ref: 557968a22dc65351d89ea0e1c34963b8faf22ed1
parent: 81388eb40d29f10599ac30dde90e683a3c254375
author: Tor Andersson <tor.andersson@artifex.com>
date: Mon Aug 14 10:37:14 EDT 2017
Reduce minimum stack use in regexec by using recursive implementation.
--- a/regexp.c
+++ b/regexp.c
@@ -14,7 +14,6 @@
#define nelem(a) (int)(sizeof (a) / sizeof (a)[0])
#define REPINF 255
-#define MAXTHREAD 1000
#define MAXSUB REG_MAXSUB
#define MAXPROG (32 << 10)
@@ -959,188 +958,155 @@
return 0;
}
-struct Rethread {- Reinst *pc;
- const char *sp;
- Resub sub;
-};
-
-static void spawn(Rethread *t, Reinst *pc, const char *sp, Resub *sub)
-{- t->pc = pc;
- t->sp = sp;
- memcpy(&t->sub, sub, sizeof t->sub);
-}
-
static int match(Reinst *pc, const char *sp, const char *bol, int flags, Resub *out)
{- Rethread ready[MAXTHREAD];
Resub scratch;
- Resub sub;
- Rune c;
- int nready;
int i;
+ Rune c;
- /* queue initial thread */
- spawn(ready + 0, pc, sp, out);
- nready = 1;
-
- /* run threads in stack order */
- while (nready > 0) {- --nready;
- pc = ready[nready].pc;
- sp = ready[nready].sp;
- memcpy(&sub, &ready[nready].sub, sizeof sub);
- for (;;) {- switch (pc->opcode) {- case I_END:
- for (i = 0; i < MAXSUB; ++i) {- out->sub[i].sp = sub.sub[i].sp;
- out->sub[i].ep = sub.sub[i].ep;
- }
+ for (;;) {+ switch (pc->opcode) {+ case I_END:
+ return 1;
+ case I_JUMP:
+ pc = pc->x;
+ break;
+ case I_SPLIT:
+ scratch = *out;
+ if (match(pc->x, sp, bol, flags, &scratch)) {+ *out = scratch;
return 1;
- case I_JUMP:
- pc = pc->x;
- continue;
- case I_SPLIT:
- if (nready >= MAXTHREAD) {- /* fprintf(stderr, "regexec: backtrack overflow!\n"); */
- return 0;
- }
- spawn(&ready[nready++], pc->y, sp, &sub);
- pc = pc->x;
- continue;
+ }
+ pc = pc->y;
+ break;
- case I_PLA:
- if (!match(pc->x, sp, bol, flags, &sub))
- goto dead;
- pc = pc->y;
- continue;
- case I_NLA:
- memcpy(&scratch, &sub, sizeof scratch);
- if (match(pc->x, sp, bol, flags, &scratch))
- goto dead;
- pc = pc->y;
- continue;
+ case I_PLA:
+ if (!match(pc->x, sp, bol, flags, out))
+ return 0;
+ pc = pc->y;
+ break;
+ case I_NLA:
+ scratch = *out;
+ if (match(pc->x, sp, bol, flags, &scratch))
+ return 0;
+ pc = pc->y;
+ break;
- case I_ANYNL:
- sp += chartorune(&c, sp);
- if (c == 0)
- goto dead;
+ case I_ANYNL:
+ sp += chartorune(&c, sp);
+ if (c == 0)
+ return 0;
+ pc = pc + 1;
+ break;
+ case I_ANY:
+ sp += chartorune(&c, sp);
+ if (c == 0)
+ return 0;
+ if (isnewline(c))
+ return 0;
+ pc = pc + 1;
+ break;
+ case I_CHAR:
+ sp += chartorune(&c, sp);
+ if (c == 0)
+ return 0;
+ if (flags & REG_ICASE)
+ c = canon(c);
+ if (c != pc->c)
+ return 0;
+ pc = pc + 1;
+ break;
+ case I_CCLASS:
+ sp += chartorune(&c, sp);
+ if (c == 0)
+ return 0;
+ if (flags & REG_ICASE) {+ if (!incclasscanon(pc->cc, canon(c)))
+ return 0;
+ } else {+ if (!incclass(pc->cc, c))
+ return 0;
+ }
+ pc = pc + 1;
+ break;
+ case I_NCCLASS:
+ sp += chartorune(&c, sp);
+ if (c == 0)
+ return 0;
+ if (flags & REG_ICASE) {+ if (incclasscanon(pc->cc, canon(c)))
+ return 0;
+ } else {+ if (incclass(pc->cc, c))
