use weak cache for ClassFiles

src/de/inetsoftware/classparser/ClassFile.java

@@ -1,5 +1,5 @@
 /*
-   Copyright 2011 - 2018 Volker Berlin (i-net software)
+   Copyright 2011 - 2019 Volker Berlin (i-net software)
 
    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
@@ -20,6 +20,8 @@ import java.io.DataInputStream;
 import java.io.IOException;
 import java.io.InputStream;
 
+import javax.annotation.Nullable;
+
 import de.inetsoftware.classparser.Attributes.AttributeInfo;
 
 /**
@@ -30,6 +32,8 @@ import de.inetsoftware.classparser.Attributes.AttributeInfo;
  */
 public class ClassFile {
 
+    private static final WeakValueCache<String,ClassFile> CACHE = new WeakValueCache<>(); 
+
     private final DataInputStream input;
 
     private final int             minorVersion;
@@ -56,6 +60,30 @@ public class ClassFile {
 
     private String                superSignature;
 
+    /**
+     * Get the ClassFile from cache or load it.
+     * 
+     * @param className
+     *            the class name
+     * @param loader
+     *            the ClassLoader to load
+     * @return the ClassFile or null
+     * @throws IOException
+     *             If any I/O error occur
+     */
+    @Nullable
+    public static ClassFile get( String className, ClassLoader loader ) throws IOException {
+        ClassFile classFile = CACHE.get( className );
+        if( classFile != null ) {
+            return classFile;
+        }
+        InputStream stream = loader.getResourceAsStream( className + ".class" );
+        if( stream != null ) {
+            return new ClassFile( stream );
+        }
+        return null;
+    }
+
     /**
      * Load a class file and create a model of the class.
      *
@@ -109,6 +137,7 @@ public class ClassFile {
                 }
             }
         }
+        CACHE.put( thisClass.getName(), this );
     }
 
     /**

src/de/inetsoftware/classparser/WeakValueCache.java

@@ -0,0 +1,58 @@
+/*
+   Copyright 2019 Volker Berlin (i-net software)
+
+   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 de.inetsoftware.classparser;
+
+import java.lang.ref.WeakReference;
+import java.util.HashMap;
+
+/**
+ * A simple cache for weak values.
+ *
+ * @param <K>
+ *            the key type
+ * @param <V>
+ *            the value type
+ * @author Volker Berlin
+ */
+public class WeakValueCache<K, V> {
+
+    private final HashMap<K, WeakReference<V>> map = new HashMap<>();
+
+    /**
+     * Put a value
+     * 
+     * @param key
+     *            the key
+     * @param value
+     *            the value
+     */
+    public void put( K key, V value ) {
+        map.put( key, new WeakReference<V>( value ) );
+    }
+
+    /**
+     * Get the value if in the cache
+     * 
+     * @param key
+     *            the key
+     * @return the value or null
+     */
+    public V get( K key ) {
+        WeakReference<V> valueRef = map.get( key );
+        return valueRef == null ? null : valueRef.get();
+    }
+}

src/de/inetsoftware/jwebassembly/module/ModuleGenerator.java

@@ -162,15 +162,14 @@ public class ModuleGenerator {
     public void finish() throws IOException {
         FunctionName next;
         while( (next = functions.nextWriteLater()) != null ) {
-            InputStream stream = libraries.getResourceAsStream( next.className + ".class" );
-            if( stream == null ) {
+            ClassFile classFile = ClassFile.get( next.className, libraries );
+            if( classFile == null ) {
                 if( next instanceof SyntheticFunctionName ) {
                     writeMethodImpl( next, true, ((SyntheticFunctionName)next).getCodeBuilder( watParser ) );
                 } else {
                     throw new WasmException( "Missing function: " + next.signatureName, -1 );
                 }
             } else {
-                ClassFile classFile = new ClassFile( stream );
                 iterateMethods( classFile, method -> {
                     try {
                         FunctionName name;
@@ -250,11 +249,10 @@ public class ModuleGenerator {
      *             if any I/O error occur
      */
     private void listStructFields( String className, List<NamedStorageType> list ) throws IOException {
-        InputStream stream = libraries.getResourceAsStream( className + ".class" );
-        if( stream == null ) {
+        ClassFile classFile = ClassFile.get( className, libraries );
+        if( classFile == null ) {
             throw new WasmException( "Missing class: " + className, -1 );
         }
-        ClassFile classFile = new ClassFile( stream );
 
         ConstantClass superClass = classFile.getSuperClass();
         if( superClass != null ) {