Add support for global usage maps which are reference type maps. fixes issue #138

git-svn-id: https://svn.code.sf.net/p/jackcess/code/jackcess/trunk@1056 f203690c-595d-4dc9-a70b-905162fa7fd2

8 files changed, 311 insertions, 129 deletions

diff --git a/src/changes/changes.xml b/src/changes/changes.xml
index 3e58c16..974eb01 100644
--- a/src/changes/changes.xml
+++ b/src/changes/changes.xml
@@ -11,6 +11,9 @@
         open the channel as read-only (instead of throwing an exception if
         readOnly is false).
       </action>
+      <action dev="jahlborn" type="fix" system="SourceForge2" issue="138">
+        Add support for global usage maps which are reference type maps.
+      </action>
     </release>
     <release version="2.1.5" date="2016-10-03">
       <action dev="jahlborn" type="update">
diff --git a/src/main/java/com/healthmarketscience/jackcess/impl/IndexData.java b/src/main/java/com/healthmarketscience/jackcess/impl/IndexData.java
index a55259e..ba8be57 100644
--- a/src/main/java/com/healthmarketscience/jackcess/impl/IndexData.java
+++ b/src/main/java/com/healthmarketscience/jackcess/impl/IndexData.java
@@ -465,7 +465,7 @@ public class IndexData {
       }
     }
 
-    _ownedPages = UsageMap.read(getTable().getDatabase(), tableBuffer, false);
+    _ownedPages = UsageMap.read(getTable().getDatabase(), tableBuffer);
     
     _rootPageNumber = tableBuffer.getInt();
 
diff --git a/src/main/java/com/healthmarketscience/jackcess/impl/LongValueColumnImpl.java b/src/main/java/com/healthmarketscience/jackcess/impl/LongValueColumnImpl.java
index 8a137ea..73648b3 100644
--- a/src/main/java/com/healthmarketscience/jackcess/impl/LongValueColumnImpl.java
+++ b/src/main/java/com/healthmarketscience/jackcess/impl/LongValueColumnImpl.java
@@ -523,7 +523,7 @@ class LongValueColumnImpl extends ColumnImpl
     public void clear() throws IOException {
       int pageNumber = getPageNumber();
       if(pageNumber != PageChannel.INVALID_PAGE_NUMBER) {
-        _freeSpacePages.removePageNumber(pageNumber, true);
+        _freeSpacePages.removePageNumber(pageNumber);
       }
       super.clear();
     }
diff --git a/src/main/java/com/healthmarketscience/jackcess/impl/PageChannel.java b/src/main/java/com/healthmarketscience/jackcess/impl/PageChannel.java
index 00dabbe..19d15fd 100644
--- a/src/main/java/com/healthmarketscience/jackcess/impl/PageChannel.java
+++ b/src/main/java/com/healthmarketscience/jackcess/impl/PageChannel.java
@@ -347,9 +347,7 @@ public class PageChannel implements Channel, Flushable {
     // meaningful data, we do _not_ encode the page.
     _channel.write(_forceBytes, offset);
 
-    // note, we "force" page removal because we know that this is an unused
-    // page (since we just added it to the file)
-    _globalUsageMap.removePageNumber(pageNumber, true);
+    _globalUsageMap.removePageNumber(pageNumber);
     return pageNumber;
   }
 
diff --git a/src/main/java/com/healthmarketscience/jackcess/impl/TableImpl.java b/src/main/java/com/healthmarketscience/jackcess/impl/TableImpl.java
index e5a6316..5155b16 100644
--- a/src/main/java/com/healthmarketscience/jackcess/impl/TableImpl.java
+++ b/src/main/java/com/healthmarketscience/jackcess/impl/TableImpl.java
@@ -244,9 +244,9 @@ public class TableImpl implements Table
     _indexCount = tableBuffer.getInt(getFormat().OFFSET_NUM_INDEXES);
 
     tableBuffer.position(getFormat().OFFSET_OWNED_PAGES);
-    _ownedPages = UsageMap.read(getDatabase(), tableBuffer, false);
+    _ownedPages = UsageMap.read(getDatabase(), tableBuffer);
     tableBuffer.position(getFormat().OFFSET_FREE_SPACE_PAGES);
-    _freeSpacePages = UsageMap.read(getDatabase(), tableBuffer, false);
+    _freeSpacePages = UsageMap.read(getDatabase(), tableBuffer);
     
