text: //
  // © 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.IO;
  using System.Runtime.InteropServices;
  using System.Text;
  
  
  namespace DotZLib
  {
  
      #region Internal types
  
      /// <summary>
      /// Defines constants for the various flush types used with zlib
      /// </summary>
      internal enum FlushTypes
      {
          None,  Partial,  Sync,  Full,  Finish,  Block
      }
  
      #region ZStream structure
      // internal mapping of the zlib zstream structure for marshalling
      [StructLayoutAttribute(LayoutKind.Sequential, Pack=4, Size=0, CharSet=CharSet.Ansi)]
      internal struct ZStream
      {
          public IntPtr next_in;
          public uint avail_in;
          public uint total_in;
  
          public IntPtr next_out;
          public uint avail_out;
          public uint total_out;
  
          [MarshalAs(UnmanagedType.LPStr)]
          string msg;
          uint state;
  
          uint zalloc;
          uint zfree;
          uint opaque;
  
          int data_type;
          public uint adler;
          uint reserved;
      }
  
      #endregion
  
      #endregion
  
      #region Public enums
      /// <summary>
      /// Defines constants for the available compression levels in zlib
      /// </summary>
      public enum CompressLevel : int
      {
          /// <summary>
          /// The default compression level with a reasonable compromise between compression and speed
          /// </summary>
          Default = -1,
          /// <summary>
          /// No compression at all. The data are passed straight through.
          /// </summary>
          None = 0,
          /// <summary>
          /// The maximum compression rate available.
          /// </summary>
          Best = 9,
          /// <summary>
          /// The fastest available compression level.
          /// </summary>
          Fastest = 1
      }
      #endregion
  
      #region Exception classes
      /// <summary>
      /// The exception that is thrown when an error occurs on the zlib dll
      /// </summary>
      public class ZLibException : ApplicationException
      {
          /// <summary>
          /// Initializes a new instance of the <see cref="ZLibException"/> class with a specified
          /// error message and error code
          /// </summary>
          /// <param name="errorCode">The zlib error code that caused the exception</param>
          /// <param name="msg">A message that (hopefully) describes the error</param>
          public ZLibException(int errorCode, string msg) : base(String.Format("ZLib error {0} {1}", errorCode, msg))
          {
          }
  
          /// <summary>
          /// Initializes a new instance of the <see cref="ZLibException"/> class with a specified
          /// error code
          /// </summary>
          /// <param name="errorCode">The zlib error code that caused the exception</param>
          public ZLibException(int errorCode) : base(String.Format("ZLib error {0}", errorCode))
          {
          }
      }
      #endregion
  
      #region Interfaces
  
      /// <summary>
      /// Declares methods and properties that enables a running checksum to be calculated
      /// </summary>
      public interface ChecksumGenerator
      {
          /// <summary>
          /// Gets the current value of the checksum
          /// </summary>
          uint Value { get; }
  
          /// <summary>
          /// Clears the current checksum to 0
          /// </summary>
          void Reset();
  
          /// <summary>
          /// Updates the current checksum with an array of bytes
          /// </summary>
          /// <param name="data">The data to update the checksum with</param>
          void Update(byte[] data);
  
          /// <summary>
          /// Updates the current checksum with part of an array of bytes
          /// </summary>
          /// <param name="data">The data to update the checksum with</param>
          /// <param name="offset">Where in <c>data</c> to start updating</param>
          /// <param name="count">The number of bytes from <c>data</c> to use</param>
          /// <exception cref="ArgumentException">The sum of offset and count is larger than the length of <c>data</c></exception>
          /// <exception cref="ArgumentNullException"><c>data</c> is a null reference</exception>
          /// <exception cref="ArgumentOutOfRangeException">Offset or count is negative.</exception>
          void Update(byte[] data, int offset, int count);
  
          /// <summary>
          /// Updates the current checksum with the data from a string
          /// </summary>
          /// <param name="data">The string to update the checksum with</param>
          /// <remarks>The characters in the string are converted by the UTF-8 encoding</remarks>
          void Update(string data);
  
