char byte_array[10];

char byte_mask[10];

for ( i = 10 ; i-- > 0 ; )
    result_array[i] = byte_array[i] & byte_mask[i];

uint32_t* input32 = (uint32_t*)byte_array;
uint32_t* mask32 = (uint32_t*)byte_mask;
uint32_t* result32 = (uint32_t*)result_array;
for ( i = 4 ; i-- > 0 ; )
    result32[i] = input32[i] & mask32[i];

char byte_array[12];
char byte_mask[12];
/* Checks for proper alignment */
assert(((unsigned int)(void *)byte_array) & 3 == 0);
assert(((unsigned int)(void *)byte_mask) & 3 == 0);
for (i = 0; i < (10+3)/4; i++) {
  ((unsigned int *)(byte_array))[i] &= ((unsigned int *)(byte_mask))[i];
}

char          byte_array [CHAR_ARRAY_SIZE];
unsigned int  int_array [INT_ARRAY_SIZE];

arr_result.int_array [i] = arr_src.int_array[i] & arr_mask.int_array [i];