     for (int i = 0; i < _indexCount; i++) {
       _indexDatas.add(IndexData.create(this, tableBuffer, i, getFormat()));
@@ -1948,8 +1948,8 @@ public class TableImpl implements Table
     UsageMap colOwnedPages = null;
     UsageMap colFreeSpacePages = null;
     try {
-      colOwnedPages = UsageMap.read(getDatabase(), tableBuffer, false);
-      colFreeSpacePages = UsageMap.read(getDatabase(), tableBuffer, false);
+      colOwnedPages = UsageMap.read(getDatabase(), tableBuffer);
+      colFreeSpacePages = UsageMap.read(getDatabase(), tableBuffer);
     } catch(IllegalStateException e) {
       // ignore invalid usage map info
       colOwnedPages = null;
@@ -2547,7 +2547,7 @@ public class TableImpl implements Table
       if(modifiedPage) {
         writeDataPage(dataPage, pageNumber);
       }
-      _freeSpacePages.removePageNumber(pageNumber, true);
+      _freeSpacePages.removePageNumber(pageNumber);
 
       dataPage = newDataPage();
     }
diff --git a/src/main/java/com/healthmarketscience/jackcess/impl/UsageMap.java b/src/main/java/com/healthmarketscience/jackcess/impl/UsageMap.java
index 898031f..4a9eab0 100644
--- a/src/main/java/com/healthmarketscience/jackcess/impl/UsageMap.java
+++ b/src/main/java/com/healthmarketscience/jackcess/impl/UsageMap.java
@@ -92,15 +92,14 @@ public class UsageMap
   public PageChannel getPageChannel() {
     return getDatabase().getPageChannel();
   }
-  
+
   /**
    * @param database database that contains this usage map
    * @param buf buffer which contains the usage map row info
    * @return Either an InlineUsageMap or a ReferenceUsageMap, depending on
    *         which type of map is found
    */
-  public static UsageMap read(DatabaseImpl database, ByteBuffer buf,
-                              boolean assumeOutOfRangeBitsOn)
+  public static UsageMap read(DatabaseImpl database, ByteBuffer buf)
     throws IOException
   {
     int umapRowNum = buf.get();
@@ -112,11 +111,12 @@ public class UsageMap
    * @param database database that contains this usage map
    * @param pageNum Page number that this usage map is contained in
    * @param rowNum Number of the row on the page that contains this usage map
+   * @param isGlobal whether or not we are reading the "global" usage map
    * @return Either an InlineUsageMap or a ReferenceUsageMap, depending on
    *         which type of map is found
    */
-  public static UsageMap read(DatabaseImpl database, int pageNum,
-                              int rowNum, boolean assumeOutOfRangeBitsOn)
+  static UsageMap read(DatabaseImpl database, int pageNum,
+                       int rowNum, boolean isGlobal)
     throws IOException
   {
     if(pageNum <= 0) {
@@ -133,17 +133,19 @@ public class UsageMap
     tableBuffer.limit(rowEnd);    
     byte mapType = tableBuffer.get(rowStart);
     UsageMap rtn = new UsageMap(database, tableBuffer, pageNum, rowStart);
-    rtn.initHandler(mapType, assumeOutOfRangeBitsOn);
+    rtn.initHandler(mapType, isGlobal);
     return rtn;
   }
 
-  private void initHandler(byte mapType, boolean assumeOutOfRangeBitsOn)
+  private void initHandler(byte mapType, boolean isGlobal)
     throws IOException
   {
     if (mapType == MAP_TYPE_INLINE) {
-      _handler = new InlineHandler(assumeOutOfRangeBitsOn);
+      _handler = (isGlobal ? new GlobalInlineHandler() : 
+                  new InlineHandler());
     } else if (mapType == MAP_TYPE_REFERENCE) {
-      _handler = new ReferenceHandler();
+      _handler = (isGlobal ? new GlobalReferenceHandler() : 
+                  new ReferenceHandler());
     } else {
       throw new IOException(MSG_PREFIX_UNRECOGNIZED_MAP + mapType);
     }
@@ -315,7 +317,13 @@ public class UsageMap
   /**
    * Remove a page number from this usage map
    */
-  protected void removePageNumber(int pageNumber, boolean force) 
+  public void removePageNumber(int pageNumber) 
+    throws IOException 
+  {
+    removePageNumber(pageNumber, true);
+  }
+  
+  private void removePageNumber(int pageNumber, boolean force) 
     throws IOException 
   {
     ++_modCount;
@@ -467,28 +475,26 @@ public class UsageMap
    */
   private class InlineHandler extends Handler
   {
-    private final boolean _assumeOutOfRangeBitsOn;
     private final int _maxInlinePages;
     
