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// ASM: a very small and fast Java bytecode manipulation framework
// Copyright (c) 2000-2011 INRIA, France Telecom
// All rights reserved.
//
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// modification, are permitted provided that the following conditions
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// 2. Redistributions in binary form must reproduce the above copyright
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package org.objectweb.asm;
/**
* A non standard class, field, method or Code attribute, as defined in the Java Virtual Machine
* Specification (JVMS).
*
* @see JVMS
* 4.7
* @see JVMS
* 4.7.3
* @author Eric Bruneton
* @author Eugene Kuleshov
*/
public class Attribute {
/** The type of this attribute, also called its name in the JVMS. */
public final String type;
/**
* The raw content of this attribute, only used for unknown attributes (see {@link #isUnknown()}).
* The 6 header bytes of the attribute (attribute_name_index and attribute_length) are not
* included.
*/
private byte[] content;
/**
* The next attribute in this attribute list (Attribute instances can be linked via this field to
* store a list of class, field, method or Code attributes). May be {@literal null}.
*/
Attribute nextAttribute;
/**
* Constructs a new empty attribute.
*
* @param type the type of the attribute.
*/
protected Attribute(final String type) {
this.type = type;
}
/**
* Returns {@literal true} if this type of attribute is unknown. This means that the attribute
* content can't be parsed to extract constant pool references, labels, etc. Instead, the
* attribute content is read as an opaque byte array, and written back as is. This can lead to
* invalid attributes, if the content actually contains constant pool references, labels, or other
* symbolic references that need to be updated when there are changes to the constant pool, the
* method bytecode, etc. The default implementation of this method always returns {@literal true}.
*
* @return {@literal true} if this type of attribute is unknown.
*/
public boolean isUnknown() {
return true;
}
/**
* Returns {@literal true} if this type of attribute is a Code attribute.
*
* @return {@literal true} if this type of attribute is a Code attribute.
*/
public boolean isCodeAttribute() {
return false;
}
/**
* Returns the labels corresponding to this attribute.
*
* @return the labels corresponding to this attribute, or {@literal null} if this attribute is not
* a Code attribute that contains labels.
*/
protected Label[] getLabels() {
return new Label[0];
}
/**
* Reads a {@link #type} attribute. This method must return a new {@link Attribute} object,
* of type {@link #type}, corresponding to the 'length' bytes starting at 'offset', in the given
* ClassReader.
*
* @param classReader the class that contains the attribute to be read.
* @param offset index of the first byte of the attribute's content in {@link ClassReader}. The 6
* attribute header bytes (attribute_name_index and attribute_length) are not taken into
* account here.
* @param length the length of the attribute's content (excluding the 6 attribute header bytes).
* @param charBuffer the buffer to be used to call the ClassReader methods requiring a
* 'charBuffer' parameter.
* @param codeAttributeOffset index of the first byte of content of the enclosing Code attribute
* in {@link ClassReader}, or -1 if the attribute to be read is not a Code attribute. The 6
* attribute header bytes (attribute_name_index and attribute_length) are not taken into
* account here.
* @param labels the labels of the method's code, or {@literal null} if the attribute to be read
* is not a Code attribute.
* @return a new {@link Attribute} object corresponding to the specified bytes.
*/
protected Attribute read(
final ClassReader classReader,
final int offset,
final int length,
final char[] charBuffer,
final int codeAttributeOffset,
final Label[] labels) {
Attribute attribute = new Attribute(type);
attribute.content = new byte[length];
System.arraycopy(classReader.classFileBuffer, offset, attribute.content, 0, length);
return attribute;
}
/**
* Returns the byte array form of the content of this attribute. The 6 header bytes
* (attribute_name_index and attribute_length) must not be added in the returned
* ByteVector.
*
* @param classWriter the class to which this attribute must be added. This parameter can be used
* to add the items that corresponds to this attribute to the constant pool of this class.
* @param code the bytecode of the method corresponding to this Code attribute, or {@literal null}
* if this attribute is not a Code attribute. Corresponds to the 'code' field of the Code
* attribute.
* @param codeLength the length of the bytecode of the method corresponding to this code
* attribute, or 0 if this attribute is not a Code attribute. Corresponds to the 'code_length'
* field of the Code attribute.
* @param maxStack the maximum stack size of the method corresponding to this Code attribute, or
* -1 if this attribute is not a Code attribute.
