我怎样才能创建这个结构？

Question

我想创建一个这样的结构：

import ctypes

class MyStruct(ctypes.Structure):
    _fields_ = [('field1', /* size of 16 bytes */),
                ('field2', /* size of 4 bytes */)
                ('field3', /* size of 8 bytes */)]

对于这些大小的字段，我需要在这里写什么类型？我希望field1 的最大大小为 16 个字节，因此所需的值将被写入那里，并且所有其他字节将为零（如有必要，最多 16 个字节）。对于field2 和field3 也是如此。

Answer 1

两种方式。 16 位字段使它有点棘手：

import ctypes

class MyStruct(ctypes.Structure):
    _pack_ = 1
    _fields_ = (('field1', ctypes.c_ubyte * 16), # C char[16] field1
                ('field2', ctypes.c_uint32),     # C uint32_t field2
                ('field3', ctypes.c_uint64))     # C uint64_t field3
    def __init__(self,a,b,c):
        self.field1[:] = a.to_bytes(16,'little') # [:] trick to copy bytes to c_ubyte array
        self.field2 = b
        self.field3 = c

s = MyStruct(0x100, 0x200, 0x300)
print(bytes(s).hex(' '))

with open('out.bin','wb') as f:
    f.write(bytes(s))

或者

import struct

b = struct.pack('<16sLQ',(0x100).to_bytes(16,'little'),0x200,0x300)
print(b.hex(' '))

with open('out.bin','wb') as f:
    f.write(b)

输出：

00 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 02 00 00 00 03 00 00 00 00 00 00
00 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 02 00 00 00 03 00 00 00 00 00 00