Flash Write without Erase Checker Func

flash_util.h

#pragma once

/** 
 * Check if a section of flash memory can be written to a new value without a
 * sector erase. 
 * 
 * @param old_mem   current contents of flash memory region
 * @param new_mem   desired contents of flash memory region
 * @param len       number of bytes desired to write
 * 
 * @return 1 if can be written, 0 if not
 */
int writable_without_erase(unsigned char *old_mem, unsigned char *new_mem,
                           int len) {
    for (int i = 0; i < len; i++) {
        int cant_write = (old_mem[i] ^ new_mem[i]) & new_mem[i];
        if (cant_write) {
            return 0;
        }
    }
    return 1;
}

test.c

#include <stdio.h>
#include <assert.h>
#include <time.h>
#include "flash_util.h"


void test0(void) {
    unsigned char old_mem[] = {0b11111111};
    unsigned char new_mem[] = {0b11111110};
    assert(writable_without_erase(old_mem, new_mem, 1));
    printf("Test 0 passed\n");
}

void test1(void) {
    unsigned char old_mem[] = {0b11111110};
    unsigned char new_mem[] = {0b11111111};
    assert(!writable_without_erase(old_mem, new_mem, 1));
    printf("Test 1 passed\n");
}

void test2(void) {
    unsigned char old_mem[] = {0b11111111};
    unsigned char new_mem[] = {0b11111111};
    assert(writable_without_erase(old_mem, new_mem, 1));
    printf("Test 2 passed\n");
}

void test3(void) {
    clock_t start, end;
    double cpu_time_used;
    start = clock();

    unsigned char old_mem[1024] = {0};
    unsigned char new_mem[1024] = {0};
    new_mem[1023] = 1;
    assert(!writable_without_erase(old_mem, new_mem, 1024));

    end = clock();
    cpu_time_used = ((double) (end - start)) / CLOCKS_PER_SEC;
    printf("Test 3 passed in %.03e sec\n", cpu_time_used);
}

int main(void) {
    printf("Test Start\n");

    test0();
    test1();
    test2();
    test3();
    return 0;
}