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authorTycho Bickerstaff <work.tycho@gmail.com>2014-01-02 18:43:57 +0100
committerTycho Bickerstaff <work.tycho@gmail.com>2014-01-02 18:43:57 +0100
commitd522619ce2ac05831febedea675d121445dcbdbe (patch)
treec6f803c250131562368fa69bf2636520a8022e5a /src/OSSupport
parentfixed a few remaining issues with worldstorage (diff)
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Diffstat (limited to 'src/OSSupport')
-rw-r--r--src/OSSupport/Queue.h52
1 files changed, 45 insertions, 7 deletions
diff --git a/src/OSSupport/Queue.h b/src/OSSupport/Queue.h
index 153e201c1..1f0c19f40 100644
--- a/src/OSSupport/Queue.h
+++ b/src/OSSupport/Queue.h
@@ -1,34 +1,55 @@
+// Queue.h
+
+// Implements the cQueue class representing a thread safe queue
+
#pragma once
#include <list>
-//this empty struct allows function inlining
+/*
+Usage:
+To use the callback functions Delete and Combine create a class with the two
+methods and pass it as a second template parameter to cQueue. The class does
+not need to inherit cQueueFuncs but you do so to document the classes purpose.
+The second template parmeter is optional if not overriding the callback
+functions
+*/
+
+// this empty struct allows for the callback functions to be inlined
template<class T>
struct cQueueFuncs
{
public:
+ // Called when an Item is deleted form the queue without being returned
static void Delete(T) {};
- static void Combine(T&, const T) {};
+ // Called when an Item is inserted with EnqueueItemIfNotPresent and
+ // there is another equal value already inserted
+ static void Combine(T& a_existing, const T a_new) {};
};
template<class ItemType, class Funcs = cQueueFuncs<ItemType> >
class cQueue
{
-
+// internal typedef for a List of Items
typedef typename std::list<ItemType> ListType;
-//magic typedef to persuade clang that the iterator is a type
+// magic typedef to persuade clang that the iterator is a type
typedef typename ListType::iterator iterator;
public:
cQueue() {}
~cQueue() {}
+ // Enqueues an item to the queue, may block if other threads are accessing
+ // the queue.
void EnqueueItem(ItemType a_item)
{
cCSLock Lock(m_CS);
m_contents.push_back(a_item);
m_evtAdded.Set();
}
+
+ // Enqueues an item to the queue if not already present as determined with
+ // operator ==. Will block other threads from accessing the queue.
void EnqueueItemIfNotPresent(ItemType a_item)
{
cCSLock Lock(m_CS);
@@ -44,6 +65,11 @@ public:
m_contents.push_back(a_item);
m_evtAdded.Set();
}
+
+ // Dequeues an Item from the queue if any are present, provides no
+ // guarantees about success if the list is empty but an item is enqueued at
+ // the same time. Returns true if successful. Value of item is undefined if
+ // Dequeuing was unsuccessful.
bool TryDequeueItem(ItemType& item)
{
cCSLock Lock(m_CS);
@@ -53,6 +79,8 @@ public:
m_evtRemoved.Set();
return true;
}
+
+ // Dequeues an Item from the Queue, blocking until an Item is Available.
ItemType DequeueItem()
{
cCSLock Lock(m_CS);
@@ -66,12 +94,17 @@ public:
m_evtRemoved.Set();
return item;
}
+
+ // Blocks Until the queue is Empty, Has a slight race condition which may
+ // cause it to miss the queue being empty.
void BlockTillEmpty() {
- //There is a very slight race condition here if the load completes between the check
- //and the wait.
+ // There is a very slight race condition here if the load completes between the check
+ // and the wait.
while(!(Size() == 0)){m_evtRemoved.Wait();}
}
- //can all be inlined when delete is a noop
+
+ // Removes all Items from the Queue, calling Delete on each of them.
+ // can all be inlined when delete is a noop
void Clear()
{
cCSLock Lock(m_CS);
@@ -82,11 +115,16 @@ public:
m_contents.pop_front();
}
}
+
+ // Returns the Size at time of being called
+ // Do not use to detirmine weather to call DequeueItem, use TryDequeue instead
size_t Size()
{
cCSLock Lock(m_CS);
return m_contents.size();
}
+
+ // Removes an Item from the queue
bool Remove(ItemType item)
{
cCSLock Lock(m_CS);