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/kernel.h>
11 #include <linux/types.h>
12 #include <linux/string.h>
13 
14 #ifndef __HAVE_ARCH_STRSTR
15 /**
16  * strstr - Find the first substring in a %NUL terminated string
17  * @s1: The string to be searched
18  * @s2: The string to search for
19  */
20 char *strstr(const char *s1, const char *s2)
21 {
22 	size_t l1, l2;
23 
24 	l2 = strlen(s2);
25 	if (!l2)
26 		return (char *)s1;
27 	l1 = strlen(s1);
28 	while (l1 >= l2) {
29 		l1--;
30 		if (!memcmp(s1, s2, l2))
31 			return (char *)s1;
32 		s1++;
33 	}
34 	return NULL;
35 }
36 #endif
37 
38 #ifndef __HAVE_ARCH_STRNCMP
39 /**
40  * strncmp - Compare two length-limited strings
41  * @cs: One string
42  * @ct: Another string
43  * @count: The maximum number of bytes to compare
44  */
45 int strncmp(const char *cs, const char *ct, size_t count)
46 {
47 	unsigned char c1, c2;
48 
49 	while (count) {
50 		c1 = *cs++;
51 		c2 = *ct++;
52 		if (c1 != c2)
53 			return c1 < c2 ? -1 : 1;
54 		if (!c1)
55 			break;
56 		count--;
57 	}
58 	return 0;
59 }
60 #endif
61 
62 /* Works only for digits and letters, but small and fast */
63 #define TOLOWER(x) ((x) | 0x20)
64 
65 static unsigned int simple_guess_base(const char *cp)
66 {
67 	if (cp[0] == '0') {
68 		if (TOLOWER(cp[1]) == 'x' && isxdigit(cp[2]))
69 			return 16;
70 		else
71 			return 8;
72 	} else {
73 		return 10;
74 	}
75 }
76 
77 /**
78  * simple_strtoull - convert a string to an unsigned long long
79  * @cp: The start of the string
80  * @endp: A pointer to the end of the parsed string will be placed here
81  * @base: The number base to use
82  */
83 
84 unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int base)
85 {
86 	unsigned long long result = 0;
87 
88 	if (!base)
89 		base = simple_guess_base(cp);
90 
91 	if (base == 16 && cp[0] == '0' && TOLOWER(cp[1]) == 'x')
92 		cp += 2;
93 
94 	while (isxdigit(*cp)) {
95 		unsigned int value;
96 
97 		value = isdigit(*cp) ? *cp - '0' : TOLOWER(*cp) - 'a' + 10;
98 		if (value >= base)
99 			break;
100 		result = result * base + value;
101 		cp++;
102 	}
103 	if (endp)
104 		*endp = (char *)cp;
105 
106 	return result;
107 }
108 
109 long simple_strtol(const char *cp, char **endp, unsigned int base)
110 {
111 	if (*cp == '-')
112 		return -simple_strtoull(cp + 1, endp, base);
113 
114 	return simple_strtoull(cp, endp, base);
115 }
116