src/main/java/org/apache/bcel/classfile/ConstantUtf8.java - commons-bcel - Git at Google

 /*
  * 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
  *
  *   https://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.bcel.classfile;

 import java.io.DataInput;
 import java.io.DataOutputStream;
 import java.io.IOException;
 import java.util.HashMap;
 import java.util.LinkedHashMap;
 import java.util.Map;
 import java.util.Objects;

 import org.apache.bcel.Const;

 /**
  * Extends the abstract {@link Constant} to represent a reference to a UTF-8 encoded string.
  * <p>
  * The following system properties govern caching this class performs.
  * </p>
  * <ul>
  * <li>{@link #SYS_PROP_CACHE_MAX_ENTRIES} (since 6.4): The size of the cache, by default 0, meaning caching is
  * disabled.</li>
  * <li>{@link #SYS_PROP_CACHE_MAX_ENTRY_SIZE} (since 6.0): The maximum size of the values to cache, by default 200, 0
  * disables caching. Values larger than this are <em>not</em> cached.</li>
  * <li>{@link #SYS_PROP_STATISTICS} (since 6.0): Prints statistics on the console when the JVM exits.</li>
  * </ul>
  * <p>
  * Here is a sample Maven invocation with caching disabled:
  * </p>
  *
  * <pre>
  * mvn test -Dbcel.statistics=true -Dbcel.maxcached.size=0 -Dbcel.maxcached=0
  * </pre>
  * <p>
  * Here is a sample Maven invocation with caching enabled:
  * </p>
  *
  * <pre>
  * mvn test -Dbcel.statistics=true -Dbcel.maxcached.size=100000 -Dbcel.maxcached=5000000
  * </pre>
  *
  * @see Constant
  */
 public final class ConstantUtf8 extends Constant {

     private static final class Cache {

         private static final boolean BCEL_STATISTICS = Boolean.getBoolean(SYS_PROP_STATISTICS);
         private static final int MAX_ENTRIES = Integer.getInteger(SYS_PROP_CACHE_MAX_ENTRIES, 0).intValue();
         private static final int INITIAL_CAPACITY = (int) (MAX_ENTRIES / 0.75);

         private static final HashMap<String, ConstantUtf8> CACHE = new LinkedHashMap<String, ConstantUtf8>(INITIAL_CAPACITY, 0.75f, true) {

             private static final long serialVersionUID = -8506975356158971766L;

             @Override
             protected boolean removeEldestEntry(final Map.Entry<String, ConstantUtf8> eldest) {
                 return size() > MAX_ENTRIES;
             }
         };

         // Set the size to 0 or below to skip caching entirely
         private static final int MAX_ENTRY_SIZE = Integer.getInteger(SYS_PROP_CACHE_MAX_ENTRY_SIZE, 200).intValue();

         static boolean isEnabled() {
             return MAX_ENTRIES > 0 && MAX_ENTRY_SIZE > 0;
         }

     }

     // TODO these should perhaps be AtomicInt?
     private static volatile int considered;
     private static volatile int created;
     private static volatile int hits;
     private static volatile int skipped;

     private static final String SYS_PROP_CACHE_MAX_ENTRIES = "bcel.maxcached";
     private static final String SYS_PROP_CACHE_MAX_ENTRY_SIZE = "bcel.maxcached.size";
     private static final String SYS_PROP_STATISTICS = "bcel.statistics";

     static {
         if (Cache.BCEL_STATISTICS) {
             Runtime.getRuntime().addShutdownHook(new Thread(ConstantUtf8::printStats));
         }
     }

     /**
      * Clears the cache.
      *
      * @since 6.4.0
      */
     public static synchronized void clearCache() {
         Cache.CACHE.clear();
     }

     // for access by test code
     static synchronized void clearStats() {
         hits = considered = skipped = created = 0;
     }

     // Avoid Spotbugs complaint about Write to static field
     private static synchronized void countCreated() {
         created++;
     }