-    private InlineHandler(boolean assumeOutOfRangeBitsOn)
+    protected InlineHandler()
       throws IOException
     {
-      _assumeOutOfRangeBitsOn = assumeOutOfRangeBitsOn;
       _maxInlinePages = (getInlineDataEnd() - getInlineDataStart()) * 8;
       int startPage = getTableBuffer().getInt(getRowStart() + 1);
       setInlinePageRange(startPage);
       processMap(getTableBuffer(), 0);
     }
 
-    private int getMaxInlinePages() {
+    protected final int getMaxInlinePages() {
       return _maxInlinePages;
     }
 
-    private int getInlineDataStart() {
+    protected final int getInlineDataStart() {
       return getRowStart() + getFormat().OFFSET_USAGE_MAP_START;
     }
 
-    private int getInlineDataEnd() {
+    protected final int getInlineDataEnd() {
       return getRowEnd();
     }
     
@@ -499,13 +505,6 @@ public class UsageMap
     private void setInlinePageRange(int startPage) {
       setPageRange(startPage, startPage + getMaxInlinePages());
     }      
-
-    @Override
-    public boolean containsPageNumber(int pageNumber) {
-      return(super.containsPageNumber(pageNumber) ||
-             (_assumeOutOfRangeBitsOn && (pageNumber >= 0) &&
-              !isPageWithinRange(pageNumber)));
-    }
     
     @Override
     public void addOrRemovePageNumber(int pageNumber, boolean add,
@@ -523,68 +522,55 @@ public class UsageMap
         
       } else {
 
-        // uh-oh, we've split our britches.  what now?  determine what our
-        // status is
+        // uh-oh, we've split our britches.  what now?
+        addOrRemovePageNumberOutsideRange(pageNumber, add, force);
+      }
+    }
+
+    protected void addOrRemovePageNumberOutsideRange(
+        int pageNumber, boolean add, boolean force)
+      throws IOException
+    {
+      // determine what our status is before taking action
+        
+      if(add) {
+
         int firstPage = getFirstPageNumber();
         int lastPage = getLastPageNumber();
-        
-        if(add) {
 
-          // we can ignore out-of-range page addition if we are already
-          // assuming out-of-range bits are "on".  Note, we are leaving small
-          // holes in the database here (leaving behind some free pages), but
-          // it's not the end of the world.
-          if(!_assumeOutOfRangeBitsOn) {
-            
-            // we are adding, can we shift the bits and stay inline?
-            if(firstPage <= PageChannel.INVALID_PAGE_NUMBER) {
-              // no pages currently
-              firstPage = pageNumber;
-              lastPage = pageNumber;
-            } else if(pageNumber > lastPage) {
-              lastPage = pageNumber;
-            } else {
-              firstPage = pageNumber;
-            }
-            if((lastPage - firstPage + 1) < getMaxInlinePages()) {
+        // we are adding, can we shift the bits and stay inline?
+        if(firstPage <= PageChannel.INVALID_PAGE_NUMBER) {
+          // no pages currently
+          firstPage = pageNumber;
+          lastPage = pageNumber;
+        } else if(pageNumber > lastPage) {
+          lastPage = pageNumber;
+        } else {
+          firstPage = pageNumber;
+        }
+        if((lastPage - firstPage + 1) < getMaxInlinePages()) {
 
-              // we can still fit within an inline map
-              moveToNewStartPage(firstPage, pageNumber);
+          // we can still fit within an inline map
+          moveToNewStartPage(firstPage, pageNumber);
             
