1 files changed, 78 insertions, 0 deletions
diff --git a/libphonenumber/src/com/google/i18n/phonenumbers/internal/RegexCache.java b/libphonenumber/src/com/google/i18n/phonenumbers/internal/RegexCache.java
new file mode 100644
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+++ b/libphonenumber/src/com/google/i18n/phonenumbers/internal/RegexCache.java
@@ -0,0 +1,78 @@
+/*
+ * Copyright (C) 2010 The Libphonenumber Authors
+ *
+ * Licensed 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 com.google.i18n.phonenumbers.internal;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+import java.util.regex.Pattern;
+
+/**
+ * LRU Cache for compiled regular expressions used by the libphonenumbers libary.
+ *
+ * @author Shaopeng Jia
+ */
+public class RegexCache {
+  private LRUCache<String, Pattern> cache;
+
+  public RegexCache(int size) {
+    cache = new LRUCache<String, Pattern>(size);
+  }
+
+  public Pattern getPatternForRegex(String regex) {
+    Pattern pattern = cache.get(regex);
+    if (pattern == null) {
+      pattern = Pattern.compile(regex);
+      cache.put(regex, pattern);
+    }
+    return pattern;
+  }
+
+  // @VisibleForTesting
+  boolean containsRegex(String regex) {
+    return cache.containsKey(regex);
+  }
+
+  private static class LRUCache<K, V> {
+    // LinkedHashMap offers a straightforward implementation of LRU cache.
+    private LinkedHashMap<K, V> map;
+    private int size;
+
+    @SuppressWarnings("serial")
+    public LRUCache(int size) {
+      this.size = size;
+      // Using access-order instead of insertion-order.
+      map = new LinkedHashMap<K, V>(size * 4 / 3 + 1, 0.75f, true) {
+        @Override
+        protected boolean removeEldestEntry(Map.Entry<K, V> eldest) {
+          return size() > LRUCache.this.size;
+        }
+      };
+    }
+
+    public synchronized V get(K key) {
+      return map.get(key);
+    }
+
+    public synchronized void put(K key, V value) {
+      map.put(key, value);
+    }
+
+    public synchronized boolean containsKey(K key) {
+      return map.containsKey(key);
+    }
+  }
+}