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
25namespace android {
26
27class SharedBuffer
28{
29public:
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
91private:
92        inline 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
105const void* SharedBuffer::data() const {
106    return this + 1;
107}
108
109void* SharedBuffer::data() {
110    return this + 1;
111}
112
113size_t SharedBuffer::size() const {
114    return mSize;
115}
116
117SharedBuffer* SharedBuffer::bufferFromData(void* data) {
118    return data ? static_cast<SharedBuffer *>(data)-1 : 0;
119}
120
121const SharedBuffer* SharedBuffer::bufferFromData(const void* data) {
122    return data ? static_cast<const SharedBuffer *>(data)-1 : 0;
123}
124
125size_t SharedBuffer::sizeFromData(const void* data) {
126    return data ? bufferFromData(data)->mSize : 0;
127}
128
129bool SharedBuffer::onlyOwner() const {
130    return (mRefs == 1);
131}
132
133}; // namespace android
134
135// ---------------------------------------------------------------------------
136
137#endif // ANDROID_VECTOR_H
138