strtoul.c

微操作系统（c＋＋）

/* 
 * Copyright (c) 1995-1994 The University of Utah and
 * the Computer Systems Laboratory at the University of Utah (CSL).
 * All rights reserved.
 *
 * Permission to use, copy, modify and distribute this software is hereby
 * granted provided that (1) source code retains these copyright, permission,
 * and disclaimer notices, and (2) redistributions including binaries
 * reproduce the notices in supporting documentation, and (3) all advertising
 * materials mentioning features or use of this software display the following
 * acknowledgement: ``This product includes software developed by the
 * Computer Systems Laboratory at the University of Utah.''
 *
 * THE UNIVERSITY OF UTAH AND CSL ALLOW FREE USE OF THIS SOFTWARE IN ITS "AS
 * IS" CONDITION.  THE UNIVERSITY OF UTAH AND CSL DISCLAIM ANY LIABILITY OF
 * ANY KIND FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 *
 * CSL requests users of this software to return to [e-mail] any
 * improvements that they make and grant CSL redistribution rights.
 */

#include <ctype.h>
#include <string.h>

unsigned long strtoul(const char *p, char **out_p, int base)
{
	unsigned long v = 0;

	while (isspace(*p))
		p++;
	if (((base == 16) || (base == 0)) &&
	    ((*p == '0') && ((p[1] == 'x') || (p[1] == 'X'))))
	{
		p += 2;
		base = 16;
	}
	if (base == 0)
	{
		if (*p == '0')
			base = 8;
		else
			base = 10;
	}
	while (1)
	{
		char c = *p;
		if ((c >= '0') && (c <= '9') && (c - '0' < base))
			v = (v * base) + (c - '0');
		else if ((c >= 'a') && (c <= 'z') && (c - 'a' + 10 < base))
			v = (v * base) + (c - 'a' + 10);
		else if ((c >= 'A') && (c <= 'Z') && (c - 'A' + 10 < base))
			v = (v * base) + (c - 'A' + 10);
		else
			break;
		p++;
	}

	if (out_p) *out_p = (char*)p;
	return v;
}