+/*
+ * regcomp and regexec -- regsub and regerror are elsewhere
+ *
+ * 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.
+ *** THIS IS AN ALTERED VERSION. It was altered by John Gilmore,
+ *** hoptoad!gnu, on 27 Dec 1986, to add \n as an alternative to |
+ *** to assist in implementing egrep.
+ *** THIS IS AN ALTERED VERSION. It was altered by John Gilmore,
+ *** hoptoad!gnu, on 27 Dec 1986, to add \< and \> for word-matching
+ *** as in BSD grep and ex.
+ *** THIS IS AN ALTERED VERSION. It was altered by John Gilmore,
+ *** hoptoad!gnu, on 28 Dec 1986, to optimize characters quoted with \.
+ *** THIS IS AN ALTERED VERSION. It was altered by James A. Woods,
+ *** ames!jaw, on 19 June 1987, to quash a regcomp() redundancy.
+ *
+ * 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>
+#include <ctype.h>
+#include <regexp.h>
+#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 WORDA 12 /* no Match "" at wordchar, where prev is nonword */
+#define WORDZ 13 /* no Match "" at nonwordchar, where prev is word */
+#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) == '?')
+
+/*
+ * 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
+STATIC 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. */
+ if (exp[0] == '.' && exp[1] == '*') exp += 2; /* aid grep */
+ 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 == '\n') {
+ 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 != '\n' && *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++) {
+ /* FIXME: these chars only have meaning at beg/end of pat? */
+ 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 '\n':
+ case ')':
+ FAIL("internal urp"); /* Supposed to be caught earlier. */
+ break;
+ case '?':
+ case '+':
+ case '*':
+ FAIL("?+* follows nothing");
+ break;
+ case '\\':
+ switch (*regparse++) {
+ case '\0':
+ FAIL("trailing \\");
+ break;
+ case '<':
+ ret = regnode(WORDA);
+ break;
+ case '>':
+ ret = regnode(WORDZ);
+ break;
+ /* FIXME: Someday handle \1, \2, ... */
+ default:
+ /* Handle general quoted chars in exact-match routine */
+ goto de_fault;
+ }
+ break;
+ de_fault:
+ default:
+ /*
+ * Encode a string of characters to be matched exactly.
+ *
+ * This is a bit tricky due to quoted chars and due to
+ * '*', '+', and '?' taking the SINGLE char previous
+ * as their operand.
+ *
+ * On entry, the char at regparse[-1] is going to go
+ * into the string, no matter what it is. (It could be
+ * following a \ if we are entered from the '\' case.)
+ *
+ * Basic idea is to pick up a good char in ch and
+ * examine the next char. If it's *+? then we twiddle.
+ * If it's \ then we frozzle. If it's other magic char
+ * we push ch and terminate the string. If none of the
+ * above, we push ch on the string and go around again.
+ *
+ * regprev is used to remember where "the current char"
+ * starts in the string, if due to a *+? we need to back
+ * up and put the current char in a separate, 1-char, string.
+ * When regprev is NULL, ch is the only char in the
+ * string; this is used in *+? handling, and in setting
+ * flags |= SIMPLE at the end.
+ */
+ {
+ char *regprev;
+ register char ch;
+
+ regparse--; /* Look at cur char */
+ ret = regnode(EXACTLY);
+ for ( regprev = 0 ; ; ) {
+ ch = *regparse++; /* Get current char */
+ switch (*regparse) { /* look at next one */
+
+ default:
+ regc(ch); /* Add cur to string */
+ break;
+
+ case '.': case '[': case '(':
+ case ')': case '|': case '\n':
+ case '$': case '^':
+ case '\0':
+ /* FIXME, $ and ^ should not always be magic */
+ magic:
+ regc(ch); /* dump cur char */
+ goto done; /* and we are done */
+
+ case '?': case '+': case '*':
+ if (!regprev) /* If just ch in str, */
+ goto magic; /* use it */
+ /* End mult-char string one early */
+ regparse = regprev; /* Back up parse */
+ goto done;
+
+ case '\\':
+ regc(ch); /* Cur char OK */
+ switch (regparse[1]){ /* Look after \ */
+ case '\0':
+ case '<':
+ case '>':
+ /* FIXME: Someday handle \1, \2, ... */
+ goto done; /* Not quoted */
+ default:
+ /* Backup point is \, scan * point is after it. */
+ regprev = regparse;
+ regparse++;
+ continue; /* NOT break; */
+ }
+ }
+ regprev = regparse; /* Set backup point */
+ }
+ done:
+ regc('\0');
+ *flagp |= HASWIDTH;
+ if (!regprev) /* One char? */
+ *flagp |= SIMPLE;
+ }
+ 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 WORDA:
+ /* Must be looking at a letter, digit, or _ */
+ if ((!isalnum(*reginput)) && *reginput != '_')
+ return(0);
+ /* Prev must be BOL or nonword */
+ if (reginput > regbol &&
+ (isalnum(reginput[-1]) || reginput[-1] == '_'))
+ return(0);
+ break;
+ case WORDZ:
+ /* Must be looking at non letter, digit, or _ */
+ if (isalnum(*reginput) || *reginput == '_')
+ return(0);
+ /* We don't care what the previous char was */
+ 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;
+ case WORDA:
+ p = "WORDA";
+ break;
+ case WORDZ:
+ p = "WORDZ";
+ 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
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