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diff --git a/oox/source/ole/vbainputstream.cxx b/oox/source/ole/vbainputstream.cxx
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+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * 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/.
+ *
+ * This file incorporates work covered by the following license notice:
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed
+ * with this work for additional information regarding copyright
+ * ownership. The ASF licenses this file to you under the Apache
+ * License, Version 2.0 (the "License"); you may not use this file
+ * except in compliance with the License. You may obtain a copy of
+ * the License at http://www.apache.org/licenses/LICENSE-2.0 .
+ */
+
+#include <oox/ole/vbainputstream.hxx>
+#include <osl/diagnose.h>
+
+namespace oox::ole {
+
+namespace {
+
+const sal_uInt8 VBASTREAM_SIGNATURE = 1;
+
+const sal_uInt16 VBACHUNK_SIGMASK = 0x7000;
+const sal_uInt16 VBACHUNK_SIG = 0x3000;
+const sal_uInt16 VBACHUNK_COMPRESSED = 0x8000;
+const sal_uInt16 VBACHUNK_LENMASK = 0x0FFF;
+
+} // namespace
+
+VbaInputStream::VbaInputStream( BinaryInputStream& rInStrm ) :
+ BinaryStreamBase( false ),
+ mpInStrm( &rInStrm ),
+ mnChunkPos( 0 )
+{
+ maChunk.reserve( 4096 );
+
+ sal_uInt8 nSig = rInStrm.readuInt8();
+ OSL_ENSURE( nSig == VBASTREAM_SIGNATURE, "VbaInputStream::VbaInputStream - wrong signature" );
+ mbEof = mbEof || rInStrm.isEof() || (nSig != VBASTREAM_SIGNATURE);
+}
+
+sal_Int64 VbaInputStream::size() const
+{
+ return -1;
+}
+
+sal_Int64 VbaInputStream::tell() const
+{
+ return -1;
+}
+
+void VbaInputStream::seek( sal_Int64 )
+{
+}
+
+void VbaInputStream::close()
+{
+ mpInStrm = nullptr;
+ mbEof = true;
+}
+
+sal_Int32 VbaInputStream::readData( StreamDataSequence& orData, sal_Int32 nBytes, size_t nAtomSize )
+{
+ sal_Int32 nRet = 0;
+ if( !mbEof )
+ {
+ orData.realloc( ::std::max< sal_Int32 >( nBytes, 0 ) );
+ if( nBytes > 0 )
+ {
+ nRet = readMemory( orData.getArray(), nBytes, nAtomSize );
+ if( nRet < nBytes )
+ orData.realloc( nRet );
+ }
+ }
+ return nRet;
+}
+
+sal_Int32 VbaInputStream::readMemory( void* opMem, sal_Int32 nBytes, size_t /*nAtomSize*/ )
+{
+ sal_Int32 nRet = 0;
+ sal_uInt8* opnMem = static_cast< sal_uInt8* >( opMem );
+ while( (nBytes > 0) && updateChunk() )
+ {
+ sal_Int32 nChunkLeft = static_cast< sal_Int32 >( maChunk.size() - mnChunkPos );
+ sal_Int32 nReadBytes = ::std::min( nBytes, nChunkLeft );
+ memcpy( opnMem, &*(maChunk.begin() + mnChunkPos), nReadBytes );
+ opnMem += nReadBytes;
+ mnChunkPos += static_cast< size_t >( nReadBytes );
+ nBytes -= nReadBytes;
+ nRet += nReadBytes;
+ }
+ return nRet;
+}
+
+void VbaInputStream::skip( sal_Int32 nBytes, size_t /*nAtomSize*/ )
+{
+ while( (nBytes > 0) && updateChunk() )
+ {
+ sal_Int32 nChunkLeft = static_cast< sal_Int32 >( maChunk.size() - mnChunkPos );
+ sal_Int32 nSkipBytes = ::std::min( nBytes, nChunkLeft );
+ mnChunkPos += static_cast< size_t >( nSkipBytes );
+ nBytes -= nSkipBytes;
+ }
+}
+
+// private --------------------------------------------------------------------
+
+bool VbaInputStream::updateChunk()
+{
