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
25 namespace android {
26 namespace tinyutils {
27
28 class SharedBuffer
29 {
30 public:
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
95 private:
SharedBuffer()96 inline SharedBuffer() { }
~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
sharedBuffer(const void * data)108 const SharedBuffer* SharedBuffer::sharedBuffer(const void* data) {
109 return data ? reinterpret_cast<const SharedBuffer *>(data)-1 : 0;
110 }
111
data()112 const void* SharedBuffer::data() const {
113 return this + 1;
114 }
115
data()116 void* SharedBuffer::data() {
117 return this + 1;
118 }
119
size()120 size_t SharedBuffer::size() const {
121 return mSize;
122 }
123
bufferFromData(void * data)124 SharedBuffer* SharedBuffer::bufferFromData(void* data)
125 {
126 return ((SharedBuffer*)data)-1;
127 }
128
bufferFromData(const void * data)129 const SharedBuffer* SharedBuffer::bufferFromData(const void* data)
130 {
131 return ((const SharedBuffer*)data)-1;
132 }
133
sizeFromData(const void * data)134 size_t SharedBuffer::sizeFromData(const void* data)
135 {
136 return (((const SharedBuffer*)data)-1)->mSize;
137 }
138
onlyOwner()139 bool 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