dos/strntoumax.c

   1 /*
   2  * strntoumax.c
   3  *
   4  * The strntoumax() function and associated
   5  */
   6
   7 #include <stddef.h>
   8 #include <stdint.h>
   9 #include <ctype.h>
  10
  11 static inline int digitval(int ch)
  12 {
  13     if (ch >= '0' && ch <= '9') {
  14         return ch - '0';
  15     } else if (ch >= 'A' && ch <= 'Z') {
  16         return ch - 'A' + 10;
  17     } else if (ch >= 'a' && ch <= 'z') {
  18         return ch - 'a' + 10;
  19     } else {
  20         return -1;
  21     }
  22 }
  23
  24 uintmax_t strntoumax(const char *nptr, char **endptr, int base, size_t n)
  25 {
  26     int minus = 0;
  27     uintmax_t v = 0;
  28     int d;
  29
  30     while (n && isspace((unsigned char)*nptr)) {
  31         nptr++;
  32         n--;
  33     }
  34
  35     /* Single optional + or - */
  36     if (n && *nptr == '-') {
  37         minus = 1;
  38         nptr++;
  39         n--;
  40     } else if (n && *nptr == '+') {
  41         nptr++;
  42     }
  43
  44     if (base == 0) {
  45         if (n >= 2 && nptr[0] == '0' && (nptr[1] == 'x' || nptr[1] == 'X')) {
  46             n -= 2;
  47             nptr += 2;
  48             base = 16;
  49         } else if (n >= 1 && nptr[0] == '0') {
  50             n--;
  51             nptr++;
  52             base = 8;
  53         } else {
  54             base = 10;
  55         }
  56     } else if (base == 16) {
  57         if (n >= 2 && nptr[0] == '0' && (nptr[1] == 'x' || nptr[1] == 'X')) {
  58             n -= 2;
  59             nptr += 2;
  60         }
  61     }
  62
  63     while (n && (d = digitval(*nptr)) >= 0 && d < base) {
  64         v = v * base + d;
  65         n--;
  66         nptr++;
  67     }
  68
  69     if (endptr)
  70         *endptr = (char *)nptr;
  71
  72     return minus ? -v : v;
  73 }