diff --git a/Foundation/include/Poco/Buffer.h b/Foundation/include/Poco/Buffer.h
index d2f244722..b80c110e3 100644
--- a/Foundation/include/Poco/Buffer.h
+++ b/Foundation/include/Poco/Buffer.h
@@ -60,6 +60,7 @@ class Buffer
 public:
 	Buffer(std::size_t size):
 		_size(size),
+		_used(size),
 		_ptr(new T[size])
 		/// Creates and allocates the Buffer.
 	{
@@ -79,21 +80,30 @@ public:
 	{
 		poco_assert(newSize);
 
-		T* ptr = new T[newSize];
-		if (preserveContent)
+		if (newSize > _size)
 		{
-			std::size_t n = newSize > _size ? _size : newSize;
-			std::memcpy(ptr, _ptr, n);
+			T* ptr = new T[newSize];
+			if (preserveContent)
+				std::memcpy(ptr, _ptr, newSize);
+
+			delete [] _ptr;
+			_ptr  = ptr;
+			_size = newSize;
 		}
-		delete [] _ptr;
-		_ptr  = ptr;
-		_size = newSize;
+		
+		_used = newSize;
+	}
+
+	std::size_t allocated() const
+		/// Returns the allocated memory size.
+	{
+		return _size;
 	}
 
 	std::size_t size() const
-		/// Returns the size of the buffer.
+		/// Returns the used size of the buffer.
 	{
-		return _size;
+		return _used;
 	}
 	
 	T* begin()
@@ -111,25 +121,25 @@ public:
 	T* end()
 		/// Returns a pointer to end of the buffer.
 	{
-		return _ptr + _size;
+		return _ptr + _used;
 	}
 	
 	const T* end() const
 		/// Returns a pointer to the end of the buffer.
 	{
-		return _ptr + _size;
+		return _ptr + _used;
 	}
 	
 	T& operator [] (std::size_t index)
 	{
-		poco_assert (index < _size);
+		poco_assert (index < _used);
 		
 		return _ptr[index];
 	}
 
 	const T& operator [] (std::size_t index) const
 	{
-		poco_assert (index < _size);
+		poco_assert (index < _used);
 		
 		return _ptr[index];
 	}
@@ -140,6 +150,7 @@ private:
 	Buffer& operator = (const Buffer&);
 
 	std::size_t _size;
+	std::size_t _used;
 	T* _ptr;
 };
 
diff --git a/Foundation/include/Poco/FIFOBuffer.h b/Foundation/include/Poco/FIFOBuffer.h
index 37a06dcc7..b34602935 100644
--- a/Foundation/include/Poco/FIFOBuffer.h
+++ b/Foundation/include/Poco/FIFOBuffer.h
@@ -89,6 +89,7 @@ public:
 
 	FIFOBuffer(std::size_t size, bool notify = false):
 		_buffer(size),
+		_begin(0),
 		_used(0),
 		_notify(notify)
 		/// Creates and allocates the FIFOBuffer.
@@ -124,7 +125,7 @@ public:
 		/// Peeks into the data currently in the FIFO
 		/// without actually extracting it.
 		/// Resizes the supplied buffer to the size of
-		///.data written to it. If length is not
+		/// data written to it. If length is not
 		/// supplied by the caller, the current FIFO used length
 		/// is substituted for it.
 		/// 
@@ -135,7 +136,7 @@ public:
 		if (0 == length || length > _used) length = _used;
 		poco_assert (length <= _buffer.size());
 		buffer.resize(length);
-		std::memcpy(buffer.begin(), _buffer.begin(), length * sizeof(T));
+		std::memcpy(buffer.begin(), _buffer.begin() + _begin, length * sizeof(T));
 
 		return length;
 	}
@@ -144,7 +145,7 @@ public:
 		/// Copies the data currently in the FIFO
 		/// into the supplied buffer.
 		/// Resizes the supplied buffer to the size of
-		///.data written to it.
+		/// data written to it.
 		/// 
 		/// Returns the reference to the buffer.
 	{
@@ -156,9 +157,9 @@ public:
 		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 (0 == _used) _begin = 0;
+		else _begin += length;
+
 		if (_notify) notify(usedBefore);
 
 		return readLen;
@@ -174,11 +175,16 @@ public:
 	{
 		Mutex::ScopedLock lock(_mutex);
 
-		poco_assert (_used <= _buffer.size());
+		if (_buffer.size() - (_begin + _used) < buffer.size())
+		{
+			std::memmove(_buffer.begin(), _buffer.begin() + _begin, _used);
+			_begin = 0;
+		}
+
 		std::size_t usedBefore = _used;
-		std::size_t available =  _buffer.size() - _used;
+		std::size_t available =  _buffer.size() - _used - _begin;
 		std::size_t len = buffer.size() > available ? available : buffer.size();
-		std::memcpy(_buffer.begin() + _used, buffer.begin(), len * sizeof(T));
+		std::memcpy(_buffer.begin() + _begin + _used, buffer.begin(), len * sizeof(T));
 		_used += len;
 		poco_assert (_used <= _buffer.size());
 		if (_notify) notify(usedBefore);
@@ -212,7 +218,7 @@ public:
 		if (index >= _used)
 			throw InvalidAccessException(format("Index out of bounds: %z (max index allowed: %z)", index, _used - 1));
 
-		return _buffer[index];
+		return _buffer[_begin + index];
 	}
 
 	const T& operator [] (std::size_t index) const
@@ -223,7 +229,7 @@ public:
 		if (index >= _used)
 			throw InvalidAccessException(format("Index out of bounds: %z (max index allowed: %z)", index, _used - 1));
 
-		return _buffer[index];
+		return _buffer[_begin + index];
 	}
 
 	bool isEmpty() const
@@ -251,6 +257,7 @@ private:
 	FIFOBuffer& operator = (const FIFOBuffer&);
 
 	Buffer<T>     _buffer;
+	std::size_t   _begin;
 	std::size_t   _used;
 	bool          _notify;
 	mutable Mutex _mutex;
diff --git a/Foundation/testsuite/src/CoreTest.cpp b/Foundation/testsuite/src/CoreTest.cpp
index 62549dae4..e36e9f1ea 100644
--- a/Foundation/testsuite/src/CoreTest.cpp
+++ b/Foundation/testsuite/src/CoreTest.cpp
@@ -197,6 +197,8 @@ void CoreTest::testBuffer()
 {
 	std::size_t s = 10;
 	Buffer<int> b(s);
+	assert (b.size() == s);
+	assert (b.allocated() == s);
 	std::vector<int> v;
 	for (int i = 0; i < s; ++i)
 		v.push_back(i);
@@ -207,6 +209,26 @@ void CoreTest::testBuffer()
 	for (int i = 0; i < s; ++i)
 		assert (b[i] == i);
 
+	b.resize(s/2);
+	for (int i = 0; i < s/2; ++i)
+		assert (b[i] == i);
+
+	assert (b.size() == s/2);
+	assert (b.allocated() == s);
+
+	b.resize(s*2);
+	v.clear();
+	for (int i = 0; i < s*2; ++i)
+		v.push_back(i);
+
+	std::memcpy(b.begin(), &v[0], sizeof(int) * v.size());
+
+	for (int i = 0; i < s*2; ++i)
+		assert (b[i] == i);
+
+	assert (b.size() == s*2);
+	assert (b.allocated() == s*2);
+
 #if ENABLE_BUGCHECK_TEST
 	try { int i = b[s]; fail ("must fail"); }
 	catch (Exception&) { }