Lots more documentation on how we read in POIFS files and process the sectors/blocks and FATs. Also add a test that shows that bug #46391 is invalid

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@933663 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Nick Burch 2010-04-13 15:04:45 +00:00
parent fc53ead4ca
commit d1486edc42
10 changed files with 124 additions and 16 deletions

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@ -32,10 +32,21 @@ public interface POIFSConstants
/** Some use 4096 bytes */
public static final int LARGER_BIG_BLOCK_SIZE = 0x1000;
public static final int END_OF_CHAIN = -2;
public static final int PROPERTY_SIZE = 0x0080;
/** The highest sector number you're allowed, 0xFFFFFFFA */
public static final int LARGEST_REGULAR_SECTOR_NUMBER = -5;
/** Indicates the sector holds a DIFAT block (0xFFFFFFFC) */
public static final int DIFAT_SECTOR_BLOCK = -4;
/** Indicates the sector holds a FAT block (0xFFFFFFFD) */
public static final int FAT_SECTOR_BLOCK = -3;
/** Indicates the sector is the end of a chain (0xFFFFFFFE) */
public static final int END_OF_CHAIN = -2;
/** Indicates the sector is not used (0xFFFFFFFF) */
public static final int UNUSED_BLOCK = -1;
/** The first 4 bytes of an OOXML file, used in detection */
public static final byte[] OOXML_FILE_HEADER =
new byte[] { 0x50, 0x4b, 0x03, 0x04 };
} // end public interface POIFSConstants;

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@ -89,17 +89,35 @@ public final class BlockAllocationTableReader {
+ " is too high. POI maximum is " + MAX_BLOCK_COUNT + ".");
}
// acquire raw data blocks containing the BAT block data
RawDataBlock blocks[] = new RawDataBlock[ block_count ];
// We want to get the whole of the FAT table
// To do this:
// * Work through raw_block_list, which points to the
// first (up to) 109 BAT blocks
// * Jump to the XBAT offset, and read in XBATs which
// point to more BAT blocks
int limit = Math.min(block_count, block_array.length);
int block_index;
// This will hold all of the BAT blocks in order
RawDataBlock blocks[] = new RawDataBlock[ block_count ];
// Process the first (up to) 109 BAT blocks
for (block_index = 0; block_index < limit; block_index++)
{
// Check that the sector number of the BAT block is a valid one
int nextOffset = block_array[ block_index ];
if(nextOffset > raw_block_list.blockCount()) {
throw new IOException("Your file contains " + raw_block_list.blockCount() +
" sectors, but the initial DIFAT array at index " + block_index +
" referenced block # " + nextOffset + ". This isn't allowed and " +
" your file is corrupt");
}
// Record the sector number of this BAT block
blocks[ block_index ] =
( RawDataBlock ) raw_block_list
.remove(block_array[ block_index ]);
( RawDataBlock ) raw_block_list.remove(nextOffset);
}
// Process additional BAT blocks via the XBATs
if (block_index < block_count)
{
@ -113,6 +131,9 @@ public final class BlockAllocationTableReader {
int max_entries_per_block = BATBlock.entriesPerXBATBlock();
int chain_index_offset = BATBlock.getXBATChainOffset();
// Each XBAT block contains either:
// (maximum number of sector indexes) + index of next XBAT
// some sector indexes + FREE sectors to max # + EndOfChain
for (int j = 0; j < xbat_count; j++)
{
limit = Math.min(block_count - block_index,
@ -139,8 +160,8 @@ public final class BlockAllocationTableReader {
throw new IOException("Could not find all blocks");
}
// now that we have all of the raw data blocks, go through and
// create the indices
// Now that we have all of the raw data blocks which make
// up the FAT, go through and create the indices
setEntries(blocks, raw_block_list);
}

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@ -79,5 +79,7 @@ public interface BlockList
public void setBAT(final BlockAllocationTableReader bat)
throws IOException;
public int blockCount();
} // end public interface BlockList

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@ -138,4 +138,21 @@ abstract class BlockListImpl implements BlockList {
}
_bat = bat;
}
/**
* Returns the count of the number of blocks
*/
public int blockCount() {
return _blocks.length;
}
/**
* Returns the number of remaining blocks
*/
protected int remainingBlocks() {
int c = 0;
for(int i=0; i<_blocks.length; i++) {
if(_blocks[i] != null) c++;
}
return c;
}
}

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@ -33,6 +33,11 @@ public interface HeaderBlockConstants
(POIFSConstants.BIG_BLOCK_SIZE - _bat_array_offset)
/ LittleEndianConsts.INT_SIZE;
// Note - in Microsoft terms:
// BAT ~= FAT
// SBAT ~= MiniFAT
// XBAT ~= DIFat
// useful offsets
public static final int _signature_offset = 0;
public static final int _bat_count_offset = 0x2C;

