Author: damrakoc

C++ race condition helper

Posted on by damrakoc

Condition.h
C++
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#pragma once
 
#include <condition_variable>
#include <deque>
 
class Condition
{
public:
Condition();
~Condition();
void BeginSynchronized();
void EndSynchronized();
uint32_t Wait(time_t timeout);
uint32_t Wait();
void Signal();
void Broadcast();
 
private:
int m_nLockCount;
 
std::condition_variable m_condition;
std::mutex m_lock;
};

Condition.cpp
C++
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#include "stdafx.h"
#include "Condition.h"
 
Condition::Condition() : m_nLockCount(0) {}
 
void Condition::BeginSynchronized() {
  m_lock.lock();
  ++m_nLockCount;
}
 
void Condition::EndSynchronized() {
  --m_nLockCount;
  m_lock.unlock();
}
 
uint32_t Condition::Wait(time_t timeout) {
  std::unique_lock<std::mutex> lock(m_lock);
  m_condition.wait_for(lock, std::chrono::milliseconds(timeout));
  return 0;
}
 
uint32_t Condition::Wait() {
  std::unique_lock<std::mutex> lock(m_lock);
  m_condition.wait(lock);
  return 0;
}
 
void Condition::Signal() { m_condition.notify_one(); }
 
void Condition::Broadcast() { m_condition.notify_all(); }
 
Condition::~Condition() {}

    Usage:

RWLock.h
C++
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#pragma once
 
#include "Condition.h"
 
class RWLock
{
public:
RWLock();
void AcquireReadLock();
void ReleaseReadLock();
void AcquireWriteLock();
void ReleaseWriteLock();
 
private:
Condition _cond;
volatile uint32_t _readers;
volatile uint32_t _writers;
};

RWLock.cpp
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#include "stdafx.h"
#include "RWLock.h"
 
RWLock::RWLock() { _readers = _writers = 0; }
 
void RWLock::AcquireReadLock() {
  _cond.BeginSynchronized();
  _readers++;
  _cond.EndSynchronized();
}
 
void RWLock::ReleaseReadLock() {
  _cond.BeginSynchronized();
  if (!(--_readers))
    if (_writers)
      _cond.Signal();
  _cond.EndSynchronized();
}
 
void RWLock::AcquireWriteLock() {
  _cond.BeginSynchronized();
  _writers++;
  if (_readers)
    _cond.Wait();
}
 
void RWLock::ReleaseWriteLock() {
  if (--_writers)
    _cond.Signal();
  _cond.EndSynchronized();
}

     

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How can an enum have abstract methods?

Posted on by damrakoc

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public enum RecyclerViewLayoutManager {
LINEAR {
  public ViewGroup.LayoutParams getLayoutParams() {
   return new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
  }
 
  ;
},
GRID {
  public ViewGroup.LayoutParams getLayoutParams() {
   return new GridLayoutManager.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
  }
 
  ;
},
STAGGERED {
  public ViewGroup.LayoutParams getLayoutParams() {
   return new StaggeredGridLayoutManager.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
  }
 
  ;
};
 
public abstract ViewGroup.LayoutParams getLayoutParams();
}

 

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Thread Safe Singleton Abstract class

Posted on by damrakoc

Thread Safe Singleton Abstract class

Thread Safe Singleton Abstract class
Java
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package com.damrakoc.java;
 
import android.util.Log;
 
import java.lang.reflect.Constructor;
import java.util.HashMap;
import java.util.Map;
 
/**
* Created by damra on 08/08/2017.
*
USAGE:
public class TestSingleton extends ThreadSafeSingleton<TestSingleton> {
    public static TestSingleton getInstance() {
        return ThreadSafeSingleton.getInstance(TestSingleton.class);
    }
}
 
*/
 
@SuppressWarnings({"all"})
public abstract class ThreadSafeSingleton<T> {
 
    private static final Map<Class<? extends ThreadSafeSingleton>, ThreadSafeSingleton> INSTANCES = new HashMap<>();
    private static final String TAG = ThreadSafeSingleton.class.getSimpleName();
 
    private static class SingletonHolder<T> {
        private static <T> T getInstance(Class<T> clazz){
            Constructor<T> constructor = (Constructor<T>) clazz.getDeclaredConstructors()[0];
            constructor.setAccessible(true);
 
            try{
                return constructor.newInstance(null);
            }catch (Exception e){
                Log.d(TAG, "getInstance: "+e.getLocalizedMessage());
                return null;
            }
        }
    }
 
    protected ThreadSafeSingleton() {
        Log.d(TAG, "Initializing ThreadSafeSingleton");
    }
 
    protected static <T extends ThreadSafeSingleton<T>> T getInstance(Class<T> clazz) {
        if(INSTANCES.containsKey(clazz)) {
            return (T) INSTANCES.get(clazz);
        } else {
 
            try{
                T instance = SingletonHolder.getInstance(clazz);
                INSTANCES.put(clazz, instance);
                return instance;
            }catch (Exception e ){
                return null;
            }
        }
    }
 
    protected static <T extends ThreadSafeSingleton<T>> void putInstance(Class<T> clazz, T instance) {
        if(!INSTANCES.containsKey(clazz)) {
            INSTANCES.put(clazz, instance);
        }
    }
}

 

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