Improve comments in mpi_shrink
@@ -158,9 +158,10 @@ int mbedtls_mpi_shrink( mbedtls_mpi *X, size_t nblimbs )
if( nblimbs > MBEDTLS_MPI_MAX_LIMBS )
return( MBEDTLS_ERR_MPI_ALLOC_FAILED );
- /* Actually resize up in this case */
+ /* Actually resize up if there are currently fewer than nblimbs limbs. */
if( X->n <= nblimbs )
return( mbedtls_mpi_grow( X, nblimbs ) );
+ /* Now X->n > nblimbs >= 0. */
for( i = X->n - 1; i > 0; i-- )
if( X->p[i] != 0 )
