#nullable disable

// ZlibCodec.cs
// ------------------------------------------------------------------
//
// Copyright (c) 2009 Dino Chiesa and Microsoft Corporation.
// All rights reserved.
//
// This code module is part of DotNetZip, a zipfile class library.
//
// ------------------------------------------------------------------
//
// This code is licensed under the Microsoft Public License.
// See the file License.txt for the license details.
// More info on: http://dotnetzip.codeplex.com
//
// ------------------------------------------------------------------
//
// last saved (in emacs):
// Time-stamp: <2009-November-03 15:40:51>
//
// ------------------------------------------------------------------
//
// This module defines a Codec for ZLIB compression and
// decompression. This code extends code that was based the jzlib
// implementation of zlib, but this code is completely novel.  The codec
// class is new, and encapsulates some behaviors that are new, and some
// that were present in other classes in the jzlib code base.  In
// keeping with the license for jzlib, the copyright to the jzlib code
// is included below.
//
// ------------------------------------------------------------------
//
// Copyright (c) 2000,2001,2002,2003 ymnk, JCraft,Inc. 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. The names of the authors may not be used to endorse or promote products
// derived from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED 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 JCRAFT,
// INC. OR ANY CONTRIBUTORS TO THIS SOFTWARE 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.
//
// -----------------------------------------------------------------------
//
// This program is based on zlib-1.1.3; credit to authors
// Jean-loup Gailly(jloup@gzip.org) and Mark Adler(madler@alumni.caltech.edu)
// and contributors of zlib.
//
// -----------------------------------------------------------------------

using System;
using SharpCompress.Common;

namespace SharpCompress.Compressors.Deflate;

/// <summary>
/// Encoder and Decoder for ZLIB and DEFLATE (IETF RFC1950 and RFC1951).
/// </summary>
///
/// <remarks>
/// This class compresses and decompresses data according to the Deflate algorithm
/// and optionally, the ZLIB format, as documented in <see
/// href="http://www.ietf.org/rfc/rfc1950.txt">RFC 1950 - ZLIB</see> and <see
/// href="http://www.ietf.org/rfc/rfc1951.txt">RFC 1951 - DEFLATE</see>.
/// </remarks>
internal sealed class ZlibCodec
{
    /// <summary>
    /// The buffer from which data is taken.
    /// </summary>
    public byte[] InputBuffer;

    /// <summary>
    /// An index into the InputBuffer array, indicating where to start reading.
    /// </summary>
    public int NextIn;

    /// <summary>
    /// The number of bytes available in the InputBuffer, starting at NextIn.
    /// </summary>
    /// <remarks>
    /// Generally you should set this to InputBuffer.Length before the first Inflate() or Deflate() call.
    /// The class will update this number as calls to Inflate/Deflate are made.
    /// </remarks>
    public int AvailableBytesIn;

    /// <summary>
    /// Total number of bytes read so far, through all calls to Inflate()/Deflate().
    /// </summary>
    public long TotalBytesIn;

    /// <summary>
    /// Buffer to store output data.
    /// </summary>
    public byte[] OutputBuffer;

    /// <summary>
    /// An index into the OutputBuffer array, indicating where to start writing.
    /// </summary>
    public int NextOut;

    /// <summary>
    /// The number of bytes available in the OutputBuffer, starting at NextOut.
    /// </summary>
    /// <remarks>
    /// Generally you should set this to OutputBuffer.Length before the first Inflate() or Deflate() call.
    /// The class will update this number as calls to Inflate/Deflate are made.
    /// </remarks>
    public int AvailableBytesOut;

    /// <summary>
    /// Total number of bytes written to the output so far, through all calls to Inflate()/Deflate().
    /// </summary>
    public long TotalBytesOut;

    /// <summary>
    /// used for diagnostics, when something goes wrong!
    /// </summary>
    public string Message;

    internal DeflateManager dstate;
    internal InflateManager istate;

    internal uint _adler32;

    /// <summary>
    /// The compression level to use in this codec.  Useful only in compression mode.
    /// </summary>
    public CompressionLevel CompressLevel = CompressionLevel.Default;

    /// <summary>
    /// The number of Window Bits to use.
    /// </summary>
    /// <remarks>
    /// This gauges the size of the sliding window, and hence the
    /// compression effectiveness as well as memory consumption. It's best to just leave this
    /// setting alone if you don't know what it is.  The maximum value is 15 bits, which implies
    /// a 32k window.
    /// </remarks>
    public int WindowBits = ZlibConstants.WindowBitsDefault;

