cvt.c

00001 #include <math.h>
00002 #define CVTBUFSIZE 80
00003 static char CVTBUF[CVTBUFSIZE];
00004 
00005 static char *cvt(double arg, int ndigits, int *decpt, int *sign, char *buf, int eflag)
00006 {
00007   int r2;
00008   double fi, fj;
00009   char *p, *p1;
00010 
00011   if (ndigits < 0) ndigits = 0;
00012   if (ndigits >= CVTBUFSIZE - 1) ndigits = CVTBUFSIZE - 2;
00013   r2 = 0;
00014   *sign = 0;
00015   p = &buf[0];
00016   if (arg < 0)
00017   {
00018     *sign = 1;
00019     arg = -arg;
00020   }
00021   arg = modf(arg, &fi);
00022   p1 = &buf[CVTBUFSIZE];
00023 
00024   if (fi != 0) 
00025   {
00026     p1 = &buf[CVTBUFSIZE];
00027     while (fi != 0) 
00028     {
00029       fj = modf(fi / 10, &fi);
00030       *--p1 = (int)((fj + .03) * 10) + '0';
00031       r2++;
00032     }
00033     while (p1 < &buf[CVTBUFSIZE]) *p++ = *p1++;
00034   } 
00035   else if (arg > 0)
00036   {
00037     while ((fj = arg * 10) < 1) 
00038     {
00039       arg = fj;
00040       r2--;
00041     }
00042   }
00043   p1 = &buf[ndigits];
00044   if (eflag == 0) p1 += r2;
00045   *decpt = r2;
00046   if (p1 < &buf[0]) 
00047   {
00048     buf[0] = '\0';
00049     return buf;
00050   }
00051   while (p <= p1 && p < &buf[CVTBUFSIZE])
00052   {
00053     arg *= 10;
00054     arg = modf(arg, &fj);
00055     *p++ = (int) fj + '0';
00056   }
00057   if (p1 >= &buf[CVTBUFSIZE]) 
00058   {
00059     buf[CVTBUFSIZE - 1] = '\0';
00060     return buf;
00061   }
00062   p = p1;
00063   *p1 += 5;
00064   while (*p1 > '9') 
00065   {
00066     *p1 = '0';
00067     if (p1 > buf)
00068       ++*--p1;
00069     else 
00070     {
00071       *p1 = '1';
00072       (*decpt)++;
00073       if (eflag == 0) 
00074       {
00075         if (p > buf) *p = '0';
00076         p++;
00077       }
00078     }
00079   }
00080   *p = '\0';
00081   return buf;
00082 }
00083 
00084 char *ecvt(double arg, int ndigits, int *decpt, int *sign)
00085 {
00086   return cvt(arg, ndigits, decpt, sign, CVTBUF, 1);
00087 }
00088 
00089 char *ecvtbuf(double arg, int ndigits, int *decpt, int *sign, char *buf)
00090 {
00091   return cvt(arg, ndigits, decpt, sign, buf, 1);
00092 }
00093 
00094 char *fcvt(double arg, int ndigits, int *decpt, int *sign)
00095 {
00096   return cvt(arg, ndigits, decpt, sign, CVTBUF, 0);
00097 }
00098 
00099 char *fcvtbuf(double arg, int ndigits, int *decpt, int *sign, char *buf)
00100 {
00101   return cvt(arg, ndigits, decpt, sign, buf, 0);
00102 }