Python：ctypes如何将c_char_Array转换为c_char_p

Question

The function create_string_buffer(b"foo", 3) returns a type c_char_Array_3 . Trying to pass this in where c_char_p is expected blows up with TypeError: incompatible types, c_char_Array_3 instance instead of c_char_p instance . How do I pass the output of create_string_buffer into a field that expects c_char_p ?

I think this person had the same question: https://ctypes-users.narkive.com/620LJv10/why-doesn-tc-char-array-get-coerced-on-assignment-to-a-pointer

However, it's unclear to me what the answer was.

Answer 1

You can pass a create_string_buffer object to a function with a c_char_p as an .argtypes parameter, but not when it is a member of a structure. cast can work around it. This was mentioned in the link you provided in the question.

from ctypes import *

class foo(Structure):
    _fields_ = [('bar',c_char_p)]

s = create_string_buffer(b'test')

f = foo()
f.bar = cast(s,c_char_p)
print(f.bar)
s[0] = b'q'
print(f.bar)

Output:

b'test'
b'qest'