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Further improvements to lib/krb5/n-fold.c:

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o  implement add1() using 32 bit ints, this makes _krb5_n_fold()
	   about 5% faster on an amd64 platform.  64 bit ints yield a
	   further improvement but we would need to test the platform
	   to see if they are natively supported.  This should yield
	   better performance improvements on big endian machines as
	   we have to byte swap on little endian boxen.

	o  fix two cases where a malloc(3)d pointer may be dereferenced
	   before we test that it is not NULL.
This commit is contained in:
Roland C. Dowdeswell
2013-02-14 16:46:40 +08:00
parent 183b15c11b
commit 66f4c441e9
1 changed files with 44 additions and 19 deletions
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63
lib/krb5/n-fold.c
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@@ -63,22 +63,48 @@ rr13(uint8_t *dst1, uint8_t *dst2, uint8_t *src, size_t len)
return;
}
/* Add `b' to `a', both being one's complement numbers. */
/*
* Add `b' to `a', both being one's complement numbers.
* This function assumes that inputs *a, *b are aligned
* to 4 bytes.
*/
static void
add1(uint8_t *a, uint8_t *b, size_t len)
{
int i;
int carry = 0;
for(i = len - 1; i >= 0; i--){
int x = a[i] + b[i] + carry;
uint32_t x;
uint32_t left, right;
for (i = len - 1; (i+1) % 4; i--) {
x = a[i] + b[i] + carry;
carry = x > 0xff;
a[i] = x & 0xff;
}
for(i = len - 1; carry && i >= 0; i--){
int x = a[i] + carry;
for (i = len / 4 - 1; i >= 0; i--) {
left = ntohl(((uint32_t *)a)[i]);
right = ntohl(((uint32_t *)b)[i]);
x = left + right + carry;
carry = x < left || x < right;
((uint32_t *)a)[i] = x;
}
for (i = len - 1; (i+1) % 4; i--) {
x = a[i] + carry;
carry = x > 0xff;
a[i] = x & 0xff;
}
for (i = len / 4 - 1; carry && i >= 0; i--) {
left = ((uint32_t *)a)[i];
x = left + carry;
carry = x < left;
((uint32_t *)a)[i] = x;
}
for (i = len / 4 - 1; i >=0; i--)
((uint32_t *)a)[i] = htonl(((uint32_t *)a)[i]);
}
KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
@@ -86,18 +112,19 @@ _krb5_n_fold(const void *str, size_t len, void *key, size_t size)
{
/* if len < size we need at most N * len bytes, ie < 2 * size;
if len > size we need at most 2 * len */
krb5_error_code ret = 0;
size_t maxlen = 2 * max(size, len);
size_t l = 0;
uint8_t *tmp = malloc(maxlen + 2 * len);
uint8_t *tmp;
uint8_t *tmpbuf;
uint8_t *buf1 = tmp + maxlen;
uint8_t *buf2 = tmp + maxlen + len;
uint8_t *buf1;
uint8_t *buf2;
if (tmp == NULL) {
ret = ENOMEM;
goto out;
}
tmp = malloc(maxlen + 2 * len);
if (tmp == NULL)
return ENOMEM;
buf1 = tmp + maxlen;
buf2 = tmp + maxlen + len;
memset(key, 0, size);
memcpy(buf1, str, len);
@@ -116,10 +143,8 @@ _krb5_n_fold(const void *str, size_t len, void *key, size_t size)
buf1 = buf2;
buf2 = tmpbuf;
} while(l != 0);
out:
if (tmp) {
memset(tmp, 0, maxlen + 2 * len);
free(tmp);
}
return ret;
memset(tmp, 0, maxlen + 2 * len);
free(tmp);
return 0;
}