    /// <summary>
    /// The compression strategy to use.
    /// </summary>
    /// <remarks>
    /// This is only effective in compression.  The theory offered by ZLIB is that different
    /// strategies could potentially produce significant differences in compression behavior
    /// for different data sets.  Unfortunately I don't have any good recommendations for how
    /// to set it differently.  When I tested changing the strategy I got minimally different
    /// compression performance. It's best to leave this property alone if you don't have a
    /// good feel for it.  Or, you may want to produce a test harness that runs through the
    /// different strategy options and evaluates them on different file types. If you do that,
    /// let me know your results.
    /// </remarks>
    public CompressionStrategy Strategy = CompressionStrategy.Default;

    /// <summary>
    /// The Adler32 checksum on the data transferred through the codec so far. You probably don't need to look at this.
    /// </summary>
    public int Adler32 => (int)_adler32;

    /// <summary>
    /// Create a ZlibCodec.
    /// </summary>
    /// <remarks>
    /// If you use this default constructor, you will later have to explicitly call
    /// InitializeInflate() or InitializeDeflate() before using the ZlibCodec to compress
    /// or decompress.
    /// </remarks>
    public ZlibCodec() { }

    /// <summary>
    /// Create a ZlibCodec that either compresses or decompresses.
    /// </summary>
    /// <param name="mode">
    /// Indicates whether the codec should compress (deflate) or decompress (inflate).
    /// </param>
    public ZlibCodec(CompressionMode mode)
    {
        if (mode == CompressionMode.Compress)
        {
            var rc = InitializeDeflate();
            if (rc != ZlibConstants.Z_OK)
            {
                throw new ZlibException("Cannot initialize for deflate.");
            }
        }
        else if (mode == CompressionMode.Decompress)
        {
            var rc = InitializeInflate();
            if (rc != ZlibConstants.Z_OK)
            {
                throw new ZlibException("Cannot initialize for inflate.");
            }
        }
        else
        {
            throw new ZlibException("Invalid ZlibStreamFlavor.");
        }
    }

    /// <summary>
    /// Initialize the inflation state.
    /// </summary>
    /// <remarks>
    /// It is not necessary to call this before using the ZlibCodec to inflate data;
    /// It is implicitly called when you call the constructor.
    /// </remarks>
    /// <returns>Z_OK if everything goes well.</returns>
    public int InitializeInflate() => InitializeInflate(WindowBits);

    /// <summary>
    /// Initialize the inflation state with an explicit flag to
    /// govern the handling of RFC1950 header bytes.
    /// </summary>
    ///
    /// <remarks>
    /// By default, the ZLIB header defined in <see
    /// href="http://www.ietf.org/rfc/rfc1950.txt">RFC 1950</see> is expected.  If
    /// you want to read a zlib stream you should specify true for
    /// expectRfc1950Header.  If you have a deflate stream, you will want to specify
    /// false. It is only necessary to invoke this initializer explicitly if you
    /// want to specify false.
    /// </remarks>
    ///
    /// <param name="expectRfc1950Header">whether to expect an RFC1950 header byte
    /// pair when reading the stream of data to be inflated.</param>
    ///
    /// <returns>Z_OK if everything goes well.</returns>
    public int InitializeInflate(bool expectRfc1950Header) =>
        InitializeInflate(WindowBits, expectRfc1950Header);

    /// <summary>
    /// Initialize the ZlibCodec for inflation, with the specified number of window bits.
    /// </summary>
    /// <param name="windowBits">The number of window bits to use. If you need to ask what that is,
    /// then you shouldn't be calling this initializer.</param>
    /// <returns>Z_OK if all goes well.</returns>
    public int InitializeInflate(int windowBits)
    {
        WindowBits = windowBits;
        return InitializeInflate(windowBits, true);
    }