          /// <summary>
          /// Updates the current checksum with the data from a string, using a specific encoding
          /// </summary>
          /// <param name="data">The string to update the checksum with</param>
          /// <param name="encoding">The encoding to use</param>
          void Update(string data, Encoding encoding);
      }
  
  
      /// <summary>
      /// Represents the method that will be called from a codec when new data
      /// are available.
      /// </summary>
      /// <paramref name="data">The byte array containing the processed data</paramref>
      /// <paramref name="startIndex">The index of the first processed byte in <c>data</c></paramref>
      /// <paramref name="count">The number of processed bytes available</paramref>
      /// <remarks>On return from this method, the data may be overwritten, so grab it while you can.
      /// You cannot assume that startIndex will be zero.
      /// </remarks>
      public delegate void DataAvailableHandler(byte[] data, int startIndex, int count);
  
      /// <summary>
      /// Declares methods and events for implementing compressors/decompressors
      /// </summary>
      public interface Codec
      {
          /// <summary>
          /// Occurs when more processed data are available.
          /// </summary>
          event DataAvailableHandler DataAvailable;
  
          /// <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>
          /// <remarks>Adding data may, or may not, raise the <c>DataAvailable</c> event</remarks>
          void Add(byte[] data);
  
          /// <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>
          void Add(byte[] data, int offset, int count);
  
          /// <summary>
          /// Finishes up any pending data that needs to be processed and handled.
          /// </summary>
          void Finish();
  
          /// <summary>
          /// Gets the checksum of the data that has been added so far
          /// </summary>
          uint Checksum { get; }
  
  
      }
  
      #endregion
  
      #region Classes
      /// <summary>
      /// Encapsulates general information about the ZLib library
      /// </summary>
      public class Info
      {
          #region DLL imports
          [DllImport("ZLIB1.dll", CallingConvention=CallingConvention.Cdecl)]
          private static extern uint zlibCompileFlags();
  
          [DllImport("ZLIB1.dll", CallingConvention=CallingConvention.Cdecl)]
          private static extern string zlibVersion();
          #endregion
  
          #region Private stuff
          private uint _flags;
  
          // helper function that unpacks a bitsize mask
          private static int bitSize(uint bits)
          {
              switch (bits)
              {
                  case 0: return 16;
                  case 1: return 32;
                  case 2: return 64;
              }
              return -1;
          }
          #endregion
  
          /// <summary>
          /// Constructs an instance of the <c>Info</c> class.
          /// </summary>
          public Info()
          {
              _flags = zlibCompileFlags();
          }
  
          /// <summary>
          /// True if the library is compiled with debug info
          /// </summary>
          public bool HasDebugInfo { get { return 0 != (_flags & 0x100); } }
  
          /// <summary>
          /// True if the library is compiled with assembly optimizations
          /// </summary>
          public bool UsesAssemblyCode { get { return 0 != (_flags & 0x200); } }
  
          /// <summary>
          /// Gets the size of the unsigned int that was compiled into Zlib
          /// </summary>
          public int SizeOfUInt { get { return bitSize(_flags & 3); } }
  
          /// <summary>
          /// Gets the size of the unsigned long that was compiled into Zlib
          /// </summary>
          public int SizeOfULong { get { return bitSize((_flags >> 2) & 3); } }
  
          /// <summary>
          /// Gets the size of the pointers that were compiled into Zlib
          /// </summary>
          public int SizeOfPointer { get { return bitSize((_flags >> 4) & 3); } }
  
          /// <summary>
          /// Gets the size of the z_off_t type that was compiled into Zlib
          /// </summary>
          public int SizeOfOffset { get { return bitSize((_flags >> 6) & 3); } }
  
          /// <summary>
          /// Gets the version of ZLib as a string, e.g. "1.2.1"
          /// </summary>
          public static string Version { get { return zlibVersion(); } }
      }
  
      #endregion
  
  }
  