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Overview
Comment:Prevent the in-memory journal read cursor from entering an inconsistent state when it reads the last few bytes out of the journal file. Fix for ticket [7f7f8026eda38].
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SHA1: c4b9c611bdcd85f31d68aaf114ee34a9f27eba6d
User & Date: drh 2016-04-07 18:42:23
Context
2016-04-07
21:22
Prevent the in-memory journal read cursor from entering an inconsistent state when it reads the last few bytes out of the journal file. Fix for ticket [7f7f8026eda38]. check-in: c232b99e user: drh tags: branch-3.12.0
21:14
Add test cases for ticket [7f7f8026eda387d544]. check-in: 87aa9357 user: drh tags: trunk
18:42
Prevent the in-memory journal read cursor from entering an inconsistent state when it reads the last few bytes out of the journal file. Fix for ticket [7f7f8026eda38]. check-in: c4b9c611 user: drh tags: trunk
14:16
Avoid decrementing a pointer off the front end of the buffer in OP_MakeRecord. check-in: 153135bf user: drh tags: trunk
Changes
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Changes to src/memjournal.c.

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#ifdef SQLITE_ENABLE_ATOMIC_WRITE
  if( (iAmt+iOfst)>p->endpoint.iOffset ){
    return SQLITE_IOERR_SHORT_READ;
  }
#endif

  assert( (iAmt+iOfst)<=p->endpoint.iOffset );

  if( p->readpoint.iOffset!=iOfst || iOfst==0 ){
    sqlite3_int64 iOff = 0;
    for(pChunk=p->pFirst; 
        ALWAYS(pChunk) && (iOff+p->nChunkSize)<=iOfst;
        pChunk=pChunk->pNext
    ){
      iOff += p->nChunkSize;
    }
  }else{
    pChunk = p->readpoint.pChunk;

  }

  iChunkOffset = (int)(iOfst%p->nChunkSize);
  do {
    int iSpace = p->nChunkSize - iChunkOffset;
    int nCopy = MIN(nRead, (p->nChunkSize - iChunkOffset));
    memcpy(zOut, (u8*)pChunk->zChunk + iChunkOffset, nCopy);
    zOut += nCopy;
    nRead -= iSpace;
    iChunkOffset = 0;
  } while( nRead>=0 && (pChunk=pChunk->pNext)!=0 && nRead>0 );
  p->readpoint.iOffset = iOfst+iAmt;
  p->readpoint.pChunk = pChunk;

  return SQLITE_OK;
}

/*
** Free the list of FileChunk structures headed at MemJournal.pFirst.







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#ifdef SQLITE_ENABLE_ATOMIC_WRITE
  if( (iAmt+iOfst)>p->endpoint.iOffset ){
    return SQLITE_IOERR_SHORT_READ;
  }
#endif

  assert( (iAmt+iOfst)<=p->endpoint.iOffset );
  assert( p->readpoint.iOffset==0 || p->readpoint.pChunk!=0 );
  if( p->readpoint.iOffset!=iOfst || iOfst==0 ){
    sqlite3_int64 iOff = 0;
    for(pChunk=p->pFirst; 
        ALWAYS(pChunk) && (iOff+p->nChunkSize)<=iOfst;
        pChunk=pChunk->pNext
    ){
      iOff += p->nChunkSize;
    }
  }else{
    pChunk = p->readpoint.pChunk;
    assert( pChunk!=0 );
  }

  iChunkOffset = (int)(iOfst%p->nChunkSize);
  do {
    int iSpace = p->nChunkSize - iChunkOffset;
    int nCopy = MIN(nRead, (p->nChunkSize - iChunkOffset));
    memcpy(zOut, (u8*)pChunk->zChunk + iChunkOffset, nCopy);
    zOut += nCopy;
    nRead -= iSpace;
    iChunkOffset = 0;
  } while( nRead>=0 && (pChunk=pChunk->pNext)!=0 && nRead>0 );
  p->readpoint.iOffset = pChunk ? iOfst+iAmt : 0;
  p->readpoint.pChunk = pChunk;

  return SQLITE_OK;
}

/*
** Free the list of FileChunk structures headed at MemJournal.pFirst.