular expression");
return(0);
}
if (*sp == '^') {
circf = 1;
sp++;
}
else
circf = 0;
for (;;) {
if (ep >= &expbuf[ESIZE])
comerr(retoolong);
if ((c = *sp++) == '\0') {
if (bracketp != bracket)
comerr("unmatched \\(");
*ep++ = CEOF;
*ep++ = 0;
return(0);
}
if (c != '*')
lastep = ep;
switch (c) {
case '.':
*ep++ = CDOT;
continue;
case '*':
if (lastep == 0 || *lastep == CBRA || *lastep == CKET)
goto defchar;
*lastep |= CSTAR;
continue;
case '$':
if (*sp != '\0')
goto defchar;
*ep++ = CDOL;
continue;
case '[':
*ep++ = CCL;
*ep++ = 0;
cclcnt = 1;
if ((c = *sp++) == '^') {
c = *sp++;
ep[-2] = NCCL;
}
do {
if (c == '\0')
comerr("missing ]");
if (c == '-' && ep [-1] != 0) {
if ((c = *sp++) == ']') {
*ep++ = '-';
cclcnt++;
break;
}
while (ep[-1] < c) {
*ep = ep[-1] + 1;
ep++;
cclcnt++;
if (ep >= &expbuf[ESIZE])
comerr(retoolong);
}
}
*ep++ = c;
cclcnt++;
if (ep >= &expbuf[ESIZE])
comerr(retoolong);
} while ((c = *sp++) != ']');
lastep[1] = cclcnt;
continue;
case '\\':
if ((c = *sp++) == '(') {
if (numbra >= NBRA)
comerr("too many \\(\\) pairs");
*bracketp++ = numbra;
*ep++ = CBRA;
*ep++ = numbra++;
continue;
}
if (c == ')') {
if (bracketp <= bracket)
comerr("unmatched \\)");
*ep++ = CKET;
*ep++ = *--bracketp;
continue;
}
if (c >= '1' && c < ('1' + NBRA)) {
*ep++ = CBACK;
*ep++ = c - '1';
continue;
}
*ep++ = CCHR;
*ep++ = c;
continue;
defchar:
default:
*ep++ = CCHR;
*ep++ = c;
}
}
}
/*
* match the argument string against the compiled re
*/
int
re_exec(p1)
register char *p1;
{
register char *p2 = expbuf;
register int c;
int rv;
for (c = 0; c < NBRA; c++) {
braslist[c] = 0;
braelist[c] = 0;
}
if (circf)
return((advance(p1, p2)));
/*
* fast check for first character
*/
if (*p2 == CCHR) {
c = p2[1];
do {
if (*p1 != c)
continue;
if (rv = advance(p1, p2))
return(rv);
} while (*p1++);
return(0);
}
/*
* regular algorithm
*/
do
if (rv = advance(p1, p2))
return(rv);
while (*p1++);
return(0);
}
/*
* try to match the next thing in the dfa
*/
static int
advance(lp, ep)
register char *lp, *ep;
{
register char *curlp;
int ct, i;
int rv;
for (;;)
switch (*ep++) {
case CCHR:
if (*ep++ == *lp++)
continue;
return(0);
case CDOT:
if (*lp++)
continue;
return(0);
case CDOL:
if (*lp == '\0')
continue;
return(0);
case CEOF:
return(1);
case CCL:
if (cclass(ep, *lp++, 1)) {
ep += *ep;
continue;
}
return(0);
case NCCL:
if (cclass(ep, *lp++, 0)) {
ep += *ep;
continue;
}
return(0);
case CBRA:
braslist[*ep++] = lp;
continue;
case CKET:
braelist[*ep++] = lp;
continue;
case CBACK:
if (braelist[i = *ep++] == 0)
return(-1);
if (backref(i, lp)) {
lp += braelist[i] - braslist[i];
continue;
}
return(0);
case CBACK|CSTAR:
if (braelist[i = *ep++] == 0)
return(-1);
curlp = lp;
ct = braelist[i] - braslist[i];
while (backref(i, lp))
lp += ct;
while (lp >= curlp) {
if (rv = advance(lp, ep))
return(rv);
lp -= ct;
}
continue;
case CDOT|CSTAR:
curlp = lp;
while (*lp++)
;
goto star;
case CCHR|CSTAR:
curlp = lp;
while (*lp++ == *ep)
;
ep++;
goto star;
case CCL|CSTAR:
case NCCL|CSTAR:
curlp = lp;
while (cclass(ep, *lp++, ep[-1] == (CCL|CSTAR)))
;
ep += *ep;
goto star;
star:
do {
lp--;
if (rv = advance(lp, ep))
return(rv);
} while (lp > curlp);
return(0);
default:
return(-1);
}
}
backref(i, lp)
register int i;
register char *lp;
{
register char *bp;
bp = braslist[i];
while (*bp++ == *lp++)
if (bp >= braelist[i])
return(1);
return(0);
}
int
cclass(set, c, af)
register char *set, c;
int af;
{
register int n;
if (c == 0)
return(0);
n = *set++;
while (--n)
if (*set++ == c)
return(af);
return(! af);
}