D21418: KCompressionDevice::seek: Fix previous fix ^_^

[Albert Astals Cid]

aacid created this revision.
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REVISION SUMMARY
  The previous fix that made sure we returned the actual data in KCompressionDevice::readData
  because it is sometimes buffered, didn't take into account this line
  
    QByteArray dummy(qMin(bytesToRead, qint64(SEEK_BUFFER_SIZE)), 0);
  
  in KCompressionDevice::seek, i.e. sometimes the dummy buffer is not as big as we need to seek,
  basically because we don't want to be allocating lots of memory.
  
  The previous solution worked because never incremented the data pointer, that meant that the
  internal QIODevice buffer might end in a bad state, so we fixed it but forgot about the case
  where the dummy buffer we're using is not big enough and this was causing invalid memory writes.
  
  To fix that now we have a while loop that reads as many times over the dummy buffer to seek
  to the correct position.
  
  Comes with an extended autottest, that has a big buffer and without this fix would crash.

REPOSITORY
  R243 KArchive

BRANCH
  master

REVISION DETAIL
  https://phabricator.kde.org/D21418

AFFECTED FILES
  autotests/kcompressiondevicetest.cpp
  autotests/kcompressiondevicetest.h
  src/kcompressiondevice.cpp
  src/kcompressiondevice_p.h

To: aacid
Cc: kde-frameworks-devel, michaelh, ngraham, bruns
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