com32/lib/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' &&
  46          (nptr[1] == 'x' || nptr[1] == 'X') ) {
  47       n -= 2;
  48       nptr += 2;
  49       base = 16;
  50     } else if ( n >= 1 && nptr[0] == '0' ) {
  51       n--;
  52       nptr++;
  53       base = 8;
  54     } else {
  55       base = 10;
  56     }
  57   } else if ( base == 16 ) {
  58     if ( n >= 2 && nptr[0] == '0' &&
  59          (nptr[1] == 'x' || nptr[1] == 'X') ) {
  60       n -= 2;
  61       nptr += 2;
  62     }
  63   }
  64
  65   while ( n && (d = digitval(*nptr)) >= 0 && d < base ) {
  66     v = v*base + d;
  67     n--;
  68     nptr++;
  69   }
  70
  71   if ( endptr )
  72     *endptr = (char *)nptr;
  73
  74   return minus ? -v : v;
  75 }