[Mulgara-svn] r2086 - in trunk/src/jar: query/java/org/mulgara/query tuples/java/org/mulgara/store/tuples

[pag at mulgara.org]

Author: pag
Date: 2012-01-05 19:10:12 +0000 (Thu, 05 Jan 2012)
New Revision: 2086

Modified:
   trunk/src/jar/query/java/org/mulgara/query/AnswerOperations.java
   trunk/src/jar/tuples/java/org/mulgara/store/tuples/TuplesOperations.java
Log:
Added common functions to calculate hashcodes from large data sets

Modified: trunk/src/jar/query/java/org/mulgara/query/AnswerOperations.java
===================================================================
--- trunk/src/jar/query/java/org/mulgara/query/AnswerOperations.java	2012-01-05 19:09:13 UTC (rev 2085)
+++ trunk/src/jar/query/java/org/mulgara/query/AnswerOperations.java	2012-01-05 19:10:12 UTC (rev 2086)
@@ -151,4 +151,29 @@
       }
     }
   }
+  
+  public static int hashCode(Answer a) throws TuplesException {
+    // Clone the arguments to avoid interfering with their cursors
+    a = (Answer)a.clone();
+
+    // Check that columns match
+    int numberOfVariables = a.getNumberOfVariables();
+    int result = numberOfVariables;
+
+    try {
+      // Check that all row values match
+      a.beforeFirst();
+      while (a.next()) {
+        // Verify that the rows match
+        for (int i = 0; i < numberOfVariables; i++) {
+          Object o = a.getObject(i);
+          if (o != null) result ^= o.hashCode();
+        }
+      }
+    } finally {
+      // Close our clones
+      a.close();
+    }
+    return result;
+  }
 }

Modified: trunk/src/jar/tuples/java/org/mulgara/store/tuples/TuplesOperations.java
===================================================================
--- trunk/src/jar/tuples/java/org/mulgara/store/tuples/TuplesOperations.java	2012-01-05 19:09:13 UTC (rev 2085)
+++ trunk/src/jar/tuples/java/org/mulgara/store/tuples/TuplesOperations.java	2012-01-05 19:10:12 UTC (rev 2086)
@@ -1180,6 +1180,34 @@
     return buff;
   }
 
+  /**
+   * Calculates a consistent hash code for a tuples.
+   * @param t The tuples to get the hash code for.
+   * @return The hash code value.
+   */
+  public static int hashCode(Tuples t) {
+    t = (Tuples)t.clone();
+    int result = t.getVariables().hashCode();
+    try {
+      t.beforeFirst();
+      int cols = t.getNumberOfVariables();
+      while (t.next()) {
+        for (int i = 0; i < cols; i++) {
+          long val = t.getColumnValue(i);
+          result ^= (int)(val ^ (val >>> 32));
+        }
+      }
+    } catch (TuplesException e) {
+      throw new RuntimeException(e.toString(), e);
+    } finally {
+      try {
+        if (t != null) t.close();
+      } catch (TuplesException ex) {
+        throw new RuntimeException(ex.toString(), ex);
+      }
+    }
+    return result;
+  }
 
   /**
    * Find the list of variables which appear in both the lhs and rhs tuples.