Hex editing

I cannot parse that. You want functions to edit offsets??? Or, do you mean edit a value (represented in hexadeciaml) at an offset?

Explain better what you want to achieve, and I''m sure someone will be able to help you out.

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I want to edit a value represented in hexadecimal at an offset.

So basically, you''re writing a hex editor? If all you want is to be able to display a number as hex, then parse a hex number (stored in a string), use sprintf to convert to a string, then use strtol to parse the hex number. Just set the base to 16.

Does this help?

To make a hex string is really easy. Watch this function:

void long_to_hex_ascii(unsigned long val, char *buffer, int digits)
{
    buffer += digits;  // buffer points to after our new string
    *--buffer = ''\0'';  // Terminate it

    int digit;
    while(digits--) {
        digit = val & 0x0000000f;  // Get rightmost 4 bits
        val >>= 4;  // Discard it
        if(digit <= 9) digit += ''0'';  // Make ascii digits 0-9
        else digit += ''A'' - 10;  // Make ascii A-F
        *--buffer = digit;
    }
}
 
// Although untested, it should work
char buffer[9];  // can store 8 digits
long_to_hex_ascii(65537, buffer, 8);

Notice that this function starts to fill out the hex string at the terminating character and works its way to the left.

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Do I have too much time on my hands? Ehm, anyway here's a function for the other way around:

unsigned long hex_ascii_to_long(const char *buffer, int digits)
{
    unsigned long val = 0;
 
    int digit;
    while(digits-- && (digit = *buffer)) {
        val <<= 4;  // start on next digit
        if(digit >= '0' && digit <= '9)
            digit -= '0';  // numeric value of hex ascii 0-9
        else if(digit >= 'A' && digit <= 'F')
            digit -= 'A' + 10;  // numeric value of hex ascii A-F
        else {
            // error in string
        }
        val |= digit;  // add this digit to the right of value
    }
 
    return val;
}
 
char hexstring[] = "1337DEAD";
unsigned long = hex_ascii_to_long(hexstring, strlen(hexstring));
 

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[edited by - CWizard on April 28, 2003 8:31:00 PM]

Wouldn''t it just be easier to use:

sprintf(buffer, "%X", myInt);

to convert to asciii hex and:

myInt = strtol(buffer, 0, 16);

to convert back? "Work smarter, not harder" ;-)

I am making a level editor for a rom, and most of the variables and data, i want edit are in hex. I wanted to read the hex data and then use it to display the levels as they are in the game. i know where all the data is already, i just needed to get the functions, to read, edit, and get the hex values.
drslush how do i implement your way?

sprintf()
strtol()

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quote:

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Original post by Ultra The Vampire
I am making a level editor for a rom, and most of the variables and data, i want edit are in hex. I wanted to read the hex data and then use it to display the levels as they are in the game. i know where all the data is already, i just needed to get the functions, to read, edit, and get the hex values.
drslush how do i implement your way?

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Values are not stored as hex, they are stored as binary. They may then be displayed as hex or decimal or octal etc... Just load the number into a byte sized field and manipulate it.

If the hex numbers are represented as strings and then saved as strings, just load then and parse the hex to a value that is easy for you to use.

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First make it work,
then make it fast.
--Brian Kernighan

"I’m happy to share what I can, because I’m in it for the love of programming. The Ferraris are just gravy, honest!" --John Carmack: Forward to Graphics Programming Black Book

Ultra The Vampire? Any relation to Trevor The Vampire?