-            } else {
-              // not going to happen, need to promote the usage map to a
-              // reference map
-              promoteInlineHandlerToReferenceHandler(pageNumber);
-            }
-          }
         } else {
+          // not going to happen, need to promote the usage map to a
+          // reference map
+          promoteInlineHandlerToReferenceHandler(pageNumber);
+        }
 
-          // we are removing, what does that mean?
-          if(_assumeOutOfRangeBitsOn) {
+      } else {
 
-            // we are using an inline map and assuming that anything not
-            // within the current range is "on".  so, if we attempt to set a
-            // bit which is before the current page, ignore it, we are not
-            // going back for it.
-            if((firstPage <= PageChannel.INVALID_PAGE_NUMBER) ||
-               (pageNumber > lastPage)) {
+        // we are removing, what does that mean?
+        if(!force) {
 
-              // move to new start page, filling in as we move
-              moveToNewStartPageForRemove(firstPage, pageNumber);
-              
-            }
-            
-          } else if(!force) {
-
-            // this should not happen, we are removing a page which is not in
-            // the map
-            throw new IOException("Page number " + pageNumber +
-                                  " already removed from usage map" +
-                                  ", expected range " +
-                                  _startPage + " to " + _endPage);
-          }
+          // this should not happen, we are removing a page which is not in
+          // the map
+          throw new IOException("Page number " + pageNumber +
+                                " already removed from usage map" +
+                                ", expected range " +
+                                _startPage + " to " + _endPage);
         }
-
       }
     }
 
@@ -594,7 +580,7 @@ public class UsageMap
      * @param newPageNumber optional page number to add once the map has been
      *                      shifted to the new start page
      */
-    private void moveToNewStartPage(int newStartPage, int newPageNumber)
+    protected final void moveToNewStartPage(int newStartPage, int newPageNumber)
       throws IOException
     {
       int oldStartPage = getStartPage();
@@ -617,6 +603,57 @@ public class UsageMap
       // put the pages back in
       reAddPages(oldStartPage, oldPageNumbers, newPageNumber);
     }
+  }
+
+  /**
+   * Modified version of an "inline" usage map used for the global usage map.
+   * When an inline usage map is used for the global usage map, we assume
+   * out-of-range bits are on.  We never promote the global usage map to a
+   * reference usage map (although ms access may).
+   *
+   * Note, this UsageMap does not implement all the methods "correctly".  Only
+   * addPageNumber and removePageNumber should be called by PageChannel.
+   */
+  private class GlobalInlineHandler extends InlineHandler
+  {
+    private GlobalInlineHandler() throws IOException {
+    }
+
+    @Override
+    public boolean containsPageNumber(int pageNumber) {
+      // should never be called on global map
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    protected void addOrRemovePageNumberOutsideRange(
+        int pageNumber, boolean add, boolean force)
+      throws IOException
+    {
+      // determine what our status is
+
+      // for the global usage map, we can ignore out-of-range page addition
+      // since we assuming out-of-range bits are "on".  Note, we are leaving
+      // small holes in the database here (leaving behind some free pages),
+      // but it's not the end of the world.
+        
+      if(!add) {
+
+        int firstPage = getFirstPageNumber();
+        int lastPage = getLastPageNumber();
+
+        // we are using an inline map and assuming that anything not
+        // within the current range is "on".  so, if we attempt to set a
+        // bit which is before the current page, ignore it, we are not
+        // going back for it.
+        if((firstPage <= PageChannel.INVALID_PAGE_NUMBER) ||
+           (pageNumber > lastPage)) {
+
+          // move to new start page, filling in as we move
+          moveToNewStartPageForRemove(firstPage, pageNumber);
+        }
+      }
+    }
 
     /**
      * Shifts the inline usage map so that it now starts with the given
@@ -675,13 +712,16 @@ public class UsageMap
     /** Buffer that contains the current reference map page */ 
     private final TempPageHolder _mapPageHolder =
       TempPageHolder.newHolder(TempBufferHolder.Type.SOFT);
+    private final int _maxPagesPerUsageMapPage;
   
     private ReferenceHandler()
       throws IOException
     {
+      _maxPagesPerUsageMapPage = ((getFormat().PAGE_SIZE - 
+                                   getFormat().OFFSET_USAGE_MAP_PAGE_DATA) * 8);
       int numUsagePages = (getRowEnd() - getRowStart() - 1) / 4;
       setStartOffset(getFormat().OFFSET_USAGE_MAP_PAGE_DATA);
-      setPageRange(0, (numUsagePages * getMaxPagesPerUsagePage()));
+      setPageRange(0, (numUsagePages * _maxPagesPerUsageMapPage));
       
