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contrib/dhcpcd/compat/consttime_memequal.h
- This file was added.
| /* | |||||
| * 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 */ | |||||