src/userspace/mlibc/string/strlen.c


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#include <mlibc/stdlib.h>

size_t strlen(const char *str)
{
    const char *char_ptr;
    const unsigned long int *longword_ptr;
    unsigned long int longword, himagic, lomagic;

    for (char_ptr = str; ((unsigned long int) char_ptr & (sizeof(longword) - 1)) != 0; ++char_ptr)
        if (*char_ptr == '\0')
            return char_ptr - str;

    longword_ptr = (unsigned long int *) char_ptr;

    himagic = 0x80808080L;
    lomagic = 0x01010101L;

    for (;;) {
        longword = *longword_ptr++;

        if (((longword - lomagic) & himagic) != 0) {
            const char *cp = (const char *) (longword_ptr - 1);

            if (cp[0] == 0)
                return cp - str;
            if (cp[1] == 0)
                return cp - str + 1;
            if (cp[2] == 0)
                return cp - str + 2;
            if (cp[3] == 0)
                return cp - str + 3;
        }
    }
}