1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Taken from:
  4 *  linux/lib/string.c
  5 *
  6 *  Copyright (C) 1991, 1992  Linus Torvalds
  7 */
  8
  9#include <linux/ctype.h>
 10#include <linux/types.h>
 11#include <linux/string.h>
 12
 13#ifndef __HAVE_ARCH_STRSTR
 14/**
 15 * strstr - Find the first substring in a %NUL terminated string
 16 * @s1: The string to be searched
 17 * @s2: The string to search for
 18 */
 19char *strstr(const char *s1, const char *s2)
 20{
 21	size_t l1, l2;
 22
 23	l2 = strlen(s2);
 24	if (!l2)
 25		return (char *)s1;
 26	l1 = strlen(s1);
 27	while (l1 >= l2) {
 28		l1--;
 29		if (!memcmp(s1, s2, l2))
 30			return (char *)s1;
 31		s1++;
 32	}
 33	return NULL;
 34}
 35#endif
 36
 37#ifndef __HAVE_ARCH_STRNCMP
 38/**
 39 * strncmp - Compare two length-limited strings
 40 * @cs: One string
 41 * @ct: Another string
 42 * @count: The maximum number of bytes to compare
 43 */
 44int strncmp(const char *cs, const char *ct, size_t count)
 45{
 46	unsigned char c1, c2;
 47
 48	while (count) {
 49		c1 = *cs++;
 50		c2 = *ct++;
 51		if (c1 != c2)
 52			return c1 < c2 ? -1 : 1;
 53		if (!c1)
 54			break;
 55		count--;
 56	}
 57	return 0;
 58}
 59#endif
 60
 61/* Works only for digits and letters, but small and fast */
 62#define TOLOWER(x) ((x) | 0x20)
 63
 64static unsigned int simple_guess_base(const char *cp)
 65{
 66	if (cp[0] == '0') {
 67		if (TOLOWER(cp[1]) == 'x' && isxdigit(cp[2]))
 68			return 16;
 69		else
 70			return 8;
 71	} else {
 72		return 10;
 73	}
 74}
 75
 76/**
 77 * simple_strtoull - convert a string to an unsigned long long
 78 * @cp: The start of the string
 79 * @endp: A pointer to the end of the parsed string will be placed here
 80 * @base: The number base to use
 81 */
 82
 83unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int base)
 84{
 85	unsigned long long result = 0;
 86
 87	if (!base)
 88		base = simple_guess_base(cp);
 89
 90	if (base == 16 && cp[0] == '0' && TOLOWER(cp[1]) == 'x')
 91		cp += 2;
 92
 93	while (isxdigit(*cp)) {
 94		unsigned int value;
 95
 96		value = isdigit(*cp) ? *cp - '0' : TOLOWER(*cp) - 'a' + 10;
 97		if (value >= base)
 98			break;
 99		result = result * base + value;
100		cp++;
101	}
102	if (endp)
103		*endp = (char *)cp;
104
105	return result;
106}
107
108long simple_strtol(const char *cp, char **endp, unsigned int base)
109{
110	if (*cp == '-')
111		return -simple_strtoull(cp + 1, endp, base);
112
113	return simple_strtoull(cp, endp, base);
114}