text: /*
   * libc/stdlib/strtoimax.c
   */
  
  #include <ctype.h>
  #include <errno.h>
  #include <limits.h>
  #include <stdlib.h>
  
  /*
   * Convert a string to an intmax_t
   *
   * Ignores 'locale' stuff.  Assumes that the upper and lower case
   * alphabets and digits are each contiguous.
   */
  intmax_t strtoimax(const char * nptr, char ** endptr, int base)
  {
  	const char *s;
  	intmax_t acc, cutoff;
  	int c;
  	int neg, any, cutlim;
  
  	/*
  	 * Skip white space and pick up leading +/- sign if any.
  	 * If base is 0, allow 0x for hex and 0 for octal, else
  	 * assume decimal; if base is already 16, allow 0x.
  	 */
  	s = nptr;
  	do {
  		c = (unsigned char) *s++;
  	} while (isspace(c));
  
  	if (c == '-')
  	{
  		neg = 1;
  		c = *s++;
  	}
  	else
  	{
  		neg = 0;
  		if (c == '+')
  			c = *s++;
  	}
  
  	if ((base == 0 || base == 16) && c == '0' && (*s == 'x' || *s == 'X'))
  	{
  		c = s[1];
  		s += 2;
  		base = 16;
  	}
  
  	if (base == 0)
  		base = c == '0' ? 8 : 10;
  
  	/*
  	 * Compute the cutoff value between legal numbers and illegal
  	 * numbers.  That is the largest legal value, divided by the
  	 * base.  An input number that is greater than this value, if
  	 * followed by a legal input character, is too big.  One that
  	 * is equal to this value may be valid or not; the limit
  	 * between valid and invalid numbers is then based on the last
  	 * digit.  For instance, if the range for intmax_t is
  	 * [-9223372036854775808..9223372036854775807] and the input base
  	 * is 10, cutoff will be set to 922337203685477580 and cutlim to
  	 * either 7 (neg==0) or 8 (neg==1), meaning that if we have
  	 * accumulated a value > 922337203685477580, or equal but the
  	 * next digit is > 7 (or 8), the number is too big, and we will
  	 * return a range error.
  	 *
  	 * Set any if any `digits' consumed; make it negative to indicate
  	 * overflow.
  	 */
  
  	switch (base)
  	{
  	case 4:
  		if (neg)
  		{
  			cutlim = INTMAX_MIN % 4;
  			cutoff = INTMAX_MIN / 4;
  		} else
  		{
  			cutlim = INTMAX_MAX % 4;
  			cutoff = INTMAX_MAX / 4;
  		}
  		break;
  
      case 8:
  		if (neg)
  		{
  			cutlim = INTMAX_MIN % 8;
  			cutoff = INTMAX_MIN / 8;
  		}
  		else
  		{
  			cutlim = INTMAX_MAX % 8;
  			cutoff = INTMAX_MAX / 8;
  		}
  		break;
  
      case 10:
  		if (neg)
  		{
  			cutlim = INTMAX_MIN % 10;
  			cutoff = INTMAX_MIN / 10;
  		}
  		else
  		{
  			cutlim = INTMAX_MAX % 10;
  			cutoff = INTMAX_MAX / 10;
  		}
  		break;
  
      case 16:
  		if (neg)
  		{
  			cutlim = INTMAX_MIN % 16;
  			cutoff = INTMAX_MIN / 16;
  		}
  		else
  		{
  			cutlim = INTMAX_MAX % 16;
  			cutoff = INTMAX_MAX / 16;
  		}
  		break;
  
  	default:
  		cutoff = neg ? INTMAX_MIN : INTMAX_MAX;
  		cutlim = cutoff % base;
  		cutoff /= base;
  		break;
  	}
  
  	if (neg)
  	{
  		if (cutlim > 0)
  		{
  			cutlim -= base;
  			cutoff += 1;
  		}
  		cutlim = -cutlim;
  	}
  
  	for (acc = 0, any = 0;; c = (unsigned char) *s++)
  	{
  		if (isdigit(c))
  			c -= '0';
  		else if (isalpha(c))
  			c -= isupper(c) ? 'A' - 10 : 'a' - 10;
  		else
  			break;
  
  		if (c >= base)
  			break;
  
  		if (any < 0)
  			continue;
  
  		if (neg)
  		{
  			if (acc < cutoff || (acc == cutoff && c > cutlim))
  			{
  				any = -1;
  				acc = INTMAX_MIN;
  				errno = ERANGE;
  			}
  			else
  			{
  				any = 1;
  				acc *= base;
  				acc -= c;
  			}
  		}
  		else
  		{
  			if (acc > cutoff || (acc == cutoff && c > cutlim))
  			{
  				any = -1;
  				acc = INTMAX_MAX;
  				errno = ERANGE;
  			}
  			else
  			{
  				any = 1;
  				acc *= base;
  				acc += c;
  			}
  		}
  	}
  
  	if (endptr != 0)
  		*endptr = (char *) (any ? s - 1 : nptr);
  
  	return (acc);
  }
  