dist/ntp/libntp/dofptoa.c

   1 /*      $NetBSD$        */
   2
   3 /*
   4  * dofptoa - do the grunge work to convert an fp number to ascii
   5  */
   6 #include <stdio.h>
   7
   8 #include "ntp_fp.h"
   9 #include "lib_strbuf.h"
  10 #include "ntp_string.h"
  11 #include "ntp_stdlib.h"
  12
  13 char *
  14 dofptoa(
  15         u_fp fpv,
  16         int neg,
  17         short ndec,
  18         int msec
  19         )
  20 {
  21         register u_char *cp, *cpend;
  22         register u_long val;
  23         register short dec;
  24         u_char cbuf[12];
  25         u_char *cpdec;
  26         char *buf;
  27         char *bp;
  28
  29         /*
  30          * Get a string buffer before starting
  31          */
  32         LIB_GETBUF(buf);
  33
  34         /*
  35          * Zero out the buffer
  36          */
  37         memset((char *)cbuf, 0, sizeof cbuf);
  38
  39         /*
  40          * Set the pointers to point at the first
  41          * decimal place.  Get a local copy of the value.
  42          */
  43         cp = cpend = &cbuf[5];
  44         val = fpv;
  45
  46         /*
  47          * If we have to, decode the integral part
  48          */
  49         if (!(val & 0xffff0000))
  50             cp--;
  51         else {
  52                 register u_short sv = (u_short)(val >> 16);
  53                 register u_short tmp;
  54                 register u_short ten = 10;
  55
  56                 do {
  57                         tmp = sv;
  58                         sv = (u_short) (sv/ten);
  59                         *(--cp) = (u_char)(tmp - ((sv<<3) + (sv<<1)));
  60                 } while (sv != 0);
  61         }
  62
  63         /*
  64          * Figure out how much of the fraction to do
  65          */
  66         if (msec) {
  67                 dec = (short)(ndec + 3);
  68                 if (dec < 3)
  69                     dec = 3;
  70                 cpdec = &cbuf[8];
  71         } else {
  72                 dec = ndec;
  73                 cpdec = cpend;
  74         }
  75
  76         if (dec > 6)
  77             dec = 6;
  78
  79         if (dec > 0) {
  80                 do {
  81                         val &= 0xffff;
  82                         val = (val << 3) + (val << 1);
  83                         *cpend++ = (u_char)(val >> 16);
  84                 } while (--dec > 0);
  85         }
  86
  87         if (val & 0x8000) {
  88                 register u_char *tp;
  89                 /*
  90                  * Round it. Ick.
  91                  */
  92                 tp = cpend;
  93                 *(--tp) += 1;
  94                 while (*tp >= 10) {
  95                         *tp = 0;
  96                         *(--tp) += 1;
  97                 }
  98         }
  99
 100         /*
 101          * Remove leading zeroes if necessary
 102          */
 103         while (cp < (cpdec -1) && *cp == 0)
 104             cp++;
 105
 106         /*
 107          * Copy it into the buffer, asciizing as we go.
 108          */
 109         bp = buf;
 110         if (neg)
 111             *bp++ = '-';
 112
 113         while (cp < cpend) {
 114                 if (cp == cpdec)
 115                     *bp++ = '.';
 116                 *bp++ = (char)(*cp++ + '0');
 117         }
 118         *bp = '\0';
 119         return buf;
 120 }