     /**
      * Gets a new or cached instance of the given value.
      * <p>
      * See {@link ConstantUtf8} class Javadoc for details.
      * </p>
      *
      * @param value the value.
      * @return a new or cached instance of the given value.
      * @since 6.0
      */
     public static synchronized ConstantUtf8 getCachedInstance(final String value) {
         if (value.length() > Cache.MAX_ENTRY_SIZE) {
             skipped++;
             return new ConstantUtf8(value);
         }
         considered++;
         synchronized (ConstantUtf8.class) { // might be better with a specific lock object
             ConstantUtf8 result = Cache.CACHE.get(value);
             if (result != null) {
                 hits++;
                 return result;
             }
             result = new ConstantUtf8(value);
             Cache.CACHE.put(value, result);
             return result;
         }
     }

     /**
      * Gets a new or cached instance of the given value.
      * <p>
      * See {@link ConstantUtf8} class Javadoc for details.
      * </p>
      *
      * @param dataInput the value.
      * @return a new or cached instance of the given value.
      * @throws IOException if an I/O error occurs.
      * @since 6.0
      */
     public static ConstantUtf8 getInstance(final DataInput dataInput) throws IOException {
         return getInstance(dataInput.readUTF());
     }

     /**
      * Gets a new or cached instance of the given value.
      * <p>
      * See {@link ConstantUtf8} class Javadoc for details.
      * </p>
      *
      * @param value the value.
      * @return a new or cached instance of the given value.
      * @since 6.0
      */
     public static ConstantUtf8 getInstance(final String value) {
         return Cache.isEnabled() ? getCachedInstance(value) : new ConstantUtf8(value);
     }

     // for access by test code
     static void printStats() {
         final String prefix = "[Apache Commons BCEL]";
         System.err.printf("%s Cache hit %,d/%,d, %d skipped.%n", prefix, hits, considered, skipped);
         System.err.printf("%s Total of %,d ConstantUtf8 objects created.%n", prefix, created);
         System.err.printf("%s Configuration: %s=%,d, %s=%,d.%n", prefix, SYS_PROP_CACHE_MAX_ENTRIES, Cache.MAX_ENTRIES, SYS_PROP_CACHE_MAX_ENTRY_SIZE,
             Cache.MAX_ENTRY_SIZE);
     }

     private final String value;

     /**
      * Initializes from another object.
      *
      * @param constantUtf8 the value.
      */
     public ConstantUtf8(final ConstantUtf8 constantUtf8) {
         this(constantUtf8.getBytes());
     }

     /**
      * Initializes instance from file data.
      *
      * @param dataInput Input stream.
      * @throws IOException if an I/O error occurs.
      */
     ConstantUtf8(final DataInput dataInput) throws IOException {
         super(Const.CONSTANT_Utf8);
         value = dataInput.readUTF();
         countCreated();
     }

     /**
      * Constructs a ConstantUtf8.
      *
      * @param value Data.
      */
     public ConstantUtf8(final String value) {
         super(Const.CONSTANT_Utf8);
         this.value = Objects.requireNonNull(value, "value");
         countCreated();
     }

     /**
      * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
      * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
      *
      * @param v Visitor object.
      */
     @Override
     public void accept(final Visitor v) {
         v.visitConstantUtf8(this);
     }

     /**
      * Dumps String in Utf8 format to file stream.
      *
      * @param file Output file stream.
      * @throws IOException if an I/O error occurs.
      */
     @Override
     public void dump(final DataOutputStream file) throws IOException {
         file.writeByte(super.getTag());
         file.writeUTF(value);
     }

     /**
      * Gets the data converted to string.
      *
      * @return Data converted to string.
      */
     public String getBytes() {
         return value;
     }

     /**
      * @param bytes the raw bytes of this UTF-8.
      * @deprecated (since 6.0)
      */
     @java.lang.Deprecated
     public void setBytes(final String bytes) {
         throw new UnsupportedOperationException();
     }

