Investigate why the COOKED_READ_DATA ctor takes a string_view for wchar_t data?

[zadjii-msft]

COOKED_READ_DATA takes an initialData parameter of a string_view

terminal/src/host/readDataCooked.cpp

Lines 46 to 54 in d6cae40

	COOKED_READ_DATA::COOKED_READ_DATA(_In_ InputBuffer* const pInputBuffer,
	_In_ INPUT_READ_HANDLE_DATA* const pInputReadHandleData,
	SCREEN_INFORMATION& screenInfo,
	_In_ size_t UserBufferSize,
	_In_ PWCHAR UserBuffer,
	_In_ ULONG CtrlWakeupMask,
	_In_ CommandHistory* CommandHistory,
	const std::wstring_view exeName,
	const std::string_view initialData) :

However, when it memcpy's it, it copies it as a wchar_t buffer:

terminal/src/host/readDataCooked.cpp

Lines 97 to 103 in d6cae40

	if (!initialData.empty())
	{
	memcpy_s(_bufPtr, _bufferSize, initialData.data(), initialData.size());
	_bytesRead += initialData.size();
	const size_t cchInitialData = initialData.size() / sizeof(wchar_t);

As you can see here, _bufPtr is a wchar_t* which is initialized to _bufPtr = reinterpret_cast<wchar_t*>(_buffer.get())

terminal/src/host/readDataCooked.hpp

Lines 124 to 136 in d6cae40

	wchar_t* _bufPtr; // current position to insert chars at
	// should be const. the first char of the buffer
	wchar_t* _backupLimit;
	size_t _userBufferSize; // doubled size in ansi case
	wchar_t* _userBuffer;
	size_t* _pdwNumBytes;
	std::unique_ptr<byte[]> _buffer;
	std::wstring _exeName;
	std::unique_ptr<ConsoleHandleData> _tempHandle;

As I'm writing tests that use some cooked read data for #1856, I'm finding that the string I'm initializing the cooked read with is getting horribly mangled, because I'm passing a char buffer in.

Why is it like this? Does this magically just normally work when users call ReadConsole with wchar_t data in the buffer? I couldn't really figure it out in just a morning, so I'm filing this to make sure to follow up.

The test in question is ConptyRoundtripTests::TestResizeWithCookedRead.

[DHowett-MSFT]

AFAIK this is related to how we share cooked read between A and W APIs?

[DHowett-MSFT]

Actually, yeah, that doesn't make sense.

[DHowett]

IT TURNS OUT

That this was because initialData was explicitly documented as being broken for ReadConsoleA, and only worked for ReadConsoleW. We didn't need to support the ANSI version, so we were just being weirdos using string_view to pass around a pointer+length.