arch/x86/boot/string.c

   1 /* -*- linux-c -*- ------------------------------------------------------- *
   2  *
   3  *   Copyright (C) 1991, 1992 Linus Torvalds
   4  *   Copyright 2007 rPath, Inc. - All Rights Reserved
   5  *
   6  *   This file is part of the Linux kernel, and is made available under
   7  *   the terms of the GNU General Public License version 2.
   8  *
   9  * ----------------------------------------------------------------------- */
  10
  11 /*
  12  * Very basic string functions
  13  */
  14
  15 #include <linux/types.h>
  16 #include "ctype.h"
  17
  18 int memcmp(const void *s1, const void *s2, size_t len)
  19 {
  20         u8 diff;
  21         asm("repe; cmpsb; setnz %0"
  22             : "=qm" (diff), "+D" (s1), "+S" (s2), "+c" (len));
  23         return diff;
  24 }
  25
  26 int strcmp(const char *str1, const char *str2)
  27 {
  28         const unsigned char *s1 = (const unsigned char *)str1;
  29         const unsigned char *s2 = (const unsigned char *)str2;
  30         int delta = 0;
  31
  32         while (*s1 || *s2) {
  33                 delta = *s2 - *s1;
  34                 if (delta)
  35                         return delta;
  36                 s1++;
  37                 s2++;
  38         }
  39         return 0;
  40 }
  41
  42 int strncmp(const char *cs, const char *ct, size_t count)
  43 {
  44         unsigned char c1, c2;
  45
  46         while (count) {
  47                 c1 = *cs++;
  48                 c2 = *ct++;
  49                 if (c1 != c2)
  50                         return c1 < c2 ? -1 : 1;
  51                 if (!c1)
  52                         break;
  53                 count--;
  54         }
  55         return 0;
  56 }
  57
  58 size_t strnlen(const char *s, size_t maxlen)
  59 {
  60         const char *es = s;
  61         while (*es && maxlen) {
  62                 es++;
  63                 maxlen--;
  64         }
  65
  66         return (es - s);
  67 }
  68
  69 unsigned int atou(const char *s)
  70 {
  71         unsigned int i = 0;
  72         while (isdigit(*s))
  73                 i = i * 10 + (*s++ - '0');
  74         return i;
  75 }
  76
  77 /* Works only for digits and letters, but small and fast */
  78 #define TOLOWER(x) ((x) | 0x20)
  79
  80 static unsigned int simple_guess_base(const char *cp)
  81 {
  82         if (cp[0] == '0') {
  83                 if (TOLOWER(cp[1]) == 'x' && isxdigit(cp[2]))
  84                         return 16;
  85                 else
  86                         return 8;
  87         } else {
  88                 return 10;
  89         }
  90 }
  91
  92 /**
  93  * simple_strtoull - convert a string to an unsigned long long
  94  * @cp: The start of the string
  95  * @endp: A pointer to the end of the parsed string will be placed here
  96  * @base: The number base to use
  97  */
  98
  99 unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int base)
 100 {
 101         unsigned long long result = 0;
 102
 103         if (!base)
 104                 base = simple_guess_base(cp);
 105
 106         if (base == 16 && cp[0] == '0' && TOLOWER(cp[1]) == 'x')
 107                 cp += 2;
 108
 109         while (isxdigit(*cp)) {
 110                 unsigned int value;
 111
 112                 value = isdigit(*cp) ? *cp - '0' : TOLOWER(*cp) - 'a' + 10;
 113                 if (value >= base)
 114                         break;
 115                 result = result * base + value;
 116                 cp++;
 117         }
 118         if (endp)
 119                 *endp = (char *)cp;
 120
 121         return result;
 122 }
 123
 124 /**
 125  * strlen - Find the length of a string
 126  * @s: The string to be sized
 127  */
 128 size_t strlen(const char *s)
 129 {
 130         const char *sc;
 131
 132         for (sc = s; *sc != '\0'; ++sc)
 133                 /* nothing */;
 134         return sc - s;
 135 }
 136
 137 /**
 138  * strstr - Find the first substring in a %NUL terminated string
 139  * @s1: The string to be searched
 140  * @s2: The string to search for
 141  */
 142 char *strstr(const char *s1, const char *s2)
 143 {
 144         size_t l1, l2;
 145
 146         l2 = strlen(s2);
 147         if (!l2)
 148                 return (char *)s1;
 149         l1 = strlen(s1);
 150         while (l1 >= l2) {
 151                 l1--;
 152                 if (!memcmp(s1, s2, l2))
 153                         return (char *)s1;
 154                 s1++;
 155         }
 156         return NULL;
 157 }