       // there is no "start page" for a reference usage map, so we get an
       // extra page reference on top of the number of page references that fit
@@ -699,14 +739,13 @@ public class UsageMap
                                   pageType);
           }
           mapPageBuffer.position(getFormat().OFFSET_USAGE_MAP_PAGE_DATA);
-          processMap(mapPageBuffer, (getMaxPagesPerUsagePage() * i));
+          processMap(mapPageBuffer, (_maxPagesPerUsageMapPage * i));
         }
       }
     }
 
-    private int getMaxPagesPerUsagePage() {
-      return((getFormat().PAGE_SIZE - getFormat().OFFSET_USAGE_MAP_PAGE_DATA)
-             * 8);
+    protected final int getMaxPagesPerUsagePage() {
+      return _maxPagesPerUsageMapPage;
     }
         
     @Override
@@ -745,10 +784,7 @@ public class UsageMap
      */
     private ByteBuffer createNewUsageMapPage(int pageIndex) throws IOException
     {
-      ByteBuffer mapPageBuffer = _mapPageHolder.setNewPage(getPageChannel());
-      mapPageBuffer.put(PageTypes.USAGE_MAP);
-      mapPageBuffer.put((byte) 0x01);  //Unknown
-      mapPageBuffer.putShort((short) 0); //Unknown
+      ByteBuffer mapPageBuffer = allocateNewUsageMapPage(pageIndex);
       int mapPageNum = _mapPageHolder.getPageNumber();
       getTableBuffer().putInt(calculateMapPagePointerOffset(pageIndex),
                               mapPageNum);
@@ -760,6 +796,108 @@ public class UsageMap
       return getRowStart() + getFormat().OFFSET_REFERENCE_MAP_PAGE_NUMBERS +
         (pageIndex * 4);
     }
+
+    protected ByteBuffer allocateNewUsageMapPage(int pageIndex) 
+      throws IOException 
+    {
+      ByteBuffer mapPageBuffer = _mapPageHolder.setNewPage(getPageChannel());
+      mapPageBuffer.put(PageTypes.USAGE_MAP);
+      mapPageBuffer.put((byte) 0x01);  //Unknown
+      mapPageBuffer.putShort((short) 0); //Unknown
+      return mapPageBuffer;
+    }
+  }
+
+  /**
+   * Modified version of a "reference" usage map used for the global usage
+   * map.  Since reference usage maps require allocating pages for their own
+   * use, we need to handle potential cycles where the PageChannel is
+   * attempting to allocate a new page (and remove it from the global usage
+   * map) and this usage map also needs to allocate a new page.  When that
+   * happens, we stash the pending information from the PageChannel and handle
+   * it after we have retrieved the new page.
+   *
+   * Note, this UsageMap does not implement all the methods "correctly".  Only
+   * addPageNumber and removePageNumber should be called by PageChannel.
+   */
+  private class GlobalReferenceHandler extends ReferenceHandler
+  {
+    private boolean _allocatingPage;
+    private Integer _pendingPage;
+
+    private GlobalReferenceHandler() throws IOException {
+    }
+
+    @Override
+    public boolean containsPageNumber(int pageNumber) {
+      // should never be called on global map
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public void addOrRemovePageNumber(int pageNumber, boolean add,
+                                      boolean force)
+      throws IOException
+    {
+      if(_allocatingPage && !add) {
+        // we are in the midst of allocating a page for ourself, keep track of
+        // this new page so we can mark it later...
+        if(_pendingPage != null) {
+          throw new IllegalStateException("should only have single pending page");
+        }
+        _pendingPage = pageNumber;
+        return;
+      }
+
+      super.addOrRemovePageNumber(pageNumber, add, force);
+
+      while(_pendingPage != null) {
+        
+        // while updating our usage map, we needed to allocate a new page (and
+        // thus mark a new page as used).  we delayed that marking so that we
+        // didn't get into an infinite loop.  now that we completed the
+        // original updated, handle the new page.  (we use a loop under the
+        // off the wall chance that adding this page requires allocating a new
+        // page.  in theory, we could do this more than once, but not
+        // forever).
+        int removedPageNumber = _pendingPage;
+        _pendingPage = null;
+
+        super.addOrRemovePageNumber(removedPageNumber, false, true);
+      } 
+    }    
+
+    @Override
+    protected ByteBuffer allocateNewUsageMapPage(int pageIndex)
+      throws IOException 
+    {
+      try {
+        // keep track of the fact that we are actively allocating a page for our
+        // own use so that we can break the potential cycle.
+        _allocatingPage = true;
+
+        ByteBuffer mapPageBuffer = super.allocateNewUsageMapPage(pageIndex);
+
+        // for the global usage map, all pages are "on" by default.  so
+        // whenever we add a new backing page to the usage map, we need to
+        // turn all the pages that it represents to "on" (we essentially lazy
+        // load this map, which is fine because we should only add pages which
+        // represent the size of the database currently in use).
+        int dataStart = getFormat().OFFSET_USAGE_MAP_PAGE_DATA;
+        ByteUtil.fillRange(mapPageBuffer, dataStart, 
+                           getFormat().PAGE_SIZE - dataStart);
+
+        int maxPagesPerUmapPage = getMaxPagesPerUsagePage();
+        int firstNewPage = (pageIndex * maxPagesPerUmapPage);
+        int lastNewPage = firstNewPage + maxPagesPerUmapPage;
+        _pageNumbers.set(firstNewPage, lastNewPage);
+
+        return mapPageBuffer;
+
+      } finally {
+        _allocatingPage = false;
+      }
+    }
   }
 
