source: trunk/sys/dietlibc/strtoull.c @ 112

#include <ctype.h>
#include <stdlib.h>
#include <errno.h>
#include <limits.h>
#include <inttypes.h>

unsigned long long int strtoull(const char *ptr, char **endptr, int base)
{
  int neg = 0, overflow = 0;
  long long int v=0;
  const char* orig;
  const char* nptr=ptr;

  while(isspace(*nptr)) ++nptr;

  if (*nptr == '-') { neg=1; nptr++; }
  else if (*nptr == '+') ++nptr;
  orig=nptr;
  if (base==16 && nptr[0]=='0') goto skip0x;
  if (base) {
    register unsigned int b=base-2;
    if (b>34) { errno=EINVAL; return 0; }
  } else {
    if (*nptr=='0') {
      base=8;
skip0x:
      if (((*(nptr+1)=='x')||(*(nptr+1)=='X')) && isxdigit(nptr[2])) {
        nptr+=2;
        base=16;
      }
    } else
      base=10;
  }
  while(*nptr) {
    register unsigned char c=*nptr;
    c=(c>='a'?c-'a'+10:c>='A'?c-'A'+10:c<='9'?c-'0':0xff);
    if (c>=base) break; /* out of base */
    {
      register unsigned long x=(v&0xff)*base+c;
      register unsigned long long w=(v>>8)*base+(x>>8);
      if (w>(ULLONG_MAX>>8)) overflow=1;
      v=(w<<8)+(x&0xff);
    }
    ++nptr;
  }
  if (nptr==orig) {             /* no conversion done */
    nptr=ptr;
    errno=EINVAL;
    v=0;
  }
  if (endptr) *endptr=(char *)nptr;
  if (overflow) {
    errno=ERANGE;
    return ULLONG_MAX;
  }
  return (neg?-v:v);
}

/* die, BSD, die!!! */
unsigned long long int strtouq(const char *nptr, char **endptr, int base)
        __attribute__((alias("strtoull")));

uintmax_t strtoumax(const char *nptr, char **endptr, int base)
        __attribute__((alias("strtoull")));