hexdump.c

hexdump.c

#include <stdio.h>

void hexDump(char *desc, void *addr, int len) 
{
    int i;
    unsigned char buff[17];
    unsigned char *pc = addr;

    // Output description if given.
    if (desc != NULL)
        printf("%p (%s):\n", addr, desc);
    else
        printf("%p:\n", addr);
    
    // Process every byte in the data.
    for (i = 0; i < len; i++) {
        // Multiple of 16 means new line (with line offset).

        if ((i % 16) == 0) {
            // Just don't print ASCII for the zeroth line.
            if (i != 0)
                printf ("  %s\n", buff);

            // Output the offset.
            printf ("  %04x ", i);
        }

        // Now the hex code for the specific character.
        printf (" %02x", pc[i]);

        // And store a printable ASCII character for later.
        if ((pc[i] < 0x20) || (pc[i] > 0x7e))
            buff[i % 16] = '.';
        else
            buff[i % 16] = pc[i];
        buff[(i % 16) + 1] = '\0';
    }

    // Pad out last line if not exactly 16 characters.
    while ((i % 16) != 0) {
        printf ("   ");
        i++;
    }

    // And print the final ASCII bit.
    printf ("  %s\n", buff);
}

int main (int argc, char *argv[]) 
{
    char my_str[] = "a char string greater than 16 chars";
    printf("%#p\n", my_str);
    hexDump ("my_str", my_str, sizeof (my_str));
    return 0;
}