摘自：luajit源碼lj_str.c/* Fast string data comparison. Caveat: unaligned access to 1st string! */
static LJ_AINLINE int str_fastcmp(const char *a, const char *b, MSize len)
{
MSize i = 0;
lua_assert(len > 0);
lua_assert((((uintptr_t)a + len) & (LJ_PAGESIZE-1)) <= LJ_PAGESIZE-4);
do { /* Note: innocuous access up to end of string + 3. */
uint32_t v = lj_getu32(a+i) ^ *(const uint32_t *)(b+i);
if (v) {
i -= len;
#if LJ_LE
return (int32_t)i >= -3 ? (v << (32+(i<<3))) : 1;
#else
return (int32_t)i >= -3 ? (v >> (32+(i<<3))) : 1;
#endif
}
i += 4;
} while (i < len);
return 0;
}