ctypes笔记

作者：刘宾， thomas_liub@hotmail.com
请尊重作者著作权，转载请注明出处，谢谢！

类型表

加载DLL

1. 标准cdecl调用

dll = ctypes.CDLL("dllpath")

2. Win dll

dll = ctypes.WinDLL("dllpath")

调用dll中方法

1. 函数返回类型，函数默认返回c_int类型，如果需要返回其他类型，需要设置函数的restype属性

dll.method_in_dll.restype = ctypes.c_short

2. 调用方法

ret = dll.method_in_dll()

数据类型转换

• 指针

# 取对象指针
    ptr = ctypes.pointer(ct_obj)
    ptr.contents 为 ct_obj
# 初始化空指针
    ptr = ctypes.POINTER(ctypes.c_int)
# 字符串对象
    obj = c_wchar_p("Hello, World")
    obj
        c_wchar_p('Hello, World')
    obj.value
        u'Hello, World'
# 缓冲区
    # create a 3 byte buffer, initialized to NUL bytes
    p = create_string_buffer(3)
    # create a buffer containing a NUL terminated string
    p = create_string_buffer(b"Hello")
    # create a 10 byte buffer
    p = create_string_buffer(b"Hello", 10) 

• 引用

ref = ctypes.byref(ct_obj)

• 普通类型

i = c_int(42)
print i.value

• 数组

buf = c_int * 10  
m = buf(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
print m[1]

• 结构体和联合

class IODBPSD(ct.Structure):
    """ CNC parameter """
    class IODBDATA(ct.Union):
        class REALPRM(ct.Structure):
            _fields_ = [('prm_val', ct.c_long),
                        ('dec_val', ct.c_long)]
        _fields_ = [('cdata', ct.c_byte),
                    ('idata', ct.c_short),
                    ('ldata', ct.c_long),
                    ('rdata', REALPRM),
                    ('cdatas', ct.c_byte*f_globalv.MAX_AXIS),
                    ('idatas', ct.c_short*f_globalv.MAX_AXIS),
                    ('ldatas', ct.c_long*f_globalv.MAX_AXIS),
                    ('rdatas', REALPRM*f_globalv.MAX_AXIS)]
    _anonymous_ = ('u',)
    _fields_ = [('datano', ct.c_short),
                ('type', ct.c_short),
                ('u', IODBDATA)]

• bitmap,仅对int有效

class Int(Structure):
    _fields_ = [("first_16", c_int, 16),
                ("second_16", c_int, 16)]

• 链表

class Test(Structure):  
    pass  
Test._fields_ = [('x', c_int),  
                ('y', c_char),  
                ('next', POINTER(Test))]