FIFOBuffer::drain() and partial write

Foundation/include/Poco/Buffer.h

@@ -58,10 +58,10 @@ class Buffer
 	/// is needed.
 {
 public:
-	Buffer(std::size_t size):
-		_capacity(size),
-		_used(size),
-		_ptr(new T[size])
+	Buffer(std::size_t capacity):
+		_capacity(capacity),
+		_used(capacity),
+		_ptr(new T[capacity])
 		/// Creates and allocates the Buffer.
 	{
 	}
@@ -75,8 +75,8 @@ public:
 	void resize(std::size_t newCapacity, bool preserveContent = true)
 		/// Resizes the buffer. If preserveContent is true,
 		/// the content of the old buffer is copied over to the
-		/// new buffer. NewSize can be larger or smaller than
-		/// the current size, but it must not be 0.
+		/// new buffer. The new capacity can be larger or smaller than
+		/// the current one, but it must not be 0.
 	{
 		poco_assert(newCapacity);
 

Foundation/include/Poco/FIFOBuffer.h

@@ -54,10 +54,10 @@ namespace Poco {
 template <class T>
 class BasicFIFOBuffer
 	/// A simple buffer class with support for re-entrant,
-	/// 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.
+	/// FIFO-style read/write operations, as well as (optional)
+	/// empty/non-empty/full (i.e. writable/readable) transition
+	/// notifications. Buffer size, as well as amount of unread data
+	/// and available space introspections are supported as well.
 	///
 	/// This class is useful anywhere where a FIFO functionality
 	/// is needed.
@@ -167,17 +167,22 @@ public:
 		return readLen;
 	}
 
-	std::size_t write(const Buffer<T>& buffer)
-		/// Writes data.size() to the FIFO buffer.
+	std::size_t write(const Buffer<T>& buffer, std::size_t length = 0)
+		/// Writes data from supplied buffer to the FIFO buffer.
 		/// If there is no sufficient space for the whole
 		/// buffer to be written, data up to available 
 		/// length is written.
+		/// The length of data to be written is determined from the
+		/// length argument or buffer size (when length argument is
+		/// default zero or greater than buffer size).
 		/// 
 		/// Returns the length of data written.
 	{
 		Mutex::ScopedLock lock(_mutex);
 
-		if (_buffer.size() - (_begin + _used) < buffer.size())
+		if (0 == length || length > buffer.size()) length = buffer.size();
+
+		if (_buffer.size() - (_begin + _used) < length)
 		{
 			std::memmove(_buffer.begin(), _buffer.begin() + _begin, _used);
 			_begin = 0;
@@ -185,7 +190,7 @@ public:
 
 		std::size_t usedBefore = _used;
 		std::size_t available =  _buffer.size() - _used - _begin;
-		std::size_t len = buffer.size() > available ? available : buffer.size();
+		std::size_t len = length > available ? available : length;
 		std::memcpy(_buffer.begin() + _begin + _used, buffer.begin(), len * sizeof(T));
 		_used += len;
 		poco_assert (_used <= _buffer.size());
@@ -212,6 +217,24 @@ public:
 		return _buffer.size() - _used;
 	}
 
+	void drain(std::size_t length = 0)
+		/// Drains length number of elements from the buffer.
+		/// If length is zero or greater than buffer current
+		/// content length, buffer is emptied.
+	{
+		std::size_t usedBefore = _used;
+
+		if (0 == length || length >= _used)
+		{
+			_begin = 0;
+			_used = 0;
+		}
+		else
+			_used -= length;
+
+		if (_notify) notify(usedBefore);
+	}
+
 	T& operator [] (std::size_t index)
 		/// Returns value at index position.
 		/// Throws InvalidAccessException if index is larger than 
@@ -234,6 +257,12 @@ public:
 		return _buffer[_begin + index];
 	}
 
+	const Buffer<T>& buffer() const
+		/// Returns const reference to the underlying buffer.
+	{
+		return _buffer;
+	}
+
 	bool isEmpty() const
 		/// Returns true is buffer is empty, flase otherwise.
 	{

Foundation/testsuite/src/CoreTest.cpp

@@ -406,6 +406,83 @@ void CoreTest::testFIFOBufferChar()
 	assert(1 == _writableToNot);
 	assert (f.isEmpty());
 
+	f.resize(10);
+	assert (10 == f.size());
+	assert (0 == f.used());
+	assert (10 == f.available());
+	assert (f.isEmpty());
+
+	assert(3 == _notToReadable);
+	assert(3 == _readableToNot);
+	assert(1 == _notToWritable);
+	assert(1 == _writableToNot);
+	f.write(b);
+	assert(4 == _notToReadable);
+	assert(3 == _readableToNot);
+	assert(1 == _notToWritable);
+	assert(1 == _writableToNot);
+
+	assert (10 == f.size());
+	assert (3 == f.used());
+	assert (7 == f.available());
+	assert (!f.isEmpty());
+
+	f.drain(1);
+	assert(4 == _notToReadable);
+	assert(3 == _readableToNot);
+	assert(1 == _notToWritable);
+	assert(1 == _writableToNot);
+
+	assert (10 == f.size());
+	assert (2 == f.used());
+	assert (8 == f.available());
+	assert (!f.isEmpty());
+
+	f.drain(2);
+	assert(4 == _notToReadable);
+	assert(4 == _readableToNot);
+	assert(1 == _notToWritable);
+	assert(1 == _writableToNot);
+
+	assert (10 == f.size());
+	assert (0 == f.used());
+	assert (10 == f.available());
+	assert (f.isEmpty());
+
+	f.write(b);
+	assert(5 == _notToReadable);
+	assert(4 == _readableToNot);
+	assert(1 == _notToWritable);
+	assert(1 == _writableToNot);
+
+	assert (10 == f.size());
+	assert (3 == f.used());
+	assert (7 == f.available());
+	assert (!f.isEmpty());
+
+	f.drain();
+	assert(5 == _notToReadable);
+	assert(5 == _readableToNot);
+	assert(1 == _notToWritable);
+	assert(1 == _writableToNot);
+	assert (10 == f.size());
+	assert (0 == f.used());
+	assert (10 == f.available());
+	assert (f.isEmpty());
+
+	f.write(b, 2);
+	assert (10 == f.size());
+	assert (2 == f.used());
+	assert (8 == f.available());
+	assert (!f.isEmpty());
+
+	f.drain();
+	assert (3 == f.write(b, 10));
+	assert (10 == f.size());
+	assert (3 == f.used());
+	assert (7 == f.available());
+	assert (!f.isEmpty());
+
 	f.Readable -= delegate(this, &CoreTest::onReadable);
 	f.Writable -= delegate(this, &CoreTest::onReadable);
 }