aml/aml_strtoul.c

/*
 * Copyright (c) 2021-2022 Amlogic, Inc. All rights reserved.
 *
 * SPDX-License-Identifier: MIT
 */

#include <limits.h>
#include <errno.h>
#include <stdlib.h>
#include "aml_strtoul.h"
#include "aml_isdigit.h"
#include "aml_isspace.h"
#include "aml_isalpha.h"
#include "aml_isupper.h"

unsigned long strtoul(const char *nptr, char **endptr, int base)
{
	const char *s = nptr;
	unsigned long acc;
	int c;
	unsigned long cutoff;
	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;
	}

	if (base == 0)
		base = c == '0' ? 8 : 10;

	cutoff = (unsigned long)ULONG_MAX / (unsigned long)base;
	cutlim = (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 *= base;
			acc += c;
		}
	}
	if (any < 0) {
		acc = ULONG_MAX;
		errno = ERANGE;
	} else if (neg)
		acc = -acc;
	if (endptr != NULL)
		*endptr = (char *)(any ? s - 1 : nptr);

	return acc;
}