Unify function parameters
Signed-off-by: gabor-mezei-arm <gabor.mezei@arm.com>
diff --git a/library/constant_time.c b/library/constant_time.c
index 2388cab..496843d 100644
--- a/library/constant_time.c
+++ b/library/constant_time.c
@@ -178,19 +178,19 @@
/** Check whether a size is out of bounds, without branches.
*
- * This is equivalent to `size > max`, but is likely to be compiled to
+ * This is equivalent to `x > y`, but is likely to be compiled to
* to code using bitwise operation rather than a branch.
*
- * \param size Size to check.
- * \param max Maximum desired value for \p size.
- * \return \c 0 if `size <= max`.
- * \return \c 1 if `size > max`.
+ * \param x Size to check.
+ * \param y Maximum desired value for \p size.
+ * \return \c 0 if `x <= y`.
+ * \return \c 1 if `x > y`.
*/
-unsigned mbedtls_cf_size_gt( size_t size,
- size_t max )
+unsigned mbedtls_cf_size_gt( size_t x,
+ size_t y )
{
- /* Return the sign bit (1 for negative) of (max - size). */
- return( ( max - size ) >> ( sizeof( size_t ) * 8 - 1 ) );
+ /* Return the sign bit (1 for negative) of (y - x). */
+ return( ( y - x ) >> ( sizeof( size_t ) * 8 - 1 ) );
}
#if defined(MBEDTLS_BIGNUM_C)
@@ -234,57 +234,58 @@
/** Choose between two integer values, without branches.
*
- * This is equivalent to `cond ? if1 : if0`, but is likely to be compiled
+ * This is equivalent to `condition ? if1 : if0`, but is likely to be compiled
* to code using bitwise operation rather than a branch.
*
- * \param cond Condition to test.
- * \param if1 Value to use if \p cond is nonzero.
- * \param if0 Value to use if \p cond is zero.
- * \return \c if1 if \p cond is nonzero, otherwise \c if0.
+ * \param condition Condition to test.
+ * \param if1 Value to use if \p condition is nonzero.
+ * \param if0 Value to use if \p condition is zero.
+ * \return \c if1 if \p condition is nonzero, otherwise \c if0.
*/
-unsigned mbedtls_cf_uint_if( unsigned cond,
+
+unsigned mbedtls_cf_uint_if( unsigned condition,
unsigned if1,
unsigned if0 )
{
- unsigned mask = mbedtls_cf_uint_mask( cond );
+ unsigned mask = mbedtls_cf_uint_mask( condition );
return( ( mask & if1 ) | (~mask & if0 ) );
}
-size_t mbedtls_cf_size_if( unsigned cond,
+size_t mbedtls_cf_size_if( unsigned condition,
size_t if1,
size_t if0 )
{
- size_t mask = mbedtls_cf_size_mask( cond );
+ size_t mask = mbedtls_cf_size_mask( condition );
return( ( mask & if1 ) | (~mask & if0 ) );
}
/**
* Select between two sign values in constant-time.
*
- * This is functionally equivalent to second ? a : b but uses only bit
+ * This is functionally equivalent to condition ? if1 : if0 but uses only bit
* operations in order to avoid branches.
*
- * \param[in] a The first sign; must be either +1 or -1.
- * \param[in] b The second sign; must be either +1 or -1.
- * \param[in] second Must be either 1 (return b) or 0 (return a).
+ * \param[in] condition Must be either 1 (return \p if1) or 0 (return \pp if0).
+ * \param[in] if1 The first sign; must be either +1 or -1.
+ * \param[in] if0 The second sign; must be either +1 or -1.
*
- * \return The selected sign value.
+ * \return \c if1 if \p condition is nonzero, otherwise \c if0.
*/
-int mbedtls_cf_cond_select_sign( int a,
- int b,
- unsigned char second )
+int mbedtls_cf_cond_select_sign( unsigned char condition,
+ int if1,
+ int if0 )
{
/* In order to avoid questions about what we can reasonnably assume about
* the representations of signed integers, move everything to unsigned
* by taking advantage of the fact that a and b are either +1 or -1. */
- unsigned ua = a + 1;
- unsigned ub = b + 1;
+ unsigned uif1 = if1 + 1;
+ unsigned uif0 = if0 + 1;
- /* second was 0 or 1, mask is 0 or 2 as are ua and ub */
- const unsigned mask = second << 1;
+ /* condition was 0 or 1, mask is 0 or 2 as are ua and ub */
+ const unsigned mask = condition << 1;
/* select ua or ub */
- unsigned ur = ( ua & ~mask ) | ( ub & mask );
+ unsigned ur = ( uif0 & ~mask ) | ( uif1 & mask );
/* ur is now 0 or 2, convert back to -1 or +1 */
return( (int) ur - 1 );
@@ -296,12 +297,12 @@
* Conditionally assign dest = src, without leaking information
* about whether the assignment was made or not.
* dest and src must be arrays of limbs of size n.
- * assign must be 0 or 1.
+ * condition must be 0 or 1.
*/
void mbedtls_cf_mpi_uint_cond_assign( size_t n,
mbedtls_mpi_uint *dest,
const mbedtls_mpi_uint *src,
- unsigned char assign )
+ unsigned char condition )
{
size_t i;
@@ -312,8 +313,8 @@
#pragma warning( disable : 4146 )
#endif
- /* all-bits 1 if assign is 1, all-bits 0 if assign is 0 */
- const mbedtls_mpi_uint mask = -assign;
+ /* all-bits 1 if condition is 1, all-bits 0 if condition is 0 */
+ const mbedtls_mpi_uint mask = -condition;
#if defined(_MSC_VER)
#pragma warning( pop )
@@ -375,7 +376,7 @@
* This function is implemented without using comparison operators, as those
* might be translated to branches by some compilers on some platforms.
*/
-void mbedtls_cf_memcpy_if_eq( unsigned char *dst,
+void mbedtls_cf_memcpy_if_eq( unsigned char *dest,
const unsigned char *src,
size_t len,
size_t c1,
@@ -385,9 +386,9 @@
const size_t equal = mbedtls_cf_size_bool_eq( c1, c2 );
const unsigned char mask = (unsigned char) mbedtls_cf_size_mask( equal );
- /* dst[i] = c1 == c2 ? src[i] : dst[i] */
+ /* dest[i] = c1 == c2 ? src[i] : dest[i] */
for( size_t i = 0; i < len; i++ )
- dst[i] = ( src[i] & mask ) | ( dst[i] & ~mask );
+ dest[i] = ( src[i] & mask ) | ( dest[i] & ~mask );
}
/*
@@ -543,7 +544,7 @@
MBEDTLS_MPI_CHK( mbedtls_mpi_grow( X, Y->n ) );
- X->s = mbedtls_cf_cond_select_sign( X->s, Y->s, assign );
+ X->s = mbedtls_cf_cond_select_sign( assign, Y->s, X->s );
mbedtls_cf_mpi_uint_cond_assign( Y->n, X->p, Y->p, assign );
@@ -594,8 +595,8 @@
MBEDTLS_MPI_CHK( mbedtls_mpi_grow( Y, X->n ) );
s = X->s;
- X->s = mbedtls_cf_cond_select_sign( X->s, Y->s, swap );
- Y->s = mbedtls_cf_cond_select_sign( Y->s, s, swap );
+ X->s = mbedtls_cf_cond_select_sign( swap, Y->s, X->s );
+ Y->s = mbedtls_cf_cond_select_sign( swap, s, Y->s );
for( i = 0; i < X->n; i++ )