LUCENE-3108: Added ValueSource based on IndexDocValues

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/docvalues@1131063 13f79535-47bb-0310-9956-ffa450edef68

lucene/src/java/org/apache/lucene/search/function/NumericIndexDocValueSource.java

@@ -0,0 +1,114 @@
+package org.apache.lucene.search.function;
+
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import java.io.IOException;
+
+import org.apache.lucene.index.IndexReader.AtomicReaderContext;
+import org.apache.lucene.index.values.IndexDocValues;
+import org.apache.lucene.index.values.ValueType;
+
+/**
+ * Expert: obtains numeric field values from a {@link IndexDocValues} field.
+ * This {@link ValueSource} is compatible with all numerical
+ * {@link IndexDocValues}
+ * 
+ * @lucene.experimental
+ * 
+ */
+public class NumericIndexDocValueSource extends ValueSource {
+
+  private final String field;
+
+  public NumericIndexDocValueSource(String field) {
+    this.field = field;
+  }
+
+  @Override
+  public DocValues getValues(AtomicReaderContext context) throws IOException {
+    final IndexDocValues.Source source = context.reader.docValues(field)
+        .getSource();
+    ValueType type = source.type();
+    switch (type) {
+    case FLOAT_32:
+    case FLOAT_64:
+      return new DocValues() {
+
+        @Override
+        public String toString(int doc) {
+          return "float: [" + floatVal(doc) + "]";
+        }
+
+        @Override
+        public float floatVal(int doc) {
+          return (float) source.getFloat(doc);
+        }
+      };
+
+    case INTS:
+      return new DocValues() {
+        @Override
+        public String toString(int doc) {
+          return "float: [" + floatVal(doc) + "]";
+        }
+
+        @Override
+        public float floatVal(int doc) {
+          return (float) source.getInt(doc);
+        }
+      };
+    default:
+      throw new IOException("Type: " + type + "is not numeric");
+    }
+
+  }
+
+  @Override
+  public String description() {
+    return toString();
+  }
+
+  @Override
+  public int hashCode() {
+    final int prime = 31;
+    int result = 1;
+    result = prime * result + ((field == null) ? 0 : field.hashCode());
+    return result;
+  }
+
+  @Override
+  public boolean equals(Object obj) {
+    if (this == obj)
+      return true;
+    if (obj == null)
+      return false;
+    if (getClass() != obj.getClass())
+      return false;
+    NumericIndexDocValueSource other = (NumericIndexDocValueSource) obj;
+    if (field == null) {
+      if (other.field != null)
+        return false;
+    } else if (!field.equals(other.field))
+      return false;
+    return true;
+  }
+
+  @Override
+  public String toString() {
+    return "DocValues float(" + field + ')';
+  }
+}