I have the below arrays on C how can i interpert them to ctypes datatypes inside structre
struct a {
BYTE a[30];
CHAR b[256];
};
should i interpert a fixed array as the datatype * the size i want like the below and if yes how can i call this structure as a parameter to fun that takes instance from this structure
class a(structure) :
_fields_ = [ ("a",c_bytes*30 ),
("b",c_char*256 ),]
You're on the right track. You're probably just missing the byref() function. Assuming the function you want to call is named *print_struct*, do the following:
from ctypes import *
class MyStruct(Structure):
_fields_ = [('a',c_byte*30), ('b',c_char*256)]
s = MyStruct() # Allocates a new instance of the structure from Python
s.a[5] = 10 # Use as normal
d = CDLL('yourdll.so')
d.print_struct( byref(s) ) # byref() passes a pointer rather than passing by copy
This should work:
from ctypes import Structure, c_bytes, c_char
class A(Structure):
_fields_ = [("a", c_bytes*30), ("b", c_char*256)]
Then you can simply access the fields of the structure using the dot operator:
>>> my_a = A()
>>> my_a.a[4] = 127
>>> my_a.a[4]
127
>>> my_a.b = "test string"
>>> my_a.b
'test string'
>>> my_a.b[2]
's'
You can also pass the structure directly to an arbitrary Python function:
def my_func(a):
print "a[0] + a[1] = %d" % (a.a[0] + a.a[1], )
print "Length of b = %d" % len(a.b)
>>> my_a = A()
>>> my_a.a[0:2] = 19, 23
>>> my_a.b = "test"
>>> my_func(my_a)
a[0] + a[1] = 42
Length of b = 4
