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package org.algorithmx.rules.asm;

// 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
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
// THE POSSIBILITY OF SUCH DAMAGE.

/**
 * An edge in the control flow graph of a method. Each node of this graph is a basic block,
 * represented with the Label corresponding to its first instruction. Each edge goes from one node
 * to another, i.e. from one basic block to another (called the predecessor and successor blocks,
 * respectively). An edge corresponds either to a jump or ret instruction or to an exception
 * handler.
 *
 * @see Label
 * @author Eric Bruneton
 */
final class Edge {

    /**
     * A control flow graph edge corresponding to a jump or ret instruction. Only used with {@link
     * ClassWriter#COMPUTE_FRAMES}.
     */
    static final int JUMP = 0;

    /**
     * A control flow graph edge corresponding to an exception handler. Only used with {@link
     * ClassWriter#COMPUTE_MAXS}.
     */
    static final int EXCEPTION = 0x7FFFFFFF;

    /**
     * Information about this control flow graph edge.
     *
     * 
     *   If {@link ClassWriter#COMPUTE_MAXS} is used, this field contains either a stack size
     *       delta (for an edge corresponding to a jump instruction), or the value EXCEPTION (for an
     *       edge corresponding to an exception handler). The stack size delta is the stack size just
     *       after the jump instruction, minus the stack size at the beginning of the predecessor
     *       basic block, i.e. the one containing the jump instruction.
     *   
If {@link ClassWriter#COMPUTE_FRAMES} is used, this field contains either the value JUMP
     *       (for an edge corresponding to a jump instruction), or the index, in the {@link
     *       ClassWriter} type table, of the exception type that is handled (for an edge corresponding
     *       to an exception handler).
     * 
     */
    final int info;

    /** The successor block of this control flow graph edge. */
    final Label successor;

    /**
     * The next edge in the list of outgoing edges of a basic block. See {@link Label#outgoingEdges}.
     */
    Edge nextEdge;

    /**
     * Constructs a new Edge.
     *
     * @param info see {@link #info}.
     * @param successor see {@link #successor}.
     * @param nextEdge see {@link #nextEdge}.
     */
    Edge(final int info, final Label successor, final Edge nextEdge) {
        this.info = info;
        this.successor = successor;
        this.nextEdge = nextEdge;
    }
}