     /**
      * @return String representation.
      */
     @Override
     public String toString() {
         return super.toString() + "(\"" + Utility.replace(value, "\n", "\\n") + "\")";
     }
 }
	/*
	* 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
	*
	* https://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.bcel.classfile;

	import java.io.DataInput;
	import java.io.DataOutputStream;
	import java.io.IOException;
	import java.util.HashMap;
	import java.util.LinkedHashMap;
	import java.util.Map;
	import java.util.Objects;

	import org.apache.bcel.Const;

	/**
	* Extends the abstract {@link Constant} to represent a reference to a UTF-8 encoded string.
	* <p>
	* The following system properties govern caching this class performs.
	* </p>
	* <ul>
	* <li>{@link #SYS_PROP_CACHE_MAX_ENTRIES} (since 6.4): The size of the cache, by default 0, meaning caching is
	* disabled.</li>
	* <li>{@link #SYS_PROP_CACHE_MAX_ENTRY_SIZE} (since 6.0): The maximum size of the values to cache, by default 200, 0
	* disables caching. Values larger than this are <em>not</em> cached.</li>
	* <li>{@link #SYS_PROP_STATISTICS} (since 6.0): Prints statistics on the console when the JVM exits.</li>
	* </ul>
	* <p>
	* Here is a sample Maven invocation with caching disabled:
	* </p>
	*
	* <pre>
	* mvn test -Dbcel.statistics=true -Dbcel.maxcached.size=0 -Dbcel.maxcached=0
	* </pre>
	* <p>
	* Here is a sample Maven invocation with caching enabled:
	* </p>
	*
	* <pre>
	* mvn test -Dbcel.statistics=true -Dbcel.maxcached.size=100000 -Dbcel.maxcached=5000000
	* </pre>
	*
	* @see Constant
	*/
	public final class ConstantUtf8 extends Constant {

	private static final class Cache {

	private static final boolean BCEL_STATISTICS = Boolean.getBoolean(SYS_PROP_STATISTICS);
	private static final int MAX_ENTRIES = Integer.getInteger(SYS_PROP_CACHE_MAX_ENTRIES, 0).intValue();
	private static final int INITIAL_CAPACITY = (int) (MAX_ENTRIES / 0.75);

	private static final HashMap<String, ConstantUtf8> CACHE = new LinkedHashMap<String, ConstantUtf8>(INITIAL_CAPACITY, 0.75f, true) {

	private static final long serialVersionUID = -8506975356158971766L;

	@Override
	protected boolean removeEldestEntry(final Map.Entry<String, ConstantUtf8> eldest) {
	return size() > MAX_ENTRIES;
	}
	};

	// Set the size to 0 or below to skip caching entirely
	private static final int MAX_ENTRY_SIZE = Integer.getInteger(SYS_PROP_CACHE_MAX_ENTRY_SIZE, 200).intValue();

	static boolean isEnabled() {
	return MAX_ENTRIES > 0 && MAX_ENTRY_SIZE > 0;
	}

	}

	// TODO these should perhaps be AtomicInt?
	private static volatile int considered;
	private static volatile int created;
	private static volatile int hits;
	private static volatile int skipped;

	private static final String SYS_PROP_CACHE_MAX_ENTRIES = "bcel.maxcached";
	private static final String SYS_PROP_CACHE_MAX_ENTRY_SIZE = "bcel.maxcached.size";
	private static final String SYS_PROP_STATISTICS = "bcel.statistics";

	static {
	if (Cache.BCEL_STATISTICS) {
	Runtime.getRuntime().addShutdownHook(new Thread(ConstantUtf8::printStats));
	}
	}

	/**
	* Clears the cache.
	*
	* @since 6.4.0
	*/
	public static synchronized void clearCache() {
	Cache.CACHE.clear();
	}

	// for access by test code
	static synchronized void clearStats() {
	hits = considered = skipped = created = 0;
	}

	// Avoid Spotbugs complaint about Write to static field
	private static synchronized void countCreated() {
	created++;
	}

