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
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19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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24 */
25
26/*
27 * This file is available under and governed by the GNU General Public
28 * License version 2 only, as published by the Free Software Foundation.
29 * However, the following notice accompanied the original version of this
30 * file, and Oracle licenses the original version of this file under the BSD
31 * license:
32 */
33/*
34   Copyright 2009-2013 Attila Szegedi
35
36   Licensed under both the Apache License, Version 2.0 (the "Apache License")
37   and the BSD License (the "BSD License"), with licensee being free to
38   choose either of the two at their discretion.
39
40   You may not use this file except in compliance with either the Apache
41   License or the BSD License.
42
43   If you choose to use this file in compliance with the Apache License, the
44   following notice applies to you:
45
46       You may obtain a copy of the Apache License at
47
48           http://www.apache.org/licenses/LICENSE-2.0
49
50       Unless required by applicable law or agreed to in writing, software
51       distributed under the License is distributed on an "AS IS" BASIS,
52       WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
53       implied. See the License for the specific language governing
54       permissions and limitations under the License.
55
56   If you choose to use this file in compliance with the BSD License, the
57   following notice applies to you:
58
59       Redistribution and use in source and binary forms, with or without
60       modification, are permitted provided that the following conditions are
61       met:
62       * Redistributions of source code must retain the above copyright
63         notice, this list of conditions and the following disclaimer.
64       * Redistributions in binary form must reproduce the above copyright
65         notice, this list of conditions and the following disclaimer in the
66         documentation and/or other materials provided with the distribution.
67       * Neither the name of the copyright holder nor the names of
68         contributors may be used to endorse or promote products derived from
69         this software without specific prior written permission.
70
71       THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
72       IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
73       TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
74       PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDER
75       BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
76       CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
77       SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
78       BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
79       WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
80       OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
81       ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
82*/
83
84package jdk.dynalink.beans;
85
86import java.lang.invoke.MethodHandle;
87import java.lang.invoke.MethodType;
88import java.util.Iterator;
89import java.util.LinkedList;
90import java.util.List;
91import jdk.dynalink.linker.ConversionComparator.Comparison;
92import jdk.dynalink.linker.LinkerServices;
93import jdk.dynalink.linker.support.TypeUtilities;
94
95/**
96 * Utility class that encapsulates the algorithm for choosing the maximally specific methods.
97 */
98class MaximallySpecific {
99    /**
100     * Given a list of methods, returns a list of maximally specific methods.
101     *
102     * @param methods the list of methods
103     * @param varArgs whether to assume the methods are varargs
104     * @return the list of maximally specific methods.
105     */
106    static List<SingleDynamicMethod> getMaximallySpecificMethods(final List<SingleDynamicMethod> methods, final boolean varArgs) {
107        return getMaximallySpecificSingleDynamicMethods(methods, varArgs, null, null);
108    }
109
110    private abstract static class MethodTypeGetter<T> {
111        abstract MethodType getMethodType(T t);
112    }
113
114    private static final MethodTypeGetter<MethodHandle> METHOD_HANDLE_TYPE_GETTER =
115            new MethodTypeGetter<MethodHandle>() {
116        @Override
117        MethodType getMethodType(final MethodHandle t) {
118            return t.type();
119        }
120    };
121
122    private static final MethodTypeGetter<SingleDynamicMethod> DYNAMIC_METHOD_TYPE_GETTER =
123            new MethodTypeGetter<SingleDynamicMethod>() {
124        @Override
125        MethodType getMethodType(final SingleDynamicMethod t) {
126            return t.getMethodType();
127        }
128    };
129
130     /**
131      * Given a list of methods handles, returns a list of maximally specific methods, applying language-runtime
132      * specific conversion preferences.
133      *
134      * @param methods the list of method handles
135      * @param varArgs whether to assume the method handles are varargs
136      * @param argTypes concrete argument types for the invocation
137      * @return the list of maximally specific method handles.
138      */
139     static List<MethodHandle> getMaximallySpecificMethodHandles(final List<MethodHandle> methods, final boolean varArgs,
140             final Class<?>[] argTypes, final LinkerServices ls) {
141         return getMaximallySpecificMethods(methods, varArgs, argTypes, ls, METHOD_HANDLE_TYPE_GETTER);
142     }
143
144     /**
145      * Given a list of methods, returns a list of maximally specific methods, applying language-runtime specific
146      * conversion preferences.
147      *
148      * @param methods the list of methods
149      * @param varArgs whether to assume the methods are varargs
150      * @param argTypes concrete argument types for the invocation
151      * @return the list of maximally specific methods.