+ return 0;
+ }
+ pc = pc + 1;
+ break;
+ case I_REF:
+ i = out->sub[pc->n].ep - out->sub[pc->n].sp;
+ if (flags & REG_ICASE) {+ if (strncmpcanon(sp, out->sub[pc->n].sp, i))
+ return 0;
+ } else {+ if (strncmp(sp, out->sub[pc->n].sp, i))
+ return 0;
+ }
+ if (i > 0)
+ sp += i;
+ pc = pc + 1;
+ break;
+
+ case I_BOL:
+ if (sp == bol && !(flags & REG_NOTBOL)) {pc = pc + 1;
- continue;
- case I_ANY:
- sp += chartorune(&c, sp);
- if (c == 0)
- goto dead;
- if (isnewline(c))
- goto dead;
- pc = pc + 1;
- continue;
- case I_CHAR:
- sp += chartorune(&c, sp);
- if (c == 0)
- goto dead;
- if (flags & REG_ICASE)
- c = canon(c);
- if (c != pc->c)
- goto dead;
- pc = pc + 1;
- continue;
- case I_CCLASS:
- sp += chartorune(&c, sp);
- if (c == 0)
- goto dead;
- if (flags & REG_ICASE) {- if (!incclasscanon(pc->cc, canon(c)))
- goto dead;
- } else {- if (!incclass(pc->cc, c))
- goto dead;
+ break;
+ }
+ if (flags & REG_NEWLINE) {+ if (sp > bol && isnewline(sp[-1])) {+ pc = pc + 1;
+ break;
}
+ }
+ return 0;
+ case I_EOL:
+ if (*sp == 0) {pc = pc + 1;
- continue;
- case I_NCCLASS:
- sp += chartorune(&c, sp);
- if (c == 0)
- goto dead;
- if (flags & REG_ICASE) {- if (incclasscanon(pc->cc, canon(c)))
- goto dead;
- } else {- if (incclass(pc->cc, c))
- goto dead;
- }
- pc = pc + 1;
- continue;
- case I_REF:
- i = sub.sub[pc->n].ep - sub.sub[pc->n].sp;
- if (flags & REG_ICASE) {- if (strncmpcanon(sp, sub.sub[pc->n].sp, i))
- goto dead;
- } else {- if (strncmp(sp, sub.sub[pc->n].sp, i))
- goto dead;
- }
- if (i > 0)
- sp += i;
- pc = pc + 1;
- continue;
-
- case I_BOL:
- if (sp == bol && !(flags & REG_NOTBOL)) {+ break;
+ }
+ if (flags & REG_NEWLINE) {+ if (isnewline(*sp)) {pc = pc + 1;
- continue;
+ break;
}
- if (flags & REG_NEWLINE) {- if (sp > bol && isnewline(sp[-1])) {- pc = pc + 1;
- continue;
- }
- }
- goto dead;
- case I_EOL:
- if (*sp == 0) {- pc = pc + 1;
- continue;
- }
- if (flags & REG_NEWLINE) {- if (isnewline(*sp)) {- pc = pc + 1;
- continue;
- }
- }
- goto dead;
- case I_WORD:
- i = sp > bol && iswordchar(sp[-1]);
- i ^= iswordchar(sp[0]);
- if (!i)
- goto dead;
- pc = pc + 1;
- continue;
- case I_NWORD:
- i = sp > bol && iswordchar(sp[-1]);
- i ^= iswordchar(sp[0]);
- if (i)
- goto dead;
- pc = pc + 1;
- continue;
-
- case I_LPAR:
- sub.sub[pc->n].sp = sp;
- pc = pc + 1;
- continue;
- case I_RPAR:
- sub.sub[pc->n].ep = sp;
- pc = pc + 1;
- continue;
- default:
- goto dead;
}
+ return 0;
+ case I_WORD:
+ i = sp > bol && iswordchar(sp[-1]);
+ i ^= iswordchar(sp[0]);
+ if (!i)
+ return 0;
+ pc = pc + 1;
+ break;
+ case I_NWORD:
+ i = sp > bol && iswordchar(sp[-1]);
+ i ^= iswordchar(sp[0]);
+ if (i)
+ return 0;
+ pc = pc + 1;
+ break;
+
+ case I_LPAR:
+ out->sub[pc->n].sp = sp;
+ pc = pc + 1;
+ break;
+ case I_RPAR:
+ out->sub[pc->n].ep = sp;
+ pc = pc + 1;
+ break;
+ default:
+ return 0;
}
-dead: ;
}
- return 0;
}
int regexec(Reprog *prog, const char *sp, Resub *sub, int eflags)
--- a/regexp.h
+++ b/regexp.h
@@ -28,7 +28,7 @@
REG_NOTBOL = 4,
/* limits */
- REG_MAXSUB = 16
+ REG_MAXSUB = 10
};
struct Resub {