1 files changed, 88 insertions, 0 deletions
diff --git a/src/java/com/healthmarketscience/jackcess/NullMask.java b/src/java/com/healthmarketscience/jackcess/NullMask.java
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+++ b/src/java/com/healthmarketscience/jackcess/NullMask.java
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+/*
+Copyright (c) 2005 Health Market Science, Inc.
+
+This library is free software; you can redistribute it and/or
+modify it under the terms of the GNU Lesser General Public
+License as published by the Free Software Foundation; either
+version 2.1 of the License, or (at your option) any later version.
+
+This library is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public
+License along with this library; if not, write to the Free Software
+Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
+USA
+
+You can contact Health Market Science at info@healthmarketscience.com
+or at the following address:
+
+Health Market Science
+2700 Horizon Drive
+Suite 200
+King of Prussia, PA 19406
+*/
+
+package com.healthmarketscience.jackcess;
+
+import java.nio.ByteBuffer;
+
+/**
+ * Bitmask that indicates whether or not each column in a row is null.  Also
+ * holds values of boolean columns.
+ * @author Tim McCune
+ */
+public class NullMask {
+  
+  /** The actual bitmask */
+  private byte[] _mask;
+  
+  /**
+   * @param columnCount Number of columns in the row that this mask will be
+   *    used for
+   */
+  public NullMask(int columnCount) {
+    _mask = new byte[(columnCount + 7) / 8];
+    for (int i = 0; i < _mask.length; i++) {
+      _mask[i] = (byte) 0xff;
+    }
+    for (int i = columnCount; i < _mask.length * 8; i++) {
+      markNull(i);
+    }
+  }
+  
+  /**
+   * Read a mask in from a buffer
+   */
+  public void read(ByteBuffer buffer) {
+    buffer.get(_mask);
+  }
+  
+  public ByteBuffer wrap() {
+    return ByteBuffer.wrap(_mask);
+  }
+  
+  /**
+   * @param columnNumber 0-based column number in this mask's row
+   * @return Whether or not the value for that column is null.  For boolean
+   *    columns, returns the actual value of the column.
+   */
+  public boolean isNull(int columnNumber) {
+    return (_mask[columnNumber / 8] & (byte) (1 << (columnNumber % 8))) == 0;
+  }
+  
+  public void markNull(int columnNumber) {
+    int maskIndex = columnNumber / 8;
+    _mask[maskIndex] = (byte) (_mask[maskIndex] & (byte) ~(1 << (columnNumber % 8)));
+  }
+  
+  /**
+   * @return Size in bytes of this mask
+   */
+  public int byteSize() {
+    return _mask.length;
+  }
+  
+}