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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; version 2 of the License.
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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, 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("%c\n", 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
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