hexadecimal_to_octal2.c File Reference

Convert hexadecimal number to octal number (with decimal intermediary) More...

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

Include dependency graph for hexadecimal_to_octal2.c:

Macros
#define	MAX_OCT_STR_LEN   23 /* 17_7777_7777_7777_7777_7777 */
#define	MAX_HEX_STR_LEN   17 /* FFFF_FFFF_FFFF_FFFF */

Functions
const char *	hex_to_oct (const char *hex)
	for printf() and fgets() More...
int	main ()
	Main function. More...

Detailed Description

Convert hexadecimal number to octal number (with decimal intermediary)

The input is valid from 0 to 0xFFFF_FFFF_FFFF_FFFF.

At first, this program converts a hex string to an unsigned long long decimal, and then to an octal string.

When there is an invalid character in input string, this program stops parsing and converts the string until that character.

See also

hexadecimal_to_octal.c

Function Documentation

hex_to_oct()

const char* hex_to_oct

(

const char *

hex

)

for printf() and fgets()

for memset()

Convert a hexadecimal number to octal number.

Parameters

hex	Hexadecimal number to convert.

Returns

A pointer to the converted octal string.

{
#define MAX_OCT_STR_LEN 23 /* 17_7777_7777_7777_7777_7777 */
    static char octal[MAX_OCT_STR_LEN];
    memset(octal, '\0', MAX_OCT_STR_LEN); // Initialize as NULL string
 
    unsigned long long decimal = 0;
    int i = 0;
    int len;
 
    if (hex == NULL)
    {
        // Return an empty string
        return octal;
    }
 
    /* Hexadecimal to decimal conversion */
    while (*hex != '\n' && *hex != '\0')
    {
        char ch = *hex;
 
        if (ch >= '0' && ch <= '9')
        {
            ch -= '0';
        }
        else if (ch >= 'a' && ch <= 'f')
        {
            ch = ch - 'a' + 10;
        }
        else if (ch >= 'A' && ch <= 'F')
        {
            ch = ch - 'A' + 10;
        }
        else
        {
            printf("Invalid hexadecimal input: %c\n", ch);
            break;
        }
 
        decimal *= 16;
        decimal += ch;
        hex++;
    }
 
    /* Decimal to octal conversion */
    if (decimal == 0)
    {
        octal[0] = '0';
        len = 1;
    }
    else
    {
        i = 0;
        while (decimal > 0)
        {
            octal[i] = '0' + decimal % 8;
            i++;
            decimal /= 8;
        }
 
        len = i;
    }
 
    octal[len] = '\0';
 
    /* Reverse the octal string */
    for (i = 0; i < len / 2; i++)
    {
        char tmp = octal[i];
        octal[i] = octal[len - i - 1];
        octal[len - i - 1] = tmp;
    }
 
    return octal;
}

main()

int main

(

void

)

Main function.

Returns

0 on exit

{
#define MAX_HEX_STR_LEN 17 /* FFFF_FFFF_FFFF_FFFF */
    char hex[MAX_HEX_STR_LEN];
 
    /* Input hexadecimal number from user */
    printf("Enter any hexadecimal number: ");
    fgets(hex, MAX_HEX_STR_LEN, stdin);
 
    const char *octal = hex_to_oct(hex);
 
    printf("Hexadecimal number = %s\n", hex);
    printf("Octal number = %s\n", octal);
 
    return 0;
}