Github user jaltekruse commented on a diff in the pull request:
https://github.com/apache/drill/pull/98#discussion_r38586355
--- Diff:
common/src/main/java/org/apache/drill/common/map/CaseInsensitiveMap.java ---
@@ -0,0 +1,141 @@
+/**
+ * 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.
+ */
+package org.apache.drill.common.map;
+
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.Maps;
+
+import java.util.Collection;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * A special type of {@link Map} with {@link String}s as keys, and the
case of a key is ignored for operations involving
+ * keys like {@link #put}, {@link #get}, etc. The keys are stored and
retrieved in lower case. Use the static methods to
+ * create instances of this class (e.g. {@link #newConcurrentMap}).
+ *
+ * @param <VALUE> the type of values to be stored in the map
+ */
+public class CaseInsensitiveMap<VALUE> implements Map<String, VALUE> {
+
+ /**
+ * Returns a new instance of {@link java.util.concurrent.ConcurrentMap}
with key case-insensitivity. See
+ * {@link java.util.concurrent.ConcurrentMap}.
+ *
+ * @param <VALUE> type of values to be stored in the map
+ * @return key case-insensitive concurrent map
+ */
+ public static <VALUE> CaseInsensitiveMap<VALUE> newConcurrentMap() {
+ return new CaseInsensitiveMap<>(Maps.<String,
VALUE>newConcurrentMap());
+ }
+
+ /**
+ * Returns a new instance of {@link java.util.HashMap} with key
case-insensitivity. See {@link java.util.HashMap}.
+ *
+ * @param <VALUE> type of values to be stored in the map
+ * @return key case-insensitive hash map
+ */
+ public static <VALUE> CaseInsensitiveMap<VALUE> newHashMap() {
+ return new CaseInsensitiveMap<>(Maps.<String, VALUE>newHashMap());
+ }
+
+ /**
+ * Returns a new instance of {@link ImmutableMap} with key
case-insensitivity. This map is built from the given
+ * map. See {@link ImmutableMap}.
+ *
+ * @param map map to copy from
+ * @param <VALUE> type of values to be stored in the map
+ * @return key case-insensitive immutable map
+ */
+ public static <VALUE> CaseInsensitiveMap<VALUE> newImmutableMap(final
Map<? extends String, ? extends VALUE> map) {
+ final ImmutableMap.Builder<String, VALUE> builder =
ImmutableMap.builder();
+ for (final Entry<? extends String, ? extends VALUE> entry :
map.entrySet()) {
+ builder.put(entry.getKey().toLowerCase(), entry.getValue());
+ }
+ return new CaseInsensitiveMap<>(builder.build());
+ }
+
+ private final Map<String, VALUE> underlyingMap;
+
+ protected CaseInsensitiveMap(final Map<String, VALUE> underlyingMap) {
+ this.underlyingMap = underlyingMap;
--- End diff --
Would it be worth enforcing that the map being wrapped is empty? As the
newImmuatableMap() method makes a copy of the map, properly importing the keys,
someone may get the wrong impression that this constructor would remove and
re-insert the values currently in the map so that they will be accessible.
Right now it would be possible to wrap a map that has uppercase in the key
names and those members would not be able to be extracted through this
interface.
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