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Optimize string_quote() for speed

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* util.c (string_quote): Speed up check for terminating NUL.
Replace strintf() with open-coded binary to hex/oct conversions -
we potentially do them for every single byte, need to be fast.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
This commit is contained in:
Denys Vlasenko 2011-08-31 12:22:56 +02:00
parent 5284557bfa
commit 8778bffdd2
1 changed files with 52 additions and 33 deletions
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85
util.c
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@ -440,8 +440,15 @@ string_quote(const char *instr, char *outstr, int len, int size)
{
const unsigned char *ustr = (const unsigned char *) instr;
char *s = outstr;
int usehex = 0, c, i;
int usehex, c, i, eol;
eol = 0x100; /* this can never match a char */
if (len < 0) {
size--;
eol = '\0';
}
usehex = 0;
if (xflag > 1)
usehex = 1;
else if (xflag) {
@ -450,13 +457,8 @@ string_quote(const char *instr, char *outstr, int len, int size)
for (i = 0; i < size; ++i) {
c = ustr[i];
/* Check for NUL-terminated string. */
if (len < 0) {
if (c == '\0')
break;
/* Quote at most size - 1 bytes. */
if (i == size - 1)
continue;
}
if (c == eol)
break;
if (!isprint(c) && !isspace(c)) {
usehex = 1;
break;
@ -471,27 +473,19 @@ string_quote(const char *instr, char *outstr, int len, int size)
for (i = 0; i < size; ++i) {
c = ustr[i];
/* Check for NUL-terminated string. */
if (len < 0) {
if (c == '\0')
break;
/* Quote at most size - 1 bytes. */
if (i == size - 1)
continue;
}
sprintf(s, "\\x%02x", c);
s += 4;
if (c == eol)
goto asciz_ended;
*s++ = '\\';
*s++ = 'x';
*s++ = "0123456789abcdef"[c >> 4];
*s++ = "0123456789abcdef"[c & 0xf];
}
} else {
for (i = 0; i < size; ++i) {
c = ustr[i];
/* Check for NUL-terminated string. */
if (len < 0) {
if (c == '\0')
break;
/* Quote at most size - 1 bytes. */
if (i == size - 1)
continue;
}
if (c == eol)
goto asciz_ended;
switch (c) {
case '\"': case '\\':
*s++ = '\\';
@ -520,13 +514,25 @@ string_quote(const char *instr, char *outstr, int len, int size)
default:
if (isprint(c))
*s++ = c;
else if (i + 1 < size
&& isdigit(ustr[i + 1])) {
sprintf(s, "\\%03o", c);
s += 4;
} else {
sprintf(s, "\\%o", c);
s += strlen(s);
else {
/* Print \octal */
*s++ = '\\';
if (i + 1 < size
&& ustr[i + 1] >= '0'
&& ustr[i + 1] <= '9'
) {
/* Print \ooo */
*s++ = '0' + (c >> 6);
*s++ = '0' + ((c >> 3) & 0x7);
} else {
/* Print \[[o]o]o */
if ((c >> 3) != 0) {
if ((c >> 6) != 0)
*s++ = '0' + (c >> 6);
*s++ = '0' + ((c >> 3) & 0x7);
}
}
*s++ = '0' + (c & 0x7);
}
break;
}
@ -536,8 +542,21 @@ string_quote(const char *instr, char *outstr, int len, int size)
*s++ = '\"';
*s = '\0';
/* Return nonzero if the string was unterminated. */
return i == size;
/* Return zero if we printed entire ASCIZ string (didn't truncate it) */
if (len < 0 && ustr[i] == '\0') {
/* We didn't see NUL yet (otherwise we'd jump to 'asciz_ended')
* but next char is NUL.
*/
return 0;
}
return 1;
asciz_ended:
*s++ = '\"';
*s = '\0';
/* Return zero: we printed entire ASCIZ string (didn't truncate it) */
return 0;
}
/*