Question

/*
* Change the value pointed to by ptr byte-by-byte so that when returned as an integer
* the value is 351351.
*
* Hint: Remember that an int is 4 bytes.
*
* Hint: Remember how little endian works for data storage, how is it different between an multiple bytes(int) and a single byte?
*
* Hint: It will be easiest to start convert 351351 into binary form and starting seeing how the endian works from there.
*
* ALLOWED:
* Pointer operators: *, &
* Binary integer operators: -, +, *
* Shorthand operators based on the above: ex. +=, *=, ++, --, etc.
* Unary integer operators: !
*
* DISALLOWED:
* Pointer operators: [] (Array Indexing Operator)
* Binary integer operators: &, &&, |, ||, <, >, <<, >>, ==, !=, ^, /, %
* Unary integer operators: ~, -
*/

int endianExperiment(int* ptr) {
char *bytePtr;
// Your code here
return *ptr;
}

Answer 1

#include <stdio.h>

/*
* Change the value pointed to by ptr byte-by-byte so that when returned as an integer
* the value is 351351.
*
* Hint: Remember that an int is 4 bytes.
*
* Hint: Remember how little endian works for data storage, how is it different between an multiple bytes(int) and a single byte?
*
* Hint: It will be easiest to start convert 351351 into binary form and starting seeing how the endian works from there.
*
* ALLOWED:
* Pointer operators: *, &
* Binary integer operators: -, +, *
* Shorthand operators based on the above: ex. +=, *=, ++, --, etc.
* Unary integer operators: !
*
* DISALLOWED:
* Pointer operators: [] (Array Indexing Operator)
* Binary integer operators: &, &&, |, ||, <, >, <<, >>, ==, !=, ^, /, %
* Unary integer operators: ~, -
*/


int endianExperiment(int* ptr) {
        char *bytePtr = (char *)ptr;

        // 351351 is 0x00055C77

        // In little endian, lower bytes stay at lower addresses
        *bytePtr = 0x77;
        bytePtr++;

        *bytePtr = 0x5C;
        bytePtr++;

        *bytePtr = 0x05;
        bytePtr++;
        
        *bytePtr = 0x00;

        // Your code here
        return *ptr;
}

int main(void) {
        int d = 0;

        printf("Value: %d\n", endianExperiment(&d));
        return 0;
}

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