// 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
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// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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// THE POSSIBILITY OF SUCH DAMAGE.
package org.objectweb.asm;
/**
* A non standard class, field, method or code attribute, 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-4.7">JVMS
* 4.7</a>
* @see <a href= "https://docs.oracle.com/javase/specs/jvms/se9/html/jvms-4.html#jvms-4.7.3">JVMS
* 4.7.3</a>
* @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 <i>not</i>
* 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 <i>new</i> {@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#b}. 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#b}, 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 <i>new</i> {@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.
b,
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 <i>not</i> 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;
}
/**
* 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;
}
}
/** 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;
}
}
}