#include <ctype.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#define BYTES_A_ROW         ((int)10)
#define ADDR_COLUMN_WIDTH   ((int)(2*sizeof(unsigned char *)))
                //num bytes of a pointer * 2 char; (1 byte = hex 2 chars)
#define BYTE_COLUMN_WIDTH   ((int)(BYTES_A_ROW * 3))
                // 1 bytes is 2 hex chars + some spaces
#define COLUMN_SEPARATOR    " "

typedef unsigned char byte_t;
void printOut(unsigned long start_addr, int length);
void printHeader();


int main(int argc, char *argv[] )

{
    int first_var = 0xaaaaaaaa; // do not change this declaration!!!
    unsigned long start_addr;
    int number_of_bytes;
 if(argc == 3)
    {
        sscanf(argv[1], "%16lx", &start_addr);
        sscanf(argv[2], "%3d", &number_of_bytes);
        printf("\n\nnumber = %3d", number_of_bytes);
        printHeader();
        printOut(start_addr, number_of_bytes);
    }
else if(argc == 1)
    {
        // print some reference addresses
        printf("FYI: address of main function in memory: %p\n", main );
        printf("FYI: address of argc: %p\n", &argc );
        printf("FYI: address of first local variable of main(): %p\n", &first_var );

        // read start address and memory size
        printf("enter start address <hex-notation> of dump: ");
        scanf("%16lx", &start_addr);


        printf("enter number of bytes to dump <negative or positive value>: " );
        scanf("%3d", &number_of_bytes);

        printHeader();
        printOut(start_addr, number_of_bytes);
    }
    else
    {
        printf("please provide a valid number of arguments.\n");
        return 0;
    }



    printf("\n");
    return 0;
}

void printHeader(){
    int i;
    // print table header
    printf("\n%-*s", ADDR_COLUMN_WIDTH, "Address");
    printf("%s", COLUMN_SEPARATOR);
    printf("%-*s", BYTE_COLUMN_WIDTH, "Bytes");
    printf("%s", COLUMN_SEPARATOR);
    printf("%-*s\n", BYTES_A_ROW, "Chars");

    for( i= 0; i < ADDR_COLUMN_WIDTH; i++)
        printf("-");
    printf("%s", COLUMN_SEPARATOR);
    for( i= 0; i < BYTE_COLUMN_WIDTH; i++)
        printf("-");
    printf("%s", COLUMN_SEPARATOR);
    for( i= 0; i < BYTES_A_ROW; i++)    // number of chars is char-column is exactly BYTES_A_ROW
        printf("-");
}

void printOut(unsigned long int start_addr, int length)
{
    byte_t *ptr;
    ptr = (unsigned char*) start_addr;
    int j = abs(length);
    int i;
    char charString[BYTES_A_ROW];



    while(j>0)
    {
        //We start by printing the start address of this row
        printf("\n%.6X ", (unsigned int) ptr);
        //Then we loop through the next ? elements
        for(i=0; i<BYTES_A_ROW; i++)
        {
            //check wether or not we want to see the next byte
            if(j!=0)
            {
                //print byte
                printf("%.2X ", *ptr);

                //Check wether or not the char represents a byte
                if(isprint(*ptr))   {charString[i] = *ptr;}
                else                {charString[i] = '.';}

                //check whether to inc/dec the pointer and do it
                if(length > 0)  {ptr++;}
                else            {ptr--;}

                //decrement j
                j--;
            }
            else
            {
                printf("   ");

            }
        }
        printf(" %s", charString);
    }
}