LXR linux/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
  18int 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
  26int 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 = *s1 - *s2;
  34                if (delta)
  35                        return delta;
  36                s1++;
  37                s2++;
  38        }
  39        return 0;
  40}
  41
  42int 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
  58size_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
  69unsigned 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
  80static 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
  99unsigned 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 */
 128size_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 */
 142char *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}
 158