* @param maxLocals the maximum number of local variables of the method corresponding to this code
* attribute, or -1 if this attribute is not a Code attribute.
* @return the byte array form of this attribute.
*/
protected ByteVector write(
final ClassWriter classWriter,
final byte[] code,
final int codeLength,
final int maxStack,
final int maxLocals) {
return new ByteVector(content);
}
/**
* Returns the number of attributes of the attribute list that begins with this attribute.
*
* @return the number of attributes of the attribute list that begins with this attribute.
*/
final int getAttributeCount() {
int count = 0;
Attribute attribute = this;
while (attribute != null) {
count += 1;
attribute = attribute.nextAttribute;
}
return count;
}
/**
* Returns the total size in bytes of all the attributes in the attribute list that begins with
* this attribute. This size includes the 6 header bytes (attribute_name_index and
* attribute_length) per attribute. Also adds the attribute type names to the constant pool.
*
* @param symbolTable where the constants used in the attributes must be stored.
* @return the size of all the attributes in this attribute list. This size includes the size of
* the attribute headers.
*/
final int computeAttributesSize(final SymbolTable symbolTable) {
final byte[] code = null;
final int codeLength = 0;
final int maxStack = -1;
final int maxLocals = -1;
return computeAttributesSize(symbolTable, code, codeLength, maxStack, maxLocals);
}
/**
* Returns the total size in bytes of all the attributes in the attribute list that begins with
* this attribute. This size includes the 6 header bytes (attribute_name_index and
* attribute_length) per attribute. Also adds the attribute type names to the constant pool.
*
* @param symbolTable where the constants used in the attributes must be stored.
* @param code the bytecode of the method corresponding to these Code attributes, or {@literal
* null} if they are not Code attributes. Corresponds to the 'code' field of the Code
* attribute.
* @param codeLength the length of the bytecode of the method corresponding to these code
* attributes, or 0 if they are not Code attributes. Corresponds to the 'code_length' field of
* the Code attribute.
* @param maxStack the maximum stack size of the method corresponding to these Code attributes, or
* -1 if they are not Code attributes.
* @param maxLocals the maximum number of local variables of the method corresponding to these
* Code attributes, or -1 if they are not Code attribute.
* @return the size of all the attributes in this attribute list. This size includes the size of
* the attribute headers.
*/
final int computeAttributesSize(
final SymbolTable symbolTable,
final byte[] code,
final int codeLength,
final int maxStack,
final int maxLocals) {
final ClassWriter classWriter = symbolTable.classWriter;
int size = 0;
Attribute attribute = this;
while (attribute != null) {
symbolTable.addConstantUtf8(attribute.type);
size += 6 + attribute.write(classWriter, code, codeLength, maxStack, maxLocals).length;
attribute = attribute.nextAttribute;
}
return size;
}
/**
* Returns the total size in bytes of all the attributes that correspond to the given field,
* method or class access flags and signature. This size includes the 6 header bytes
* (attribute_name_index and attribute_length) per attribute. Also adds the attribute type names
* to the constant pool.
*
* @param symbolTable where the constants used in the attributes must be stored.
* @param accessFlags some field, method or class access flags.
* @param signatureIndex the constant pool index of a field, method of class signature.
* @return the size of all the attributes in bytes. This size includes the size of the attribute
* headers.
*/
static int computeAttributesSize(
final SymbolTable symbolTable, final int accessFlags, final int signatureIndex) {
int size = 0;
// Before Java 1.5, synthetic fields are represented with a Synthetic attribute.
if ((accessFlags & Opcodes.ACC_SYNTHETIC) != 0
&& symbolTable.getMajorVersion() < Opcodes.V1_5) {
// Synthetic attributes always use 6 bytes.
symbolTable.addConstantUtf8(Constants.SYNTHETIC);
size += 6;
}
if (signatureIndex != 0) {
// Signature attributes always use 8 bytes.
symbolTable.addConstantUtf8(Constants.SIGNATURE);
size += 8;
}
// ACC_DEPRECATED is ASM specific, the ClassFile format uses a Deprecated attribute instead.
if ((accessFlags & Opcodes.ACC_DEPRECATED) != 0) {
// Deprecated attributes always use 6 bytes.
symbolTable.addConstantUtf8(Constants.DEPRECATED);
size += 6;
}
return size;
}
/**
* Puts all the attributes of the attribute list that begins with this attribute, in the given
* byte vector. This includes the 6 header bytes (attribute_name_index and attribute_length) per
* attribute.
