1 /*
   2  * Copyright (c) 2018, 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
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 package java.lang.constant;
  26 
  27 import java.lang.invoke.TypeDescriptor;
  28 import java.util.stream.Stream;
  29 
  30 import sun.invoke.util.Wrapper;
  31 
  32 import static java.lang.constant.ConstantUtils.binaryToInternal;
  33 import static java.lang.constant.ConstantUtils.dropLastChar;
  34 import static java.lang.constant.ConstantUtils.internalToBinary;
  35 import static java.lang.constant.ConstantUtils.validateMemberName;
  36 import static java.util.Objects.requireNonNull;
  37 import static java.util.stream.Collectors.joining;
  38 
  39 /**
  40  * A <a href="package-summary.html#nominal">nominal descriptor</a> for a
  41  * {@link Class} constant.
  42  *
  43  * <p>For common system types, including all the primitive types, there are
  44  * predefined {@linkplain ClassDesc} constants in {@link ConstantDescs}.
  45  * (The {@code java.lang.constant} APIs consider {@code void} to be a primitive type.)
  46  * To create a {@linkplain ClassDesc} for a class or interface type, use {@link #of} or
  47  * {@link #ofDescriptor(String)}; to create a {@linkplain ClassDesc} for an array
  48  * type, use {@link #ofDescriptor(String)}, or first obtain a
  49  * {@linkplain ClassDesc} for the component type and then call the {@link #arrayType()}
  50  * or {@link #arrayType(int)} methods.
  51  *
  52  * @apiNote In the future, if the Java language permits, {@linkplain ClassDesc}
  53  * may become a {@code sealed} interface, which would prohibit subclassing except
  54  * by explicitly permitted types.  Non-platform classes should not implement
  55  * {@linkplain ClassDesc} directly.
  56  *
  57  * @see ConstantDescs
  58  *
  59  * @since 12
  60  */
  61 public interface ClassDesc
  62         extends ConstantDesc,
  63                 TypeDescriptor.OfField<ClassDesc> {
  64 
  65     /**
  66      * Returns a {@linkplain ClassDesc} for a class or interface type,
  67      * given the name of the class or interface, such as {@code "java.lang.String"}.
  68      * (To create a descriptor for an array type, either use {@link #ofDescriptor(String)}
  69      * or {@link #arrayType()}; to create a descriptor for a primitive type, use
  70      * {@link #ofDescriptor(String)} or use the predefined constants in
  71      * {@link ConstantDescs}).
  72      *
  73      * @param name the fully qualified (dot-separated) binary class name
  74      * @return a {@linkplain ClassDesc} describing the desired class
  75      * @throws NullPointerException if any argument is {@code null}
  76      * @throws IllegalArgumentException if the name string is not in the
  77      * correct format
  78      */
  79     static ClassDesc of(String name) {
  80         ConstantUtils.validateBinaryClassName(requireNonNull(name));
  81         return ClassDesc.ofDescriptor("L" + binaryToInternal(name) + ";");
  82     }
  83 
  84     /**
  85      * Returns a {@linkplain ClassDesc} for a class or interface type,
  86      * given a package name and the unqualified (simple) name for the
  87      * class or interface.
  88      *
  89      * @param packageName the package name (dot-separated); if the package
  90      *                    name is the empty string, the class is considered to
  91      *                    be in the unnamed package
  92      * @param className the unqualified (simple) class name
  93      * @return a {@linkplain ClassDesc} describing the desired class
  94      * @throws NullPointerException if any argument is {@code null}
  95      * @throws IllegalArgumentException if the package name or class name are
  96      * not in the correct format
  97      */
  98     static ClassDesc of(String packageName, String className) {
  99         ConstantUtils.validateBinaryClassName(requireNonNull(packageName));
 100         validateMemberName(requireNonNull(className));
 101         return ofDescriptor(String.format("L%s%s%s;",
 102                                           binaryToInternal(packageName),
 103                                           (packageName.length() > 0 ? "/" : ""),
 104                                           className));
 105     }
 106 
 107     /**
 108      * Returns a {@linkplain ClassDesc} given a descriptor string for a class,
 109      * interface, array, or primitive type.