    /// <summary>
    /// Initialize the inflation state with an explicit flag to govern the handling of
    /// RFC1950 header bytes.
    /// </summary>
    ///
    /// <remarks>
    /// If you want to read a zlib stream you should specify true for
    /// expectRfc1950Header. In this case, the library will expect to find a ZLIB
    /// header, as defined in <see href="http://www.ietf.org/rfc/rfc1950.txt">RFC
    /// 1950</see>, in the compressed stream.  If you will be reading a DEFLATE or
    /// GZIP stream, which does not have such a header, you will want to specify
    /// false.
    /// </remarks>
    ///
    /// <param name="expectRfc1950Header">whether to expect an RFC1950 header byte pair when reading
    /// the stream of data to be inflated.</param>
    /// <param name="windowBits">The number of window bits to use. If you need to ask what that is,
    /// then you shouldn't be calling this initializer.</param>
    /// <returns>Z_OK if everything goes well.</returns>
    public int InitializeInflate(int windowBits, bool expectRfc1950Header)
    {
        WindowBits = windowBits;
        if (dstate != null)
        {
            throw new ZlibException(
                "You may not call InitializeInflate() after calling InitializeDeflate()."
            );
        }
        istate = new InflateManager(expectRfc1950Header);
        return istate.Initialize(this, windowBits);
    }

    /// <summary>
    /// Inflate the data in the InputBuffer, placing the result in the OutputBuffer.
    /// </summary>
    /// <remarks>
    /// You must have set InputBuffer and OutputBuffer, NextIn and NextOut, and AvailableBytesIn and
    /// AvailableBytesOut  before calling this method.
    /// </remarks>
    /// <example>
    /// <code>
    /// private void InflateBuffer()
    /// {
    ///     int bufferSize = 1024;
    ///     byte[] buffer = new byte[bufferSize];
    ///     ZlibCodec decompressor = new ZlibCodec();
    ///
    ///     Console.WriteLine("\n============================================");
    ///     Console.WriteLine("Size of Buffer to Inflate: {0} bytes.", CompressedBytes.Length);
    ///     MemoryStream ms = new MemoryStream(DecompressedBytes);
    ///
    ///     int rc = decompressor.InitializeInflate();
    ///
    ///     decompressor.InputBuffer = CompressedBytes;
    ///     decompressor.NextIn = 0;
    ///     decompressor.AvailableBytesIn = CompressedBytes.Length;
    ///
    ///     decompressor.OutputBuffer = buffer;
    ///
    ///     // pass 1: inflate
    ///     do
    ///     {
    ///         decompressor.NextOut = 0;
    ///         decompressor.AvailableBytesOut = buffer.Length;
    ///         rc = decompressor.Inflate(FlushType.None);
    ///
    ///         if (rc != ZlibConstants.Z_OK &amp;&amp; rc != ZlibConstants.Z_STREAM_END)
    ///             throw new Exception("inflating: " + decompressor.Message);
    ///
    ///         ms.Write(decompressor.OutputBuffer, 0, buffer.Length - decompressor.AvailableBytesOut);
    ///     }
    ///     while (decompressor.AvailableBytesIn &gt; 0 || decompressor.AvailableBytesOut == 0);
    ///
    ///     // pass 2: finish and flush
    ///     do
    ///     {
    ///         decompressor.NextOut = 0;
    ///         decompressor.AvailableBytesOut = buffer.Length;
    ///         rc = decompressor.Inflate(FlushType.Finish);
    ///
    ///         if (rc != ZlibConstants.Z_STREAM_END &amp;&amp; rc != ZlibConstants.Z_OK)
    ///             throw new Exception("inflating: " + decompressor.Message);
    ///
    ///         if (buffer.Length - decompressor.AvailableBytesOut &gt; 0)
    ///             ms.Write(buffer, 0, buffer.Length - decompressor.AvailableBytesOut);
    ///     }
    ///     while (decompressor.AvailableBytesIn &gt; 0 || decompressor.AvailableBytesOut == 0);
    ///
    ///     decompressor.EndInflate();
    /// }
    ///
    /// </code>
    /// </example>
    /// <param name="flush">The flush to use when inflating.</param>
    /// <returns>Z_OK if everything goes well.</returns>
    public int Inflate(FlushType flush)
    {
        if (istate is null)
        {
            throw new ZlibException("No Inflate State!");
        }
        return istate.Inflate(flush);
    }

    /// <summary>
    /// Ends an inflation session.
    /// </summary>
    /// <remarks>
    /// Call this after successively calling Inflate().  This will cause all buffers to be flushed.
    /// After calling this you cannot call Inflate() without a intervening call to one of the
    /// InitializeInflate() overloads.
    /// </remarks>
    /// <returns>Z_OK if everything goes well.</returns>
    public int EndInflate()
    {
        if (istate is null)
        {
            throw new ZlibException("No Inflate State!");
        }
        var ret = istate.End();
        istate = null;
        return ret;
    }

