dist/ntp/libntp/atolfp.c

   1 /*      $NetBSD$        */
   2
   3 /*
   4  * atolfp - convert an ascii string to an l_fp number
   5  */
   6 #include <stdio.h>
   7 #include <ctype.h>
   8
   9 #include "ntp_fp.h"
  10 #include "ntp_string.h"
  11
  12 /*
  13  * Powers of 10
  14  */
  15 static u_long ten_to_the_n[10] = {
  16         0,
  17         10,
  18         100,
  19         1000,
  20         10000,
  21         100000,
  22         1000000,
  23         10000000,
  24         100000000,
  25         1000000000,
  26 };
  27
  28
  29 int
  30 atolfp(
  31         const char *str,
  32         l_fp *lfp
  33         )
  34 {
  35         register const char *cp;
  36         register u_long dec_i;
  37         register u_long dec_f;
  38         char *ind;
  39         int ndec;
  40         int isneg;
  41         static const char *digits = "0123456789";
  42
  43         isneg = 0;
  44         dec_i = dec_f = 0;
  45         ndec = 0;
  46         cp = str;
  47
  48         /*
  49          * We understand numbers of the form:
  50          *
  51          * [spaces][-|+][digits][.][digits][spaces|\n|\0]
  52          */
  53         while (isspace((int)*cp))
  54             cp++;
  55
  56         if (*cp == '-') {
  57                 cp++;
  58                 isneg = 1;
  59         }
  60
  61         if (*cp == '+')
  62             cp++;
  63
  64         if (*cp != '.' && !isdigit((int)*cp))
  65             return 0;
  66
  67         while (*cp != '\0' && (ind = strchr(digits, *cp)) != NULL) {
  68                 dec_i = (dec_i << 3) + (dec_i << 1);    /* multiply by 10 */
  69                 dec_i += (ind - digits);
  70                 cp++;
  71         }
  72
  73         if (*cp != '\0' && !isspace((int)*cp)) {
  74                 if (*cp++ != '.')
  75                     return 0;
  76
  77                 while (ndec < 9 && *cp != '\0'
  78                        && (ind = strchr(digits, *cp)) != NULL) {
  79                         ndec++;
  80                         dec_f = (dec_f << 3) + (dec_f << 1);    /* *10 */
  81                         dec_f += (ind - digits);
  82                         cp++;
  83                 }
  84
  85                 while (isdigit((int)*cp))
  86                     cp++;
  87
  88                 if (*cp != '\0' && !isspace((int)*cp))
  89                     return 0;
  90         }
  91
  92         if (ndec > 0) {
  93                 register u_long tmp;
  94                 register u_long bit;
  95                 register u_long ten_fact;
  96
  97                 ten_fact = ten_to_the_n[ndec];
  98
  99                 tmp = 0;
 100                 bit = 0x80000000;
 101                 while (bit != 0) {
 102                         dec_f <<= 1;
 103                         if (dec_f >= ten_fact) {
 104                                 tmp |= bit;
 105                                 dec_f -= ten_fact;
 106                         }
 107                         bit >>= 1;
 108                 }
 109                 if ((dec_f << 1) > ten_fact)
 110                     tmp++;
 111                 dec_f = tmp;
 112         }
 113
 114         if (isneg)
 115             M_NEG(dec_i, dec_f);
 116
 117         lfp->l_ui = dec_i;
 118         lfp->l_uf = dec_f;
 119         return 1;
 120 }