SHM_Buffer.hpp
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上传日期:2022-05-23
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- /* Copyright (C) 2003 MySQL AB
- This program is free software; you can redistribute it and/or modify
- it under the terms of the GNU General Public License as published by
- the Free Software Foundation; either version 2 of the License, or
- (at your option) any later version.
- This program is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- GNU General Public License for more details.
- You should have received a copy of the GNU General Public License
- along with this program; if not, write to the Free Software
- Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
- #ifndef SHM_BUFFER_HPP
- #define SHM_BUFFER_HPP
- #include <ndb_global.h>
- #include <NdbSleep.h>
- /**
- * These classes implement a circular buffer
- *
- * One reader and one writer
- */
- /**
- * SHM_Reader
- *
- * Use as follows:
- * getReadPtr(ptr, sz);
- * for(int i = 0; i<sz; i++)
- * printf("%cn", ptr[i]);
- * updateReadPtr(sz);
- */
- class SHM_Reader {
- public:
- SHM_Reader(char * const _startOfBuffer,
- Uint32 _sizeOfBuffer,
- Uint32 _slack,
- Uint32 * _readIndex,
- Uint32 * _writeIndex) :
- m_startOfBuffer(_startOfBuffer),
- m_totalBufferSize(_sizeOfBuffer),
- m_bufferSize(_sizeOfBuffer - _slack),
- m_sharedReadIndex(_readIndex),
- m_sharedWriteIndex(_writeIndex)
- {
- }
-
- void clear() {
- m_readIndex = 0;
- }
-
- /**
- *
- */
- inline bool empty() const;
-
- /**
- * Get read pointer
- *
- * returns ptr - where to start reading
- * sz - how much can I read
- */
- inline void getReadPtr(Uint32 * & ptr, Uint32 * & eod);
- /**
- * Update read ptr
- */
- inline void updateReadPtr(Uint32 *ptr);
-
- private:
- char * const m_startOfBuffer;
- Uint32 m_totalBufferSize;
- Uint32 m_bufferSize;
- Uint32 m_readIndex;
- Uint32 * m_sharedReadIndex;
- Uint32 * m_sharedWriteIndex;
- };
- inline
- bool
- SHM_Reader::empty() const{
- bool ret = (m_readIndex == * m_sharedWriteIndex);
- return ret;
- }
- /**
- * Get read pointer
- *
- * returns ptr - where to start reading
- * sz - how much can I read
- */
- inline
- void
- SHM_Reader::getReadPtr(Uint32 * & ptr, Uint32 * & eod)
- {
- Uint32 tReadIndex = m_readIndex;
- Uint32 tWriteIndex = * m_sharedWriteIndex;
-
- ptr = (Uint32*)&m_startOfBuffer[tReadIndex];
-
- if(tReadIndex <= tWriteIndex){
- eod = (Uint32*)&m_startOfBuffer[tWriteIndex];
- } else {
- eod = (Uint32*)&m_startOfBuffer[m_bufferSize];
- }
- }
- /**
- * Update read ptr
- */
- inline
- void
- SHM_Reader::updateReadPtr(Uint32 *ptr)
- {
- Uint32 tReadIndex = ((char*)ptr) - m_startOfBuffer;
- assert(tReadIndex < m_totalBufferSize);
- if(tReadIndex >= m_bufferSize){
- tReadIndex = 0;
- }
- m_readIndex = tReadIndex;
- * m_sharedReadIndex = tReadIndex;
- }
- #define WRITER_SLACK 4
- class SHM_Writer {
- public:
- SHM_Writer(char * const _startOfBuffer,
- Uint32 _sizeOfBuffer,
- Uint32 _slack,
- Uint32 * _readIndex,
- Uint32 * _writeIndex) :
- m_startOfBuffer(_startOfBuffer),
- m_totalBufferSize(_sizeOfBuffer),
- m_bufferSize(_sizeOfBuffer - _slack),
- m_sharedReadIndex(_readIndex),
- m_sharedWriteIndex(_writeIndex)
- {
- }
-
- void clear() {
- m_writeIndex = 0;
- }
-
- inline char * getWritePtr(Uint32 sz);
- inline void updateWritePtr(Uint32 sz);
- inline Uint32 getWriteIndex() const { return m_writeIndex;}
- inline Uint32 getBufferSize() const { return m_bufferSize;}
- inline Uint32 get_free_buffer() const;
-
- inline void copyIndexes(SHM_Writer * standbyWriter);
- private:
- char * const m_startOfBuffer;
- Uint32 m_totalBufferSize;
- Uint32 m_bufferSize;
-
- Uint32 m_writeIndex;
-
- Uint32 * m_sharedReadIndex;
- Uint32 * m_sharedWriteIndex;
- };
- inline
- char *
- SHM_Writer::getWritePtr(Uint32 sz){
- Uint32 tReadIndex = * m_sharedReadIndex;
- Uint32 tWriteIndex = m_writeIndex;
-
- char * ptr = &m_startOfBuffer[tWriteIndex];
- Uint32 free;
- if(tReadIndex <= tWriteIndex){
- free = m_bufferSize + tReadIndex - tWriteIndex;
- } else {
- free = tReadIndex - tWriteIndex;
- }
-
- sz += 4;
- if(sz < free){
- return ptr;
- }
-
- return 0;
- }
- inline
- void
- SHM_Writer::updateWritePtr(Uint32 sz){
- assert(m_writeIndex == * m_sharedWriteIndex);
- Uint32 tWriteIndex = m_writeIndex;
- tWriteIndex += sz;
-
- assert(tWriteIndex < m_totalBufferSize);
- if(tWriteIndex >= m_bufferSize){
- tWriteIndex = 0;
- }
- m_writeIndex = tWriteIndex;
- * m_sharedWriteIndex = tWriteIndex;
- }
- inline
- Uint32
- SHM_Writer::get_free_buffer() const
- {
- Uint32 tReadIndex = * m_sharedReadIndex;
- Uint32 tWriteIndex = m_writeIndex;
-
- Uint32 free;
- if(tReadIndex <= tWriteIndex){
- free = m_bufferSize + tReadIndex - tWriteIndex;
- } else {
- free = tReadIndex - tWriteIndex;
- }
- return free;
- }
-
- #endif