Thread: Hex String to Decimal Possible?

Originally Posted by someprogr

Hello, I have a program that takes input from a user with gets(). Basically, the user is going to input a hexidecimal number. I will need to convert that number to an int because its going to have to be used in array indices etc. Is there a C library that can do this? Anyone know where I can locate one if not ANSI? Thanks.

1. do not use gets - read FAQ
2. read about strtol, sscanf, format %i and %x
http://msdn.microsoft.com/en-us/library/6ttkkkhh.aspx

Try this: (http://www.gidnetwork.com/b-44.html)

Code:

// This program will convert a string value into it's internal
// binary equivalent for any base up to 36. The conversion will
// stop at the first invalid character for the base specified
// (which includes the \\n or \\0)

#include <stdio.h>
int Convert(char *, int);

int main()
{
    char inbuf[32];
    int  base;      // Base for the conversion
    int  binary;    // final binary value
    int  j;         // loop counter

    printf("Enter the base (in decimal): ");
    fgets(inbuf, 32, stdin);    // Get the base for conversion
    sscanf(inbuf,"%d",&base);   // Make it a value

    printf("Enter the base %d value to convert: ", base);
    fgets(inbuf, 32, stdin);    // Get the value for conversion

    binary = Convert(inbuf, base);
    printf("%d  %Xh \n", binary, binary);  // output dec & hex
    return 0;
}

int Convert(char *buf, int cbase)
{
    int j;
    int bin;

    j = 0;
    bin = 0;                 // start the binary value at 0
    while (buf[j])
    {
        buf[j] -= 48;           // convert character for binary
        if (buf[j] > 16)
            buf[j] -= 7;        // character was probably letter
        if (buf[j] >= cbase)
            buf[j] -= 32;       // character was probably lower
        if (buf[j] >= cbase || buf[j] < 0)
            break;              // invalid character, done
        bin *= cbase;           // multiply by the base
        bin += buf[j];          // add current value
        j++;                    // next character
    }
    return bin;             // return the binary value
}

you shoudl not use magic numbers

and what is wrong with the standard functions?

so that the brain works...