EPath.java

package com.digitalpetri.enip.cip.epath;

import java.util.List;

import io.netty.buffer.ByteBuf;

public abstract class EPath {

    private final EPathSegment[] segments;

    protected EPath(EPathSegment[] segments) {
        this.segments = segments;
    }

    public EPathSegment[] getSegments() {
        return segments;
    }

    public abstract boolean isPadded();

    public static ByteBuf encode(EPath path, ByteBuf buffer) {
        // length placeholder...
        int lengthStartIndex = buffer.writerIndex();
        buffer.writeByte(0);

        // encode the path segments...
        int dataStartIndex = buffer.writerIndex();

        for (EPathSegment segment : path.getSegments()) {
            if (segment instanceof LogicalSegment) {
                LogicalSegment.encode((LogicalSegment) segment, path.isPadded(), buffer);
            } else if (segment instanceof PortSegment) {
                PortSegment.encode((PortSegment) segment, path.isPadded(), buffer);
            } else if (segment instanceof DataSegment) {
                DataSegment.encode((DataSegment) segment, path.isPadded(), buffer);
            } else {
                throw new RuntimeException("no encoder for " + segment.getClass().getSimpleName());
            }
        }

        // go back and update the length
        int bytesWritten = buffer.writerIndex() - dataStartIndex;
        int wordsWritten = bytesWritten / 2;
        buffer.markWriterIndex();
        buffer.writerIndex(lengthStartIndex);
        buffer.writeByte(wordsWritten);
        buffer.resetWriterIndex();

        return buffer;
    }

    public static final class PaddedEPath extends EPath {

        public PaddedEPath(List<EPathSegment> segments) {
            this(segments.toArray(new EPathSegment[segments.size()]));
        }

        public PaddedEPath(EPathSegment... segments) {
            super(segments);
        }

        @Override
        public boolean isPadded() {
            return true;
        }

        public PaddedEPath append(PaddedEPath other) {
            int aLen = getSegments().length;
            int bLen = other.getSegments().length;

            EPathSegment[] newSegments = new EPathSegment[aLen + bLen];

            System.arraycopy(getSegments(), 0, newSegments, 0, aLen);
            System.arraycopy(other.getSegments(), 0, newSegments, aLen, bLen);

            return new PaddedEPath(newSegments);
        }

    }

}