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Introduce mbedtls_xor

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Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
This commit is contained in:
Dave Rodgman 2022-11-22 15:01:39 +00:00
parent 339406daf9
commit c3d8041fe7
1 changed files with 27 additions and 0 deletions
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27
library/common.h
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@ -26,6 +26,7 @@
#include "mbedtls/build_info.h"
#include <stdint.h>
#include <stddef.h>
/** Helper to define a function as static except when building invasive tests.
*
@ -390,6 +391,32 @@ extern void (*mbedtls_test_hook_test_fail)( const char * test, int line, const c
}
#endif
/**
* Perform a fast block XOR operation, such that
* r[i] = a[i] ^ b[i] where 0 <= i < n
*
* \param r Pointer to result (buffer of at least \p n bytes). \p r
* may be equal to either \p a or \p b, but behaviour when
* it overlaps in other ways is undefined.
* \param a Pointer to input (buffer of at least \p n bytes)
* \param b Pointer to input (buffer of at least \p n bytes)
* \param n Number of bytes to process.
*/
static inline void mbedtls_xor( unsigned char* r, unsigned char const *a, unsigned char const *b, size_t n )
{
uint32_t *a32 = (uint32_t*)a;
uint32_t *b32 = (uint32_t*)b;
uint32_t *r32 = (uint32_t*)r;
for ( size_t i = 0; i < (n >> 2); i++ )
{
r32[i] = a32[i] ^ b32[i];
}
for ( size_t i = n - (n % 4) ; i < n; i++ )
{
r[i] = a[i] ^ b[i];
}
}
/* Fix MSVC C99 compatible issue
* MSVC support __func__ from visual studio 2015( 1900 )
* Use MSVC predefine macro to avoid name check fail.