contrib/ntp/libntp/atolfp.c

   1 /*
   2  * atolfp - convert an ascii string to an l_fp number
   3  */
   4 #include <config.h>
   5 #include <stdio.h>
   6 #include <ctype.h>
   7
   8 #include "ntp_fp.h"
   9 #include "ntp_string.h"
  10 #include "ntp_assert.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         REQUIRE(str != NULL);
  44
  45         isneg = 0;
  46         dec_i = dec_f = 0;
  47         ndec = 0;
  48         cp = str;
  49
  50         /*
  51          * We understand numbers of the form:
  52          *
  53          * [spaces][-|+][digits][.][digits][spaces|\n|\0]
  54          */
  55         while (isspace((unsigned char)*cp))
  56             cp++;
  57
  58         if (*cp == '-') {
  59                 cp++;
  60                 isneg = 1;
  61         }
  62
  63         if (*cp == '+')
  64             cp++;
  65
  66         if (*cp != '.' && !isdigit((unsigned char)*cp))
  67             return 0;
  68
  69         while (*cp != '\0' && (ind = strchr(digits, *cp)) != NULL) {
  70                 dec_i = (dec_i << 3) + (dec_i << 1);    /* multiply by 10 */
  71                 dec_i += (u_long)(ind - digits);
  72                 cp++;
  73         }
  74
  75         if (*cp != '\0' && !isspace((unsigned char)*cp)) {
  76                 if (*cp++ != '.')
  77                     return 0;
  78
  79                 while (ndec < 9 && *cp != '\0'
  80                        && (ind = strchr(digits, *cp)) != NULL) {
  81                         ndec++;
  82                         dec_f = (dec_f << 3) + (dec_f << 1);    /* *10 */
  83                         dec_f += (u_long)(ind - digits);
  84                         cp++;
  85                 }
  86
  87                 while (isdigit((unsigned char)*cp))
  88                     cp++;
  89
  90                 if (*cp != '\0' && !isspace((unsigned char)*cp))
  91                     return 0;
  92         }
  93
  94         if (ndec > 0) {
  95                 register u_long tmp;
  96                 register u_long bit;
  97                 register u_long ten_fact;
  98
  99                 ten_fact = ten_to_the_n[ndec];
 100
 101                 tmp = 0;
 102                 bit = 0x80000000;
 103                 while (bit != 0) {
 104                         dec_f <<= 1;
 105                         if (dec_f >= ten_fact) {
 106                                 tmp |= bit;
 107                                 dec_f -= ten_fact;
 108                         }
 109                         bit >>= 1;
 110                 }
 111                 if ((dec_f << 1) > ten_fact)
 112                     tmp++;
 113                 dec_f = tmp;
 114         }
 115
 116         if (isneg)
 117             M_NEG(dec_i, dec_f);
 118
 119         lfp->l_ui = dec_i;
 120         lfp->l_uf = dec_f;
 121         return 1;
 122 }