A simple example of returning an array and converting it to a tensor

.gitignore

@@ -1,2 +1,4 @@
 __pycache__/
 env/
+build/
+logs/

CMakeLists.txt

@@ -2,6 +2,13 @@ cmake_minimum_required(VERSION 3.0)
 
 project(data_loader)
 
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED 17)
+
 add_library(data_loader SHARED data_loader.cpp)
 
+find_package(Threads REQUIRED)
+
+target_link_libraries(data_loader Threads::Threads)
+
 install(TARGETS data_loader RUNTIME DESTINATION .)

data_loader.cpp

@@ -15,4 +15,21 @@ extern "C" {
         std::cout<< "test successful\n";
     }
 
+    struct TestDataCollection
+    {
+        int size;
+        int* data;
+    };
+
+    EXPORT TestDataCollection* CDECL create_data_collection()
+    {
+        return new TestDataCollection{ 10, new int[10]{} };
+    }
+
+    EXPORT void CDECL destroy_data_collection(TestDataCollection* ptr)
+    {
+        delete ptr->data;
+        delete ptr;
+    }
+
 }

test_dll_call.py

@@ -1,10 +1,46 @@
-from ctypes import *
-from ctypes.util import find_library
+import ctypes
+import numpy as np
 
-filename = 'data_loader.dll'
-dll = CDLL(filename)
+dll = ctypes.CDLL('./data_loader.dll')
 print(dll)
 print(dll.test)
 dll.test()
 
+import torch
 
+print(dll.create_data_collection)
+print(dll.destroy_data_collection)
+
+class TestDataCollection(ctypes.Structure):
+    _fields_ = [
+        ('size', ctypes.c_int),
+        ('data', ctypes.POINTER(ctypes.c_int))
+    ]
+
+    def __str__(self):
+        return str(self.size) + ' ' + str([self.data[i] for i in range(self.size)])
+
+    def get_tensor(self):
+        return torch.LongTensor(np.ctypeslib.as_array(self.data, shape=(self.size,)))
+
+TestDataCollectionPtr = ctypes.POINTER(TestDataCollection)
+
+create_data_collection = dll.create_data_collection
+create_data_collection.restype = TestDataCollectionPtr
+
+destroy_data_collection = dll.destroy_data_collection
+destroy_data_collection.argtypes = [TestDataCollectionPtr]
+
+v = dll.create_data_collection()
+print(v)
+vobj = v.contents
+print(vobj)
+
+tensor = vobj.get_tensor();
+print(tensor)
+
+destroy_data_collection(v)
+
+for i in range(1000000):
+    v = create_data_collection()
+    destroy_data_collection(v)