pickle.py 文件源码

def save_int(self, obj, pack=struct.pack):
        if self.bin:
            # If the int is small enough to fit in a signed 4-byte 2's-comp
            # format, we can store it more efficiently than the general
            # case.
            # First one- and two-byte unsigned ints:
            if obj >= 0:
                if obj <= 0xff:
                    self.write(BININT1 + chr(obj))
                    return
                if obj <= 0xffff:
                    self.write("%c%c%c" % (BININT2, obj&0xff, obj>>8))
                    return
            # Next check for 4-byte signed ints:
            high_bits = obj >> 31  # note that Python shift sign-extends
            if high_bits == 0 or high_bits == -1:
                # All high bits are copies of bit 2**31, so the value
                # fits in a 4-byte signed int.
                self.write(BININT + pack("<i", obj))
                return
        # Text pickle, or int too big to fit in signed 4-byte format.
        self.write(INT + repr(obj) + '\n')