1 files changed, 51 insertions, 0 deletions
diff --git a/libjava/gnu/gcj/awt/BitMaskExtent.java b/libjava/gnu/gcj/awt/BitMaskExtent.java
new file mode 100644
index 00000000000..2da39f86196
--- /dev/null
+++ b/libjava/gnu/gcj/awt/BitMaskExtent.java
@@ -0,0 +1,51 @@
+/* Copyright © 2000  Free Software Foundation
+
+   This file is part of libgcj.
+
+This software is copyrighted work licensed under the terms of the
+Libgcj License.  Please consult the file "LIBGCJ_LICENSE" for
+details.  */
+
+package gnu.gcj.awt;
+
+/** 
+ * Simple transparent utility class that can be used to perform bit
+ * mask extent calculations.
+ */
+public final class BitMaskExtent
+{
+  /** The number of the least significant bit of the bit mask extent. */
+  public byte leastSignificantBit;
+
+  /** The number of bits in the bit mask extent. */
+  public byte bitWidth;
+  
+  /**
+   * Set the bit mask. This will calculate and set the leastSignificantBit
+   * and bitWidth fields.
+   *
+   * @see #leastSignificantBit
+   * @see #bitWidth
+   */
+  public void setMask(long mask)
+  {
+    leastSignificantBit = 0;
+    bitWidth = 0;
+    if (mask == 0) return;
+    long shiftMask = mask;
+    for (; (shiftMask&1) == 0; shiftMask >>>=1) leastSignificantBit++;
+    for (; (shiftMask&1) != 0; shiftMask >>>=1) bitWidth++;
+    
+    if (shiftMask != 0)
+      throw new IllegalArgumentException("mask must be continuous");
+  }
+  
+  /** 
+   * Calculate the bit mask based on the values of the
+   * leastSignificantBit and bitWidth fields.
+   */
+  public long toMask()
+  {
+    return ((1<<bitWidth)-1) << leastSignificantBit;
+  }  
+}