| // SPDX-License-Identifier: BSD-2-Clause |
| /* LibTomCrypt, modular cryptographic library -- Tom St Denis |
| * |
| * LibTomCrypt is a library that provides various cryptographic |
| * algorithms in a highly modular and flexible manner. |
| * |
| * The library is free for all purposes without any express |
| * guarantee it works. |
| */ |
| #include "tomcrypt_private.h" |
| |
| /** |
| @file copy_or_zeromem.c |
| Either copy or zero a block of memory in constant time, Steffen Jaeckel |
| */ |
| |
| /** |
| Either copy or zero a block of memory in constant time |
| @param src The source where to read from |
| @param dest The destination where to write to |
| @param len The length of the area to process (octets) |
| @param coz Copy (on 0) Or Zero (> 0) |
| */ |
| void copy_or_zeromem(const unsigned char* src, unsigned char* dest, unsigned long len, int coz) |
| { |
| unsigned long y; |
| #ifdef LTC_FAST |
| unsigned long z; |
| LTC_FAST_TYPE fastMask = ~(LTC_FAST_TYPE)0; /* initialize fastMask at all ones */ |
| #endif |
| unsigned char mask = 0xff; /* initialize mask at all ones */ |
| |
| LTC_ARGCHKVD(src != NULL); |
| LTC_ARGCHKVD(dest != NULL); |
| |
| if (coz != 0) coz = 1; |
| y = 0; |
| mask *= 1 - coz; /* mask = ( coz ? 0 : 0xff ) */ |
| #ifdef LTC_FAST |
| fastMask *= 1 - coz; |
| if (len & ~15) { |
| for (; y < (len & ~15); y += 16) { |
| for (z = 0; z < 16; z += sizeof(LTC_FAST_TYPE)) { |
| *(LTC_FAST_TYPE_PTR_CAST(&dest[y+z])) = *(LTC_FAST_TYPE_PTR_CAST(&src[y+z])) & fastMask; |
| } |
| } |
| } |
| #endif |
| for (; y < len; y++) { |
| dest[y] = src[y] & mask; |
| } |
| #ifdef LTC_CLEAN_STACK |
| #ifdef LTC_FAST |
| fastMask = 0; |
| #endif |
| mask = 0; |
| #endif |
| } |
| |
| /* ref: $Format:%D$ */ |
| /* git commit: $Format:%H$ */ |
| /* commit time: $Format:%ai$ */ |