   /**
diff --git a/src/test/data/V2000/testRefGlobalV2000.mdb b/src/test/data/V2000/testRefGlobalV2000.mdb
new file mode 100644
index 0000000..7ebd402
--- /dev/null
+++ b/src/test/data/V2000/testRefGlobalV2000.mdb
diff --git a/src/test/java/com/healthmarketscience/jackcess/impl/UsageMapTest.java b/src/test/java/com/healthmarketscience/jackcess/impl/UsageMapTest.java
index aad1ddf..539a7c0 100644
--- a/src/test/java/com/healthmarketscience/jackcess/impl/UsageMapTest.java
+++ b/src/test/java/com/healthmarketscience/jackcess/impl/UsageMapTest.java
@@ -2,11 +2,18 @@ package com.healthmarketscience.jackcess.impl;
 
 import java.io.File;
 import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
 
+import com.healthmarketscience.jackcess.ColumnBuilder;
+import com.healthmarketscience.jackcess.DataType;
 import com.healthmarketscience.jackcess.Database;
 import com.healthmarketscience.jackcess.DatabaseBuilder;
-import static com.healthmarketscience.jackcess.impl.JetFormatTest.*;
+import com.healthmarketscience.jackcess.Table;
+import com.healthmarketscience.jackcess.TableBuilder;
 import junit.framework.TestCase;
+import static com.healthmarketscience.jackcess.TestUtil.*;
+import static com.healthmarketscience.jackcess.impl.JetFormatTest.*;
 
 /**
  * @author Dan Rollo
@@ -15,40 +22,76 @@ import junit.framework.TestCase;
  */
 public final class UsageMapTest extends TestCase {
 
