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
25 namespace 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
32 class Flattenable
33 {
34 public:
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
59 protected:
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 */
72 template <typename T>
73 class LightFlattenable {
74 public:
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
89 template <typename T>
isFixedSize()90 inline bool LightFlattenable<T>::isFixedSize() const {
91 return static_cast<T const*>(this)->T::isFixedSize();
92 }
93 template <typename T>
getSize()94 inline size_t LightFlattenable<T>::getSize() const {
95 return static_cast<T const*>(this)->T::getSize();
96 }
97 template <typename T>
flatten(void * buffer)98 inline status_t LightFlattenable<T>::flatten(void* buffer) const {
99 return static_cast<T const*>(this)->T::flatten(buffer);
100 }
101 template <typename T>
unflatten(void const * buffer,size_t size)102 inline 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 */
110 template <typename T>
111 class LightFlattenablePod : public LightFlattenable<T> {
112 public:
isFixedSize()113 inline bool isFixedSize() const {
114 return true;
115 }
116
getSize()117 inline size_t getSize() const {
118 return sizeof(T);
119 }
flatten(void * buffer)120 inline status_t flatten(void* buffer) const {
121 *reinterpret_cast<T*>(buffer) = *static_cast<T const*>(this);
122 return NO_ERROR;
123 }
unflatten(void const * buffer,size_t)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