fdprintf.c

   1 /*
   2   File name        : fprintf.c
   3   Date of creation : 05/12/2022
   4   Version          : 1.0
   5   Copyright        : Soft'n'design
   6   Author           : Laurent Mazet <mazet@softndesign.org>
   7
   8   Description      : This file contains embedded printf
   9
  10   History          :
  11   - initial version
  12 */
  13
  14 #include <stdarg.h>
  15 #include <stdint.h>
  16 #include <unistd.h>
  17
  18 #include "fdprintf.h"
  19
  20 int stdfdin = STDIN_FILENO;
  21 int stdfdout = STDOUT_FILENO;
  22 int stdfderr = STDERR_FILENO;
  23
  24 unsigned int nextpow (unsigned int x, int base) {
  25     unsigned int n = 0;
  26     while (x) {
  27         n++;
  28         x = x / base;
  29     }
  30     return (n == 0) ? 1 : n;
  31 }
  32
  33 char *itoa (char *str, unsigned u, unsigned int sz)
  34 {
  35     unsigned int i = (sz == 0 ) ? nextpow (u, 10) : sz;
  36     char *s = str;
  37     while (i > 0) {
  38         str[i - 1] = '0' + (u % 10);
  39         u /= 10;
  40         i--;
  41         s++;
  42     }
  43     return s;
  44 }
  45
  46 double tenpower(int n)
  47 {
  48     double t = 1.0;
  49     int i;
  50     for (i = 0; i < n; i++) {
  51         t *= 10;
  52     }
  53     for (i = 0; i > n; i--) {
  54         t /= 10;
  55     }
  56     return t;
  57 }
  58
  59 int getexponant (double *f, int maxexp)
  60 {
  61     int exp = 0;
  62     while (*f > 10) {
  63         *f /= 10;
  64         exp++;
  65     }
  66     while (*f < 1) {
  67         *f *= 10;
  68         exp--;
  69     }
  70     *f += tenpower (maxexp - 1);
  71     if (*f >= 10) {
  72         *f /= 10;
  73         exp++;
  74     }
  75
  76     return exp;
  77 }
  78 /* simple fprintf function */
  79
  80 int fdprintf (int fd, const char *fmt, ...)
  81 {
  82     char buffer[1024 + 1] = { 0 };
  83     char *str = buffer;
  84
  85     va_list ap;
  86     va_start (ap, fmt);
  87     while (*fmt) {
  88         char *s;
  89         double f = 0.0;
  90         int d = 0;
  91         unsigned int u;
  92         char c = *fmt++;
  93
  94         /* copy standard char */
  95         if (c != '%') {
  96             *str++ = c;
  97         } else {
  98             int t = 0;
  99             char w = '0';
 100             int i, sz = 0;
 101             void *p = NULL;
 102
 103             /* stamp */
 104             if ((*fmt == ' ') || (*fmt == '0')) {
 105                 w = *fmt++;
 106             }
 107
 108             /* size */
 109             if ((*fmt >= '1') && (*fmt <= '9')) {
 110                 sz = *fmt++ - '0';
 111             }
 112
 113             /* process format char */
 114             switch (*fmt++) {
 115             case '%': /* percent */
 116                 *str++ = '%';
 117                 break;
 118             case 'c': /* char */
 119                 c = (char) va_arg (ap, int);
 120                 *str++ = c;
 121                 break;
 122             case 'd': /* int */
 123                 d = va_arg (ap, int);
 124                 if (d < 0) {
 125                     *str++ = '-';
 126                     d = -d;
 127                 }
 128                 t = 1;
 129                 /* fall through */
 130             case 'u': /* unsigned int */
 131                 str = itoa (str, (t) ? (unsigned int)d : va_arg (ap, unsigned int), 0);
 132                 break;
 133             case 'f': /* float */
 134                 f = va_arg (ap, double);
 135                 if (f == 0) {
 136                     *str++ = '0';
 137                     break;
 138                 }
 139                 if (f < 0) {
 140                     *str++ = '-';
 141                     f = -f;
 142                 }
 143                 if (sz == 0) sz = 6;
 144                 t = getexponant (&f, -sz);
 145                 u = (int)f;
 146                 str = itoa (str, u, 0);
 147                 d = (int)((f - u) * tenpower (sz));
 148                 if (d > 0) {
 149                     *str++ = '.';
 150                     str = itoa (str, d, sz);
 151                 }
 152                 while (*(str - 1) == '0') {
 153                     str--;
 154                 }
 155                 if (t != 0) {
 156                     *str++ = 'e';
 157                     if (t < 0) {
 158                         *str++ = '-';
 159                         t = -t;
 160                     }
 161                     str = itoa (str, t, 0);
 162                 }
 163                 break;
 164             case 'p': /* pointer */
 165                 *str++ = '0';
 166                 *str++ = 'x';
 167                 w = '0';
 168                 sz = sizeof (void *) * 2;
 169                 p = va_arg (ap, void *);
 170                 /* fall through */
 171             case 'x': /* integer hexa */
 172                 if (!p) {
 173                     u = va_arg (ap, unsigned int);
 174                     if (sz == 0) {
 175                         sz = nextpow (u, 16);
 176                     }
 177                 } else {
 178                     u = (uintptr_t)p;
 179                 }
 180                 for (i = sz, t = 1; i > 0; i--) {
 181                     char x = (char)((u >> (i * 4 - 4)) & 0xf);
 182                     if ((t == 1) && (x == 0)) {
 183                         *str++ = w;
 184                     } else {
 185                         *str++ = (x > 9) ? 'a' + x - 10 : '0' + x;
 186                         t = 0;
 187                     }
 188                 }
 189                 break;
 190             case 's': /* string */
 191                 s = va_arg (ap, char *);
 192                 while (s && *s)
 193                     *str++ = *s++;
 194                 break;
 195             default:
 196                 *str++ = '?';
 197             }
 198         }
 199     }
 200     va_end (ap);
 201
 202     /* output string */
 203     int n = str - buffer;
 204     if (n < (int)sizeof (buffer) - 1) {
 205         return write (fd, buffer, n);
 206     }
 207     return 0;
 208 }
 209
 210 /* vim: set ts=4 sw=4 et: */