//

// © Copyright Henrik Ravn 2004

//

// Use, modification and distribution are subject to the Boost Software License, Version 1.0. 

// (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

//

using System;

using System.Diagnostics;

using System.Runtime.InteropServices;

namespace DotZLib

{

    /// <summary>

    /// Implements a data compressor, using the deflate algorithm in the ZLib dll

    /// </summary>

	public sealed class Deflater : CodecBase

	{

        #region Dll imports

        [DllImport("ZLIB1.dll", CallingConvention=CallingConvention.Cdecl, CharSet=CharSet.Ansi)]

        private static extern int deflateInit_(ref ZStream sz, int level, string vs, int size);

        [DllImport("ZLIB1.dll", CallingConvention=CallingConvention.Cdecl)]

        private static extern int deflate(ref ZStream sz, int flush);

        [DllImport("ZLIB1.dll", CallingConvention=CallingConvention.Cdecl)]

        private static extern int deflateReset(ref ZStream sz);

        [DllImport("ZLIB1.dll", CallingConvention=CallingConvention.Cdecl)]

        private static extern int deflateEnd(ref ZStream sz);

        #endregion

        /// <summary>

        /// Constructs an new instance of the <c>Deflater</c>

        /// </summary>

        /// <param name="level">The compression level to use for this <c>Deflater</c></param>

		public Deflater(CompressLevel level) : base()

		{

            int retval = deflateInit_(ref _ztream, (int)level, Info.Version, Marshal.SizeOf(_ztream));

            if (retval != 0)

                throw new ZLibException(retval, "Could not initialize deflater");

            resetOutput();

		}

        /// <summary>

        /// Adds more data to the codec to be processed.

        /// </summary>

        /// <param name="data">Byte array containing the data to be added to the codec</param>

        /// <param name="offset">The index of the first byte to add from <c>data</c></param>

        /// <param name="count">The number of bytes to add</param>

        /// <remarks>Adding data may, or may not, raise the <c>DataAvailable</c> event</remarks>

        public override void Add(byte[] data, int offset, int count)

        {

            if (data == null) throw new ArgumentNullException();

            if (offset < 0 || count < 0) throw new ArgumentOutOfRangeException();

            if ((offset+count) > data.Length) throw new ArgumentException();

            int total = count;

            int inputIndex = offset;

            int err = 0;

            while (err >= 0 && inputIndex < total)

            {

                copyInput(data, inputIndex, Math.Min(total - inputIndex, kBufferSize));

                while (err >= 0 && _ztream.avail_in > 0)

                {

                    err = deflate(ref _ztream, (int)FlushTypes.None);

                    if (err == 0)

                        while (_ztream.avail_out == 0)

                        {

                            OnDataAvailable();

                            err = deflate(ref _ztream, (int)FlushTypes.None);

                        }

                    inputIndex += (int)_ztream.total_in;

                }

            }

            setChecksum( _ztream.adler );

        }

        /// <summary>

        /// Finishes up any pending data that needs to be processed and handled.

        /// </summary>

        public override void Finish()

        {

            int err;

            do 

            {

                err = deflate(ref _ztream, (int)FlushTypes.Finish);

                OnDataAvailable();

            }

            while (err == 0);

            setChecksum( _ztream.adler );

            deflateReset(ref _ztream);

            resetOutput();

        }

        /// <summary>

        /// Closes the internal zlib deflate stream

        /// </summary>

        protected override void CleanUp() { deflateEnd(ref _ztream); }

    }

}