zlib.cs

// zlib.cs -- interface of the 'zlib' general purpose compression library
// Copyright (C) 1995-2010 Jean-loup Gailly and Mark Adler
// Copyright (C) 2007-2011 by the Authors
// For conditions of distribution and use, see copyright notice in License.txt

using System;

namespace Free.Ports.zLib
{
	public static partial class zlib
	{
		// Maximum value for memLevel in deflateInit2
		private const int MAX_MEM_LEVEL=9;

		// Maximum value for windowBits in deflateInit2 and inflateInit2.
		private const int MAX_WBITS=15; // 32K LZ77 window
		private const int DEF_WBITS=MAX_WBITS; // default windowBits for decompression. MAX_WBITS is for compression only

		// The memory requirements for deflate are (in bytes):
		//    (1 << (windowBits+2)) +  (1 << (memLevel+9))
		// that is: 128K for windowBits=15  +  128K for memLevel = 8  (default values)
		// plus a few kilobytes for small objects. For example, if you want to reduce
		// the default memory requirements from 256K to 128K, compile with
		//    make CFLAGS="-O -DMAX_WBITS=14 -DMAX_MEM_LEVEL=7"
		// Of course this will generally degrade compression (there's no free lunch).

		// The memory requirements for inflate are (in bytes) 1 << windowBits
		// that is, 32K for windowBits=15 (default value) plus a few kilobytes
		// for small objects.

		private const int DEF_MEM_LEVEL=8; // default memLevel

		// The three kinds of block type
		private const int STORED_BLOCK=0;
		private const int STATIC_TREES=1;
		private const int DYN_TREES=2;

		// The minimum and maximum match lengths
		private const int MIN_MATCH=3;
		private const int MAX_MATCH=258;

		public const string ZLIB_VERSION="1.2.5";
		public const uint ZLIB_VERNUM=0x1250;

		// The 'zlib' compression library provides in-memory compression and
		// decompression functions, including integrity checks of the uncompressed
		// data. This version of the library supports only one compression method
		// (deflation) but other algorithms will be added later and will have the same
		// stream interface.
		//
		//  Compression can be done in a single step if the buffers are large enough,
		// or can be done by repeated calls of the compression function. In the latter
		//  case, the application must provide more input and/or consume the output
		// (providing more output space) before each call.
		//
		//  The compressed data format used by default by the in-memory functions is
		// the zlib format, which is a zlib wrapper documented in RFC 1950, wrapped
		// around a deflate stream, which is itself documented in RFC 1951.
		//
		//  The zlib format was designed to be compact and fast for use in memory
		// and on communications channels. 
		//
		//  The library does not install any signal handler. The decoder checks
		// the consistency of the compressed data, so the library should never crash
		// even in case of corrupted input.

		public class z_stream
		{
			public byte[] in_buf;	// input buffer
			public uint next_in;	// next input byte index
			public uint avail_in;	// number of bytes available at next_in
			public uint total_in;	// total nb of input bytes read so far

			public byte[] out_buf;	// output buffer
			public int next_out;	// next output byte should be put there
			public uint avail_out;	// remaining free space at next_out
			public uint total_out;	// total nb of bytes output so far

			public string msg;		// last error message, NULL if no error
			public object state;	// not visible by applications

			public uint adler;		// adler32 value of the uncompressed data

			public void CopyTo(z_stream s)
			{
				s.adler=adler;
				s.avail_in=avail_in;
				s.avail_out=avail_out;
				s.in_buf=in_buf;
				s.msg=msg;
				s.next_in=next_in;
				s.next_out=next_out;
				s.out_buf=out_buf;
				s.state=state;
				s.total_in=total_in;
				s.total_out=total_out;
			}
		}

		// gzip header information passed to and from zlib routines.  See RFC 1952
		// for more details on the meanings of these fields.
		public class gz_header
		{
			public int text;			// true if compressed data believed to be text
			public uint time;			// modification time
			public int xflags;			// extra flags (not used when writing a gzip file)
			public int os;				// operating system
			public byte[] extra;		// pointer to extra field or Z_NULL if none
			public uint extra_len;		// extra field length (valid if extra != Z_NULL)
			public uint extra_max;		// space at extra (only when reading header)
			public byte[] name;			// pointer to zero-terminated file name or Z_NULL
			public uint name_max;		// space at name (only when reading header)
			public byte[] comment;		// pointer to zero-terminated comment or Z_NULL
			public uint comm_max;		// space at comment (only when reading header)
			public int hcrc;			// true if there was or will be a header crc
			public int done;			// true when done reading gzip header (not used when writing a gzip file)
		}

		// The application must update next_in and avail_in when avail_in has
		// dropped to zero. It must update next_out and avail_out when avail_out
		// has dropped to zero. All other fields are set by the
		// compression library and must not be updated by the application.
		//
		// The fields total_in and total_out can be used for statistics or
		// progress reports. After compression, total_in holds the total size of
		// the uncompressed data and may be saved for use in the decompressor
		// (particularly if the decompressor wants to decompress everything in
		// a single step).

		// constants

		// Allowed flush values; see deflate() and inflate() below for details
		public const int Z_NO_FLUSH=0;
		public const int Z_PARTIAL_FLUSH=1;
		public const int Z_SYNC_FLUSH=2;
		public const int Z_FULL_FLUSH=3;
		public const int Z_FINISH=4;
		public const int Z_BLOCK=5;
		public const int Z_TREES=6;

		// Return codes for the compression/decompression functions. Negative
		// values are errors, positive values are used for special but normal events.
		public const int Z_OK=0;
		public const int Z_STREAM_END=1;
		public const int Z_NEED_DICT=2;
		public const int Z_ERRNO=-1;
		public const int Z_STREAM_ERROR=-2;
		public const int Z_DATA_ERROR=-3;
		public const int Z_MEM_ERROR=-4;
		public const int Z_BUF_ERROR=-5;
		public const int Z_VERSION_ERROR=-6;

		// compression levels
		public const int Z_NO_COMPRESSION=0;
		public const int Z_BEST_SPEED=1;
		public const int Z_BEST_COMPRESSION=9;
		public const int Z_DEFAULT_COMPRESSION=(-1);

		// compression strategy; see deflateInit2() below for details
		public const int Z_FILTERED=1;
		public const int Z_HUFFMAN_ONLY=2;
		public const int Z_RLE=3;
		public const int Z_FIXED=4;
		public const int Z_DEFAULT_STRATEGY=0;

		// The deflate compression method (the only one supported in this version)
		public const int Z_DEFLATED=8;

		public const string zlib_version=ZLIB_VERSION; // for compatibility with versions < 1.0.2
	}
}