string.c

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/* -*- linux-c -*- ------------------------------------------------------- *
 *
 *   Copyright (C) 1991, 1992 Linus Torvalds
 *   Copyright 2007 rPath, Inc. - All Rights Reserved
 *
 *   This file is part of the Linux kernel, and is made available under
 *   the terms of the GNU General Public License version 2.
 *
 * ----------------------------------------------------------------------- */

/*
 * Very basic string functions
 */

#include "boot.h"

int strcmp(const char *str1, const char *str2)
{
    const unsigned char *s1 = (const unsigned char *)str1;
    const unsigned char *s2 = (const unsigned char *)str2;
    int delta = 0;

    while (*s1 || *s2) {
        delta = *s2 - *s1;
        if (delta)
            return delta;
        s1++;
        s2++;
    }
    return 0;
}

int strncmp(const char *cs, const char *ct, size_t count)
{
    unsigned char c1, c2;

    while (count) {
        c1 = *cs++;
        c2 = *ct++;
        if (c1 != c2)
            return c1 < c2 ? -1 : 1;
        if (!c1)
            break;
        count--;
    }
    return 0;
}

size_t strnlen(const char *s, size_t maxlen)
{
    const char *es = s;
    while (*es && maxlen) {
        es++;
        maxlen--;
    }

    return (es - s);
}

unsigned int atou(const char *s)
{
    unsigned int i = 0;
    while (isdigit(*s))
        i = i * 10 + (*s++ - '0');
    return i;
}

/* Works only for digits and letters, but small and fast */
#define TOLOWER(x) ((x) | 0x20)

static unsigned int simple_guess_base(const char *cp)
{
    if (cp[0] == '0') {
        if (TOLOWER(cp[1]) == 'x' && isxdigit(cp[2]))
            return 16;
        else
            return 8;
    } else {
        return 10;
    }
}

unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int base)
{
    unsigned long long result = 0;

    if (!base)
        base = simple_guess_base(cp);

    if (base == 16 && cp[0] == '0' && TOLOWER(cp[1]) == 'x')
        cp += 2;

    while (isxdigit(*cp)) {
        unsigned int value;

        value = isdigit(*cp) ? *cp - '0' : TOLOWER(*cp) - 'a' + 10;
        if (value >= base)
            break;
        result = result * base + value;
        cp++;
    }
    if (endp)
        *endp = (char *)cp;

    return result;
}

size_t strlen(const char *s)
{
    const char *sc;

    for (sc = s; *sc != '\0'; ++sc)
        /* nothing */;
    return sc - s;
}

char *strstr(const char *s1, const char *s2)
{
    size_t l1, l2;

    l2 = strlen(s2);
    if (!l2)
        return (char *)s1;
    l1 = strlen(s1);
    while (l1 >= l2) {
        l1--;
        if (!memcmp(s1, s2, l2))
            return (char *)s1;
        s1++;
    }
    return NULL;
}