1 // Protocol Buffers - Google's data interchange format
2 // Copyright 2008 Google Inc. All rights reserved.
3 // https://developers.google.com/protocol-buffers/
4 //
5 // Redistribution and use in source and binary forms, with or without
6 // modification, are permitted provided that the following conditions are
7 // met:
8 //
9 // * Redistributions of source code must retain the above copyright
10 // notice, this list of conditions and the following disclaimer.
11 // * Redistributions in binary form must reproduce the above
12 // copyright notice, this list of conditions and the following disclaimer
13 // in the documentation and/or other materials provided with the
14 // distribution.
15 // * Neither the name of Google Inc. nor the names of its
16 // contributors may be used to endorse or promote products derived from
17 // this software without specific prior written permission.
18 //
19 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
20 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
21 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
22 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
23 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
24 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
25 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
26 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
27 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
28 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
29 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30
31 // This file can be included by other C++ libraries, typically extension modules
32 // which want to interact with the Python Messages coming from the "cpp"
33 // implementation of protocol buffers.
34 //
35 // Usage:
36 // Declare a (probably static) variable to hold the API:
37 // const PyProto_API* py_proto_api;
38 // In some initialization function, write:
39 // py_proto_api = static_cast<const PyProto_API*>(PyCapsule_Import(
40 // PyProtoAPICapsuleName(), 0));
41 // if (!py_proto_api) { ...handle ImportError... }
42 // Then use the methods of the returned class:
43 // py_proto_api->GetMessagePointer(...);
44
45 #ifndef GOOGLE_PROTOBUF_PYTHON_PROTO_API_H__
46 #define GOOGLE_PROTOBUF_PYTHON_PROTO_API_H__
47
48 #include <Python.h>
49
50 #include <google/protobuf/descriptor_database.h>
51 #include <google/protobuf/message.h>
52
53 namespace google {
54 namespace protobuf {
55 namespace python {
56
57 // Note on the implementation:
58 // This API is designed after
59 // https://docs.python.org/3/extending/extending.html#providing-a-c-api-for-an-extension-module
60 // The class below contains no mutable state, and all methods are "const";
61 // we use a C++ class instead of a C struct with functions pointers just because
62 // the code looks more readable.
63 struct PyProto_API {
64 // The API object is created at initialization time and never freed.
65 // This destructor is never called.
~PyProto_APIPyProto_API66 virtual ~PyProto_API() {}
67
68 // Operations on Messages.
69
70 // If the passed object is a Python Message, returns its internal pointer.
71 // Otherwise, returns NULL with an exception set.
72 virtual const Message* GetMessagePointer(PyObject* msg) const = 0;
73
74 // If the passed object is a Python Message, returns a mutable pointer.
75 // Otherwise, returns NULL with an exception set.
76 // This function will succeed only if there are no other Python objects
77 // pointing to the message, like submessages or repeated containers.
78 // With the current implementation, only empty messages are in this case.
79 virtual Message* GetMutableMessagePointer(PyObject* msg) const = 0;
80
81 // Expose the underlying DescriptorPool and MessageFactory to enable C++ code
82 // to create Python-compatible message.
83 virtual const DescriptorPool* GetDefaultDescriptorPool() const = 0;
84 virtual MessageFactory* GetDefaultMessageFactory() const = 0;
85 };
86
PyProtoAPICapsuleName()87 inline const char* PyProtoAPICapsuleName() {
88 static const char kCapsuleName[] =
89 "google.protobuf.pyext._message.proto_API";
90 return kCapsuleName;
91 }
92
93 } // namespace python
94 } // namespace protobuf
95 } // namespace google
96
97 #endif // GOOGLE_PROTOBUF_PYTHON_PROTO_API_H__
98