StructureLoader.java revision 1829:dbe6b239d681 
1/*
2 * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.  Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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23 * questions.
24 */
25
26package jdk.nashorn.internal.runtime;
27
28import static jdk.nashorn.internal.codegen.Compiler.SCRIPTS_PACKAGE;
29import static jdk.nashorn.internal.codegen.Compiler.binaryName;
30import static jdk.nashorn.internal.codegen.CompilerConstants.JS_OBJECT_DUAL_FIELD_PREFIX;
31import static jdk.nashorn.internal.codegen.CompilerConstants.JS_OBJECT_SINGLE_FIELD_PREFIX;
32
33import java.lang.module.ModuleDescriptor;
34import java.lang.reflect.Module;
35import java.security.ProtectionDomain;
36import jdk.nashorn.internal.codegen.ObjectClassGenerator;
37
38/**
39 * Responsible for on the fly construction of structure classes.
40 */
41final class StructureLoader extends NashornLoader {
42    private static final String SINGLE_FIELD_PREFIX = binaryName(SCRIPTS_PACKAGE) + '.' + JS_OBJECT_SINGLE_FIELD_PREFIX.symbolName();
43    private static final String DUAL_FIELD_PREFIX   = binaryName(SCRIPTS_PACKAGE) + '.' + JS_OBJECT_DUAL_FIELD_PREFIX.symbolName();
44
45    private final Module structuresModule;
46
47    /**
48     * Constructor.
49     */
50    StructureLoader(final ClassLoader parent) {
51        super(parent);
52
53        // new structures module, it's exports, read edges
54        structuresModule = createModule("jdk.scripting.nashorn.structures");
55
56        // specific exports from nashorn to the structures module
57        NASHORN_MODULE.addExports(SCRIPTS_PKG, structuresModule);
58        NASHORN_MODULE.addExports(RUNTIME_PKG, structuresModule);
59
60        // nashorn has to read fields from classes of the new module
61        NASHORN_MODULE.addReads(structuresModule);
62    }
63
64    private Module createModule(final String moduleName) {
65        final ModuleDescriptor descriptor
66                = ModuleDescriptor.module(moduleName)
67                    .requires("java.base")
68                    .requires(NASHORN_MODULE.getName())
69                    .contains(SCRIPTS_PKG)
70                    .build();
71
72        final Module mod = Context.createModuleTrusted(descriptor, this);
73        loadModuleManipulator();
74        return mod;
75    }
76
77    /**
78     * Returns true if the class name represents a structure object with dual primitive/object fields.
79     * @param name a class name
80     * @return true if a dual field structure class
81     */
82    private static boolean isDualFieldStructure(final String name) {
83        return name.startsWith(DUAL_FIELD_PREFIX);
84    }
85
86    /**
87     * Returns true if the class name represents a structure object with single object-only fields.
88     * @param name a class name
89     * @return true if a single field structure class
90     */
91    static boolean isSingleFieldStructure(final String name) {
92        return name.startsWith(SINGLE_FIELD_PREFIX);
93    }
94
95    /**
96     * Returns true if the class name represents a Nashorn structure object.
97     * @param name a class name
98     * @return true if a structure class
99     */
100    static boolean isStructureClass(final String name) {
101        return isDualFieldStructure(name) || isSingleFieldStructure(name);
102    }
103
104    Module getModule() {
105        return structuresModule;
106    }
107
108    @Override
109    protected Class<?> findClass(final String name) throws ClassNotFoundException {
110        if (isDualFieldStructure(name)) {
111            return generateClass(name, name.substring(DUAL_FIELD_PREFIX.length()), true);
112        } else if (isSingleFieldStructure(name)) {
113            return generateClass(name, name.substring(SINGLE_FIELD_PREFIX.length()), false);
114        }
115        return super.findClass(name);
116    }
117
118    /**
119     * Generate a layout class.
120     * @param name       Name of class.
121     * @param descriptor Layout descriptor.
122     * @return Generated class.
123     */
124    private Class<?> generateClass(final String name, final String descriptor, final boolean dualFields) {
125        final Context context = Context.getContextTrusted();
126
127        final byte[] code = new ObjectClassGenerator(context, dualFields).generate(descriptor);
128        return defineClass(name, code, 0, code.length, new ProtectionDomain(null, getPermissions(null)));
129    }
130}
131