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; /** * A {@link FieldVisitor} that generates a corresponding 'field_info' structure, as defined in the * Java Virtual Machine Specification (JVMS). * * @see <a href="https://docs.oracle.com/javase/specs/jvms/se9/html/jvms-4.html#jvms-4.5">JVMS * 4.5</a> * @author Eric Bruneton */ final class FieldWriter extends FieldVisitor { /** Where the constants used in this FieldWriter must be stored. */ private final SymbolTable symbolTable; // Note: fields are ordered as in the field_info structure, and those related to attributes are // ordered as in Section 4.7 of the JVMS. /** * The access_flags field of the field_info JVMS structure. This field can contain ASM specific * access flags, such as {@link Opcodes#ACC_DEPRECATED}, which are removed when generating the * ClassFile structure. */ private final int accessFlags; /** The name_index field of the field_info JVMS structure. */ private final int nameIndex; /** The descriptor_index field of the field_info JVMS structure. */ private final int descriptorIndex; /** * The signature_index field of the Signature attribute of this field_info, or 0 if there is no * Signature attribute. */ private int signatureIndex; /** * The constantvalue_index field of the ConstantValue attribute of this field_info, or 0 if there * is no ConstantValue attribute. */ private int constantValueIndex; /** * The last runtime visible annotation of this field. The previous ones can be accessed with the * {@link AnnotationWriter#previousAnnotation} field. May be {@literal null}. */ private AnnotationWriter lastRuntimeVisibleAnnotation; /** * The last runtime invisible annotation of this field. The previous ones can be accessed with the * {@link AnnotationWriter#previousAnnotation} field. May be {@literal null}. */ private AnnotationWriter lastRuntimeInvisibleAnnotation; /** * The last runtime visible type annotation of this field. The previous ones can be accessed with * the {@link AnnotationWriter#previousAnnotation} field. May be {@literal null}. */ private AnnotationWriter lastRuntimeVisibleTypeAnnotation; /** * The last runtime invisible type annotation of this field. The previous ones can be accessed * with the {@link AnnotationWriter#previousAnnotation} field. May be {@literal null}. */ private AnnotationWriter lastRuntimeInvisibleTypeAnnotation; /** * The first non standard attribute of this field. The next ones can be accessed with the {@link * Attribute#nextAttribute} field. May be {@literal null}. * * <p><b>WARNING</b>: this list stores the attributes in the <i>reverse</i> order of their visit. * firstAttribute is actually the last attribute visited in {@link #visitAttribute}. The {@link * #putFieldInfo} method writes the attributes in the order defined by this list, i.e. in the * reverse order specified by the user. */ private Attribute firstAttribute; // ----------------------------------------------------------------------------------------------- // Constructor // ----------------------------------------------------------------------------------------------- /** * Constructs a new {@link FieldWriter}. * * @param symbolTable where the constants used in this FieldWriter must be stored. * @param access the field's access flags (see {@link Opcodes}). * @param name the field's name. * @param descriptor the field's descriptor (see {@link Type}). * @param signature the field's signature. May be {@literal null}. * @param constantValue the field's constant value. May be {@literal null}. */ FieldWriter(final SymbolTable symbolTable, final int access, final String name, final String descriptor, final String signature, final Object constantValue) { super(/* latest api = */ Opcodes.ASM7); this.symbolTable = symbolTable; this.accessFlags = access; this.nameIndex = symbolTable.addConstantUtf8(name); this.descriptorIndex = symbolTable.addConstantUtf8(descriptor); if (signature != null) { this.signatureIndex = symbolTable.addConstantUtf8(signature); } if (constantValue != null) { this.constantValueIndex = symbolTable.addConstant(constantValue).index; } } // ----------------------------------------------------------------------------------------------- // Implementation of the FieldVisitor abstract class // ----------------------------------------------------------------------------------------------- @Override public AnnotationVisitor visitAnnotation(final String descriptor, final boolean visible) { if (visible) { return lastRuntimeVisibleAnnotation = AnnotationWriter.create(symbolTable, descriptor, lastRuntimeVisibleAnnotation); } else { return lastRuntimeInvisibleAnnotation = AnnotationWriter.create(symbolTable, descriptor, lastRuntimeInvisibleAnnotation); } } @Override public AnnotationVisitor visitTypeAnnotation(final int typeRef, final TypePath typePath, final String descriptor, final boolean visible) { if (visible) { return lastRuntimeVisibleTypeAnnotation = AnnotationWriter.create(symbolTable, typeRef, typePath, descriptor, lastRuntimeVisibleTypeAnnotation); } else { return lastRuntimeInvisibleTypeAnnotation = AnnotationWriter.create(symbolTable, typeRef, typePath, descriptor, lastRuntimeInvisibleTypeAnnotation); } } @Override public void visitAttribute(final Attribute attribute) { // Store the attributes in the <i>reverse</i> order of their visit by this method. attribute.nextAttribute = firstAttribute; firstAttribute = attribute; } @Override public void visitEnd() { // Nothing to do. } // ----------------------------------------------------------------------------------------------- // Utility methods // ----------------------------------------------------------------------------------------------- /** * Returns the size of the field_info JVMS structure generated by this FieldWriter. Also adds the * names of the attributes of this field in the constant pool. * * @return the size in bytes of the field_info JVMS structure. */ int computeFieldInfoSize() { // The access_flags, name_index, descriptor_index and attributes_count fields use 8 bytes. int size = 8; // For ease of reference, we use here the same attribute order as in Section 4.7 of the JVMS. if (constantValueIndex != 0) { // ConstantValue attributes always use 8 bytes. symbolTable.addConstantUtf8(Constants.CONSTANT_VALUE); size += 8; } size += Attribute.computeAttributesSize(symbolTable, accessFlags, signatureIndex); size += AnnotationWriter.computeAnnotationsSize(lastRuntimeVisibleAnnotation, lastRuntimeInvisibleAnnotation, lastRuntimeVisibleTypeAnnotation, lastRuntimeInvisibleTypeAnnotation); if (firstAttribute != null) { size += firstAttribute.computeAttributesSize(symbolTable); } return size; } /** * Puts the content of the field_info JVMS structure generated by this FieldWriter into the given * ByteVector. * * @param output where the field_info structure must be put. */ void putFieldInfo(final ByteVector output) { boolean useSyntheticAttribute = symbolTable.getMajorVersion() < Opcodes.V1_5; // Put the access_flags, name_index and descriptor_index fields. int mask = useSyntheticAttribute ? Opcodes.ACC_SYNTHETIC : 0; output.putShort(accessFlags & ~mask).putShort(nameIndex).putShort(descriptorIndex); // Compute and put the attributes_count field. // For ease of reference, we use here the same attribute order as in Section 4.7 of the JVMS. int attributesCount = 0; if (constantValueIndex != 0) { ++attributesCount; } if ((accessFlags & Opcodes.ACC_SYNTHETIC) != 0 && useSyntheticAttribute) { ++attributesCount; } if (signatureIndex != 0) { ++attributesCount; } if ((accessFlags & Opcodes.ACC_DEPRECATED) != 0) { ++attributesCount; } if (lastRuntimeVisibleAnnotation != null) { ++attributesCount; } if (lastRuntimeInvisibleAnnotation != null) { ++attributesCount; } if (lastRuntimeVisibleTypeAnnotation != null) { ++attributesCount; } if (lastRuntimeInvisibleTypeAnnotation != null) { ++attributesCount; } if (firstAttribute != null) { attributesCount += firstAttribute.getAttributeCount(); } output.putShort(attributesCount); // Put the field_info attributes. // For ease of reference, we use here the same attribute order as in Section 4.7 of the JVMS. if (constantValueIndex != 0) { output.putShort(symbolTable.addConstantUtf8(Constants.CONSTANT_VALUE)).putInt(2) .putShort(constantValueIndex); } Attribute.putAttributes(symbolTable, accessFlags, signatureIndex, output); AnnotationWriter.putAnnotations(symbolTable, lastRuntimeVisibleAnnotation, lastRuntimeInvisibleAnnotation, lastRuntimeVisibleTypeAnnotation, lastRuntimeInvisibleTypeAnnotation, output); if (firstAttribute != null) { firstAttribute.putAttributes(symbolTable, output); } } /** * Collects the attributes of this field into the given set of attribute prototypes. * * @param attributePrototypes a set of attribute prototypes. */ final void collectAttributePrototypes(final Attribute.Set attributePrototypes) { attributePrototypes.addAttributes(firstAttribute); } }