1/*
2 * Copyright (C) 2010 Apple Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 *    notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 *    notice, this list of conditions and the following disclaimer in the
11 *    documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
14 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
15 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
17 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
18 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
19 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
20 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
21 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
22 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
23 * THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#ifndef APIClient_h
27#define APIClient_h
28
29#include <algorithm>
30#include <array>
31
32namespace API {
33
34template<typename ClientInterface> struct ClientTraits;
35
36template<typename ClientInterface> class Client {
37    typedef typename ClientTraits<ClientInterface>::Versions ClientVersions;
38    static const int latestClientVersion = std::tuple_size<ClientVersions>::value - 1;
39    typedef typename std::tuple_element<latestClientVersion, ClientVersions>::type LatestClientInterface;
40
41    // Helper class that can return an std::array of element sizes in a tuple.
42    template<typename> struct InterfaceSizes;
43    template<typename... Interfaces> struct InterfaceSizes<std::tuple<Interfaces...>> {
44        static std::array<size_t, sizeof...(Interfaces)> sizes()
45        {
46            return { { sizeof(Interfaces)... } };
47        }
48    };
49
50public:
51    Client()
52    {
53#if !ASSERT_DISABLED
54        auto interfaceSizes = InterfaceSizes<ClientVersions>::sizes();
55        ASSERT(std::is_sorted(interfaceSizes.begin(), interfaceSizes.end()));
56#endif
57
58        initialize(nullptr);
59    }
60
61    void initialize(const ClientInterface* client)
62    {
63        if (client && client->version == latestClientVersion) {
64            m_client = *reinterpret_cast<const LatestClientInterface*>(client);
65            return;
66        }
67
68        memset(&m_client, 0, sizeof(m_client));
69
70        if (client && client->version < latestClientVersion) {
71            auto interfaceSizes = InterfaceSizes<ClientVersions>::sizes();
72
73            memcpy(&m_client, client, interfaceSizes[client->version]);
74        }
75    }
76
77    const LatestClientInterface& client() const { return m_client; }
78
79protected:
80    LatestClientInterface m_client;
81};
82
83} // namespace API
84
85#endif // APIClient_h
86