[Mulgara-svn] r2066 - trunk/src/jar/util/java/org/mulgara/util/io

[pag at mulgara.org]

Author: pag
Date: 2011-10-07 22:30:03 +0000 (Fri, 07 Oct 2011)
New Revision: 2066

Modified:
   trunk/src/jar/util/java/org/mulgara/util/io/FileHashMap.java
   trunk/src/jar/util/java/org/mulgara/util/io/IOUtil.java
   trunk/src/jar/util/java/org/mulgara/util/io/LLHashMapUnitTest.java
Log:
Fixed a test, and re-organized to allow for variable-length objects in the mapping

Modified: trunk/src/jar/util/java/org/mulgara/util/io/FileHashMap.java
===================================================================
--- trunk/src/jar/util/java/org/mulgara/util/io/FileHashMap.java	2011-10-07 16:56:03 UTC (rev 2065)
+++ trunk/src/jar/util/java/org/mulgara/util/io/FileHashMap.java	2011-10-07 22:30:03 UTC (rev 2066)
@@ -1,5 +1,5 @@
 /*
- * Copyright 2010 Paul Gearon.
+ * Copyright 2011 Paul Gearon.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -35,6 +35,14 @@
 
 /**
  * A file-based hashmap.
+ * This class maps {@link java.nio.ByteBuffer}s of fixed length to {@link java.nio.ByteBuffer}s
+ * of fixed length. To map another data type, wrap this class in a class that converts
+ * keys and values into ByteBuffers.
+ * For an example of mapping a fixed data type, see {@link LLHashMap}, which maps Long to Long.
+ * 
+ * Mapping non-fixed types can be done using a custom {@link #hashCode(Object)} function for hashing,
+ * and a custom {@link #equalsKey(ByteBuffer, ByteBuffer)} method. These are protected methods that
+ * can be overridden in a subclass.
  */
 public class FileHashMap implements Map<ByteBuffer,ByteBuffer>, Closeable {
 
@@ -632,15 +640,17 @@
   }
 
   /**
-   * Tests if a file buffer contains a given key
-   * @param kb The byte buffer of the key.
+   * Tests if a file buffer contains a given key.
+   * Note that the file buffer contains the entire record (key+value).
+   * Override this to expand key equality test.
+   * @param filekb The byte buffer of the key.
    * @param key The key to look for.
    * @return <code>true</code> iff the buffer contains the key.
    */
-  private final boolean equalsKey(ByteBuffer kb, ByteBuffer key) {
+  protected final boolean equalsKey(ByteBuffer filekb, ByteBuffer key) {
     // compare remaining bytes, if any
     for (int i = keySize - 1; i >= 0; i--) {
-      if (kb.get(i) != key.get(i)) return false;
+      if (filekb.get(i) != key.get(i)) return false;
     }
     return true;
   }
@@ -658,35 +668,20 @@
     return fileRecords;
   }
 
+  protected long hashCode(Object b) {
+    return IOUtil.longHash(b.hashCode());
+  }
+
   /**
    * Calculate the location for a record, based on its key.
    * @param key The ByteBuffer for the key.
    * @return The record number in the file that the key specifies.
    */
   private final long recordPosition(ByteBuffer key) {
-    return longHash(key.hashCode()) % (long)fileRecords;
+    return hashCode(key) % (long)fileRecords;
   }
 
   /**
-   * Mix an int into a long in a reasonably cheap way.
-   * @param The int to mix.
-   * @return A long value with the integer mixed into it. Positive numbers only.
-   */
-  private static final long longHash(int h) {
-    long v = (long)h;
-    v ^= v << 5;
-    v ^= (v << 11) + 1049;
-    v ^= ((v >> 32) | (v << 32));
-    v ^= (v << 17) + 131041;
-    v ^= ((v >> 56) | (v << 56));
-    v ^= (v << 23) + 8313581;
-    v ^= (((v >> 8) & 0xFF000000L) | ((v << 8) & 0xFF00000000L));
-    v ^= (v << 37) + 2147483659L;
-    v ^= ((v >> 32) | (v << 32));
-    return v & 0x7FFFFFFFFFFFFFFFL;
-  }
-
-  /**
    * Returns the index of the first prime that is greater than or equal to the requested size.
    * @param s The requested size.
    * @return The index into PRIMES to use.

Modified: trunk/src/jar/util/java/org/mulgara/util/io/IOUtil.java
===================================================================
--- trunk/src/jar/util/java/org/mulgara/util/io/IOUtil.java	2011-10-07 16:56:03 UTC (rev 2065)
+++ trunk/src/jar/util/java/org/mulgara/util/io/IOUtil.java	2011-10-07 22:30:03 UTC (rev 2066)
@@ -139,4 +139,24 @@
         (order == NATIVE_ORDER ? ByteBuffer.allocateDirect(size) : ByteBuffer.allocateDirect(size).order(order)) :
         (order == NATIVE_ORDER ? ByteBuffer.allocate(size) : ByteBuffer.allocate(size).order(order));
   }
+
+  /**
+   * Mix an int into a long in a reasonably cheap way.
+   * @param The int to mix.
+   * @return A long value with the integer mixed into it. Positive numbers only.
+   */
+  public static final long longHash(int h) {
+    long v = (long)h;
+    v ^= v << 5;
+    v ^= (v << 11) + 1049;
+    v ^= ((v >> 32) | (v << 32));
+    v ^= (v << 17) + 131041;
+    v ^= ((v >> 56) | (v << 56));
+    v ^= (v << 23) + 8313581;
+    v ^= (((v >> 8) & 0xFF000000L) | ((v << 8) & 0xFF00000000L));
+    v ^= (v << 37) + 2147483659L;
+    v ^= ((v >> 32) | (v << 32));
+    return v & 0x7FFFFFFFFFFFFFFFL;
+  }
+
 }

Modified: trunk/src/jar/util/java/org/mulgara/util/io/LLHashMapUnitTest.java
===================================================================
--- trunk/src/jar/util/java/org/mulgara/util/io/LLHashMapUnitTest.java	2011-10-07 16:56:03 UTC (rev 2065)
+++ trunk/src/jar/util/java/org/mulgara/util/io/LLHashMapUnitTest.java	2011-10-07 22:30:03 UTC (rev 2066)
@@ -55,7 +55,7 @@
     assertEquals(-1L, map.get(4));
     assertEquals(null, map.get(Long.valueOf(4)));
     map.close();
-    assertEquals(131 * 16, f.length());
+    assertEquals(67 * 16, f.length());
     clean(f);
   }