strtoul.c File Reference

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

Include dependency graph for strtoul.c:

Go to the source code of this file.

Functions
unsigned long	strtoul (char *nptr, char **endptr, int base) const

Function Documentation

strtoul()

unsigned long strtoul	(	char*	nptr,
		char**	endptr,
		int	base
	)		const

Definition at line 78 of file strtoul.c.

{
    register const char* s = nptr;
    register unsigned long acc;
    register int c;
    register unsigned long cutoff;
    register int neg = 0, any, cutlim;

    /*
     * See strtol for comments as to the logic used.
     */
    do
    {
        c = *s++;
    } while(isspace(c));
    if(c == '-')
    {
        neg = 1;
        c = *s++;
    }
    else if(c == '+')
    {
        c = *s++;
    }
    if((base == 0 || base == 16) && c == '0' && (*s == 'x' || *s == 'X'))
    {
        c = s[1];
        s += 2;
        base = 16;
    }
    else if((base == 0 || base == 2) && c == '0' && (*s == 'b' || *s == 'B'))
    {
        c = s[1];
        s += 2;
        base = 2;
    }
    if(base == 0)
    {
        {
            base = c == '0' ? 8 : 10;
        }
    }
    cutoff = (unsigned long)ULONG_MAX / (unsigned long)base;
    cutlim = (int)((unsigned long)ULONG_MAX % (unsigned long)base);
    for(acc = 0, any = 0;; c = *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 || acc > cutoff || (acc == cutoff && c > cutlim))
        {
            any = -1;
        }
        else
        {
            any = 1;
            acc *= (unsigned long)base;
            acc += (unsigned long)c;
        }
    }
    if(any < 0)
    {
        acc = ULONG_MAX;
        //      errno = ERANGE;
    }
    else if(neg)
    {
        acc = -acc;
    }
    if(endptr != 0)
    {
        *endptr = (char*)(uintptr_t)(any ? s - 1 : nptr);
    }
    return (acc);
}

References isalpha(), isdigit(), isspace(), isupper(), and ULONG_MAX.