FIFOBuffer events and tests

Foundation/include/Poco/FIFOBuffer.h

@@ -43,6 +43,7 @@
 #include "Poco/Foundation.h"
 #include "Poco/Exception.h"
 #include "Poco/Buffer.h"
+#include "Poco/BasicEvent.h"
 #include "Poco/Mutex.h"
 #include "Poco/Format.h"
 
@@ -53,17 +54,43 @@ namespace Poco {
 template <class T>
 class FIFOBuffer
 	/// A simple buffer class with support for re-entrant,
-	/// FIFO-style read/write operations as well as 
-	/// introspection into the size of buffer, amount of unread data
-	/// and available space.
+	/// FIFO-style read/write operations. as well as 
+	/// empty/full transition notifications. Buffer size
+	/// introspection as well as amount of unread data and 
+	/// available space are supported as well.
 	///
-	/// This class is useful everywhere where a FIFO functionality
+	/// This class is useful anywhere where a FIFO functionality
 	/// is needed.
 {
 public:
-	FIFOBuffer(std::size_t size):
+	mutable Poco::BasicEvent<bool> Writeable;
+		/// Event indicating "writeability" of the buffer,
+		/// triggerred as follows:
+		///
+		///	* when buffer transitions from non-full to full, 
+		///	  Writeable event observers are notified, with 
+		///	  false value as the argument
+		///
+		///	* when buffer transitions from full to non-full,
+		///	  Writeable event observers are notified, with 
+		///	  true value as the argument
+
+	mutable Poco::BasicEvent<bool> Readable;
+		/// Event indicating "readability" of the buffer,
+		/// triggerred as follows:
+		///
+		///	* when buffer transitions from non-empty to empty,
+		///	  Readable event observers are notified, with false  
+		///	  value as the argument
+		///
+		///	* when FIFOBuffer transitions from empty to non-empty,
+		///	  Readable event observers are notified, with true value
+		///	  as the argument
+
+	FIFOBuffer(std::size_t size, bool notify = false):
 		_buffer(size),
-		_used(0)
+		_used(0),
+		_notify(notify)
 		/// Creates and allocates the FIFOBuffer.
 	{
 	}
@@ -87,11 +114,13 @@ public:
 		if (preserveContent && (newSize < _used))
 			throw InvalidAccessException("Can not resize FIFO without data loss.");
 		
+		std::size_t usedBefore = _used;
 		_buffer.resize(newSize, preserveContent);
 		if (!preserveContent) _used = 0;
+		if (_notify) notify(usedBefore);
 	}
 	
-	Buffer<T>& peek(Poco::Buffer<T>& buffer, std::size_t length = 0) const
+	std::size_t peek(Poco::Buffer<T>& buffer, std::size_t length = 0) const
 		/// Peeks into the data currently in the FIFO
 		/// without actually extracting it.
 		/// Resizes the supplied buffer to the size of
@@ -108,10 +137,10 @@ public:
 		buffer.resize(length);
 		std::memcpy(buffer.begin(), _buffer.begin(), length * sizeof(T));
 
-		return buffer;
+		return length;
 	}
 	
-	Buffer<T>& read(Poco::Buffer<T>& buffer, std::size_t length = 0)
+	std::size_t read(Poco::Buffer<T>& buffer, std::size_t length = 0)
 		/// Copies the data currently in the FIFO
 		/// into the supplied buffer.
 		/// Resizes the supplied buffer to the size of
@@ -121,13 +150,18 @@ public:
 	{
 		Mutex::ScopedLock lock(_mutex);
 
-		std::size_t usedBefore = _used;
-		peek(buffer, length);
-		_used -= buffer.size();
-		if (_used)
-			std::memmove(_buffer.begin(), _buffer.begin() + usedBefore - _used, _used);
+		if (0 == _used) return 0;
 
-		return buffer;
+		std::size_t usedBefore = _used;
+		std::size_t readLen = peek(buffer, length);
+		poco_assert (_used >= readLen);
+		_used -= readLen;
+		if (_used > 0)
+			std::memmove(_buffer.begin(), _buffer.begin() + usedBefore - _used, _used);
+		
+		if (_notify) notify(usedBefore);
+
+		return readLen;
 	}
 
 	std::size_t write(const Buffer<T>& buffer)
@@ -141,11 +175,13 @@ public:
 		Mutex::ScopedLock lock(_mutex);
 
 		poco_assert (_used <= _buffer.size());
+		std::size_t usedBefore = _used;
 		std::size_t available =  _buffer.size() - _used;
 		std::size_t len = buffer.size() > available ? available : buffer.size();
 		std::memcpy(_buffer.begin() + _used, buffer.begin(), len * sizeof(T));
 		_used += len;
 		poco_assert (_used <= _buffer.size());
+		if (_notify) notify(usedBefore);
 
 		return len;
 	}
@@ -197,12 +233,26 @@ public:
 	}
 
 private:
+	void notify(std::size_t usedBefore)
+	{
+		bool t = true, f = false;
+		if (usedBefore == 0 && _used > 0)
+			Readable.notify(this, t);
+		else if (usedBefore > 0 && 0 == _used)
+			Readable.notify(this, f);
+		else if (usedBefore == _buffer.size() && _used < _buffer.size())
+			Writeable.notify(this, t);
+		else if (usedBefore < _buffer.size() && _used == _buffer.size())
+			Writeable.notify(this, f);
+	}
+
 	FIFOBuffer();
 	FIFOBuffer(const FIFOBuffer&);
 	FIFOBuffer& operator = (const FIFOBuffer&);
 
