1/*
2 * Copyright (C) 2010 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef ANDROID_UTILS_FLATTENABLE_H
18#define ANDROID_UTILS_FLATTENABLE_H
19
20
21#include <stdint.h>
22#include <sys/types.h>
23#include <utils/Errors.h>
24
25namespace android {
26
27/*
28 * The Flattenable interface allows an object to serialize itself out
29 * to a byte-buffer and an array of file descriptors.
30 */
31
32class Flattenable
33{
34public:
35    // size in bytes of the flattened object
36    virtual size_t getFlattenedSize() const = 0;
37
38    // number of file descriptors to flatten
39    virtual size_t getFdCount() const = 0;
40
41    // flattens the object into buffer.
42    // size should be at least of getFlattenedSize()
43    // file descriptors are written in the fds[] array but ownership is
44    // not transfered (ie: they must be dupped by the caller of
45    // flatten() if needed).
46    virtual status_t flatten(void* buffer, size_t size,
47            int fds[], size_t count) const = 0;
48
49    // unflattens the object from buffer.
50    // size should be equal to the value of getFlattenedSize() when the
51    // object was flattened.
52    // unflattened file descriptors are found in the fds[] array and
53    // don't need to be dupped(). ie: the caller of unflatten doesn't
54    // keep ownership. If a fd is not retained by unflatten() it must be
55    // explicitly closed.
56    virtual status_t unflatten(void const* buffer, size_t size,
57            int fds[], size_t count) = 0;
58
59protected:
60    virtual ~Flattenable() = 0;
61
62};
63
64/*
65 * LightFlattenable is a protocol allowing object to serialize themselves out
66 * to a byte-buffer.
67 *
68 * LightFlattenable objects must implement this protocol.
69 *
70 * LightFlattenable doesn't require the object to be virtual.
71 */
72template <typename T>
73class LightFlattenable {
74public:
75    // returns whether this object always flatten into the same size.
76    // for efficiency, this should always be inline.
77    inline bool isFixedSize() const;
78
79    // returns size in bytes of the flattened object. must be a constant.
80    inline size_t getSize() const;
81
82    // flattens the object into buffer.
83    inline status_t flatten(void* buffer) const;
84
85    // unflattens the object from buffer of given size.
86    inline status_t unflatten(void const* buffer, size_t size);
87};
88
89template <typename T>
90inline bool LightFlattenable<T>::isFixedSize() const {
91    return static_cast<T const*>(this)->T::isFixedSize();
92}
93template <typename T>
94inline size_t LightFlattenable<T>::getSize() const {
95    return static_cast<T const*>(this)->T::getSize();
96}
97template <typename T>
98inline status_t LightFlattenable<T>::flatten(void* buffer) const {
99    return static_cast<T const*>(this)->T::flatten(buffer);
100}
101template <typename T>
102inline status_t LightFlattenable<T>::unflatten(void const* buffer, size_t size) {
103    return static_cast<T*>(this)->T::unflatten(buffer, size);
104}
105
106/*
107 * LightFlattenablePod is an implementation of the LightFlattenable protocol
108 * for POD (plain-old-data) objects.
109 */
110template <typename T>
111class LightFlattenablePod : public LightFlattenable<T> {
112public:
113    inline bool isFixedSize() const {
114        return true;
115    }
116
117    inline size_t getSize() const {
118        return sizeof(T);
119    }
120    inline status_t flatten(void* buffer) const {
121        *reinterpret_cast<T*>(buffer) = *static_cast<T const*>(this);
122        return NO_ERROR;
123    }
124    inline status_t unflatten(void const* buffer, size_t) {
125        *static_cast<T*>(this) = *reinterpret_cast<T const*>(buffer);
126        return NO_ERROR;
127    }
128};
129
130
131}; // namespace android
132
133
134#endif /* ANDROID_UTILS_FLATTENABLE_H */
135