    /// <summary>
    /// I don't know what this does!
    /// </summary>
    /// <returns>Z_OK if everything goes well.</returns>
    public int SyncInflate()
    {
        if (istate is null)
        {
            throw new ZlibException("No Inflate State!");
        }
        return istate.Sync();
    }

    /// <summary>
    /// Initialize the ZlibCodec for deflation operation.
    /// </summary>
    /// <remarks>
    /// The codec will use the MAX window bits and the default level of compression.
    /// </remarks>
    /// <example>
    /// <code>
    ///  int bufferSize = 40000;
    ///  byte[] CompressedBytes = new byte[bufferSize];
    ///  byte[] DecompressedBytes = new byte[bufferSize];
    ///
    ///  ZlibCodec compressor = new ZlibCodec();
    ///
    ///  compressor.InitializeDeflate(CompressionLevel.Default);
    ///
    ///  compressor.InputBuffer = System.Text.ASCIIEncoding.ASCII.GetBytes(TextToCompress);
    ///  compressor.NextIn = 0;
    ///  compressor.AvailableBytesIn = compressor.InputBuffer.Length;
    ///
    ///  compressor.OutputBuffer = CompressedBytes;
    ///  compressor.NextOut = 0;
    ///  compressor.AvailableBytesOut = CompressedBytes.Length;
    ///
    ///  while (compressor.TotalBytesIn != TextToCompress.Length &amp;&amp; compressor.TotalBytesOut &lt; bufferSize)
    ///  {
    ///    compressor.Deflate(FlushType.None);
    ///  }
    ///
    ///  while (true)
    ///  {
    ///    int rc= compressor.Deflate(FlushType.Finish);
    ///    if (rc == ZlibConstants.Z_STREAM_END) break;
    ///  }
    ///
    ///  compressor.EndDeflate();
    ///
    /// </code>
    /// </example>
    /// <returns>Z_OK if all goes well. You generally don't need to check the return code.</returns>
    public int InitializeDeflate() => _InternalInitializeDeflate(true);

    /// <summary>
    /// Initialize the ZlibCodec for deflation operation, using the specified CompressionLevel.
    /// </summary>
    /// <remarks>
    /// The codec will use the maximum window bits (15) and the specified
    /// CompressionLevel.  It will emit a ZLIB stream as it compresses.
    /// </remarks>
    /// <param name="level">The compression level for the codec.</param>
    /// <returns>Z_OK if all goes well.</returns>
    public int InitializeDeflate(CompressionLevel level)
    {
        CompressLevel = level;
        return _InternalInitializeDeflate(true);
    }

    /// <summary>
    /// Initialize the ZlibCodec for deflation operation, using the specified CompressionLevel,
    /// and the explicit flag governing whether to emit an RFC1950 header byte pair.
    /// </summary>
    /// <remarks>
    /// The codec will use the maximum window bits (15) and the specified CompressionLevel.
    /// If you want to generate a zlib stream, you should specify true for
    /// wantRfc1950Header. In this case, the library will emit a ZLIB
    /// header, as defined in <see href="http://www.ietf.org/rfc/rfc1950.txt">RFC
    /// 1950</see>, in the compressed stream.
    /// </remarks>
    /// <param name="level">The compression level for the codec.</param>
    /// <param name="wantRfc1950Header">whether to emit an initial RFC1950 byte pair in the compressed stream.</param>
    /// <returns>Z_OK if all goes well.</returns>
    public int InitializeDeflate(CompressionLevel level, bool wantRfc1950Header)
    {
        CompressLevel = level;
        return _InternalInitializeDeflate(wantRfc1950Header);
    }

    /// <summary>
    /// Initialize the ZlibCodec for deflation operation, using the specified CompressionLevel,
    /// and the specified number of window bits.
    /// </summary>
    /// <remarks>
    /// The codec will use the specified number of window bits and the specified CompressionLevel.
    /// </remarks>
    /// <param name="level">The compression level for the codec.</param>
    /// <param name="bits">the number of window bits to use.  If you don't know what this means, don't use this method.</param>
    /// <returns>Z_OK if all goes well.</returns>
    public int InitializeDeflate(CompressionLevel level, int bits)
    {
        CompressLevel = level;
        WindowBits = bits;
        return _InternalInitializeDeflate(true);
    }

