/*
 * Copyright (c) 2009, 2011, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package com.oracle.graal.api.code;

import java.io.*;

import com.oracle.graal.api.meta.*;

/**
 * Represents a code position, that is, a chain of inlined methods with bytecode locations, that is
 * communicated from the compiler to the runtime system. A code position can be used by the runtime
 * system to reconstruct a source-level stack trace for exceptions and to create
 * {@linkplain BytecodeFrame frames} for deoptimization.
 */
public abstract class BytecodePosition implements Serializable {

    private static final long serialVersionUID = 8633885274526033515L;

    private final BytecodePosition caller;
    private final ResolvedJavaMethod method;
    private final int bci;

    /**
     * Constructs a new object representing a given parent/caller, a given method, and a given BCI.
     * 
     * @param caller the parent position
     * @param method the method
     * @param bci a BCI within the method
     */
    public BytecodePosition(BytecodePosition caller, ResolvedJavaMethod method, int bci) {
        assert method != null;
        this.caller = caller;
        this.method = method;
        this.bci = bci;
    }

    /**
     * Converts this code position to a string representation.
     * 
     * @return a string representation of this code position
     */
    @Override
    public String toString() {
        return CodeUtil.append(new StringBuilder(100), this).toString();
    }

    /**
     * Deep equality test.
     */
    @Override
    public boolean equals(Object obj) {
        if (obj == this) {
            return true;
        }
        if (obj instanceof BytecodePosition) {
            BytecodePosition other = (BytecodePosition) obj;
            if (other.getMethod().equals(getMethod()) && other.getBCI() == getBCI()) {
                if (getCaller() == null) {
                    return other.getCaller() == null;
                }
                return getCaller().equals(other.getCaller());
            }
        }
        return false;
    }

    @Override
    public int hashCode() {
        return getBCI();
    }

    /**
     * @return The location within the method, as a bytecode index. The constant {@code -1} may be
     *         used to indicate the location is unknown, for example within code synthesized by the
     *         compiler.
     */
    public int getBCI() {
        return bci;
    }

    /**
     * @return The runtime interface method for this position.
     */
    public ResolvedJavaMethod getMethod() {
        return method;
    }

    /**
     * The position where this position has been called, {@code null} if none.
     */
    public BytecodePosition getCaller() {
        return caller;
    }
}