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@ -22,6 +22,7 @@ import static org.apache.poi.poifs.storage.HeaderBlockConstants._bat_count_offse
import static org.apache.poi.poifs.storage.HeaderBlockConstants._max_bats_in_header;
import static org.apache.poi.poifs.storage.HeaderBlockConstants._property_start_offset;
import static org.apache.poi.poifs.storage.HeaderBlockConstants._sbat_start_offset;
import static org.apache.poi.poifs.storage.HeaderBlockConstants._sbat_block_count_offset;
import static org.apache.poi.poifs.storage.HeaderBlockConstants._signature;
import static org.apache.poi.poifs.storage.HeaderBlockConstants._signature_offset;
import static org.apache.poi.poifs.storage.HeaderBlockConstants._xbat_count_offset;
@ -49,21 +50,37 @@ public final class HeaderBlockReader {
*/
private final int bigBlockSize;
/** number of big block allocation table blocks (int) */
/**
* number of big block allocation table blocks (int).
* (Number of FAT Sectors in Microsoft parlance)
*/
private final int _bat_count;
/** start of the property set block (int index of the property set
* chain's first big block)
/**
* Start of the property set block (int index of the property set
* chain's first big block).
*/
private final int _property_start;
/** start of the small block allocation table (int index of small
/**
* start of the small block allocation table (int index of small
* block allocation table's first big block)
*/
private final int _sbat_start;
/**
* Number of small block allocation table blocks (int)
* (Number of MiniFAT Sectors in Microsoft parlance)
*/
private final int _sbat_count;
/** big block index for extension to the big block allocation table */
/**
* Big block index for extension to the big block allocation table
*/
private final int _xbat_start;
/**
* Number of big block allocation table blocks (int)
* (Number of DIFAT Sectors in Microsoft parlance)
*/
private final int _xbat_count;
private final byte[] _data;
@ -132,6 +149,7 @@ public final class HeaderBlockReader {
_bat_count = getInt(_bat_count_offset, _data);
_property_start = getInt(_property_start_offset, _data);
_sbat_start = getInt(_sbat_start_offset, _data);
_sbat_count = getInt(_sbat_block_count_offset, _data);
_xbat_start = getInt(_xbat_start_offset, _data);
_xbat_count = getInt(_xbat_count_offset, _data);
}
@ -169,11 +187,14 @@ public final class HeaderBlockReader {
}
/**
* @return start of small block allocation table
* @return start of small block (MiniFAT) allocation table
*/
public int getSBATStart() {
return _sbat_start;
}
public int getSBATCount() {
return _sbat_count;
}
/**
* @return number of BAT blocks
@ -183,7 +204,10 @@ public final class HeaderBlockReader {
}
/**
* @return BAT array
* Returns the offsets to the first (up to) 109
* BAT sectors.
* Any additional BAT sectors
* @return BAT offset array
*/
public int[] getBATArray() {
int[] result = new int[ _max_bats_in_header ];
@ -197,14 +221,14 @@ public final class HeaderBlockReader {
}
/**
* @return XBAT count
* @return XBAT (DIFAT) count
*/
public int getXBATCount() {
return _xbat_count;
}
/**
* @return XBAT index
* @return XBAT (DIFAT) index
*/
public int getXBATIndex() {
return _xbat_start;

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@ -111,6 +111,10 @@ public class RawDataBlock
public boolean hasData() {
return _hasData;
}
public String toString() {
return "RawDataBlock of size " + _data.length;
}
/* ********** START implementation of ListManagedBlock ********** */

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@ -148,6 +148,26 @@ public final class TestPOIFSFileSystem extends TestCase {
// Check sizes
}
}
/**
* Check that we do the right thing when the list of which
* sectors are BAT blocks points off the list of
* sectors that exist in the file.
*/
public void testFATandDIFATsectors() throws Exception {
POIDataSamples _samples = POIDataSamples.getPOIFSInstance();
// Open the file up
try {
POIFSFileSystem fs = new POIFSFileSystem(
_samples.openResourceAsStream("ReferencesInvalidSectors.mpp")
);
fail("File is corrupt and shouldn't have been opened");
} catch(IOException e) {
String msg = e.getMessage();
assertTrue(msg.startsWith("Your file contains 695 sectors"));
}
}
private static InputStream openSampleStream(String sampleFileName) {
return HSSFTestDataSamples.openSampleFileStream(sampleFileName);

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@ -181,4 +181,8 @@ public final class LocalRawDataBlockList extends RawDataBlockList {
_array = _list.toArray(new RawDataBlock[ 0 ]);
}
}
public int blockCount() {
return _list.size();
}
}

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