    /// <summary>
    /// Initialize the ZlibCodec for deflation operation, using the specified
    /// CompressionLevel, the specified number of window bits, and the explicit flag
    /// governing whether to emit an RFC1950 header byte pair.
    /// </summary>
    ///
    /// <param name="level">The compression level for the codec.</param>
    /// <param name="wantRfc1950Header">whether to emit an initial RFC1950 byte pair in the compressed stream.</param>
    /// <param name="bits">the number of window bits to use.  If you don't know what this means, don't use this method.</param>
    /// <returns>Z_OK if all goes well.</returns>
    public int InitializeDeflate(CompressionLevel level, int bits, bool wantRfc1950Header)
    {
        CompressLevel = level;
        WindowBits = bits;
        return _InternalInitializeDeflate(wantRfc1950Header);
    }

    private int _InternalInitializeDeflate(bool wantRfc1950Header)
    {
        if (istate != null)
        {
            throw new ZlibException(
                "You may not call InitializeDeflate() after calling InitializeInflate()."
            );
        }
        dstate = new DeflateManager();
        dstate.WantRfc1950HeaderBytes = wantRfc1950Header;

        return dstate.Initialize(this, CompressLevel, WindowBits, Strategy);
    }

    /// <summary>
    /// Deflate one batch of data.
    /// </summary>
    /// <remarks>
    /// You must have set InputBuffer and OutputBuffer before calling this method.
    /// </remarks>
    /// <example>
    /// <code>
    /// private void DeflateBuffer(CompressionLevel level)
    /// {
    ///     int bufferSize = 1024;
    ///     byte[] buffer = new byte[bufferSize];
    ///     ZlibCodec compressor = new ZlibCodec();
    ///
    ///     Console.WriteLine("\n============================================");
    ///     Console.WriteLine("Size of Buffer to Deflate: {0} bytes.", UncompressedBytes.Length);
    ///     MemoryStream ms = new MemoryStream();
    ///
    ///     int rc = compressor.InitializeDeflate(level);
    ///
    ///     compressor.InputBuffer = UncompressedBytes;
    ///     compressor.NextIn = 0;
    ///     compressor.AvailableBytesIn = UncompressedBytes.Length;
    ///
    ///     compressor.OutputBuffer = buffer;
    ///
    ///     // pass 1: deflate
    ///     do
    ///     {
    ///         compressor.NextOut = 0;
    ///         compressor.AvailableBytesOut = buffer.Length;
    ///         rc = compressor.Deflate(FlushType.None);
    ///
    ///         if (rc != ZlibConstants.Z_OK &amp;&amp; rc != ZlibConstants.Z_STREAM_END)
    ///             throw new Exception("deflating: " + compressor.Message);
    ///
    ///         ms.Write(compressor.OutputBuffer, 0, buffer.Length - compressor.AvailableBytesOut);
    ///     }
    ///     while (compressor.AvailableBytesIn &gt; 0 || compressor.AvailableBytesOut == 0);
    ///
    ///     // pass 2: finish and flush
    ///     do
    ///     {
    ///         compressor.NextOut = 0;
    ///         compressor.AvailableBytesOut = buffer.Length;
    ///         rc = compressor.Deflate(FlushType.Finish);
    ///
    ///         if (rc != ZlibConstants.Z_STREAM_END &amp;&amp; rc != ZlibConstants.Z_OK)
    ///             throw new Exception("deflating: " + compressor.Message);
    ///
    ///         if (buffer.Length - compressor.AvailableBytesOut &gt; 0)
    ///             ms.Write(buffer, 0, buffer.Length - compressor.AvailableBytesOut);
    ///     }
    ///     while (compressor.AvailableBytesIn &gt; 0 || compressor.AvailableBytesOut == 0);
    ///
    ///     compressor.EndDeflate();
    ///
    ///     ms.Seek(0, SeekOrigin.Begin);
    ///     CompressedBytes = new byte[compressor.TotalBytesOut];
    ///     ms.Read(CompressedBytes, 0, CompressedBytes.Length);
    /// }
    /// </code>
    /// </example>
    /// <param name="flush">whether to flush all data as you deflate. Generally you will want to
    /// use Z_NO_FLUSH here, in a series of calls to Deflate(), and then call EndDeflate() to
    /// flush everything.
    /// </param>
    /// <returns>Z_OK if all goes well.</returns>
    public int Deflate(FlushType flush)
    {
        if (dstate is null)
        {
            throw new ZlibException("No Deflate State!");
        }
        return dstate.Deflate(flush);
    }

