1/*
2 * Copyright 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_PIXELFLINGER_SHARED_BUFFER_H
18#define ANDROID_PIXELFLINGER_SHARED_BUFFER_H
19
20#include <stdint.h>
21#include <sys/types.h>
22
23// ---------------------------------------------------------------------------
24
25namespace android {
26namespace tinyutils {
27
28class SharedBuffer
29{
30public:
31
32    /* flags to use with release() */
33    enum {
34        eKeepStorage = 0x00000001
35    };
36
37    /*! allocate a buffer of size 'size' and acquire() it.
38     *  call release() to free it.
39     */
40    static          SharedBuffer*           alloc(size_t size);
41
42    /*! free the memory associated with the SharedBuffer.
43     * Fails if there are any users associated with this SharedBuffer.
44     * In other words, the buffer must have been release by all its
45     * users.
46     */
47    static          ssize_t                 dealloc(const SharedBuffer* released);
48
49    //! get the SharedBuffer from the data pointer
50    static  inline  const SharedBuffer*     sharedBuffer(const void* data);
51
52    //! access the data for read
53    inline          const void*             data() const;
54
55    //! access the data for read/write
56    inline          void*                   data();
57
58    //! get size of the buffer
59    inline          size_t                  size() const;
60
61    //! get back a SharedBuffer object from its data
62    static  inline  SharedBuffer*           bufferFromData(void* data);
63
64    //! get back a SharedBuffer object from its data
65    static  inline  const SharedBuffer*     bufferFromData(const void* data);
66
67    //! get the size of a SharedBuffer object from its data
68    static  inline  size_t                  sizeFromData(const void* data);
69
70    //! edit the buffer (get a writtable, or non-const, version of it)
71                    SharedBuffer*           edit() const;
72
73    //! edit the buffer, resizing if needed
74                    SharedBuffer*           editResize(size_t size) const;
75
76    //! like edit() but fails if a copy is required
77                    SharedBuffer*           attemptEdit() const;
78
79    //! resize and edit the buffer, loose it's content.
80                    SharedBuffer*           reset(size_t size) const;
81
82    //! acquire/release a reference on this buffer
83                    void                    acquire() const;
84
85    /*! release a reference on this buffer, with the option of not
86     * freeing the memory associated with it if it was the last reference
87     * returns the previous reference count
88     */
89                    int32_t                 release(uint32_t flags = 0) const;
90
91    //! returns wether or not we're the only owner
92    inline          bool                    onlyOwner() const;
93
94
95private:
96        inline SharedBuffer() { }
97        inline ~SharedBuffer() { }
98        inline SharedBuffer(const SharedBuffer&);
99
100        // 16 bytes. must be sized to preserve correct alingment.
101        mutable int32_t        mRefs;
102                size_t         mSize;
103                uint32_t       mReserved[2];
104};
105
106// ---------------------------------------------------------------------------
107
108const SharedBuffer* SharedBuffer::sharedBuffer(const void* data) {
109    return data ? reinterpret_cast<const SharedBuffer *>(data)-1 : 0;
110}
111
112const void* SharedBuffer::data() const {
113    return this + 1;
114}
115
116void* SharedBuffer::data() {
117    return this + 1;
118}
119
120size_t SharedBuffer::size() const {
121    return mSize;
122}
123
124SharedBuffer* SharedBuffer::bufferFromData(void* data)
125{
126    return ((SharedBuffer*)data)-1;
127}
128
129const SharedBuffer* SharedBuffer::bufferFromData(const void* data)
130{
131    return ((const SharedBuffer*)data)-1;
132}
133
134size_t SharedBuffer::sizeFromData(const void* data)
135{
136    return (((const SharedBuffer*)data)-1)->mSize;
137}
138
139bool SharedBuffer::onlyOwner() const {
140    return (mRefs == 1);
141}
142
143} // namespace tinyutils
144} // namespace android
145
146// ---------------------------------------------------------------------------
147
148#endif // ANDROID_PIXELFLINGER_SHARED_BUFFER_H
149