+ if( mbEof || (mnChunkPos < maChunk.size()) ) return !mbEof;
+ // try to read next chunk header, this may trigger EOF
+ sal_uInt16 nHeader = mpInStrm->readuInt16();
+
+ mbEof = mpInStrm->isEof();
+ if( mbEof ) return false;
+
+ // check header signature
+ bool bIgnoreBrokenSig = ( (nHeader & VBACHUNK_SIGMASK) != VBACHUNK_SIG );
+
+ // decode length of chunk data and compression flag
+ bool bCompressed = getFlag( nHeader, VBACHUNK_COMPRESSED );
+ sal_uInt16 nChunkLen = (nHeader & VBACHUNK_LENMASK) + 1;
+ OSL_ENSURE( bCompressed || (nChunkLen == 4096), "VbaInputStream::updateChunk - invalid uncompressed chunk size" );
+
+ // From the amazing bit detective work of Valek Filippov<frob@gnome.org>
+ // this tweak and the one at the bottom of the method to seek to the
+ // start of the next chunk we can read those strange broken
+ // ( I guess from a MSO bug ) compressed streams > 4k
+
+ if ( bIgnoreBrokenSig )
+ {
+ bCompressed = true;
+ nChunkLen = 4094;
+ }
+
+ sal_Int64 target = mpInStrm->tell() + nChunkLen;
+ if( bCompressed )
+ {
+ maChunk.clear();
+ sal_uInt8 nBitCount = 4;
+ sal_uInt16 nChunkPos = 0;
+ while( !mbEof && !mpInStrm->isEof() && (nChunkPos < nChunkLen) )
+ {
+ sal_uInt8 nTokenFlags = mpInStrm->readuInt8();
+ ++nChunkPos;
+ for( int nBit = 0; !mbEof && !mpInStrm->isEof() && (nBit < 8) && (nChunkPos < nChunkLen); ++nBit, nTokenFlags >>= 1 )
+ {
+ if( nTokenFlags & 1 )
+ {
+ sal_uInt16 nCopyToken = mpInStrm->readuInt16();
+ nChunkPos = nChunkPos + 2;
+ // update bit count used for offset/length in the token
+ while( ( static_cast<size_t>(1) << nBitCount ) < maChunk.size() ) ++nBitCount;
+ // extract length from lower (16-nBitCount) bits, plus 3
+ sal_uInt16 nLength = extractValue< sal_uInt16 >( nCopyToken, 0, 16 - nBitCount ) + 3;
+ // extract offset from high nBitCount bits, plus 1
+ sal_uInt16 nOffset = extractValue< sal_uInt16 >( nCopyToken, 16 - nBitCount, nBitCount ) + 1;
+ mbEof = (nOffset > maChunk.size()) || (maChunk.size() + nLength > 4096);
+ OSL_ENSURE( !mbEof, "VbaInputStream::updateChunk - invalid offset or size in copy token" );
+ if( !mbEof )
+ {
+ // append data to buffer
+ maChunk.resize( maChunk.size() + nLength );
+ sal_uInt8* pnTo = &*(maChunk.end() - nLength);
+ const sal_uInt8* pnEnd = pnTo + nLength;
+ const sal_uInt8* pnFrom = pnTo - nOffset;
+ // offset may be less than length, effectively duplicating source data several times
+ size_t nRunLen = ::std::min< size_t >( nLength, nOffset );
+ while( pnTo < pnEnd )
+ {
+ size_t nStepLen = ::std::min< size_t >( nRunLen, pnEnd - pnTo );
+ memcpy( pnTo, pnFrom, nStepLen );
+ pnTo += nStepLen;
+ }
+ }
+ }
+ // we suspect this will never be called
+ else
+ {
+ maChunk.emplace_back();
+ maChunk.back() = mpInStrm->readuChar();
+ ++nChunkPos;
+ }
+ }
+ }
+ }
+ else
+ {
+ maChunk.resize( nChunkLen );
+ mpInStrm->readMemory(maChunk.data(), nChunkLen);
+ }
+ // decompression sometimes leaves the stream pos offset 1 place ( at
+ // least ) past or before the expected stream pos.
+ // here we make sure we are on the chunk boundary
+ mpInStrm->seek( target );
+ mnChunkPos = 0;
+ return !mbEof;
+}
+
+} // namespace oox::ole
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */