buddy.hpp

/*
   Copyright (C) 2003-2006 MySQL AB
    All rights reserved. Use is subject to license terms.

   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 St, Fifth Floor, Boston, MA 02110-1301  USA
*/

#ifndef BUDDY_H
#define BUDDY_H

#include <ndb_global.h>

typedef unsigned int Uint32;
typedef unsigned short Uint16;
typedef unsigned long long Uint64;

//
const int UNDEFINED_CHUNK = -2; // XXX Set to hex

//
const int END_OF_CHUNK_LIST = -1; // XXX Set to hex

// A timeout (no of seconds) for the memory segments in the TransporterRegistry 
// memory pool. If a segment has been occupied (free=false) for a longer period 
// than this timeout, it will be released.
const int ALLOCATION_TIMEOUT = 10000;

// Free segments should always be as large as possible
// and are only allowed to be in any of these sizes
enum FreeSegmentSize {
  sz_256  = 0,
  sz_512  = 1,
  sz_1024 = 2,
  sz_2048 = 3,
  sz_4096 = 4,
  sz_8192 = 5,
  sz_16384 = 6,
  sz_32768 = 7,
  sz_65536 = 8,
  sz_131072 = 9,
  sz_GET_MAX = 5,
  sz_MAX = 9
};

struct Segment;

class BuddyMemory {
public:

  // Return true if there is at least 8 kB memory available
  bool memoryAvailable();

  // 
  bool allocate(int nChunksToAllocate);

  // Remove the segment from the freeSegment list
  void removeFromFreeSegmentList(int sz, int index);
  
  // Release the segment of size
  void release(int releaseId, int size);
  
  // Add a segment to the freeSegment list
  void addToFreeSegmentList(int sz, int index);

  bool getSegment(Uint32 size, Segment * dst);

  void refreshTime(Uint32 time);
  
  //Calculate log2(arg) + 1
  Uint32 logTwoPlus(Uint32 arg);
  
  // The current time
  Uint32 currentTime;
  
  // Pointer to the first free segment of size FreeSegmentSize
  Uint32 freeSegment[sz_MAX];
  
  // Start address of the memory block allocated
  Uint32* startOfMemoryBlock;
  
  // Total number of 256 byte chunks.
  Uint32 totalNoOfChunks;
  
  // Array of 256-byte chunks
  struct Chunk256* chunk;
};

struct Segment {
  Uint32 segmentSize;    // Size of the segment in no of words
  Uint16 index;          // Index in the array of SegmentListElements
  Uint16 releaseId;      // Unique no used when releasing the segment
                         // Undefined if Long_signal.deallocIndicator==0
  union {
    Uint32* segmentAddress; // Address to the memory segment
    Uint64  _padding_NOT_TO_BE_USED_;
  };
};

struct Chunk256 {
  Uint32 allocationTimeStamp;   // Bit 0 represents if the segment is free or not
                                // Bit 1-31 is the allocation time for the segment
                                // Bit 1-31 are undefined if the segment is free 
  Uint32 nextSegmentOfSameSize; // Undefined if allocated. 
                                // The first chunk in a free segment has a valid 
                                // next-pointer. In the rest of the chunks 
                                // belonging to the segment it is UNDEFINED_CHUNK.
  Uint32 prevSegmentOfSameSize; // Undefined if allocated
                                // The first chunk in a free segment has a valid 
                                // prev-pointer. In the rest of the chunks 
                                // belonging to the segment it is UNDEFINED_CHUNK.

  void setFree(bool free);

  bool getFree();

  void setAllocationTimeStamp(Uint32 cTime);

  Uint32 getAllocationTimeStamp();  
};

// inline void Chunk256::setFree(bool free){
//   // Bit 0 of allocationTimeStamp represents if the segment is free or not
//   allocationTimeStamp = 0x0;

//   printf("\nSet free segment");
//   Uint32 offMask = 0x0; // A mask to set the 0 bit to 0
//   if(free) 
//     // Set this bit to 0, if segment should be free
//     allocationTimeStamp = allocationTimeStamp & offMask;
// }

// inline bool Chunk256::getFree(){
//   // Get free segment

//   allocationTimeStamp = 0x0;
//   Uint32 offMask = 0x0; 

//   printf("\nGet free segment"); 
//   return ((allocationTimeStamp | offMask) == offMask ? true : false);
// }

// inline void Chunk256::setAllocationTimeStamp(Uint32 cTime){
//   // Bits 1-31 of allocationTimeStamp represent the allocation time for segment

//   Uint32 onMask = 0x80000000; // A mask to set the 0 bit to 1
//   allocationTimeStamp = 0x0;

//   printf("\nSet allocation time");
  
//   allocationTimeStamp = onMask | cTime;
// }

// inline Uint32 Chunk256::getAllocationTimeStamp(){

//   Uint32 onMask = 0x80000000; // A mask to set the 0 bit to 1
//   allocationTimeStamp = 0x0;

//   printf("\nGet allocation time");
//   allocationTimeStamp = allocationTimeStamp ^ onMask;
//   return allocationTimeStamp;
// };

#endif