Explain the three values written by WriteSecBuf, in particular, why the

net/http/http_auth_handler_ntlm_portable.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/http/http_auth_handler_ntlm.h"
 
 #include <stdlib.h>
 // For gethostname
 #if defined(OS_POSIX)
 #include <unistd.h>
@@ skipping 177 matching lines @@
   dword = SWAP32(dword);
 #endif
   return WriteBytes(buf, &dword, sizeof(dword));
 }
 
 static void* WriteSecBuf(void* buf, uint16 length, uint32 offset) {
 #ifdef IS_BIG_ENDIAN
   length = SWAP16(length);
   offset = SWAP32(offset);
 #endif
+  // Len: 2 bytes.
   buf = WriteBytes(buf, &length, sizeof(length));
+  // MaxLen: 2 bytes. The sender should set it to the value of Len. The
+  // recipient must ignore it.
   buf = WriteBytes(buf, &length, sizeof(length));
+  // BufferOffset: 4 bytes.
   buf = WriteBytes(buf, &offset, sizeof(offset));
   return buf;
 }
 
 #ifdef IS_BIG_ENDIAN
 /**
  * WriteUnicodeLE copies a unicode string from one buffer to another.  The
  * resulting unicode string is in little-endian format.  The input string is
  * assumed to be in the native endianness of the local machine.  It is safe
  * to pass the same buffer as both input and output, which is a handy way to
@@ skipping 511 matching lines @@
   // NOTE: Default credentials are not supported for the portable implementation
   // of NTLM.
   scoped_ptr<HttpAuthHandler> tmp_handler(new HttpAuthHandlerNTLM);
   if (!tmp_handler->InitFromChallenge(challenge, target, origin, net_log))
     return ERR_INVALID_RESPONSE;
   handler->swap(tmp_handler);
   return OK;
 }
 
 }  // namespace net