python 在 ctypes.Structure 中使用枚举
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Using enums in ctypes.Structure
提问by Kamil Kisiel
I have a struct I'm accessing via ctypes:
我有一个通过 ctypes 访问的结构：
struct attrl {
char *name;
char *resource;
char *value;
struct attrl *next;
enum batch_op op;
};
So far I have Python code like:
到目前为止，我的 Python 代码如下：
# struct attropl
class attropl(Structure):
pass
attrl._fields_ = [
("next", POINTER(attropl)),
("name", c_char_p),
("resource", c_char_p),
("value", c_char_p),
But I'm not sure what to use for the batch_openum. Should I just map it to a c_intor ?
但我不确定该batch_op枚举使用什么。我应该将它映射到 ac_int还是 ？
采纳答案by Andrey Vlasovskikh
At least for GCC enumis just a simple numeric type. It can be 8-, 16-, 32-, 64-bit or whatever (I have tested it with 64-bit values) as well as signedor unsigned. I guess it cannot exceed long long int, but practically you should check the range of your enums and choose something like c_uint.
至少对于 GCCenum来说只是一个简单的数字类型。它可以是 8 位、16 位、32 位、64 位或其他（我已经用 64 位值对其进行了测试）以及signed或unsigned. 我想它不能超过long long int，但实际上您应该检查enums的范围并选择类似c_uint.
Here is an example. The C program:
这是一个例子。C程序：
enum batch_op {
OP1 = 2,
OP2 = 3,
OP3 = -1,
};
struct attrl {
char *name;
struct attrl *next;
enum batch_op op;
};
void f(struct attrl *x) {
x->op = OP3;
}
and the Python one:
和 Python 之一：
from ctypes import (Structure, c_char_p, c_uint, c_int,
POINTER, CDLL)
class AttrList(Structure): pass
AttrList._fields_ = [
('name', c_char_p),
('next', POINTER(AttrList)),
('op', c_int),
]
(OP1, OP2, OP3) = (2, 3, -1)
enum = CDLL('./libenum.so')
enum.f.argtypes = [POINTER(AttrList)]
enum.f.restype = None
a = AttrList(name=None, next=None, op=OP2)
assert a.op == OP2
enum.f(a)
assert a.op == OP3
回答by Martin v. L?wis
Using c_intor c_uintwould be fine. Alternatively, there is a recipe in the cookbookfor an Enumeration class.
