add private atoi function

[compress.git] / fprintf.c

/*
  File name        : fprintf.c
  Date of creation : 05/12/2022
  Version          : 1.0
  Copyright        : Soft'n'design
  Author           : Laurent Mazet <mazet@softndesign.org>

  Description      : This file contains embedded printf

  History          :
  - initial version
*/

#include <stdarg.h>
#include <stddef.h>
#include <stdio.h>

inline unsigned int nextpow10 (unsigned int x) {
    unsigned int n = 0;
    while (x) {
        n++;
        x = x / 10;
    }
    return (n == 0) ? 1 : n;
}

/* simple fprintf function */

size_t _fprintf (FILE *fid, const char *fmt, ...)
{
    char buffer[1024 + 1] = { 0 };
    char *str = buffer;

    va_list ap;
    va_start (ap, fmt);
    while (*fmt) {
        char *s;
        int d = 0;
        unsigned int u;
        void *p;
        char c = *fmt++;

        /* copy standard char */
        if (c != '%') {
            *str++ = c;
        } else {
            int t = 0;
            size_t i;

            /* process format char */
            switch (*fmt++) {
            case 'c': /* char */
                c = (char) va_arg (ap, int);
                *str++ = c;
                break;
            case 'd': /* int */
                d = va_arg (ap, int);
                if (d < 0) {
                    *str++ = '-';
                    d = -d;
                }
                t = 1;
                /* fall through */
            case 'u': /* unsigned int */
                u = (t) ? (unsigned int)d : va_arg (ap, unsigned int);
                for (i = nextpow10 (u), s = str; i > 0; i--, s++) {
                    str[i - 1] = '0' + (u % 10);
                    u /= 10;
                }
                str = s;
                break;
            case 'p': /* pointer */
                p = va_arg (ap, void *);
                *str++ = '0';
                *str++ = 'x';
                for (i = sizeof (void *) * 2; i > 0; i--) {
                    char x = (char)(((uintptr_t)p >> (i * 4 - 4)) & 0xf);
                    *str++ = (x > 9) ? 'a' + x - 10 : '0' + x;
                }
                break;
            case 's': /* string */
                s = va_arg (ap, char *);
                while (s && *s)
                    *str++ = *s++;
                break;
            default:
                *str++ = '?';
            }
        }
    }
    va_end (ap);

    /* output string */
    size_t n = str - buffer;
    if (n < sizeof (buffer) - 1) {
        fwrite (buffer, n, 1, fid);
        return n;
    }
    return 0;
}

/* vim: set ts=4 sw=4 et */