sys/src/libc/port/strtol.c

   1 #include <u.h>
   2 #include <libc.h>
   3
   4 #define LONG_MAX        2147483647L
   5 #define LONG_MIN        -2147483648L
   6
   7 long
   8 strtol(char *nptr, char **endptr, int base)
   9 {
  10         char *p;
  11         long n, nn, m;
  12         int c, ovfl, v, neg, ndig;
  13
  14         p = nptr;
  15         neg = 0;
  16         n = 0;
  17         ndig = 0;
  18         ovfl = 0;
  19
  20         /*
  21          * White space
  22          */
  23         for(;; p++) {
  24                 switch(*p) {
  25                 case ' ':
  26                 case '\t':
  27                 case '\n':
  28                 case '\f':
  29                 case '\r':
  30                 case '\v':
  31                         continue;
  32                 }
  33                 break;
  34         }
  35
  36         /*
  37          * Sign
  38          */
  39         if(*p=='-' || *p=='+')
  40                 if(*p++ == '-')
  41                         neg = 1;
  42
  43         /*
  44          * Base
  45          */
  46         if(base==0) {
  47                 base = 10;
  48                 if(*p == '0') {
  49                         base = 8;
  50                         if(p[1]=='x' || p[1]=='X') {
  51                                 p += 2;
  52                                 base = 16;
  53                         }
  54                 }
  55         } else
  56         if(base==16 && *p=='0'){
  57                 if(p[1]=='x' || p[1]=='X')
  58                         p += 2;
  59         } else
  60         if(base<0 || 36<base)
  61                 goto Return;
  62
  63         /*
  64          * Non-empty sequence of digits
  65          */
  66         m = LONG_MAX/base;
  67         for(;; p++,ndig++){
  68                 c = *p;
  69                 v = base;
  70                 if('0'<=c && c<='9')
  71                         v = c - '0';
  72                 else
  73                 if('a'<=c && c<='z')
  74                         v = c - 'a' + 10;
  75                 else
  76                 if('A'<=c && c<='Z')
  77                         v = c - 'A' + 10;
  78                 if(v >= base)
  79                         break;
  80                 if(n > m)
  81                         ovfl = 1;
  82                 nn = n*base + v;
  83                 if(nn < n)
  84                         ovfl = 1;
  85                 n = nn;
  86         }
  87
  88 Return:
  89         if(ndig == 0)
  90                 p = nptr;
  91         if(endptr)
  92                 *endptr = p;
  93         if(ovfl){
  94                 if(neg)
  95                         return LONG_MIN;
  96                 return LONG_MAX;
  97         }
  98         if(neg)
  99                 return -n;
 100         return n;
 101 }