com.tangosol.dev.assembler.Attribute Maven / Gradle / Ivy
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/*
* Copyright (c) 2000, 2020, Oracle and/or its affiliates.
*
* Licensed under the Universal Permissive License v 1.0 as shown at
* http://oss.oracle.com/licenses/upl.
*/
package com.tangosol.dev.assembler;
import java.io.IOException;
import java.io.DataInput;
import java.io.DataOutput;
import java.util.Arrays;
/**
* Represents a Java Virtual Machine Attribute structure as defined by the
* Java Virtual Machine (JVM) Specification.
*
*
* attribute_info
* {
* u2 attribute_name_index;
* u4 attribute_length;
* u1 info[attribute_length];
* }
*
* This method must be overridden or supplemented by sub-classes which
* do not maintain the attribute as binary.
*
* @param stream the stream implementing java.io.DataInput from which
* to read the assembled VM structure
* @param pool the constant pool for the class which contains any
* constants referenced by this VM structure
*/
protected void disassemble(DataInput stream, ConstantPool pool)
throws IOException
{
int cb = stream.readInt();
byte[] ab = new byte[cb];
stream.readFully(ab);
m_ab = ab;
}
/**
* The pre-assembly step collects the necessary entries for the constant
* pool. During this step, all constants used by this VM structure and
* any sub-structures are registered with (but not yet bound by position
* in) the constant pool.
*
* This method must be supplemented by sub-classes which reference any
* additional constants.
*
* @param pool the constant pool for the class which needs to be
* populated with the constants required to build this
* VM structure
*/
protected void preassemble(ConstantPool pool)
{
pool.registerConstant(m_utf);
}
/**
* The assembly process assembles and writes the structure to the passed
* output stream, resolving any dependencies using the passed constant
* pool.
*
* This method must be overridden by sub-classes which do not maintain
* the attribute as binary.
*
* @param stream the stream implementing java.io.DataOutput to which to
* write the assembled VM structure
* @param pool the constant pool for the class which by this point
* contains the entire set of constants required to build
* this VM structure
*/
protected void assemble(DataOutput stream, ConstantPool pool)
throws IOException
{
stream.writeShort(pool.findConstant(m_utf));
stream.writeInt(m_ab.length);
stream.write(m_ab);
}
/**
* Determine the identity of the VM structure (if applicable).
*
* @return the string identity of the VM structure
*/
public String getIdentity()
{
return m_utf.getValue();
}
/**
* Determine if the VM structure (or any contained VM structure) has been
* modified by comparing the binary portion of the attribute.
*
* This method must be overridden by sub-classes which do not maintain
* the attribute as binary.
*
* @return true if the VM structure has been modified
*/
public boolean isModified()
{
return m_ab != m_abOrig && !Arrays.equals(m_ab, m_abOrig);
}
/**
* Reset the modified state of the VM structure.
*
* This method must be overridden by sub-classes which do not maintain
* the attribute as binary.
*/
protected void resetModified()
{
m_abOrig = m_ab;
}
// ----- Comparable operations ------------------------------------------
/**
* Compares this Object with the specified Object for order. Returns a
* negative integer, zero, or a positive integer as this Object is less
* than, equal to, or greater than the given Object.
*
* @param obj the Object to be compared.
*
* @return a negative integer, zero, or a positive integer as this Object
* is less than, equal to, or greater than the given Object.
*
* @exception ClassCastException the specified Object's type prevents it
* from being compared to this Object.
*/
public int compareTo(Object obj)
{
Attribute that = (Attribute) obj;
return this.m_utf.compareTo(that.m_utf);
}
// ----- Object operations ----------------------------------------------
/**
* Produce a human-readable string describing the attribute.
*
* @return a string describing the attribute
*/
public String toString()
{
return m_utf.getValue();
}
/**
* Compare this object to another object for equality.
*
* This method must be overridden by sub-classes which do not maintain
* the attribute as binary.
*
* @param obj the other object to compare to this
*
* @return true if this object equals that object
*/
public boolean equals(Object obj)
{
try
{
Attribute that = (Attribute) obj;
return this == that
|| this.getClass() == that.getClass()
&& this.m_utf.equals(that.m_utf)
&& Arrays.equals(this.getBytes(), that.getBytes());
}
catch (NullPointerException e)
{
// obj is null
return false;
}
catch (ClassCastException e)
{
// obj is not of this class
return false;
}
}
// ----- accessors ------------------------------------------------------
/**
* Determine the context of the attribute.
*
* @return the JVM structure containing this attribute
*/
protected VMStructure getContext()
{
return m_context;
}
/**
* Determine the attribute's name, which is immutable.
*
* @return the attribute name
*/
public String getName()
{
return m_utf.getValue();
}
/**
* Get the attribute's name constant.
*
* @return the attribute name constant
*/
public UtfConstant getNameConstant()
{
return m_utf;
}
/**
* Get the binary portion of the attribute. If the binary is unavailable,
* for example, if a sub-class is unable to produce the binary without the
* constant pool, then null is returned. This typically would occur in an
* attribute that references constants, since the attribute would require
* the constant pool for building the binary.
*
* @return the binary portion of the attribute
*/
public byte[] getBytes()
{
return m_ab;
}
/**
* Set the binary portion of the attribute. Pass null to clear the binary
* portion.
*/
public void setBytes(byte[] ab)
{
m_ab = (ab == null ? NO_BYTES : ab);
}
// ----- data members ---------------------------------------------------
/**
* The name of this class.
*/
private static final String CLASS = "Attribute";
/**
* An empty attribute.
*/
private static final byte[] NO_BYTES = new byte[0];
/**
* The virtual machine context.
*/
private VMStructure m_context;
/**
* Attribute name.
*/
private UtfConstant m_utf;
/**
* Attribute contents.
*/
private byte[] m_ab;
/**
* Original attribute contents.
*/
private byte[] m_abOrig;
}