SystemParametersInfo: buffer size in unicode characters or bytes?

The SystemParametersInfo function in Windows CE can be tricky, even deadly, when it comes to passing in buffers for SPI_GETOEMINFO or SPI_GETPLATFORMTYPE.  Each of these uiAction values fill a given buffer with a string.  The uiParam argument takes the size of that buffer.  The catch is, for SPI_GETOEMINFO, uiParam takes a size of buffer in bytes and for SPI_GETPLATFORMTYPE uiParam takes the size of the buffer in count of unicode characters.

The documentation on SPI_GETOEMINFO is not precise on which type of buffer size is requested, and if you pass the wrong one to SPI_GETPLATFORMTYPE, you could find yourself in a buffer overrun situation.  Be careful.  The code below is safe:

#include "stdafx.h"

#define _countof(x)		(sizeof(x) / sizeof(x[0]))

int _tmain(int argc, _TCHAR* argv[])
{
	/**********************
	 * Get OEM information
	 **********************/
	WCHAR wszOemInfo[50];
	UINT cbOemInfo = sizeof(wszOemInfo);

	if (SystemParametersInfoW(SPI_GETOEMINFO, cbOemInfo, wszOemInfo, 0))
		MessageBoxW(NULL, wszOemInfo, L"OEMINFO", MB_OK);
	else if (GetLastError() == ERROR_INSUFFICIENT_BUFFER)
		MessageBoxW(NULL, L"Insufficient buffer", L"OEMINFO", MB_OK);
	else
		MessageBoxW(NULL, L"Some other error.", L"OEMINFO", MB_OK);


	/**********************
	 * Get platform type
	 **********************/
	WCHAR wszPlatformType[50];
	UINT cchPlatformType = _countof(wszPlatformType);
	if (SystemParametersInfoW(SPI_GETPLATFORMTYPE, cchPlatformType, wszPlatformType, 0))
		MessageBoxW(NULL, wszPlatformType, L"Platform type", MB_OK);
	else if (GetLastError() == ERROR_INSUFFICIENT_BUFFER)
		MessageBoxW(NULL, L"Insufficient buffer", L"Platform type", MB_OK);
	else
		MessageBoxW(NULL, L"Some other error.", L"Platform type", MB_OK);

	return 0;
}