LibreOffice Module oox (master)  1
vbainputstream.cxx
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19 
21 #include <osl/diagnose.h>
22 
23 namespace oox::ole {
24 
25 namespace {
26 
27 const sal_uInt8 VBASTREAM_SIGNATURE = 1;
28 
29 const sal_uInt16 VBACHUNK_SIGMASK = 0x7000;
30 const sal_uInt16 VBACHUNK_SIG = 0x3000;
31 const sal_uInt16 VBACHUNK_COMPRESSED = 0x8000;
32 const sal_uInt16 VBACHUNK_LENMASK = 0x0FFF;
33 
34 } // namespace
35 
37  BinaryStreamBase( false ),
38  mpInStrm( &rInStrm ),
39  mnChunkPos( 0 )
40 {
41  maChunk.reserve( 4096 );
42 
43  sal_uInt8 nSig = rInStrm.readuInt8();
44  OSL_ENSURE( nSig == VBASTREAM_SIGNATURE, "VbaInputStream::VbaInputStream - wrong signature" );
45  mbEof = mbEof || rInStrm.isEof() || (nSig != VBASTREAM_SIGNATURE);
46 }
47 
48 sal_Int64 VbaInputStream::size() const
49 {
50  return -1;
51 }
52 
53 sal_Int64 VbaInputStream::tell() const
54 {
55  return -1;
56 }
57 
58 void VbaInputStream::seek( sal_Int64 )
59 {
60 }
61 
63 {
64  mpInStrm = nullptr;
65  mbEof = true;
66 }
67 
68 sal_Int32 VbaInputStream::readData( StreamDataSequence& orData, sal_Int32 nBytes, size_t nAtomSize )
69 {
70  sal_Int32 nRet = 0;
71  if( !mbEof )
72  {
73  orData.realloc( ::std::max< sal_Int32 >( nBytes, 0 ) );
74  if( nBytes > 0 )
75  {
76  nRet = readMemory( orData.getArray(), nBytes, nAtomSize );
77  if( nRet < nBytes )
78  orData.realloc( nRet );
79  }
80  }
81  return nRet;
82 }
83 
84 sal_Int32 VbaInputStream::readMemory( void* opMem, sal_Int32 nBytes, size_t /*nAtomSize*/ )
85 {
86  sal_Int32 nRet = 0;
87  sal_uInt8* opnMem = static_cast< sal_uInt8* >( opMem );
88  while( (nBytes > 0) && updateChunk() )
89  {
90  sal_Int32 nChunkLeft = static_cast< sal_Int32 >( maChunk.size() - mnChunkPos );
91  sal_Int32 nReadBytes = ::std::min( nBytes, nChunkLeft );
92  memcpy( opnMem, &*(maChunk.begin() + mnChunkPos), nReadBytes );
93  opnMem += nReadBytes;
94  mnChunkPos += static_cast< size_t >( nReadBytes );
95  nBytes -= nReadBytes;
96  nRet += nReadBytes;
97  }
98  return nRet;
99 }
100 
101 void VbaInputStream::skip( sal_Int32 nBytes, size_t /*nAtomSize*/ )
102 {
103  while( (nBytes > 0) && updateChunk() )
104  {
105  sal_Int32 nChunkLeft = static_cast< sal_Int32 >( maChunk.size() - mnChunkPos );
106  sal_Int32 nSkipBytes = ::std::min( nBytes, nChunkLeft );
107  mnChunkPos += static_cast< size_t >( nSkipBytes );
108  nBytes -= nSkipBytes;
109  }
110 }
111 
112 // private --------------------------------------------------------------------
113 
115 {
116  if( mbEof || (mnChunkPos < maChunk.size()) ) return !mbEof;
117  // try to read next chunk header, this may trigger EOF
118  sal_uInt16 nHeader = mpInStrm->readuInt16();
119 
120  mbEof = mpInStrm->isEof();
121  if( mbEof ) return false;
122 
123  // check header signature
124  bool bIgnoreBrokenSig = ( (nHeader & VBACHUNK_SIGMASK) != VBACHUNK_SIG );
125 
126  // decode length of chunk data and compression flag
127  bool bCompressed = getFlag( nHeader, VBACHUNK_COMPRESSED );
128  sal_uInt16 nChunkLen = (nHeader & VBACHUNK_LENMASK) + 1;
129  OSL_ENSURE( bCompressed || (nChunkLen == 4096), "VbaInputStream::updateChunk - invalid uncompressed chunk size" );
130 
131  // From the amazing bit detective work of Valek Filippov<frob@gnome.org>
132  // this tweak and the one at the bottom of the method to seek to the
133  // start of the next chunk we can read those strange broken
134  // ( I guess from a MSO bug ) compressed streams > 4k
135 
136  if ( bIgnoreBrokenSig )
137  {
138  bCompressed = true;
139  nChunkLen = 4094;
140  }
141 
142  sal_Int64 target = mpInStrm->tell() + nChunkLen;
143  if( bCompressed )
144  {
145  maChunk.clear();
146  sal_uInt8 nBitCount = 4;
147  sal_uInt16 nChunkPos = 0;
148  while( !mbEof && !mpInStrm->isEof() && (nChunkPos < nChunkLen) )
149  {
150  sal_uInt8 nTokenFlags = mpInStrm->readuInt8();
