C++ types in VB declaration?

Hi, I found this Base64 dll written in C++ but I need to call it's functions from VB. Most of the variable types I can figure out and get to work, but there's a couple that I don't know how to translate into VB and could use some help. The list is below.

Code:

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UINT cb  =  ByVal cb As Long
LPCTSTR lpInput  =  ByVal lpInput As String    ?
LPUINT lpEqualSigns  =  ByRef lpEqualSigns As Long  ?
LPCBYTE lpInput  =  ?? (supposed to be the string to encode)
LPTSTR lpOutput  =  ?? (supposed to be the output buffer, I'm guessing it would be a string of spaces)
LPCTSTR lpInput  =  ??
LPBYTE  lpOutput  =  ??
BASE64CALLBACK lpEndCallback  =  ??
LPVOID lpvParam  =  lpvParam As Any ?? (ByVal/ByRef?)

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If anyone can shed some light on this I would really appreciate it. I'm trying to get in contact with the author but I don't know if I will be able to.