preliminary version

[calc.git] / fdprintf.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 <stdint.h>
#include <unistd.h>

#include "fdprintf.h"

int stdfdin = STDIN_FILENO;
int stdfdout = STDOUT_FILENO;
int stdfderr = STDERR_FILENO;

unsigned int nextpow (unsigned int x, int base) {
    unsigned int n = 0;
    while (x) {
        n++;
        x = x / base;
    }
    return (n == 0) ? 1 : n;
}

char *itoa (char *str, unsigned u, unsigned int sz)
{
    unsigned int i = (sz == 0 ) ? nextpow (u, 10) : sz;
    char *s = str;
    while (i > 0) {
        str[i - 1] = '0' + (u % 10);
        u /= 10;
        i--;
        s++;
    }
    return s;
}

/* simple fprintf function */

int fdprintf (int fd, const char *fmt, ...)
{
    char buffer[1024 + 1] = { 0 };
    char *str = buffer;

    va_list ap;
    va_start (ap, fmt);
    while (*fmt) {
        char *s;
        double f = 0.0;
        int d = 0;
        unsigned int u;
        char c = *fmt++;

        /* copy standard char */
        if (c != '%') {
            *str++ = c;
        } else {
            int t = 0;
	    char w = '0';
            int i, sz = 0;
            void *p = NULL;

            /* stamp */
            if ((*fmt == ' ') || (*fmt == '0')) {
                w = *fmt++;
            }

            /* size */
            if ((*fmt >= '1') && (*fmt <= '9')) {
                sz = *fmt++ - '0';
            }

            /* 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 */
                str = itoa (str, (t) ? (unsigned int)d : va_arg (ap, unsigned int), 0);
                break;
            case 'f': /* float */
                f = va_arg (ap, double);
                if (f < 0) {
                    *str++ = '-';
                    f = -f;
                }
                t = 0;
                while (f > 10) {
                    f /= 10;
                    t++;
                }
                while (f < 1) {
                    f *= 10;
                    t--;
                }
		f += 1e-7;
                if (f >= 10) {
                    f /= 10;
                    t++;
                }
                u = (int)f;
                str = itoa (str, u, 0);
                d = (int)((f - u) * 1e6);
                if (d > 0) {
                    *str++ = '.';
                    str = itoa (str, d, 6);
                }
                if (t != 0) {
                    *str++ = 'e';
                    if (t < 0) {
                        *str++ = '-';
                        t = -t;
                    }
                    str = itoa (str, t, 0);
                }
                break;
            case 'p': /* pointer */
                *str++ = '0';
                *str++ = 'x';
                w = '0';
                sz = sizeof (void *) * 2;
                p = va_arg (ap, void *);
                /* fall through */
            case 'x': /* integer hexa */
                if (!p) {
                    u = va_arg (ap, unsigned int);
                    if (sz == 0) {
                        sz = nextpow (u, 16);
                    }
                } else {
                    u = (uintptr_t)p;
                }
                for (i = sz, t = 1; i > 0; i--) {
                    char x = (char)((u >> (i * 4 - 4)) & 0xf);
                    if ((t == 1) && (x == 0)) {
                        *str++ = w;
                    } else {
                        *str++ = (x > 9) ? 'a' + x - 10 : '0' + x;
                        t = 0;
                    }
                }
                break;
            case 's': /* string */
                s = va_arg (ap, char *);
                while (s && *s)
                    *str++ = *s++;
                break;
            default:
                *str++ = '?';
            }
        }
    }
    va_end (ap);

    /* output string */
    int n = str - buffer;
    if (n < (int)sizeof (buffer) - 1) {
        return write (fd, buffer, n);
    }
    return 0;
}

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