151  ++nChunkPos;
152  for( int nBit = 0; !mbEof && !mpInStrm->isEof() && (nBit < 8) && (nChunkPos < nChunkLen); ++nBit, nTokenFlags >>= 1 )
153  {
154  if( nTokenFlags & 1 )
155  {
156  sal_uInt16 nCopyToken = mpInStrm->readuInt16();
157  nChunkPos = nChunkPos + 2;
158  // update bit count used for offset/length in the token
159  while( ( static_cast<size_t>(1) << nBitCount ) < maChunk.size() ) ++nBitCount;
160  // extract length from lower (16-nBitCount) bits, plus 3
161  sal_uInt16 nLength = extractValue< sal_uInt16 >( nCopyToken, 0, 16 - nBitCount ) + 3;
162  // extract offset from high nBitCount bits, plus 1
163  sal_uInt16 nOffset = extractValue< sal_uInt16 >( nCopyToken, 16 - nBitCount, nBitCount ) + 1;
164  mbEof = (nOffset > maChunk.size()) || (maChunk.size() + nLength > 4096);
165  OSL_ENSURE( !mbEof, "VbaInputStream::updateChunk - invalid offset or size in copy token" );
166  if( !mbEof )
167  {
168  // append data to buffer
169  maChunk.resize( maChunk.size() + nLength );
170  sal_uInt8* pnTo = &*(maChunk.end() - nLength);
171  const sal_uInt8* pnEnd = pnTo + nLength;
172  const sal_uInt8* pnFrom = pnTo - nOffset;
173  // offset may be less than length, effectively duplicating source data several times
174  size_t nRunLen = ::std::min< size_t >( nLength, nOffset );
175  while( pnTo < pnEnd )
176  {
177  size_t nStepLen = ::std::min< size_t >( nRunLen, pnEnd - pnTo );
178  memcpy( pnTo, pnFrom, nStepLen );
179  pnTo += nStepLen;
180  }
181  }
182  }
183  // we suspect this will never be called
184  else
185  {
186  maChunk.emplace_back();
187  maChunk.back() = mpInStrm->readuChar();
188  ++nChunkPos;
189  }
190  }
191  }
192  }
193  else
194  {
195  maChunk.resize( nChunkLen );
196  mpInStrm->readMemory(maChunk.data(), nChunkLen);
197  }
198  // decompression sometimes leaves the stream pos offset 1 place ( at
199  // least ) past or before the expected stream pos.
200  // here we make sure we are on the chunk boundary
201  mpInStrm->seek( target );
202  mnChunkPos = 0;
203  return !mbEof;
204 }
205 
206 } // namespace oox::ole
207 
208 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */
bool updateChunk()
If no data left in chunk buffer, reads the next chunk from stream.
Base class for binary stream classes.
VbaInputStream(BinaryInputStream &rInStrm)
virtual void seek(sal_Int64 nPos) override
Does nothing, stream is not seekable.
virtual sal_Int32 readMemory(void *opMem, sal_Int32 nBytes, size_t nAtomSize=1) override
Reads nBytes bytes to the (existing) buffer opMem.
virtual sal_Int32 readMemory(void *opMem, sal_Int32 nBytes, size_t nAtomSize=1)=0
Derived classes implement reading nBytes bytes to the (preallocated!) memory buffer opMem...
virtual sal_Int64 tell() const override
Returns -1, stream position is not tracked.
bool getFlag(Type nBitField, Type nMask)
Returns true, if at least one of the bits set in nMask is set in nBitField.
Definition: helper.hxx:135
virtual void close() override
Closes the input stream but not the wrapped stream.
Interface for binary input stream classes.
virtual sal_Int32 readData(StreamDataSequence &orData, sal_Int32 nBytes, size_t nAtomSize=1) override
Reads nBytes bytes to the passed sequence.
css::uno::Sequence< sal_Int8 > StreamDataSequence
virtual void skip(sal_Int32 nBytes, size_t nAtomSize=1) override
Seeks the stream forward by the passed number of bytes.
BinaryInputStream * mpInStrm
virtual sal_Int64 tell() const =0
Implementations return the current stream position, if possible.
short nBitCount
bool mbEof
End of stream flag.
virtual void seek(sal_Int64 nPos)=0
Implementations seek the stream to the passed position, if the stream is seekable.
unsigned char sal_uInt8
sal_Int32 nLength
bool isEof() const
Returns true, if the stream position is invalid (EOF).
virtual sal_Int64 size() const override
Returns -1, stream size is not determinable.