"The parameter is incorrect" error from LookupAccountSid() - c++

Question

I thought I read the documentation correctly over at MSDN but apparently I didn't? I am not entirely sure what the heck I'm doing wrong and I'm ready to pull my hair out.
The documentation for the EVENTLOGRECORD structure provides the offset to the SID
https://msdn.microsoft.com/en-us/library/windows/desktop/aa363646(v=vs.85).aspx
UserSidOffset
The offset of the security identifier (SID) within this event log record. To obtain the user name for this SID, use the LookupAccountSid function.
Then to convert this sid, we use the LookupAccountSid() API.
https://msdn.microsoft.com/en-us/library/windows/desktop/aa379166(v=vs.85).aspx
lpSid [in]
A pointer to the SID to look up.
I've searched endlessly and found examples that look very similar to my implementation but gave me the same result. I'm rusty with the Windows API, so I wouldn't be surprised if I am overlooking the issue.
And finally, here is my code:
size_t BytesRemaining = 0;
while (BytesRemaining < BytesInBuffer)
{
EVENTLOGRECORD *Record = reinterpret_cast<EVENTLOGRECORD *>(buffer + BytesRemaining);
char UsernameBuffer[256], DomainBuffer[256];
DWORD UsernameBufferSize = 256, DomainBufferSize = 256;
SID_NAME_USE SidType;
PSID SID = (PSID)((LPBYTE)Record + Record->UserSidOffset);
if (!LookupAccountSid(NULL, SID, UsernameBuffer, &UsernameBufferSize, DomainBuffer, &DomainBufferSize, &SidType))
{
std::cout << "Failed reading SID (" << SID << "): " << GetLastErrorMessage().c_str();
}
else {
std::cout << "I didn't shit on the SID.\n";
}
BytesRemaining += Record->Length;
}
bytesInBuffer = 0;
Edit
After doing some debugging, I discovered that the StringsOffset and UserSidOffset contain the same value. So it looks like the offsets are pointing incorrectly... Which is why I am not able to pass a valid SID to the API.
Anyone?

Answer 1

cchName [in, out]
On input, specifies the size, in TCHARs, of the lpName buffer. If the function fails because the buffer is too small or if cchName is zero, cchName receives the required buffer size, including the terminating null character.
cchReferencedDomainName [in, out]
On input, specifies the size, in TCHARs, of the lpReferencedDomainName buffer. If the function fails because the buffer is too small or if cchReferencedDomainName is zero, cchReferencedDomainName receives the required buffer size, including the terminating null character.
You need to assign the array sizes to UsernameBufferSize and DomainBufferSize before calling LookupAccountSid(). Either that, or set them to zero and then dynamically allocate UsernameBuffer and DomainBuffer, then call LookupAccountSid() again.