在Python 2中使用ctype时的偏移问题

import ctypes

class MyStruct(ctypes.Structure):
    _fields_ = [
        ('field1', ctypes.c_int),
        ('field2', ctypes.c_float),
        ('field3', ctypes.c_char * 10),
    ]

# 计算对齐方式
alignment = max(ctypes.alignment(field_type) for field_name, field_type in MyStruct._fields_)

# 计算偏移量
offset = 0
for field_name, field_type in MyStruct._fields_:
    field_size = ctypes.sizeof(field_type)
    offset = (offset + alignment - 1) // alignment * alignment  # 对齐偏移量
    setattr(MyStruct, field_name, ctypes.c_byte * offset)  # 设置偏移量
    offset += field_size

# 创建结构体实例
my_struct = MyStruct()

# 访问字段
my_struct.field1 = 10
my_struct.field2 = 3.14
my_struct.field3 = 'Hello'

# 打印偏移量
print('field1 offset:', ctypes.addressof(my_struct.field1) - ctypes.addressof(my_struct))
print('field2 offset:', ctypes.addressof(my_struct.field2) - ctypes.addressof(my_struct))
print('field3 offset:', ctypes.addressof(my_struct.field3) - ctypes.addressof(my_struct))