-    public void testRead() throws Exception {
-        for (final TestDB testDB : SUPPORTED_DBS_TEST) {
-            final int expectedFirstPage;
-            final int expectedLastPage;
-            final Database.FileFormat expectedFileFormat = testDB.getExpectedFileFormat();
-            if (Database.FileFormat.V2000.equals(expectedFileFormat)) {
-                expectedFirstPage = 743;
-                expectedLastPage = 767;
-            } else if (Database.FileFormat.V2003.equals(expectedFileFormat)) {
-                expectedFirstPage = 16;
-                expectedLastPage = 799;
-            } else if (Database.FileFormat.V2007.equals(expectedFileFormat)) {
-                expectedFirstPage = 94;
-                expectedLastPage = 511;
-            } else if (Database.FileFormat.V2010.equals(expectedFileFormat)) {
-                expectedFirstPage = 109;
-                expectedLastPage = 511;
-            } else {
-                throw new IllegalAccessException("Unknown file format: " + expectedFileFormat);
-            }
-            checkUsageMapRead(testDB.getFile(), expectedFirstPage, expectedLastPage);
-        }
+  public void testRead() throws Exception {
+    for (final TestDB testDB : SUPPORTED_DBS_TEST) {
+      final int expectedFirstPage;
+      final int expectedLastPage;
+      final Database.FileFormat expectedFileFormat = testDB.getExpectedFileFormat();
+      if (Database.FileFormat.V2000.equals(expectedFileFormat)) {
+        expectedFirstPage = 743;
+        expectedLastPage = 767;
+      } else if (Database.FileFormat.V2003.equals(expectedFileFormat)) {
+        expectedFirstPage = 16;
+        expectedLastPage = 799;
+      } else if (Database.FileFormat.V2007.equals(expectedFileFormat)) {
+        expectedFirstPage = 94;
+        expectedLastPage = 511;
+      } else if (Database.FileFormat.V2010.equals(expectedFileFormat)) {
+        expectedFirstPage = 109;
+        expectedLastPage = 511;
+      } else {
+        throw new IllegalAccessException("Unknown file format: " + expectedFileFormat);
+      }
+      checkUsageMapRead(testDB.getFile(), expectedFirstPage, expectedLastPage);
     }
+  }
+
+  private static void checkUsageMapRead(
+      final File dbFile, final int expectedFirstPage, final int expectedLastPage)
+    throws IOException {
+
+    final Database db = DatabaseBuilder.open(dbFile);
+    final UsageMap usageMap = UsageMap.read((DatabaseImpl)db,
+                                            PageChannel.PAGE_GLOBAL_USAGE_MAP,
+                                            PageChannel.ROW_GLOBAL_USAGE_MAP,
+                                            true);
+    assertEquals("Unexpected FirstPageNumber.", expectedFirstPage, 
+                 usageMap.getFirstPageNumber());
+    assertEquals("Unexpected LastPageNumber.", expectedLastPage, 
+                 usageMap.getLastPageNumber());
+  }
+
+  public void testGobalReferenceUsageMap() throws Exception
+  {
+    Database db = openCopy(
+        Database.FileFormat.V2000, 
+        new File("src/test/data/V2000/testRefGlobalV2000.mdb"));
 
-    private static void checkUsageMapRead(final File dbFile,
-                                          final int expectedFirstPage, final int expectedLastPage)
-            throws IOException {
-
-        final Database db = DatabaseBuilder.open(dbFile);
-        final UsageMap usageMap = UsageMap.read((DatabaseImpl)db,
-                PageChannel.PAGE_GLOBAL_USAGE_MAP,
-                PageChannel.ROW_GLOBAL_USAGE_MAP,
-                true);
-        assertEquals("Unexpected FirstPageNumber.", expectedFirstPage, usageMap.getFirstPageNumber());
-        assertEquals("Unexpected LastPageNumber.", expectedLastPage, usageMap.getLastPageNumber());
+    Table t = new TableBuilder("Test2")
+      .addColumn(new ColumnBuilder("id", DataType.LONG))
+      .addColumn(new ColumnBuilder("data1", DataType.TEXT))
+      .addColumn(new ColumnBuilder("data2", DataType.TEXT))
+      .toTable(db);
+
+
+    ((DatabaseImpl)db).getPageChannel().startWrite();
+    try {
+      List<Object[]> rows = new ArrayList<Object[]>();
+      for(int i = 0; i < 300000; ++i) {
+        String s1 = "r" + i + "-" + createString(100);
+        String s2 = "r" + i + "-" + createString(200);
+
+        rows.add(new Object[]{i, s1, s2});
+
+        if((i % 2000) == 0) {
+          t.addRows(rows);
+          rows.clear();
+        }
+      }
+    } finally {
+      ((DatabaseImpl)db).getPageChannel().finishWrite();
     }
+
+    db.close();
+  }
 }