include/Lock.h

   1 /***************************************************************************
   2  *   Copyright (C) 2007 by www.databasecache.com                           *
   3  *   Contact: praba_tuty@databasecache.com                                 *
   4  *                                                                         *
   5  *   This program is free software; you can redistribute it and/or modify  *
   6  *   it under the terms of the GNU General Public License as published by  *
   7  *   the Free Software Foundation; either version 2 of the License, or     *
   8  *   (at your option) any later version.                                   *
   9  *                                                                         *
  10  *   This program is distributed in the hope that it will be useful,       *
  11  *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
  12  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
  13  *   GNU General Public License for more details.                          *
  14  *                                                                         *
  15   ***************************************************************************/
  16 #ifndef LOCK_H
  17 #define LOCK_H
  18 #include<os.h>
  19 #include<Index.h>
  20 class Chunk;
  21 class Database;
  22 class Transaction;
  23
  24 class LockInfo
  25 {
  26     public:
  27     signed int noOfReaders_;
  28     //-1 indicates write lock is taken
  29
  30     unsigned char waitReaders_;
  31     unsigned char waitWriters_;
  32     LockInfo() { noOfReaders_ = 0; waitReaders_ = 0; waitWriters_ = 0; }
  33 };
  34
  35 class LockHashNode
  36 {
  37     public:
  38     void *ptrToTuple_;
  39     LockInfo lInfo_;
  40     LockHashNode *next_;
  41 };
  42
  43 class LockListIter
  44 {
  45     LockHashNode *iter;
  46     public:
  47     LockListIter(){}
  48     LockListIter(LockHashNode *head) { iter = head;}
  49     LockHashNode* next();
  50     friend class LockList;
  51 };
  52
  53 class TransHasNode
  54 {
  55     public:
  56     LockHashNode *node_;
  57     TransHasNode *next_;
  58 };
  59
  60 class DatabaseManagerImpl;
  61 //singleton
  62 //DatabaseManager has this object and give reference to it to
  63 //Table interface and so on.
  64 class LockManager
  65 {
  66     public:
  67     Database *systemDatabase_;
  68
  69     private:
  70     LockHashNode* allocLockNode(LockInfo &info, void *tuple);
  71     void deallocLockNode(LockHashNode *head, Bucket *bucket);
  72     Bucket* getLockBucket(void *tuple);
  73
  74     public:
  75
  76     LockManager(Database *sysDb_){ systemDatabase_ = sysDb_;}
  77     DbRetVal getSharedLock(void *tuple, Transaction **trans);
  78     DbRetVal getExclusiveLock(void * tuple, Transaction **trans);
  79     DbRetVal releaseLock(void *tuple);
  80     DbRetVal isExclusiveLocked(void *tuple, bool &status);
  81 };
  82
  83
  84 #endif