qore_var_rwlock_priv.h

/* -*- mode: c++; indent-tabs-mode: nil -*- */
/*
  qore_var_rwlock_priv.h
 
  internal read-write lock for variables
 
  Qore Programming Language
 
  Copyright (C) 2003 - 2023 Qore Technologies, s.r.o.
 
  Permission is hereby granted, free of charge, to any person obtaining a
  copy of this software and associated documentation files (the "Software"),
  to deal in the Software without restriction, including without limitation
  the rights to use, copy, modify, merge, publish, distribute, sublicense,
  and/or sell copies of the Software, and to permit persons to whom the
  Software is furnished to do so, subject to the following conditions:
 
  The above copyright notice and this permission notice shall be included in
  all copies or substantial portions of the Software.
 
  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  DEALINGS IN THE SOFTWARE.
 
  Note that the Qore library is released under a choice of three open-source
  licenses: MIT (as above), LGPL 2+, or GPL 2+; see README-LICENSE for more
  information.
*/
 
#ifndef _QORE_VAR_RWLOCK_PRIV_H
#define _QORE_VAR_RWLOCK_PRIV_H
 
class qore_var_rwlock_priv {
protected:
   DLLLOCAL virtual void notifyIntern() {
   }
 
   DLLLOCAL qore_var_rwlock_priv(const qore_var_rwlock_priv&);
   DLLLOCAL qore_var_rwlock_priv& operator=(const qore_var_rwlock_priv&);
 
public:
   QoreThreadLock l;
   int write_tid,
      readers,
      read_waiting,
      write_waiting;
   QoreCondition write_cond,
      read_cond;
   bool has_notify;
 
   DLLLOCAL qore_var_rwlock_priv() : write_tid(-1), readers(0), read_waiting(0), write_waiting(0), has_notify(false) {
   }
 
   DLLLOCAL virtual ~qore_var_rwlock_priv() {
   }
 
   DLLLOCAL void wrlock() {
      int tid = q_gettid();
      AutoLocker al(l);
      assert(tid != write_tid);
 
      while (readers || write_tid != -1) {
         ++write_waiting;
         write_cond.wait(l);
         --write_waiting;
      }
 
      write_tid = tid;
   }
 
   DLLLOCAL int trywrlock() {
      int tid = q_gettid();
      AutoLocker al(l);
      assert(tid != write_tid);
      if (readers || write_tid != -1)
         return -1;
 
      write_tid = tid;
      return 0;
   }
 
   DLLLOCAL void unlock() {
      int tid = q_gettid();
      AutoLocker al(l);
      if (write_tid == tid) {
         write_tid = -1;
         if (has_notify)
            notifyIntern();
 
         unlock_signal();
      }
      else {
         assert(readers);
         if (!--readers)
            unlock_read_signal();
      }
   }
 
   DLLLOCAL void rdlock() {
      AutoLocker al(l);
      assert(write_tid != q_gettid());
      while (write_tid != -1) {
         ++read_waiting;
         read_cond.wait(l);
         --read_waiting;
      }
 
      ++readers;
   }
 
   DLLLOCAL int tryrdlock() {
      AutoLocker al(l);
      assert(write_tid != q_gettid());
      if (write_tid != -1)
         return -1;
 
      ++readers;
      return 0;
   }
 
   DLLLOCAL void unlock_signal() {
      if (write_waiting)
         write_cond.signal();
      else if (read_waiting)
         read_cond.broadcast();
   }
 
   DLLLOCAL void unlock_read_signal() {
      //assert(!read_waiting);
      if (write_waiting)
         write_cond.signal();
   }
};
 
class QoreAutoVarRWReadLocker {
private:
   DLLLOCAL QoreAutoVarRWReadLocker(const QoreAutoVarRWReadLocker&);
 
   DLLLOCAL QoreAutoVarRWReadLocker& operator=(const QoreAutoVarRWReadLocker&);
 
   DLLLOCAL void *operator new(size_t);
 
protected:
   QoreVarRWLock *l;
 
public:
   DLLLOCAL QoreAutoVarRWReadLocker(QoreVarRWLock &n_l) : l(&n_l) {
      l->rdlock();
   }
 
   DLLLOCAL QoreAutoVarRWReadLocker(QoreVarRWLock *n_l) : l(n_l) {
      l->rdlock();
   }
 
   DLLLOCAL ~QoreAutoVarRWReadLocker() {
      l->unlock();
   }
};
 
class QoreAutoVarRWWriteLocker {
private:
   DLLLOCAL QoreAutoVarRWWriteLocker(const QoreAutoVarRWWriteLocker&);
 