 110      *
 111      * @apiNote
 112      *
 113      * A field type descriptor string for a non-array type is either
 114      * a one-letter code corresponding to a primitive type
 115      * ({@code "J", "I", "C", "S", "B", "D", "F", "Z", "V"}), or the letter {@code "L"}, followed
 116      * by the fully qualified binary name of a class, followed by {@code ";"}.
 117      * A field type descriptor for an array type is the character {@code "["}
 118      * followed by the field descriptor for the component type.  Examples of
 119      * valid type descriptor strings include {@code "Ljava/lang/String;"}, {@code "I"},
 120      * {@code "[I"}, {@code "V"}, {@code "[Ljava/lang/String;"}, etc.
 121      * See JVMS 4.3.2 ("Field Descriptors") for more detail.
 122      *
 123      * @param descriptor a field descriptor string
 124      * @return a {@linkplain ClassDesc} describing the desired class
 125      * @throws NullPointerException if any argument is {@code null}
 126      * @throws IllegalArgumentException if the name string is not in the
 127      * correct format
 128      * @jvms 4.3.2 Field Descriptors
 129      */
 130     static ClassDesc ofDescriptor(String descriptor) {
 131         requireNonNull(descriptor);
 132         return (descriptor.length() == 1)
 133                ? new PrimitiveClassDescImpl(descriptor)
 134                : new ReferenceClassDescImpl(descriptor);
 135     }
 136 
 137     /**
 138      * Returns a {@linkplain ClassDesc} for an array type whose component type
 139      * is described by this {@linkplain ClassDesc}.
 140      *
 141      * @return a {@linkplain ClassDesc} describing the array type
 142      */
 143     default ClassDesc arrayType() {
 144         return arrayType(1);
 145     }
 146 
 147     /**
 148      * Returns a {@linkplain ClassDesc} for an array type of the specified rank,
 149      * whose component type is described by this {@linkplain ClassDesc}.
 150      *
 151      * @param rank the rank of the array
 152      * @return a {@linkplain ClassDesc} describing the array type
 153      * @throws IllegalArgumentException if the rank is zero or negative
 154      */
 155     default ClassDesc arrayType(int rank) {
 156         if (rank <= 0)
 157             throw new IllegalArgumentException("rank: " + rank);
 158         return ClassDesc.ofDescriptor("[".repeat(rank) + descriptorString());
 159     }
 160 
 161     /**
 162      * Returns a {@linkplain ClassDesc} for a nested class of the class or
 163      * interface type described by this {@linkplain ClassDesc}.
 164      *
 165      * @apiNote
 166      *
 167      * Example: If descriptor {@code d} describes the class {@code java.util.Map}, a
 168      * descriptor for the class {@code java.util.Map.Entry} could be obtained
 169      * by {@code d.nested("Entry")}.
 170      *
 171      * @param nestedName the unqualified name of the nested class
 172      * @return a {@linkplain ClassDesc} describing the nested class
 173      * @throws NullPointerException if any argument is {@code null}
 174      * @throws IllegalStateException if this {@linkplain ClassDesc} does not
 175      * describe a class or interface type
 176      * @throws IllegalArgumentException if the nested class name is invalid
 177      */
 178     default ClassDesc nested(String nestedName) {
 179         validateMemberName(nestedName);
 180         if (!isClassOrInterface())
 181             throw new IllegalStateException("Outer class is not a class or interface type");
 182         return ClassDesc.ofDescriptor(String.format("%s$%s;", dropLastChar(descriptorString()), nestedName));
 183     }
 184 
 185     /**
 186      * Returns a {@linkplain ClassDesc} for a nested class of the class or
 187      * interface type described by this {@linkplain ClassDesc}.
