[Synaptic-devel] Percentage of file fetched shows incorrectly on large files

[David Wilson]

There is an unsigned integer overflow that occurs when calculating the
percentage downloaded when fetching large files(>40MB). The actual
overflow results when the amount of file downloaded is >= (2^32)/100.

The problem is in the calculation of the second argument in the call to
updateStatus found in gtk/rgfetchprogess.cc:

if (I->TotalSize > 0)
  updateStatus(*I->CurrentItem, I->CurrentSize*100 / I->TotalSize);
else
  updateStatus(*I->CurrentItem, 100);
}

The following logic should take care of the problem:

static unsigned int PROGRESS_PERCENT_OVERFLOW = 42949672;
if (I->TotalSize >= PROGRESS_PERCENT_OVERFLOW)
{
  // a couple of extra integer divisions should prevent the overflow
  updateStatus(*I->CurrentItem,
               (I->CurrentSize/100)*100 / (I->TotalSize/100));
}
else if (I->TotalSize > 0)
  updateStatus(*I->CurrentItem, I->CurrentSize*100 / I->TotalSize);
else
  updateStatus(*I->CurrentItem, 100);
}



-- 
David A. Wilson
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