whatluo wrote:

I'm now working on a program which will convert dec number to

hex and oct and bin respectively, I've checked the clc but with no

luck, so can anybody give me a hit how to make this done without

strtol or s/printf function.

I just happen to have this lying about

:

/* base2txt.h. Public domain by C.B. Falconer, 2005-05-12. */

/* Output values to a text stream. No buffers needed */

#ifndef H_base2txt_h

# define H_base2txt_h

# ifdef __cplusplus

extern "C"

{

# endif

#include <stdio.h>

/* ----------------------- */

/* Convert unsigned value to stream of digits in base base.

A NULL value for f returns a char count with no output

Returns count of chars. output

return is negative for any output error */

int unum2txt(unsigned long n, unsigned int base, FILE *f);

/* ----------------------- */

/* Convert signed value to stream of digits in base base.

A NULL value for f returns a char count with no output

Returns count of chars. output

return is negative for any output error */

int num2txt(long n, unsigned int base, FILE *f);

/* ----------------------- */

/* Convert unsigned value to stream of decimal digits in fld.

A NULL value for f returns a char count with no output

A negative fld left justifies, else right.

Returns count of chars. output

return is negative for any output error */

int unum2fld(unsigned long n, int fld, FILE *f);

/* ----------------------- */

/* Convert signed value to stream of decimal digits in fld.

A NULL value for f returns a char count with no output

A negative fld left justifies, else right.

Returns count of chars. output

return is negative for any output error */

int num2fld(long n, int fld, FILE *f);

# ifdef __cplusplus

}

# endif

#endif

/* base2txt.c. Public domain by C.B. Falconer, 2005-05-12. */

/* <http://cbfalconer.home.att.net> */

/* Output values to a text stream. No buffers needed */

/* To compile a test version use -DTESTING with gcc */

/* To avoid recursion use -DNORECURSE with gcc. This */

/* may be useful on some non-conforming systems. */

#include "base2txt.h"

/* ----------------------- */

/* Convert unsigned value to stream of digits in base

A NULL value for f returns a char count with no output

Returns count of chars. output

return is negative for any output error */

int unum2txt(unsigned long n, unsigned int base, FILE *f)

{

/* MUST be a power of 2 in length */

static char hexchars[] = "0123456789abcdef";

/* allow for terminal '\0' */

#define MAXBASE (sizeof(hexchars)-1)

#ifdef NORECURSE

#include <limits.h>

int count, ix;

/* sufficient for a binary expansion */

char buf[CHAR_BIT * sizeof(long)];

#else

int count, err;

#endif

if ((base < 2) || (base > MAXBASE)) base = 10;

#ifdef NORECURSE

count = ix = 0;

do {

buf[ix++] = hexchars[(n % base) & (MAXBASE-1)];

} while ((n = n / base));

while (ix--) {

count++;

if (f && (putc(buf[ix], f) < 0)) return -count;

}

#else

count = 1;

if (n / base) {

if ((err = unum2txt(n / base, base, f)) < 0) return err;

else count += err;

}

if (f && (putc(hexchars[(n % base) & (MAXBASE-1)], f) < 0))

return -count;

#endif

return count;

} /* unum2txt */

/* ----------------------- */

/* Convert signed value to stream of digits in base

A NULL value for f returns a char count with no output

Returns count of chars. output

return is negative for any output error */

int num2txt(long n, unsigned int base, FILE *f)

{

int count, err;

unsigned long val;

val = n; count = 0;

if (n < 0) {

count++; val = -(unsigned long)n;

if (f && (putc('-', f) < 0)) return - count;

}

err = unum2txt(val, base, f);

if (err < 0) return err - count;

return err + count;

} /* num2txt */

/* ----------------------- */

/* Negative return if i/o error occurs */

/* Returns number of blanks output attempted */

static int putblks(int count, FILE *f)

{

int ix;

if (f && (count > 0)) {

for (ix = 0; ix < count; ix++) {

if (putc(' ', f) < 0) return -ix - 1;

}

return ix;

}

else return 0;

} /* putblks */

/* ----------------------- */

/* Convert unsigned value to stream of decimal digits in fld.

A NULL value for f returns a char count with no output

A negative fld left justifies, else right.

Returns count of chars. output

return is negative for any output error */

int unum2fld(unsigned long n, int fld, FILE *f)

{

int err, digs, blanks;

if (fld >= 0) { /* right justify in field */

digs = unum2txt(n, 10, NULL);

if (0 > (blanks = putblks(fld - digs, f))) return blanks;

if (0 > (err = unum2txt(n, 10, f))) return err - blanks;

else return err + blanks;

}

else { /* left justify */

if ((digs = unum2txt(n, 10, f)) < 0) return digs;

if (0 > (blanks = putblks(fld - digs, f)))

return blanks - digs;

else return blanks + digs;

}

} /* unum2fld */

/* ----------------------- */

/* Convert signed value to stream of decimal digits in fld.

A NULL value for f returns a char count with no output

A negative fld left justifies, else right.

Returns count of chars. output

return is negative for any output error */

int num2fld(long n, int fld, FILE *f)

{

int err, digs, blanks;

if (fld >= 0) { /* right justify in field */

digs = num2txt(n, 10, NULL);

if (0 > (blanks = putblks(fld - digs, f))) return blanks;

if (0 > (err = num2txt(n, 10, f))) return err - blanks;

else return err + blanks;

}

else { /* left justify */

if ((digs = num2txt(n, 10, f)) < 0) return digs;

if (0 > (blanks = putblks(fld - digs, f)))

return blanks - digs;

else return blanks + digs;

}

} /* num2fld */

#ifdef TESTING

/* ----------------------- */

/* This does some questionable things in order to get values to

display. This doesn't affect the validity of the routines */

int main(int argc, char **argv)

{

unsigned int base;

long num;

int fieldused;

if ((argc < 3) || (1 != sscanf(argv[1], "%u", &base)))

puts("Usage: base2txt base value [value ...]\n"

" where the value list is in decimal");

else {

printf("Dec.Input Base %u value [digs]\n", base);

while (argc > 2) {

sscanf(argv[--argc], "%ld", &num);

printf("%11s .", argv[argc]);

fieldused = unum2txt(num, base, stdout);

if (fieldused != unum2txt(num, base, NULL))

fputs("*ERROR*", stdout);

printf(". [%d] .", fieldused);

fieldused = num2txt(num, base, stdout);

if (fieldused != num2txt(num, base, NULL))

fputs("*ERROR*", stdout);

printf(". [%d]\n", fieldused);

}

}

return 0;

} /* main, testing */

#endif

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