152      */
153     static List<SingleDynamicMethod> getMaximallySpecificSingleDynamicMethods(final List<SingleDynamicMethod> methods,
154             final boolean varArgs, final Class<?>[] argTypes, final LinkerServices ls) {
155         return getMaximallySpecificMethods(methods, varArgs, argTypes, ls, DYNAMIC_METHOD_TYPE_GETTER);
156     }
157
158    /**
159     * Given a list of methods, returns a list of maximally specific methods, applying language-runtime specific
160     * conversion preferences.
161     *
162     * @param methods the list of methods
163     * @param varArgs whether to assume the methods are varargs
164     * @param argTypes concrete argument types for the invocation
165     * @return the list of maximally specific methods.
166     */
167    private static <T> List<T> getMaximallySpecificMethods(final List<T> methods, final boolean varArgs,
168            final Class<?>[] argTypes, final LinkerServices ls, final MethodTypeGetter<T> methodTypeGetter) {
169        if(methods.size() < 2) {
170            return methods;
171        }
172        final LinkedList<T> maximals = new LinkedList<>();
173        for(final T m: methods) {
174            final MethodType methodType = methodTypeGetter.getMethodType(m);
175            boolean lessSpecific = false;
176            for(final Iterator<T> maximal = maximals.iterator(); maximal.hasNext();) {
177                final T max = maximal.next();
178                switch(isMoreSpecific(methodType, methodTypeGetter.getMethodType(max), varArgs, argTypes, ls)) {
179                    case TYPE_1_BETTER: {
180                        maximal.remove();
181                        break;
182                    }
183                    case TYPE_2_BETTER: {
184                        lessSpecific = true;
185                        break;
186                    }
187                    case INDETERMINATE: {
188                        // do nothing
189                        break;
190                    }
191                    default: {
192                        throw new AssertionError();
193                    }
194                }
195            }
196            if(!lessSpecific) {
197                maximals.addLast(m);
198            }
199        }
200        return maximals;
201    }
202
203    private static Comparison isMoreSpecific(final MethodType t1, final MethodType t2, final boolean varArgs, final Class<?>[] argTypes,
204            final LinkerServices ls) {
205        final int pc1 = t1.parameterCount();
206        final int pc2 = t2.parameterCount();
207        assert varArgs || (pc1 == pc2) && (argTypes == null || argTypes.length == pc1);
208        assert (argTypes == null) == (ls == null);
209        final int maxPc = Math.max(Math.max(pc1, pc2), argTypes == null ? 0 : argTypes.length);
210        boolean t1MoreSpecific = false;
211        boolean t2MoreSpecific = false;
212        // NOTE: Starting from 1 as overloaded method resolution doesn't depend on 0th element, which is the type of
213        // 'this'. We're only dealing with instance methods here, not static methods. Actually, static methods will have
214        // a fake 'this' of type StaticClass.
215        for(int i = 1; i < maxPc; ++i) {
216            final Class<?> c1 = getParameterClass(t1, pc1, i, varArgs);
217            final Class<?> c2 = getParameterClass(t2, pc2, i, varArgs);
218            if(c1 != c2) {
219                final Comparison cmp = compare(c1, c2, argTypes, i, ls);
220                if(cmp == Comparison.TYPE_1_BETTER && !t1MoreSpecific) {
221                    t1MoreSpecific = true;
222                    if(t2MoreSpecific) {
223                        return Comparison.INDETERMINATE;
224                    }
225                }
226                if(cmp == Comparison.TYPE_2_BETTER && !t2MoreSpecific) {
227                    t2MoreSpecific = true;
228                    if(t1MoreSpecific) {
229                        return Comparison.INDETERMINATE;
230                    }
231                }
232            }
233        }
234        if(t1MoreSpecific) {
235            return Comparison.TYPE_1_BETTER;
236        } else if(t2MoreSpecific) {
237            return Comparison.TYPE_2_BETTER;
238        }
239        return Comparison.INDETERMINATE;
240    }
241
242    private static Comparison compare(final Class<?> c1, final Class<?> c2, final Class<?>[] argTypes, final int i, final LinkerServices cmp) {
243        if(cmp != null) {
244            final Comparison c = cmp.compareConversion(argTypes[i], c1, c2);
245            if(c != Comparison.INDETERMINATE) {
246                return c;
247            }
248        }
249        if(TypeUtilities.isSubtype(c1, c2)) {
250            return Comparison.TYPE_1_BETTER;
251        } if(TypeUtilities.isSubtype(c2, c1)) {
252            return Comparison.TYPE_2_BETTER;
253        }
254        return Comparison.INDETERMINATE;
255    }
256
257    private static Class<?> getParameterClass(final MethodType t, final int l, final int i, final boolean varArgs) {
258        return varArgs && i >= l - 1 ? t.parameterType(l - 1).getComponentType() : t.parameterType(i);
259    }
260}
261