Initial release of the Windows Terminal source code

This commit introduces all of the Windows Terminal and Console Host source,
under the MIT license.

src/host/inputReadHandleData.cpp

@@ -0,0 +1,70 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT license.
+
+#include "precomp.h"
+
+#include "inputReadHandleData.h"
+
+INPUT_READ_HANDLE_DATA::INPUT_READ_HANDLE_DATA() :
+    _isInputPending{ false },
+    _isMultilineInput{ false }, 
+    _readCount{ 0 },
+    _buffer{}
+{
+}
+
+bool INPUT_READ_HANDLE_DATA::IsInputPending() const
+{
+    return _isInputPending;
+}
+
+bool INPUT_READ_HANDLE_DATA::IsMultilineInput() const
+{
+    FAIL_FAST_IF(!_isInputPending); // we shouldn't have multiline input without a pending input.
+    return _isMultilineInput;
+}
+
+void INPUT_READ_HANDLE_DATA::SaveMultilinePendingInput(std::wstring_view pending)
+{
+    _isMultilineInput = true;
+    SavePendingInput(pending);
+}
+
+void INPUT_READ_HANDLE_DATA::SavePendingInput(std::wstring_view pending)
+{
+    _isInputPending = true;
+    UpdatePending(pending);
+}
+
+void INPUT_READ_HANDLE_DATA::UpdatePending(std::wstring_view pending)
+{
+    _buffer = pending;
+}
+
+void INPUT_READ_HANDLE_DATA::CompletePending()
+{
+    _isInputPending = false;
+    _isMultilineInput = false;
+    _buffer.clear();
+}
+
+std::wstring_view INPUT_READ_HANDLE_DATA::GetPendingInput() const
+{
+    return _buffer;
+}
+
+void INPUT_READ_HANDLE_DATA::IncrementReadCount()
+{
+    _readCount++;
+}
+
+void INPUT_READ_HANDLE_DATA::DecrementReadCount()
+{
+    const size_t prevCount = _readCount.fetch_sub(1);
+    FAIL_FAST_IF(prevCount == 0); // we just underflowed, that's a programming error.
+}
+
+size_t INPUT_READ_HANDLE_DATA::GetReadCount()
+{
+    return _readCount;
+}