Does memcpy copy bytes in reverse order?

Question

I am little bit confused on usage of memcpy. I though memcpy can be used to copy chunks of binary data to address we desire. I was trying to implement a small logic to directyl convert 2 bytes of hex to 16 bit signed integer without using union.

 #include <stdio.h>
    #include <stdint.h>
    #include <string.h>
    int main()
    {   uint8_t message[2] = {0xfd,0x58};
        // int16_t roll = message[0]<<8;
        // roll|=message[1];
        int16_t roll = 0;
        memcpy((void *)&roll,(void *)&message,2);
        printf("%x",roll);
    
        return 0;
    }

Answer 1

Does memcpy copy bytes in reverse order?

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Answer 2

No, memcpy<\/code> did not reverse the bytes as it copied them. That would be a strange and wrong thing for memcpy<\/code> to do.

There's probably a canonical answer on this somewhere, but here's what you need to understand about byte order, or " endianness<\/a> ".

Suppose I write this little code fragment:

#include <stdio.h>

char string[] = "Hello";
printf("address of string:   %p\n", (void *)&string);
printf("address of 1st char: %p\n", (void *)&string[0]);
printf("address of 5th char: %p\n", (void *)&string[4]);