// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
// http://code.google.com/p/protobuf/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * 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.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
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package com.google.protobuf.micro;

import com.google.protobuf.micro.CodedOutputStreamMicro;
import java.io.IOException;

/**
 * Abstract interface implemented by Protocol Message objects.
 *
 * @author wink@google.com Wink Saville
 */
public abstract class MessageMicro {
    /**
     * Get the number of bytes required to encode this message.
     * Returns the cached size or calls getSerializedSize which
     * sets the cached size. This is used internally when serializing
     * so the size is only computed once. If a member is modified
     * then this could be stale call getSerializedSize if in doubt.
     */
    abstract public int getCachedSize();

    /**
     * Computes the number of bytes required to encode this message.
     * The size is cached and the cached result can be retrieved
     * using getCachedSize().
     */
    abstract public int getSerializedSize();

    /**
     * Serializes the message and writes it to {@code output}.  This does not
     * flush or close the stream.
     */
    abstract public void writeTo(CodedOutputStreamMicro output) throws java.io.IOException;

    /**
     * Parse {@code input} as a message of this type and merge it with the
     * message being built.
     */
    abstract public MessageMicro mergeFrom(final CodedInputStreamMicro input) throws IOException;

    /**
     * Serialize to a byte array.
     * @return byte array with the serialized data.
     */
    public byte[] toByteArray() {
        final byte[] result = new byte[getSerializedSize()];
        toByteArray(result, 0, result.length);
        return result;
    }

    /**
     * Serialize to a byte array starting at offset through length. The
     * method getSerializedSize must have been called prior to calling
     * this method so the proper length is know.  If an attempt to
     * write more than length bytes OutOfSpaceException will be thrown
     * and if length bytes are not written then IllegalStateException
     * is thrown.
     * @return byte array with the serialized data.
     */
    public void toByteArray(byte [] data, int offset, int length) {
        try {
            final CodedOutputStreamMicro output = CodedOutputStreamMicro.newInstance(data, offset, length);
            writeTo(output);
            output.checkNoSpaceLeft();
        } catch (IOException e) {
            throw new RuntimeException("Serializing to a byte array threw an IOException "
                    + "(should never happen).");
        }
    }

    /**
     * Parse {@code data} as a message of this type and merge it with the
     * message being built.
     */
    public MessageMicro mergeFrom(final byte[] data) throws InvalidProtocolBufferMicroException {
        return mergeFrom(data, 0, data.length);
    }

    /**
     * Parse {@code data} as a message of this type and merge it with the
     * message being built.
     */
    public MessageMicro mergeFrom(final byte[] data, final int off, final int len)
            throws InvalidProtocolBufferMicroException {
        try {
            final CodedInputStreamMicro input = CodedInputStreamMicro.newInstance(data, off, len);
            mergeFrom(input);
            input.checkLastTagWas(0);
            return this;
        } catch (InvalidProtocolBufferMicroException e) {
            throw e;
        } catch (IOException e) {
            throw new RuntimeException("Reading from a byte array threw an IOException (should "
                    + "never happen).");
        }
    }

    /**
     * Called by subclasses to parse an unknown field.
     * @return {@code true} unless the tag is an end-group tag.
     */
    protected boolean parseUnknownField(
        final CodedInputStreamMicro input,
        final int tag) throws IOException {
      return input.skipField(tag);
    }
}