ConstantUtf8.java
- /*
- * 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.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 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 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();
- }
- /**
- * @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);
- }
- /**
- * @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") + "\")";
- }
- }