size_t my_strlen(const char* str){    const char* ptr = str;    for (; ((int)ptr & 0x03) != 0; ++ptr)    {        if (*ptr == ‘\0‘)            return ptr - str;    }    unsigned int* ptr_d = (unsigned int*)ptr;    unsigned int magic = 0x7efefeff;    //01111110    11111110    11111110     11111111     while (true)    {        unsigned int bits32 = *ptr_d++;        if ((((bits32 + magic) ^ (bits32 ^ -1)) & ~magic) != 0) // bits32 ^ -1 等价于 ~bits32        {            ptr = (const char*)(ptr_d - 1);            if (ptr[0] == 0)                return ptr - str;            if (ptr[1] == 0)                return ptr - str + 1;            if (ptr[2] == 0)                return ptr - str + 2;            if (ptr[3] == 0)                return ptr - str + 3;        }    }}