eryksun added the comment:
Extending byref to support bytes and str objects sounds reasonable.
Here's another workaround to pass a bytes object with an offset:
from ctypes import *
from ctypes.util import find_library
class offset:
def __init__(self, arg, offset):
self.arg = arg
self.offset = offset
class my_char_p(c_char_p):
@classmethod
def from_param(cls, arg):
if isinstance(arg, offset):
t = cast(arg.arg, POINTER(c_char * 0))[0]
carg = byref(t, arg.offset)
else:
carg = super().from_param(arg)
return carg
atoi = CDLL(find_library('c')).atoi
atoi.argtypes = [my_char_p]
>>> atoi(b'12345')
12345
>>> atoi(offset(b'12345', 1))
2345
>>> atoi(offset(b'12345', 3))
45
You can also convert bytearray, memoryview, and array.array objects from_param.
If the object's buffer is writable you can use a ctypes type's from_buffer
method to create the C arg. This takes an optional offset argument. Otherwise
use from_buffer_copy or cast.
----------
nosy: +eryksun
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue11429>
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