fprintf.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 <unistd.h>
  16
  17 #include "fprintf.h"
  18
  19 int _fdout = STDOUT_FILENO;
  20 int _fderr = STDERR_FILENO;
  21
  22 inline unsigned int nextpow (unsigned int x, int base) {
  23     unsigned int n = 0;
  24     while (x) {
  25         n++;
  26         x = x / base;
  27     }
  28     return (n == 0) ? 1 : n;
  29 }
  30
  31 /* simple fprintf function */
  32
  33 int fdprintf (int fd, const char *fmt, ...)
  34 {
  35     char buffer[1024 + 1] = { 0 };
  36     char *str = buffer;
  37
  38     va_list ap;
  39     va_start (ap, fmt);
  40     while (*fmt) {
  41         char *s;
  42         int d = 0;
  43         unsigned int u;
  44         char c = *fmt++;
  45
  46         /* copy standard char */
  47         if (c != '%') {
  48             *str++ = c;
  49         } else {
  50             int t = 0;
  51                 char w = '0';
  52             int i, sz = 0;
  53             void *p = NULL;
  54
  55             /* stamp */
  56             if ((*fmt == ' ') || (*fmt == '0')) {
  57                 w = *fmt++;
  58             }
  59
  60             /* size */
  61             if ((*fmt >= '1') && (*fmt <= '9')) {
  62                 sz = *fmt++ - '0';
  63             }
  64
  65             /* process format char */
  66             switch (*fmt++) {
  67             case 'c': /* char */
  68                 c = (char) va_arg (ap, int);
  69                 *str++ = c;
  70                 break;
  71             case 'd': /* int */
  72                 d = va_arg (ap, int);
  73                 if (d < 0) {
  74                     *str++ = '-';
  75                     d = -d;
  76                 }
  77                 t = 1;
  78                 /* fall through */
  79             case 'u': /* unsigned int */
  80                 u = (t) ? (unsigned int)d : va_arg (ap, unsigned int);
  81                 for (i = nextpow (u, 10), s = str; i > 0; i--, s++) {
  82                     str[i - 1] = '0' + (u % 10);
  83                     u /= 10;
  84                 }
  85                 str = s;
  86                 break;
  87             case 'p': /* pointer */
  88                 *str++ = '0';
  89                 *str++ = 'x';
  90                 w = '0';
  91                 sz = sizeof (void *) * 2;
  92                 p = va_arg (ap, void *);
  93                 /* fall through */
  94             case 'x': /* integer hexa */
  95                 if (!p) {
  96                     u = va_arg (ap, unsigned int);
  97                     p = (void *)u;
  98                     if (sz == 0) {
  99                         sz = nextpow (u, 16);
 100                     }
 101                 }
 102                 for (i = sz, t = 1; i > 0; i--) {
 103                     char x = (char)(((uintptr_t)p >> (i * 4 - 4)) & 0xf);
 104                     if ((t == 1) && (x == 0)) {
 105                         *str++ = w;
 106                     } else {
 107                         *str++ = (x > 9) ? 'a' + x - 10 : '0' + x;
 108                         t = 0;
 109                     }
 110                 }
 111                 break;
 112             case 's': /* string */
 113                 s = va_arg (ap, char *);
 114                 while (s && *s)
 115                     *str++ = *s++;
 116                 break;
 117             default:
 118                 *str++ = '?';
 119             }
 120         }
 121     }
 122     va_end (ap);
 123
 124     /* output string */
 125     int n = str - buffer;
 126     if (n < (int)sizeof (buffer) - 1) {
 127         write (fd, buffer, n);
 128         return n;
 129     }
 130     return 0;
 131 }
 132
 133 /* vim: set ts=4 sw=4 et: */