    /// <summary>
    /// End a deflation session.
    /// </summary>
    /// <remarks>
    /// Call this after making a series of one or more calls to Deflate(). All buffers are flushed.
    /// </remarks>
    /// <returns>Z_OK if all goes well.</returns>
    public int EndDeflate()
    {
        if (dstate is null)
        {
            throw new ZlibException("No Deflate State!");
        }

        _ = dstate.End();
        dstate = null;
        return ZlibConstants.Z_OK;
    }

    /// <summary>
    /// Reset a codec for another deflation session.
    /// </summary>
    /// <remarks>
    /// Call this to reset the deflation state.  For example if a thread is deflating
    /// non-consecutive blocks, you can call Reset() after the Deflate(Sync) of the first
    /// block and before the next Deflate(None) of the second block.
    /// </remarks>
    /// <returns>Z_OK if all goes well.</returns>
    public void ResetDeflate()
    {
        if (dstate is null)
        {
            throw new ZlibException("No Deflate State!");
        }
        dstate.Reset();
    }

    /// <summary>
    /// Set the CompressionStrategy and CompressionLevel for a deflation session.
    /// </summary>
    /// <param name="level">the level of compression to use.</param>
    /// <param name="strategy">the strategy to use for compression.</param>
    /// <returns>Z_OK if all goes well.</returns>
    public int SetDeflateParams(CompressionLevel level, CompressionStrategy strategy)
    {
        if (dstate is null)
        {
            throw new ZlibException("No Deflate State!");
        }
        return dstate.SetParams(level, strategy);
    }

    /// <summary>
    /// Set the dictionary to be used for either Inflation or Deflation.
    /// </summary>
    /// <param name="dictionary">The dictionary bytes to use.</param>
    /// <returns>Z_OK if all goes well.</returns>
    public int SetDictionary(byte[] dictionary)
    {
        if (istate != null)
        {
            return istate.SetDictionary(dictionary);
        }

        if (dstate != null)
        {
            return dstate.SetDictionary(dictionary);
        }

        throw new ZlibException("No Inflate or Deflate state!");
    }

    // Flush as much pending output as possible. All deflate() output goes
    // through this function so some applications may wish to modify it
    // to avoid allocating a large strm->next_out buffer and copying into it.
    // (See also read_buf()).
    internal void flush_pending()
    {
        var len = dstate.pendingCount;

        if (len > AvailableBytesOut)
        {
            len = AvailableBytesOut;
        }
        if (len == 0)
        {
            return;
        }

        if (
            dstate.pending.Length <= dstate.nextPending
            || OutputBuffer.Length <= NextOut
            || dstate.pending.Length < (dstate.nextPending + len)
            || OutputBuffer.Length < (NextOut + len)
        )
        {
            throw new ZlibException(
                string.Format(
                    Constants.DefaultCultureInfo,
                    "Invalid State. (pending.Length={0}, pendingCount={1})",
                    dstate.pending.Length,
                    dstate.pendingCount
                )
            );
        }

        Array.Copy(dstate.pending, dstate.nextPending, OutputBuffer, NextOut, len);

        NextOut += len;
        dstate.nextPending += len;
        TotalBytesOut += len;
        AvailableBytesOut -= len;
        dstate.pendingCount -= len;
        if (dstate.pendingCount == 0)
        {
            dstate.nextPending = 0;
        }
    }

    // Read a new buffer from the current input stream, update the adler32
    // and total number of bytes read.  All deflate() input goes through
    // this function so some applications may wish to modify it to avoid
    // allocating a large strm->next_in buffer and copying from it.
    // (See also flush_pending()).
    internal int read_buf(byte[] buf, int start, int size)
    {
        var len = AvailableBytesIn;

        if (len > size)
        {
            len = size;
        }
        if (len == 0)
        {
            return 0;
        }

        AvailableBytesIn -= len;

        if (dstate.WantRfc1950HeaderBytes)
        {
            _adler32 = Algorithms.Adler32.Calculate(_adler32, InputBuffer.AsSpan(NextIn, len));
        }
        Array.Copy(InputBuffer, NextIn, buf, start, len);
        NextIn += len;
        TotalBytesIn += len;
        return len;
    }
}
