sys/src/libc/port/strtoull.c

   1 #include <u.h>
   2 #include <libc.h>
   3
   4 #define UVLONG_MAX      (1LL<<63)
   5
   6 uvlong
   7 strtoull(char *nptr, char **endptr, int base)
   8 {
   9         char *p;
  10         uvlong n, nn, m;
  11         int c, ovfl, v, neg, ndig;
  12
  13         p = nptr;
  14         neg = 0;
  15         n = 0;
  16         ndig = 0;
  17         ovfl = 0;
  18
  19         /*
  20          * White space
  21          */
  22         for(;; p++) {
  23                 switch(*p) {
  24                 case ' ':
  25                 case '\t':
  26                 case '\n':
  27                 case '\f':
  28                 case '\r':
  29                 case '\v':
  30                         continue;
  31                 }
  32                 break;
  33         }
  34
  35         /*
  36          * Sign
  37          */
  38         if(*p == '-' || *p == '+')
  39                 if(*p++ == '-')
  40                         neg = 1;
  41
  42         /*
  43          * Base
  44          */
  45         if(base == 0) {
  46                 base = 10;
  47                 if(*p == '0') {
  48                         base = 8;
  49                         if(p[1] == 'x' || p[1] == 'X'){
  50                                 p += 2;
  51                                 base = 16;
  52                         }
  53                 }
  54         } else
  55         if(base == 16 && *p == '0') {
  56                 if(p[1] == 'x' || p[1] == 'X')
  57                         p += 2;
  58         } else
  59         if(base < 0 || 36 < base)
  60                 goto Return;
  61
  62         /*
  63          * Non-empty sequence of digits
  64          */
  65         m = UVLONG_MAX/base;
  66         for(;; p++,ndig++) {
  67                 c = *p;
  68                 v = base;
  69                 if('0' <= c && c <= '9')
  70                         v = c - '0';
  71                 else
  72                 if('a' <= c && c <= 'z')
  73                         v = c - 'a' + 10;
  74                 else
  75                 if('A' <= c && c <= 'Z')
  76                         v = c - 'A' + 10;
  77                 if(v >= base)
  78                         break;
  79                 if(n > m)
  80                         ovfl = 1;
  81                 nn = n*base + v;
  82                 if(nn < n)
  83                         ovfl = 1;
  84                 n = nn;
  85         }
  86
  87 Return:
  88         if(ndig == 0)
  89                 p = nptr;
  90         if(endptr)
  91                 *endptr = p;
  92         if(ovfl)
  93                 return UVLONG_MAX;
  94         if(neg)
  95                 return -n;
  96         return n;
  97 }