	/**
	* Gets a new or cached instance of the given value.
	* <p>
	* See {@link ConstantUtf8} class Javadoc for details.
	* </p>
	*
	* @param value the value.
	* @return a new or cached instance of the given value.
	* @since 6.0
	*/
	public static synchronized ConstantUtf8 getCachedInstance(final String value) {
	if (value.length() > Cache.MAX_ENTRY_SIZE) {
	skipped++;
	return new ConstantUtf8(value);
	}
	considered++;
	synchronized (ConstantUtf8.class) { // might be better with a specific lock object
	ConstantUtf8 result = Cache.CACHE.get(value);
	if (result != null) {
	hits++;
	return result;
	}
	result = new ConstantUtf8(value);
	Cache.CACHE.put(value, result);
	return result;
	}
	}

	/**
	* Gets a new or cached instance of the given value.
	* <p>
	* See {@link ConstantUtf8} class Javadoc for details.
	* </p>
	*
	* @param dataInput the value.
	* @return a new or cached instance of the given value.
	* @throws IOException if an I/O error occurs.
	* @since 6.0
	*/
	public static ConstantUtf8 getInstance(final DataInput dataInput) throws IOException {
	return getInstance(dataInput.readUTF());
	}

	/**
	* Gets a new or cached instance of the given value.
	* <p>
	* See {@link ConstantUtf8} class Javadoc for details.
	* </p>
	*
	* @param value the value.
	* @return a new or cached instance of the given value.
	* @since 6.0
	*/
	public static ConstantUtf8 getInstance(final String value) {
	return Cache.isEnabled() ? getCachedInstance(value) : new ConstantUtf8(value);
	}

	// for access by test code
	static void printStats() {
	final String prefix = "[Apache Commons BCEL]";
	System.err.printf("%s Cache hit %,d/%,d, %d skipped.%n", prefix, hits, considered, skipped);
	System.err.printf("%s Total of %,d ConstantUtf8 objects created.%n", prefix, created);
	System.err.printf("%s Configuration: %s=%,d, %s=%,d.%n", prefix, SYS_PROP_CACHE_MAX_ENTRIES, Cache.MAX_ENTRIES, SYS_PROP_CACHE_MAX_ENTRY_SIZE,
	Cache.MAX_ENTRY_SIZE);
	}

	private final String value;

	/**
	* Initializes from another object.
	*
	* @param constantUtf8 the value.
	*/
	public ConstantUtf8(final ConstantUtf8 constantUtf8) {
	this(constantUtf8.getBytes());
	}

	/**
	* Initializes instance from file data.
	*
	* @param dataInput Input stream.
	* @throws IOException if an I/O error occurs.
	*/
	ConstantUtf8(final DataInput dataInput) throws IOException {
	super(Const.CONSTANT_Utf8);
	value = dataInput.readUTF();
	countCreated();
	}

	/**
	* Constructs a ConstantUtf8.
	*
	* @param value Data.
	*/
	public ConstantUtf8(final String value) {
	super(Const.CONSTANT_Utf8);
	this.value = Objects.requireNonNull(value, "value");
	countCreated();
	}

	/**
	* Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
	* I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
	*
	* @param v Visitor object.
	*/
	@Override
	public void accept(final Visitor v) {
	v.visitConstantUtf8(this);
	}

	/**
	* Dumps String in Utf8 format to file stream.
	*
	* @param file Output file stream.
	* @throws IOException if an I/O error occurs.
	*/
	@Override
	public void dump(final DataOutputStream file) throws IOException {
	file.writeByte(super.getTag());
	file.writeUTF(value);
	}

	/**
	* Gets the data converted to string.
	*
	* @return Data converted to string.
	*/
	public String getBytes() {
	return value;
	}

	/**
	* @param bytes the raw bytes of this UTF-8.
	* @deprecated (since 6.0)
	*/
	@java.lang.Deprecated
	public void setBytes(final String bytes) {
	throw new UnsupportedOperationException();
	}

	/**
	* @return String representation.
	*/
	@Override
	public String toString() {
	return super.toString() + "(\"" + Utility.replace(value, "\n", "\\n") + "\")";
	}
	}