 188      *
 189      * @param firstNestedName the unqualified name of the first level of nested class
 190      * @param moreNestedNames the unqualified name(s) of the remaining levels of
 191      *                       nested class
 192      * @return a {@linkplain ClassDesc} describing the nested class
 193      * @throws NullPointerException if any argument is {@code null}
 194      * @throws IllegalStateException if this {@linkplain ClassDesc} does not
 195      * describe a class or interface type
 196      * @throws IllegalArgumentException if the nested class name is invalid
 197      */
 198     default ClassDesc nested(String firstNestedName, String... moreNestedNames) {
 199         if (!isClassOrInterface())
 200             throw new IllegalStateException("Outer class is not a class or interface type");
 201         return moreNestedNames.length == 0
 202                ? nested(firstNestedName)
 203                : nested(firstNestedName + Stream.of(moreNestedNames).collect(joining("$", "$", "")));
 204     }
 205 
 206     /**
 207      * Returns whether this {@linkplain ClassDesc} describes an array type.
 208      *
 209      * @return whether this {@linkplain ClassDesc} describes an array type
 210      */
 211     default boolean isArray() {
 212         return descriptorString().startsWith("[");
 213     }
 214 
 215     /**
 216      * Returns whether this {@linkplain ClassDesc} describes a primitive type.
 217      *
 218      * @return whether this {@linkplain ClassDesc} describes a primitive type
 219      */
 220     default boolean isPrimitive() {
 221         return descriptorString().length() == 1;
 222     }
 223 
 224     /**
 225      * Returns whether this {@linkplain ClassDesc} describes a class or interface type.
 226      *
 227      * @return whether this {@linkplain ClassDesc} describes a class or interface type
 228      */
 229     default boolean isClassOrInterface() {
 230         return descriptorString().startsWith("L");
 231     }
 232 
 233     /**
 234      * Returns the component type of this {@linkplain ClassDesc}, if it describes
 235      * an array type, or {@code null} otherwise.
 236      *
 237      * @return a {@linkplain ClassDesc} describing the component type, or {@code null}
 238      * if this descriptor does not describe an array type
 239      */
 240     default ClassDesc componentType() {
 241         return isArray() ? ClassDesc.ofDescriptor(descriptorString().substring(1)) : null;
 242     }
 243 
 244     /**
 245      * Returns the package name of this {@linkplain ClassDesc}, if it describes
 246      * a class or interface type.
 247      *
 248      * @return the package name, or the empty string if the class is in the
 249      * default package, or this {@linkplain ClassDesc} does not describe a class or interface type
 250      */
 251     default String packageName() {
 252         if (!isClassOrInterface())
 253             return "";
 254         String className = internalToBinary(ConstantUtils.dropFirstAndLastChar(descriptorString()));
 255         int index = className.lastIndexOf('.');
 256         return (index == -1) ? "" : className.substring(0, index);
 257     }
 258 
 259     /**
 260      * Returns a human-readable name for the type described by this descriptor.
 261      *
 262      * @implSpec
 263      * <p>The default implementation returns the simple name
 264      * (e.g., {@code int}) for primitive types, the unqualified class name
 265      * for class or interface types, or the display name of the component type
 266      * suffixed with the appropriate number of {@code []} pairs for array types.
 267      *
 268      * @return the human-readable name
 269      */
 270     default String displayName() {
 271         if (isPrimitive())
 272             return Wrapper.forBasicType(descriptorString().charAt(0)).primitiveSimpleName();
 273         else if (isClassOrInterface()) {
 274             return descriptorString().substring(Math.max(1, descriptorString().lastIndexOf('/') + 1),
 275                                                 descriptorString().length() - 1);
 276         }
 277         else if (isArray()) {
 278             int depth = ConstantUtils.arrayDepth(descriptorString());
 279             ClassDesc c = this;
 280             for (int i=0; i<depth; i++)
 281                 c = c.componentType();
 282             return c.displayName() + "[]".repeat(depth);
 283         }
 284         else
 285             throw new IllegalStateException(descriptorString());
 286     }
 287 
 288     /**
 289      * Returns a field type descriptor string for this type
 290      *
 291      * @return the descriptor string
 292      * @jvms 4.3.2 Field Descriptors
 293      */
 294     String descriptorString();
 295 
 296     /**
 297      * Compare the specified object with this descriptor for equality.  Returns
 298      * {@code true} if and only if the specified object is also a
 299      * {@linkplain ClassDesc} and both describe the same type.
 300      *
 301      * @param o the other object
 302      * @return whether this descriptor is equal to the other object
 303      */
 304     boolean equals(Object o);
 305 }