Java tutorial
// ASM: a very small and fast Java bytecode manipulation framework // Copyright (c) 2000-2011 INRIA, France Telecom // All rights reserved. // // Redistribution and use in source and binary forms, with or without // modification, are permitted provided that the following conditions // are met: // 1. Redistributions of source code must retain the above copyright // notice, this list of conditions and the following disclaimer. // 2. Redistributions in binary form must reproduce the above copyright // notice, this list of conditions and the following disclaimer in the // documentation and/or other materials provided with the distribution. // 3. Neither the name of the copyright holders nor the names of its // contributors may be used to endorse or promote products derived from // this software without specific prior written permission. // // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" // AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE // ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE // LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR // CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF // SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS // INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN // CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) // ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF // THE POSSIBILITY OF SUCH DAMAGE. package org.objectweb.asm; /** * The path to a type argument, wildcard bound, array element type, or static inner type within an * enclosing type. * * @author Eric Bruneton */ public final class TypePath { /** A type path step that steps into the element type of an array type. See {@link #getStep}. */ public static final int ARRAY_ELEMENT = 0; /** A type path step that steps into the nested type of a class type. See {@link #getStep}. */ public static final int INNER_TYPE = 1; /** A type path step that steps into the bound of a wildcard type. See {@link #getStep}. */ public static final int WILDCARD_BOUND = 2; /** A type path step that steps into a type argument of a generic type. See {@link #getStep}. */ public static final int TYPE_ARGUMENT = 3; /** * The byte array where the 'type_path' structure - as defined in the Java Virtual Machine * Specification (JVMS) - corresponding to this TypePath is stored. The first byte of the * structure in this array is given by {@link #typePathOffset}. * * @see <a * href="https://docs.oracle.com/javase/specs/jvms/se9/html/jvms-4.html#jvms-4.7.20.2">JVMS * 4.7.20.2</a> */ private final byte[] typePathContainer; /** The offset of the first byte of the type_path JVMS structure in {@link #typePathContainer}. */ private final int typePathOffset; /** * Constructs a new TypePath. * * @param typePathContainer a byte array containing a type_path JVMS structure. * @param typePathOffset the offset of the first byte of the type_path structure in * typePathContainer. */ TypePath(final byte[] typePathContainer, final int typePathOffset) { this.typePathContainer = typePathContainer; this.typePathOffset = typePathOffset; } /** * Returns the length of this path, i.e. its number of steps. * * @return the length of this path. */ public int getLength() { // path_length is stored in the first byte of a type_path. return typePathContainer[typePathOffset]; } /** * Returns the value of the given step of this path. * * @param index an index between 0 and {@link #getLength()}, exclusive. * @return one of {@link #ARRAY_ELEMENT}, {@link #INNER_TYPE}, {@link #WILDCARD_BOUND}, or {@link * #TYPE_ARGUMENT}. */ public int getStep(final int index) { // Returns the type_path_kind of the path element of the given index. return typePathContainer[typePathOffset + 2 * index + 1]; } /** * Returns the index of the type argument that the given step is stepping into. This method should * only be used for steps whose value is {@link #TYPE_ARGUMENT}. * * @param index an index between 0 and {@link #getLength()}, exclusive. * @return the index of the type argument that the given step is stepping into. */ public int getStepArgument(final int index) { // Returns the type_argument_index of the path element of the given index. return typePathContainer[typePathOffset + 2 * index + 2]; } /** * Converts a type path in string form, in the format used by {@link #toString()}, into a TypePath * object. * * @param typePath a type path in string form, in the format used by {@link #toString()}. May be * {@literal null} or empty. * @return the corresponding TypePath object, or {@literal null} if the path is empty. */ public static TypePath fromString(final String typePath) { if (typePath == null || typePath.length() == 0) { return null; } int typePathLength = typePath.length(); ByteVector output = new ByteVector(typePathLength); output.putByte(0); int typePathIndex = 0; while (typePathIndex < typePathLength) { char c = typePath.charAt(typePathIndex++); if (c == '[') { output.put11(ARRAY_ELEMENT, 0); } else if (c == '.') { output.put11(INNER_TYPE, 0); } else if (c == '*') { output.put11(WILDCARD_BOUND, 0); } else if (c >= '0' && c <= '9') { int typeArg = c - '0'; while (typePathIndex < typePathLength) { c = typePath.charAt(typePathIndex++); if (c >= '0' && c <= '9') { typeArg = typeArg * 10 + c - '0'; } else if (c == ';') { break; } else { throw new IllegalArgumentException(); } } output.put11(TYPE_ARGUMENT, typeArg); } else { throw new IllegalArgumentException(); } } output.data[0] = (byte) (output.length / 2); return new TypePath(output.data, 0); } /** * Returns a string representation of this type path. {@link #ARRAY_ELEMENT} steps are represented * with '[', {@link #INNER_TYPE} steps with '.', {@link #WILDCARD_BOUND} steps with '*' and {@link * #TYPE_ARGUMENT} steps with their type argument index in decimal form followed by ';'. */ @Override public String toString() { int length = getLength(); StringBuilder result = new StringBuilder(length * 2); for (int i = 0; i < length; ++i) { switch (getStep(i)) { case ARRAY_ELEMENT: result.append('['); break; case INNER_TYPE: result.append('.'); break; case WILDCARD_BOUND: result.append('*'); break; case TYPE_ARGUMENT: result.append(getStepArgument(i)).append(';'); break; default: throw new AssertionError(); } } return result.toString(); } /** * Puts the type_path JVMS structure corresponding to the given TypePath into the given * ByteVector. * * @param typePath a TypePath instance, or {@literal null} for empty paths. * @param output where the type path must be put. */ static void put(final TypePath typePath, final ByteVector output) { if (typePath == null) { output.putByte(0); } else { int length = typePath.typePathContainer[typePath.typePathOffset] * 2 + 1; output.putByteArray(typePath.typePathContainer, typePath.typePathOffset, length); } } }