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Reduce CPU usage of OS scan by 50%

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expr_match was wasting cycles implementing syntax not used or documented
elsewhere (boolean AND, "+" to mean non-zero), copying and allocating new
strings. Replacement reduces number of comparisons and performs parsing
in-place on the const input expression.
This commit is contained in:
dmiller
2020-05-20 05:23:47 +00:00
parent fb1406a51a
commit df1874cedd
1 changed files with 26 additions and 108 deletions
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134
osscan.cc
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@@ -173,134 +173,52 @@ void FingerPrint::sort() {
"3B-47" or "8|A" or ">10"). Return true iff there's a match. The syntax uses
< (less than)
> (greater than)
+ (non-zero)
| (or)
- (range)
& (and)
No parentheses are allowed. */
static bool expr_match(const char *val, const char *expr) {
int andexp, orexp, expchar, numtrue;
int testfailed;
char exprcpy[512];
char *p, *q, *q1; /* OHHHH YEEEAAAAAHHHH!#!@#$!% */
const char *p, *q, *q1; /* OHHHH YEEEAAAAAHHHH!#!@#$!% */
char *endptr;
unsigned int val_num, expr_num, expr_num1;
bool is_numeric;
numtrue = andexp = orexp = 0; testfailed = 0;
Strncpy(exprcpy, expr, sizeof(exprcpy));
p = exprcpy;
if (strchr(expr, '|')) {
orexp = 1; expchar = '|';
} else {
andexp = 1; expchar = '&';
}
p = expr;
val_num = strtol(val, &endptr, 16);
is_numeric = !*endptr;
// TODO: this could be a lot faster if we compiled fingerprints to a bytecode
// instead of re-parsing every time.
do {
q = strchr(p, expchar);
if (q)
*q = '\0';
if (strcmp(p, "+") == 0) {
if (!*val) {
if (andexp) {
testfailed = 1;
break;
q = strchr(p, '|');
if (is_numeric && (*p == '<' || *p == '>')) {
expr_num = strtol(p + 1, &endptr, 16);
if (endptr == q || !*endptr) {
if ((*p == '<' && val_num < expr_num)
|| (*p == '>' && val_num > expr_num)) {
return true;
}
} else {
val_num = strtol(val, &endptr, 16);
if (val_num == 0 || *endptr) {
if (andexp) {
testfailed = 1;
break;
}
} else if (is_numeric && ((q1 = strchr(p, '-')) != NULL)) {
expr_num = strtol(p, &endptr, 16);
if (endptr == q1) {
expr_num1 = strtol(q1 + 1, &endptr, 16);
if (endptr == q || !*endptr) {
assert(expr_num1 > expr_num);
if (val_num >= expr_num && val_num <= expr_num1) {
return true;
}
} else {
numtrue++;
if (orexp)
break;
}
}
} else if (*p == '<' && isxdigit((int) (unsigned char) p[1])) {
if (!*val) {
if (andexp) {
testfailed = 1;
break;
}
}
expr_num = strtol(p + 1, &endptr, 16);
val_num = strtol(val, &endptr, 16);
if (val_num >= expr_num || *endptr) {
if (andexp) {
testfailed = 1;
break;
}
} else {
numtrue++;
if (orexp)
break;
}
} else if (*p == '>' && isxdigit((int) (unsigned char) p[1])) {
if (!*val) {
if (andexp) {
testfailed = 1;
break;
}
}
expr_num = strtol(p + 1, &endptr, 16);
val_num = strtol(val, &endptr, 16);
if (val_num <= expr_num || *endptr) {
if (andexp) {
testfailed = 1;
break;
}
} else {
numtrue++;
if (orexp)
break;
}
} else if (((q1 = strchr(p, '-')) != NULL) && isxdigit((int) (unsigned char) p[0]) && isxdigit((int) (unsigned char) q1[1])) {
if (!*val) {
if (andexp) {
testfailed = 1;
break;
}
}
*q1 = '\0';
expr_num = strtol(p, NULL, 16);
expr_num1 = strtol(q1 + 1, NULL, 16);
if (expr_num1 < expr_num && o.debugging) {
error("Range error in reference expr: %s", expr);
}
val_num = strtol(val, &endptr, 16);
if (val_num < expr_num || val_num > expr_num1 || *endptr) {
if (andexp) {
testfailed = 1;
break;
}
} else {
numtrue++;
if (orexp)
break;
}
} else {
if (strcmp(p, val)) {
if (andexp) {
testfailed = 1;
break;
}
} else {
numtrue++;
if (orexp)
break;
if ((q && !strncmp(p, val, q - p)) || (!q && !strcmp(p, val))) {
return true;
}
}
if (q)
p = q + 1;
} while (q);
if (numtrue == 0)
testfailed = 1;
return !testfailed;
return false;
}
/* Returns true if perfect match -- if num_subtests &