/usr/share/idl/thunderbird/nsIImportMimeEncode.idl is in thunderbird-dev 1:52.8.0-1~deb8u1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 | /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/*
  Encodes a file from disk into an output stream including properly
  encoded mime headers.
*/
#include "nsISupports.idl"
interface nsIFile;
[noscript, uuid(1d63892f-f660-465c-a550-95d4cb089de4)]
interface nsIImportMimeEncode : nsISupports
{
  void  EncodeFile( in nsIFile inFile, in nsIFile outFile, [const] in string fileName, [const] in string mimeType);
  boolean  DoWork( out boolean done);
  long  NumBytesProcessed();
  boolean  DoEncoding();
  void  Initialize( in nsIFile inFile, in nsIFile outFile, [const] in string fileName, [const] in string mimeType);
};
%{ C++
#define NS_IMPORTMIMEENCODE_CID                      \
{ /* e4a1a340-8de2-11d3-a206-00a0cc26da63 */         \
    0xe4a1a340,                                      \
    0x8de2,                                          \
    0x11d3,                                          \
    {0xa2, 0x06, 0x00, 0xa0, 0xcc, 0x26, 0xda, 0x63} \
}
%}
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