1 /*
2 * Copyright (C) 2005 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_SHARED_BUFFER_H
18 #define ANDROID_SHARED_BUFFER_H
19
20 #include <stdint.h>
21 #include <sys/types.h>
22
23 // ---------------------------------------------------------------------------
24
25 namespace android {
26
27 class SharedBuffer
28 {
29 public:
30
31 /* flags to use with release() */
32 enum {
33 eKeepStorage = 0x00000001
34 };
35
36 /*! allocate a buffer of size 'size' and acquire() it.
37 * call release() to free it.
38 */
39 static SharedBuffer* alloc(size_t size);
40
41 /*! free the memory associated with the SharedBuffer.
42 * Fails if there are any users associated with this SharedBuffer.
43 * In other words, the buffer must have been release by all its
44 * users.
45 */
46 static ssize_t dealloc(const SharedBuffer* released);
47
48 //! access the data for read
49 inline const void* data() const;
50
51 //! access the data for read/write
52 inline void* data();
53
54 //! get size of the buffer
55 inline size_t size() const;
56
57 //! get back a SharedBuffer object from its data
58 static inline SharedBuffer* bufferFromData(void* data);
59
60 //! get back a SharedBuffer object from its data
61 static inline const SharedBuffer* bufferFromData(const void* data);
62
63 //! get the size of a SharedBuffer object from its data
64 static inline size_t sizeFromData(const void* data);
65
66 //! edit the buffer (get a writtable, or non-const, version of it)
67 SharedBuffer* edit() const;
68
69 //! edit the buffer, resizing if needed
70 SharedBuffer* editResize(size_t size) const;
71
72 //! like edit() but fails if a copy is required
73 SharedBuffer* attemptEdit() const;
74
75 //! resize and edit the buffer, loose it's content.
76 SharedBuffer* reset(size_t size) const;
77
78 //! acquire/release a reference on this buffer
79 void acquire() const;
80
81 /*! release a reference on this buffer, with the option of not
82 * freeing the memory associated with it if it was the last reference
83 * returns the previous reference count
84 */
85 int32_t release(uint32_t flags = 0) const;
86
87 //! returns wether or not we're the only owner
88 inline bool onlyOwner() const;
89
90
91 private:
SharedBuffer()92 inline SharedBuffer() { }
~SharedBuffer()93 inline ~SharedBuffer() { }
94 SharedBuffer(const SharedBuffer&);
95 SharedBuffer& operator = (const SharedBuffer&);
96
97 // 16 bytes. must be sized to preserve correct alignment.
98 mutable int32_t mRefs;
99 size_t mSize;
100 uint32_t mReserved[2];
101 };
102
103 // ---------------------------------------------------------------------------
104
data()105 const void* SharedBuffer::data() const {
106 return this + 1;
107 }
108
data()109 void* SharedBuffer::data() {
110 return this + 1;
111 }
112
size()113 size_t SharedBuffer::size() const {
114 return mSize;
115 }
116
bufferFromData(void * data)117 SharedBuffer* SharedBuffer::bufferFromData(void* data) {
118 return data ? static_cast<SharedBuffer *>(data)-1 : 0;
119 }
120
bufferFromData(const void * data)121 const SharedBuffer* SharedBuffer::bufferFromData(const void* data) {
122 return data ? static_cast<const SharedBuffer *>(data)-1 : 0;
123 }
124
sizeFromData(const void * data)125 size_t SharedBuffer::sizeFromData(const void* data) {
126 return data ? bufferFromData(data)->mSize : 0;
127 }
128
onlyOwner()129 bool SharedBuffer::onlyOwner() const {
130 return (mRefs == 1);
131 }
132
133 }; // namespace android
134
135 // ---------------------------------------------------------------------------
136
137 #endif // ANDROID_VECTOR_H
138