   DLLLOCAL QoreAutoVarRWWriteLocker& operator=(const QoreAutoVarRWWriteLocker&);
 
   DLLLOCAL void *operator new(size_t);
 
protected:
   QoreVarRWLock *l;
 
public:
   DLLLOCAL QoreAutoVarRWWriteLocker(QoreVarRWLock &n_l) : l(&n_l) {
      l->wrlock();
   }
 
   DLLLOCAL QoreAutoVarRWWriteLocker(QoreVarRWLock *n_l) : l(n_l) {
      l->wrlock();
   }
 
   DLLLOCAL ~QoreAutoVarRWWriteLocker() {
      l->unlock();
   }
};
 
class QoreSafeVarRWReadLocker {
private:
   DLLLOCAL QoreSafeVarRWReadLocker(const QoreSafeVarRWReadLocker&);
 
   DLLLOCAL QoreSafeVarRWReadLocker& operator=(const QoreSafeVarRWReadLocker&);
 
   DLLLOCAL void *operator new(size_t);
 
protected:
   QoreVarRWLock *l;
 
   bool locked;
 
public:
   DLLLOCAL QoreSafeVarRWReadLocker(QoreVarRWLock &n_l) : l(&n_l) {
      l->rdlock();
      locked = true;
   }
 
   DLLLOCAL QoreSafeVarRWReadLocker(QoreVarRWLock *n_l) : l(n_l) {
      l->rdlock();
      locked = true;
   }
 
   DLLLOCAL ~QoreSafeVarRWReadLocker() {
      if (locked)
         l->unlock();
   }
 
   DLLLOCAL void lock() {
      assert(!locked);
      l->rdlock();
      locked = true;
   }
 
   DLLLOCAL void unlock() {
      assert(locked);
      locked = false;
      l->unlock();
   }
 
   DLLLOCAL void stay_locked() {
      assert(locked);
      locked = false;
   }
};
 
class QoreSafeVarRWWriteLocker {
private:
   DLLLOCAL QoreSafeVarRWWriteLocker(const QoreSafeVarRWWriteLocker&);
 
   DLLLOCAL QoreSafeVarRWWriteLocker& operator=(const QoreSafeVarRWWriteLocker&);
 
   DLLLOCAL void *operator new(size_t);
 
protected:
   QoreVarRWLock *l;
 
   bool locked;
 
public:
   DLLLOCAL QoreSafeVarRWWriteLocker(QoreVarRWLock &n_l) : l(&n_l) {
      l->wrlock();
      locked = true;
   }
 
   DLLLOCAL QoreSafeVarRWWriteLocker(QoreVarRWLock *n_l) : l(n_l) {
      l->wrlock();
      locked = true;
   }
 
   DLLLOCAL ~QoreSafeVarRWWriteLocker() {
      if (locked)
         l->unlock();
   }
 
   DLLLOCAL void lock() {
      assert(!locked);
      l->wrlock();
      locked = true;
   }
 
   DLLLOCAL void unlock() {
      assert(locked);
      locked = false;
      l->unlock();
   }
 
   DLLLOCAL void stay_locked() {
      assert(locked);
      locked = false;
   }
};
 
class QoreOptionalVarRWWriteLocker {
protected:
   QoreVarRWLock* l;
 
public:
   DLLLOCAL QoreOptionalVarRWWriteLocker(QoreVarRWLock* n_l) : l(n_l->trywrlock() ? 0 : n_l) {
   }
 
   DLLLOCAL QoreOptionalVarRWWriteLocker(QoreVarRWLock& n_l) : l(n_l.trywrlock() ? 0 : &n_l) {
   }
 
   DLLLOCAL ~QoreOptionalVarRWWriteLocker() {
      if (l)
         l->unlock();
   }
 
   DLLLOCAL operator bool() const {
      return (bool)l;
   }
};
 
class QoreOptionalVarRWReadLocker {
protected:
   QoreVarRWLock* l;
 
public:
   DLLLOCAL QoreOptionalVarRWReadLocker(QoreVarRWLock* n_l) : l(n_l->tryrdlock() ? 0 : n_l) {
   }
 
   DLLLOCAL QoreOptionalVarRWReadLocker(QoreVarRWLock& n_l) : l(n_l.tryrdlock() ? 0 : &n_l) {
   }
 
   DLLLOCAL ~QoreOptionalVarRWReadLocker() {
      if (l)
         l->unlock();
   }
 
   DLLLOCAL operator bool() const {
      return (bool)l;
   }
};
 
#endif