lib/ack/libp/cvt.c

   1 /* $Header$ */
   2 #ifndef NOFLOAT
   3
   4 #if __STDC__
   5 #include <float.h>
   6 #else
   7 #include <math.h>
   8 #define DBL_MAX M_MAX_D
   9 #endif
  10
  11 static char *cvt();
  12 #define NDIGITS 128
  13
  14 char *
  15 _ecvt(value, ndigit, decpt, sign)
  16         double value;
  17         int ndigit, *decpt, *sign;
  18 {
  19         return cvt(value, ndigit, decpt, sign, 1);
  20 }
  21
  22 char *
  23 _fcvt(value, ndigit, decpt, sign)
  24         double value;
  25         int ndigit, *decpt, *sign;
  26 {
  27         return cvt(value, ndigit, decpt, sign, 0);
  28 }
  29
  30 static struct powers_of_10 {
  31         double pval;
  32         double rpval;
  33         int exp;
  34 } p10[] = {
  35         1.0e32, 1.0e-32, 32,
  36         1.0e16, 1.0e-16, 16,
  37         1.0e8, 1.0e-8, 8,
  38         1.0e4, 1.0e-4, 4,
  39         1.0e2, 1.0e-2, 2,
  40         1.0e1, 1.0e-1, 1,
  41         1.0e0, 1.0e0, 0
  42 };
  43
  44 static char *
  45 cvt(value, ndigit, decpt, sign, ecvtflag)
  46         double value;
  47         int ndigit, *decpt, *sign;
  48 {
  49         static char buf[NDIGITS+1];
  50         register char *p = buf;
  51         register char *pe;
  52
  53         if (ndigit < 0) ndigit = 0;
  54         if (ndigit > NDIGITS) ndigit = NDIGITS;
  55         pe = &buf[ndigit];
  56         buf[0] = '\0';
  57
  58         *sign = 0;
  59         if (value < 0) {
  60                 *sign = 1;
  61                 value = -value;
  62         }
  63
  64         *decpt = 0;
  65         if (value >= DBL_MAX) {
  66                 value = DBL_MAX;
  67         }
  68         if (value != 0.0) {
  69                 register struct powers_of_10 *pp = &p10[0];
  70
  71                 if (value >= 10.0) do {
  72                         while (value >= pp->pval) {
  73                                 value *= pp->rpval;
  74                                 *decpt += pp->exp;
  75                         }
  76                 } while ((++pp)->exp > 0);
  77
  78                 pp = &p10[0];
  79                 if (value < 1.0) do {
  80                         while (value * pp->pval < 10.0) {
  81                                 value *= pp->pval;
  82                                 *decpt -= pp->exp;
  83                         }
  84                 } while ((++pp)->exp > 0);
  85
  86                 (*decpt)++;     /* because now value in [1.0, 10.0) */
  87         }
  88         if (! ecvtflag) {
  89                 /* for fcvt() we need ndigit digits behind the dot */
  90                 pe += *decpt;
  91                 if (pe > &buf[NDIGITS]) pe = &buf[NDIGITS];
  92         }
  93         while (p <= pe) {
  94                 *p++ = (int)value + '0';
  95                 value = 10.0 * (value - (int)value);
  96         }
  97         if (pe >= buf) {
  98                 p = pe;
  99                 *p += 5;        /* round of at the end */
 100                 while (*p > '9') {
 101                         *p = '0';
 102                         if (p > buf) ++*--p;
 103                         else {
 104                                 *p = '1';
 105                                 ++*decpt;
 106                                 if (! ecvtflag) {
 107                                         /* maybe add another digit at the end,
 108                                            because the point was shifted right
 109                                         */
 110                                         if (pe > buf) *pe = '0';
 111                                         pe++;
 112                                 }
 113                         }
 114                 }
 115                 *pe = '\0';
 116         }
 117         return buf;
 118 }
 119 #endif