 	Buffer<T>     _buffer;
 	std::size_t   _used;
+	bool          _notify;
 	mutable Mutex _mutex;
 };
 

Foundation/testsuite/src/CoreTest.cpp

@@ -43,6 +43,8 @@
 #include "Poco/AtomicCounter.h"
 #include "Poco/Nullable.h"
 #include "Poco/Ascii.h"
+#include "Poco/BasicEvent.h"
+#include "Poco/Delegate.h"
 #include "Poco/Exception.h"
 #include <iostream>
 #include <vector>
@@ -59,6 +61,8 @@ using Poco::FIFOBuffer;
 using Poco::AtomicCounter;
 using Poco::Nullable;
 using Poco::Ascii;
+using Poco::BasicEvent;
+using Poco::delegate;
 using Poco::InvalidAccessException;
 
 
@@ -214,15 +218,22 @@ void CoreTest::testFIFOBufferChar()
 {
 	typedef char T;
 
-	FIFOBuffer<T> f(20);
+	FIFOBuffer<T> f(20, true);
 	Buffer<T> b(10);
 	std::vector<T> v;
 
+	f.Readable += delegate(this, &CoreTest::onReadable);
+	f.Writeable += delegate(this, &CoreTest::onReadable);
+
 	for (T c = '0'; c < '0' +  10; ++c)
 		v.push_back(c);
 
 	std::memcpy(b.begin(), &v[0], sizeof(T) * v.size());
+	assert(0 == _notToReadable);
+	assert(0 == _readableToNot);
 	f.write(b);
+	assert(1 == _notToReadable);
+	assert(0 == _readableToNot);
 	assert (20 == f.size());
 	assert (10 == f.used());
 	assert (!f.isEmpty());
@@ -290,7 +301,12 @@ void CoreTest::testFIFOBufferChar()
 	try { T i = f[5]; fail ("must fail"); }
 	catch (InvalidAccessException&) { }
 
+	assert(1 == _notToReadable);
+	assert(0 == _readableToNot);
 	f.read(b, 6);
+	assert(1 == _notToReadable);
+	assert(1 == _readableToNot);
+
 	assert (5 == b.size());
 	assert (20 == f.size());
 	assert (0 == f.used());
@@ -298,7 +314,12 @@ void CoreTest::testFIFOBufferChar()
 	catch (InvalidAccessException&) { }
 	assert (f.isEmpty());
 
+	assert(1 == _notToReadable);
+	assert(1 == _readableToNot);
 	assert (5 == f.write(b));
+	assert(2 == _notToReadable);
+	assert(1 == _readableToNot);
+
 	assert (20 == f.size());
 	assert (5 == f.used());
 	assert (!f.isEmpty());
@@ -318,10 +339,28 @@ void CoreTest::testFIFOBufferChar()
 	assert ('i' == f[3]);
 	assert ('j' == f[4]);
 
+	assert(2 == _notToReadable);
+	assert(1 == _readableToNot);
 	f.resize(3, false);
+	assert(2 == _notToReadable);
+	assert(2 == _readableToNot);
 	assert (3 == f.size());
 	assert (0 == f.used());
 	assert (f.isEmpty());
+
+	b.resize(3);
+	b[0] = 'x';
+	b[1] = 'y';
+	b[2] = 'z';
+	
+	assert(2 == _notToReadable);
+	assert(2 == _readableToNot);
+	f.write(b);
+	assert(3 == _notToReadable);
+	assert(2 == _readableToNot);
+
+	f.Readable -= delegate(this, &CoreTest::onReadable);
+	f.Writeable -= delegate(this, &CoreTest::onReadable);
 }
 
 
@@ -592,8 +631,26 @@ void CoreTest::testAscii()
 }
 
 
+void CoreTest::onReadable(bool& b)
+{
+	if (b) ++_notToReadable;
+	else ++_readableToNot;
+};
+
+
+void CoreTest::onWriteable(bool& b)
+{
+	if (b) ++_notToWriteable;
+	else ++_writeableToNot;
+}
+
+
 void CoreTest::setUp()
 {
+	_readableToNot = 0;
+	_notToReadable = 0;
+	_writeableToNot = 0;
+	_notToWriteable = 0;
 }
 
 

Foundation/testsuite/src/CoreTest.h

@@ -63,7 +63,15 @@ public:
 
 	static CppUnit::Test* suite();
 
+protected:
+	void onReadable(bool& b);
+	void onWriteable(bool& b);
+
 private:
+	int _readableToNot;
+	int _notToReadable;
+	int _writeableToNot;
+	int _notToWriteable;
 };