From 62e8d0c9c16b08f9adf9649b5e72cb13ea2bbdf6 Mon Sep 17 00:00:00 2001
From: andreast <andreast@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Tue, 21 Sep 2004 13:50:13 +0000
Subject: 2004-09-21  Sven de Marothy <sven@physto.se>

	* java/nio/ByteBuffer.java (hashCode): Implemented.
	* java/nio/CharBuffer.java: Likewise.
	* java/nio/DoubleBuffer.java: Likewise.
	* java/nio/FloatBuffer.java: Likewise.
	* java/nio/LongBuffer.java: Likewise.
	* java/nio/IntBuffer.java: Likewise.
	* java/nio/ShortBuffer.java: Likewise.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@87804 138bc75d-0d04-0410-961f-82ee72b054a4
---
 libjava/java/nio/DoubleBuffer.java | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

(limited to 'libjava/java/nio/DoubleBuffer.java')

diff --git a/libjava/java/nio/DoubleBuffer.java b/libjava/java/nio/DoubleBuffer.java
index 10055cd08d9..dd16ee04962 100644
--- a/libjava/java/nio/DoubleBuffer.java
+++ b/libjava/java/nio/DoubleBuffer.java
@@ -243,11 +243,27 @@ public abstract class DoubleBuffer extends Buffer
 
   /**
    * Calculates a hash code for this buffer.
+   *
+   * This is done with <code>long</code> arithmetic,
+   * where ** represents exponentiation, by this formula:<br>
+   * <code>s[position()] + 31 + (s[position()+1] + 30)*31**1 + ... +
+   * (s[limit()-1]+30)*31**(limit()-1)</code>.
+   * Where s is the buffer data, in Double.doubleToLongBits() form
+   * Note that the hashcode is dependent on buffer content, 
+   * and therefore is not useful if the buffer content may change.
+   *
+   * @return the hash code (casted to int)
    */
   public int hashCode ()
   {
-    // FIXME: Check what SUN calculates here.
-    return super.hashCode ();
+    long hashCode = Double.doubleToLongBits(get(position())) + 31;
+    long multiplier = 1;
+    for (int i = position() + 1; i < limit(); ++i)
+      {
+	  multiplier *= 31;
+	  hashCode += (Double.doubleToLongBits(get(i)) + 30)*multiplier;
+      }
+    return ((int)hashCode);
   }
 
   /**
-- 
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