*
* @param symbolTable where the constants used in the attributes must be stored.
* @param output where the attributes must be written.
*/
final void putAttributes(final SymbolTable symbolTable, final ByteVector output) {
final byte[] code = null;
final int codeLength = 0;
final int maxStack = -1;
final int maxLocals = -1;
putAttributes(symbolTable, code, codeLength, maxStack, maxLocals, output);
}
/**
* Puts all the attributes of the attribute list that begins with this attribute, in the given
* byte vector. This includes the 6 header bytes (attribute_name_index and attribute_length) per
* attribute.
*
* @param symbolTable where the constants used in the attributes must be stored.
* @param code the bytecode of the method corresponding to these Code attributes, or {@literal
* null} if they are not Code attributes. Corresponds to the 'code' field of the Code
* attribute.
* @param codeLength the length of the bytecode of the method corresponding to these code
* attributes, or 0 if they are not Code attributes. Corresponds to the 'code_length' field of
* the Code attribute.
* @param maxStack the maximum stack size of the method corresponding to these Code attributes, or
* -1 if they are not Code attributes.
* @param maxLocals the maximum number of local variables of the method corresponding to these
* Code attributes, or -1 if they are not Code attribute.
* @param output where the attributes must be written.
*/
final void putAttributes(
final SymbolTable symbolTable,
final byte[] code,
final int codeLength,
final int maxStack,
final int maxLocals,
final ByteVector output) {
final ClassWriter classWriter = symbolTable.classWriter;
Attribute attribute = this;
while (attribute != null) {
ByteVector attributeContent =
attribute.write(classWriter, code, codeLength, maxStack, maxLocals);
// Put attribute_name_index and attribute_length.
output.putShort(symbolTable.addConstantUtf8(attribute.type)).putInt(attributeContent.length);
output.putByteArray(attributeContent.data, 0, attributeContent.length);
attribute = attribute.nextAttribute;
}
}
/**
* Puts all the attributes that correspond to the given field, method or class access flags and
* signature, in the given byte vector. This includes the 6 header bytes (attribute_name_index and
* attribute_length) per attribute.
*
* @param symbolTable where the constants used in the attributes must be stored.
* @param accessFlags some field, method or class access flags.
* @param signatureIndex the constant pool index of a field, method of class signature.
* @param output where the attributes must be written.
*/
static void putAttributes(
final SymbolTable symbolTable,
final int accessFlags,
final int signatureIndex,
final ByteVector output) {
// Before Java 1.5, synthetic fields are represented with a Synthetic attribute.
if ((accessFlags & Opcodes.ACC_SYNTHETIC) != 0
&& symbolTable.getMajorVersion() < Opcodes.V1_5) {
output.putShort(symbolTable.addConstantUtf8(Constants.SYNTHETIC)).putInt(0);
}
if (signatureIndex != 0) {
output
.putShort(symbolTable.addConstantUtf8(Constants.SIGNATURE))
.putInt(2)
.putShort(signatureIndex);
}
if ((accessFlags & Opcodes.ACC_DEPRECATED) != 0) {
output.putShort(symbolTable.addConstantUtf8(Constants.DEPRECATED)).putInt(0);
}
}
/** A set of attribute prototypes (attributes with the same type are considered equal). */
static final class Set {
private static final int SIZE_INCREMENT = 6;
private int size;
private Attribute[] data = new Attribute[SIZE_INCREMENT];
void addAttributes(final Attribute attributeList) {
Attribute attribute = attributeList;
while (attribute != null) {
if (!contains(attribute)) {
add(attribute);
}
attribute = attribute.nextAttribute;
}
}
Attribute[] toArray() {
Attribute[] result = new Attribute[size];
System.arraycopy(data, 0, result, 0, size);
return result;
}
private boolean contains(final Attribute attribute) {
for (int i = 0; i < size; ++i) {
if (data[i].type.equals(attribute.type)) {
return true;
}
}
return false;
}
private void add(final Attribute attribute) {
if (size >= data.length) {
Attribute[] newData = new Attribute[data.length + SIZE_INCREMENT];
System.arraycopy(data, 0, newData, 0, size);
data = newData;
}
data[size++] = attribute;
}
}
}
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