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Reduce minimum stack use in regexec by using recursive implementation.

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This commit is contained in:
Tor Andersson
2017-08-15 14:08:55 +02:00
parent 81388eb40d
commit 557968a22d
2 changed files with 141 additions and 175 deletions
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regexp.c
+140 -174
View File
@@ -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 @@ static int strncmpcanon(const char *a, const char *b, int n)
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;
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_ANYNL:
sp += chartorune(&c, sp);
if (c == 0)
goto dead;
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;
}
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)) {
pc = pc + 1;
continue;
}
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;
}
pc = pc->y;
break;
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)
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;
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;
break;
}
if (flags & REG_NEWLINE) {
if (isnewline(*sp)) {
pc = pc + 1;
break;
}
}
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)
regexp.h
+1 -1
View File
@@ -28,7 +28,7 @@ enum {
REG_NOTBOL = 4,
/* limits */
REG_MAXSUB = 16
REG_MAXSUB = 10
};
struct Resub {