1 #ifndef __DALI_INTEGRATION_LOCKLESS_BUFFER_H__
2 #define __DALI_INTEGRATION_LOCKLESS_BUFFER_H__
5 // Copyright (c) 2014 Samsung Electronics Co., Ltd.
7 // Licensed under the Flora License, Version 1.0 (the License);
8 // you may not use this file except in compliance with the License.
9 // You may obtain a copy of the License at
11 // http://floralicense.org/license/
13 // Unless required by applicable law or agreed to in writing, software
14 // distributed under the License is distributed on an AS IS BASIS,
15 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 // See the License for the specific language governing permissions and
17 // limitations under the License.
24 #include <dali/public-api/common/vector-wrapper.h>
25 #include <dali/public-api/common/dali-common.h>
34 * The LocklessBuffer class implements double buffering eligible for multi-(two) threaded use,
35 * where it's possible to read from one thread and write from another
36 * without requiring a mutex lock to avoid performance hit.
37 * It's intended to be used for reading bitmap data in render thread
38 * while still possible to write data in another thread.
40 * Ideally Write() and Read() calls should be alternating, otherwise written data might be thrown away.
42 * The buffers are swapped in the reading thread, just before reading begins.
43 * In case the other thread is writing at that moment, buffers are not swapped and previously available data is read.
44 * Similarly if Write() is called before a Read() has finished the previous write buffer is overwritten.
46 class DALI_IMPORT_API LocklessBuffer
52 * @param[in] size The size of buffers in bytes.
54 LocklessBuffer( size_t size );
62 * Write data to buffer.
63 * @param[in] src data source
64 * @param[in] size size of data in bytes
66 void Write( const unsigned char *src, size_t size );
69 * Try to swap buffers and read data.
70 * @note returned value only valid until Read() is called again or object is destroyed
71 * @return current read buffer contents
73 const unsigned char* Read();
76 * @return the buffer size in bytes
78 unsigned int GetSize() const;
82 * Atomically set state.
83 * We're always writing to one buffer and reading from the other.
84 * Write() sets WRITING bit when started and unsets it when finished.
88 R0W1 = 0, ///< Read from buffer 0 write to buffer 1
89 R1W0 = 1, ///< Read from buffer 1 write to buffer 0
90 WRITING = 2, ///< Currently writing to buffer
91 UPDATED = 4, ///< Swapping buffer required; there is new data available
92 WRITE_BUFFER_MASK = 1, ///< indicates which buffer to write to
93 WRITING_MASK = 2, ///< indicates whether currently writing
94 UPDATED_MASK = 4 ///< indicates whether new data is available
98 LocklessBuffer(); ///< undefined default constructor, need to give size on construction
99 LocklessBuffer( const LocklessBuffer& ); ///< undefined copy constructor
100 LocklessBuffer& operator=( const LocklessBuffer& ); ///< undefined assignment operator
103 unsigned char* mBuffer[2]; ///< bitmap buffers
104 BufferState volatile mState; ///< readbuffer number and whether we're currently writing into writebuffer or not
105 size_t mSize; ///< size of buffers
112 #endif // __DALI_INTEGRATION_LOCKLESS_H__