com.tangosol.dev.assembler.LineNumberTableAttribute Maven / Gradle / Ivy
/*
* 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;
import java.util.Enumeration;
import java.util.NoSuchElementException;
/**
* Represents a Java Virtual Machine byte-code "LineNumberTable" attribute
* which cross-references between byte-code pc and source file line number.
*
* @version 0.50, 05/15/98, assembler/dis-assembler
* @author Cameron Purdy
*/
public class LineNumberTableAttribute extends Attribute implements Constants
{
// ----- constructors ---------------------------------------------------
/**
* Construct a LineNumberTable attribute.
*
* @param context the JVM structure containing the attribute
*/
protected LineNumberTableAttribute(VMStructure context)
{
super(context, ATTR_LINENUMBERS);
}
// ----- VMStructure operations -----------------------------------------
/**
* The disassembly process reads the structure from the passed input
* stream and uses the constant pool to dereference any constant
* references.
*
* @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
{
stream.readInt();
int count = stream.readUnsignedShort();
if (count > 0)
{
// disassemble the line number information
Entry[] aln = new Entry[count];
for (int i = 0; i < count; ++i)
{
Entry ln = new Entry();
ln.disassemble(stream, pool);
aln[i] = ln;
}
// sort the line number information by offset (to assist in
// the op decompilation process)
Arrays.sort(aln);
// build a linked list
for (int i = 1; i < count; ++i)
{
aln[i-1].setNext(aln[i]);
}
m_first = aln[0];
m_last = aln[count-1];
m_count = count;
}
else
{
m_first = null;
m_last = null;
m_count = 0;
}
}
/**
* The assembly process assembles and writes the structure to the passed
* output stream, resolving any dependencies using the passed constant
* pool.
*
* @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(super.getNameConstant()));
stream.writeInt(2 + 4 * m_count);
stream.writeShort(m_count);
for (Entry ln = m_first; ln != null; ln = ln.getNext())
{
ln.assemble(stream, pool);
}
}
/**
* Determine if the attribute has been modified.
*
* @return true if the attribute has been modified
*/
public boolean isModified()
{
return m_fModified;
}
/**
* 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_fModified = false;
}
// ----- accessors ------------------------------------------------------
/**
* Discard any line number information.
*/
public void clear()
{
m_first = null;
m_last = null;
m_fModified = true;
}
/**
* Determine if there is no line number information.
*
* @return true if there is no line number information, false otherwise
*/
public boolean isEmpty()
{
return m_first == null;
}
/**
* Add the specified line number information.
*
* @param iLine the line number
* @param of the offset (pc) of the byte code
*/
protected void add(int iLine, int of)
{
add(new Entry(iLine, of));
}
/**
* A line change was detected on this op; add its line number info.
*
* @param op
*/
protected void add(Op op)
{
add(new Entry(op));
}
/**
* Add the specified line number information.
*/
protected void add(Entry ln)
{
if (m_first == null)
{
m_first = ln;
m_last = ln;
}
else
{
m_last.setNext(ln);
m_last = ln;
}
++m_count;
m_fModified = true;
}
/**
* Enumerate the line number information.
*
* @return an enumeration of Entry objects
*/
public Enumeration entries()
{
return new Enumeration()
{
public boolean hasMoreElements()
{
return cur != null;
}
public Object nextElement()
{
if (cur == null)
{
throw new NoSuchElementException();
}
Entry ln = cur;
cur = ln.getNext();
return ln;
}
private Entry cur = m_first;
};
}
// ----- data members ---------------------------------------------------
/**
* The name of this class.
*/
private static final String CLASS = "LineNumberTableAttribute";
/**
* Tracks modification to this object.
*/
private boolean m_fModified;
/**
* The first line number.
*/
private Entry m_first;
/**
* The last line number.
*/
private Entry m_last;
/**
* The count of line number objects.
*/
private int m_count;
// ----- inner classes --------------------------------------------------
/**
* Represents a piece of debugging information that cross-references a
* Java Virtual Machine byte-code offset with a line of source code.
*
* @version 0.50, 06/22/98, assembler/dis-assembler
* @author Cameron Purdy
*/
public static class Entry extends VMStructure implements Constants, Comparable
{
// ----- constructors ----------------------------------------------
/**
* Construct a Entry object.
*/
protected Entry()
{
}
/**
* Construct a Entry object. Used during disassembly.
*
* @param iLine
* @param of
*/
protected Entry(int iLine, int of)
{
m_iLine = iLine;
m_of = of;
}
/**
* Construct a Entry object. Used during assembly.
*
* @param op
*/
protected Entry(Op op)
{
m_iLine = op.getLine();
m_op = op;
}
// ----- VMStructure operations ------------------------------------
/**
* The disassembly process reads the structure from the passed input
* stream and uses the constant pool to dereference any constant
* references.
*
* @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
{
m_of = stream.readUnsignedShort();
m_iLine = stream.readUnsignedShort();
}
/**
* 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.
*
* @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)
{
}
/**
* The assembly process assembles and writes the structure to the passed
* output stream, resolving any dependencies using the passed constant
* pool.
*
* @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(getOffset());
stream.writeShort(getLine());
}
// ----- 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)
{
// order by PC
Entry that = (Entry) obj;
int nThis = this.m_of;
int nThat = that.m_of;
return (nThis < nThat ? -1 : (nThis > nThat ? +1 : 0));
}
// ----- accessors -------------------------------------------------
/**
* Get the op.
*
* @return the op which starts this line number
*/
public Op getOp()
{
return m_op;
}
/**
* Set the op which the line number starts on. This is used during
* the disassembly process when the op is constructed that corresponds
* to the offset that this line number contains.
*
* @param op the first op for this line number
*/
protected void setOp(Op op)
{
m_op = op;
}
/**
* Get the line number.
*
* @return the line number
*/
public int getLine()
{
return m_iLine;
}
/**
* Get the byte code offset ("pc") of the line number
*
* @return the byte code offset
*/
protected int getOffset()
{
return (m_op == null ? m_of : m_op.getOffset());
}
/**
* Get the next Entry object in the linked list.
*
* @return the next Entry object
*/
protected Entry getNext()
{
return m_next;
}
/**
* Set the next Entry object in the linked list.
*
* @param next the next Entry object
*/
protected void setNext(Entry next)
{
m_next = next;
}
// ----- data members ----------------------------------------------
/**
* The name of this class.
*/
private static final String CLASS = "LineNumberTableAttribute.Entry";
/**
* The line number.
*/
private int m_iLine;
/**
* The op.
*/
private Op m_op;
/**
* The byte code offset (if op is not available).
*/
private int m_of;
/**
* The next line number object in the linked list.
*/
private Entry m_next;
}
}
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