[in, out, optional] lpcbData (aka &length) A pointer to a variable that specifies the size of the buffer pointed to by the lpData parameter, in bytes. When the

[in, out, optional] lpcbData (aka &length) A pointer to a variable that specifies the size of the buffer pointed to by the lpData parameter, in bytes. When the function returns, this variable contains the size of the data copied to lpData. In other words, it's rewritten to be the actual length before it's incremented for null termination.