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 /* simple fprintf function */
  34
  35 int fdprintf (int fd, const char *fmt, ...)
  36 {
  37     char buffer[1024 + 1] = { 0 };
  38     char *str = buffer;
  39
  40     va_list ap;
  41     va_start (ap, fmt);
  42     while (*fmt) {
  43         char *s;
  44         int d = 0;
  45         unsigned int u;
  46         char c = *fmt++;
  47
  48         /* copy standard char */
  49         if (c != '%') {
  50             *str++ = c;
  51         } else {
  52             int t = 0;
  53                 char w = '0';
  54             int i, sz = 0;
  55             void *p = NULL;
  56
  57             /* stamp */
  58             if ((*fmt == ' ') || (*fmt == '0')) {
  59                 w = *fmt++;
  60             }
  61
  62             /* size */
  63             if ((*fmt >= '1') && (*fmt <= '9')) {
  64                 sz = *fmt++ - '0';
  65             }
  66
  67             /* process format char */
  68             switch (*fmt++) {
  69             case 'c': /* char */
  70                 c = (char) va_arg (ap, int);
  71                 *str++ = c;
  72                 break;
  73             case 'd': /* int */
  74                 d = va_arg (ap, int);
  75                 if (d < 0) {
  76                     *str++ = '-';
  77                     d = -d;
  78                 }
  79                 t = 1;
  80                 /* fall through */
  81             case 'u': /* unsigned int */
  82                 u = (t) ? (unsigned int)d : va_arg (ap, unsigned int);
  83                 for (i = nextpow (u, 10), s = str; i > 0; i--, s++) {
  84                     str[i - 1] = '0' + (u % 10);
  85                     u /= 10;
  86                 }
  87                 str = s;
  88                 break;
  89             case 'p': /* pointer */
  90                 *str++ = '0';
  91                 *str++ = 'x';
  92                 w = '0';
  93                 sz = sizeof (void *) * 2;
  94                 p = va_arg (ap, void *);
  95                 /* fall through */
  96             case 'x': /* integer hexa */
  97                 if (!p) {
  98                     u = va_arg (ap, unsigned int);
  99                     if (sz == 0) {
 100                         sz = nextpow (u, 16);
 101                     }
 102                 } else {
 103                     u = (uintptr_t)p;
 104                 }
 105                 for (i = sz, t = 1; i > 0; i--) {
 106                     char x = (char)((u >> (i * 4 - 4)) & 0xf);
 107                     if ((t == 1) && (x == 0)) {
 108                         *str++ = w;
 109                     } else {
 110                         *str++ = (x > 9) ? 'a' + x - 10 : '0' + x;
 111                         t = 0;
 112                     }
 113                 }
 114                 break;
 115             case 's': /* string */
 116                 s = va_arg (ap, char *);
 117                 while (s && *s)
 118                     *str++ = *s++;
 119                 break;
 120             default:
 121                 *str++ = '?';
 122             }
 123         }
 124     }
 125     va_end (ap);
 126
 127     /* output string */
 128     int n = str - buffer;
 129     if (n < (int)sizeof (buffer) - 1) {
 130         return write (fd, buffer, n);
 131     }
 132     return 0;
 133 }
 134
 135 /* vim: set ts=4 sw=4 et: */