mirror of
https://github.com/rsmarples/dhcpcd.git
synced 2024-11-23 18:14:09 +08:00
29 lines
700 B
C
29 lines
700 B
C
/*
|
|
* Written by Matthias Drochner <drochner@NetBSD.org>.
|
|
* Public domain.
|
|
*/
|
|
|
|
#ifndef CONSTTIME_MEMEQUAL_H
|
|
#define CONSTTIME_MEMEQUAL_H
|
|
inline static int
|
|
consttime_memequal(const void *b1, const void *b2, size_t len)
|
|
{
|
|
const unsigned char *c1 = b1, *c2 = b2;
|
|
unsigned int res = 0;
|
|
|
|
while (len--)
|
|
res |= *c1++ ^ *c2++;
|
|
|
|
/*
|
|
* Map 0 to 1 and [1, 256) to 0 using only constant-time
|
|
* arithmetic.
|
|
*
|
|
* This is not simply `!res' because although many CPUs support
|
|
* branchless conditional moves and many compilers will take
|
|
* advantage of them, certain compilers generate branches on
|
|
* certain CPUs for `!res'.
|
|
*/
|
|
return (1 & ((res - 1) >> 8));
|
|
}
|
|
#endif /* CONSTTIME_MEMEQUAL_H */
|