GZipUtils.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Sys / System / IO / compression / GZipUtils.cs / 1305376 / GZipUtils.cs
                        

                        
                            namespace System.IO.Compression { 
    using System.Diagnostics;

    internal static class GZipConstants {
        internal const int CompressionLevel_3 = 3; 
        internal const int CompressionLevel_10 = 10;
 
        internal const long FileLengthModulo = 4294967296; 

        internal const byte ID1 = 0x1F; 
        internal const byte ID2 = 0x8B;
        internal const byte Deflate = 0x8;

        internal const int Xfl_HeaderPos = 8; 
        internal const byte Xfl_FastestAlgorithm = 4;
        internal const byte Xfl_MaxCompressionSlowestAlgorithm = 2; 
    } 

    internal class GZipFormatter : IFileFormatWriter { 

        private byte[] headerBytes = new byte[] {
                GZipConstants.ID1,      // ID1
                GZipConstants.ID2,      // ID2 
                GZipConstants.Deflate,  // CM = deflate
                0,                      // FLG, no text, no crc, no extra, no name, no comment 
 
                // MTIME (Modification Time) - no time available
                0, 
                0,
                0,
                0,
 
                // XFL
                // 2 = compressor used max compression, slowest algorithm 
                // 4 = compressor used fastest algorithm 
                GZipConstants.Xfl_FastestAlgorithm,
 
                // OS: 0 = FAT filesystem (MS-DOS, OS/2, NT/Win32)
                0
            };
 
        private uint _crc32;
        private long _inputStreamSize; 
 
        internal GZipFormatter() : this(GZipConstants.CompressionLevel_3) { }
 
        internal GZipFormatter(int compressionLevel) {
            if (compressionLevel == GZipConstants.CompressionLevel_10) {
                headerBytes[GZipConstants.Xfl_HeaderPos] = GZipConstants.Xfl_MaxCompressionSlowestAlgorithm;
            } 
        }
 
        public byte[] GetHeader() { 
            return headerBytes;
        } 

        public void UpdateWithBytesRead(byte[] buffer, int offset, int bytesToCopy) {
            _crc32 = Crc32Helper.UpdateCrc32(_crc32, buffer, offset, bytesToCopy);
 
            long n = _inputStreamSize + (uint)bytesToCopy;
            if (n > GZipConstants.FileLengthModulo) { 
                long temp = Math.DivRem(n, GZipConstants.FileLengthModulo, out n); 
            }
            _inputStreamSize = n; 
        }

        public byte[] GetFooter() {
            byte[] b = new byte[8]; 

            WriteUInt32(b, _crc32, 0); 
            WriteUInt32(b, (uint)_inputStreamSize, 4); 

            return b; 

        }

        internal void WriteUInt32(byte[] b, uint value, int startIndex) { 
            b[startIndex] = (byte)value;
            b[startIndex + 1] = (byte)(value >> 8); 
            b[startIndex + 2] = (byte)(value >> 16); 
            b[startIndex + 3] = (byte)(value >> 24);
        } 
    }

    internal static class Crc32Helper {
 
        // Table for CRC calculation
        static readonly uint[] crcTable = new uint[256] { 
            0x00000000u, 0x77073096u, 0xee0e612cu, 0x990951bau, 0x076dc419u, 
            0x706af48fu, 0xe963a535u, 0x9e6495a3u, 0x0edb8832u, 0x79dcb8a4u,
            0xe0d5e91eu, 0x97d2d988u, 0x09b64c2bu, 0x7eb17cbdu, 0xe7b82d07u, 
            0x90bf1d91u, 0x1db71064u, 0x6ab020f2u, 0xf3b97148u, 0x84be41deu,
            0x1adad47du, 0x6ddde4ebu, 0xf4d4b551u, 0x83d385c7u, 0x136c9856u,
            0x646ba8c0u, 0xfd62f97au, 0x8a65c9ecu, 0x14015c4fu, 0x63066cd9u,
            0xfa0f3d63u, 0x8d080df5u, 0x3b6e20c8u, 0x4c69105eu, 0xd56041e4u, 
            0xa2677172u, 0x3c03e4d1u, 0x4b04d447u, 0xd20d85fdu, 0xa50ab56bu,
            0x35b5a8fau, 0x42b2986cu, 0xdbbbc9d6u, 0xacbcf940u, 0x32d86ce3u, 
            0x45df5c75u, 0xdcd60dcfu, 0xabd13d59u, 0x26d930acu, 0x51de003au, 
            0xc8d75180u, 0xbfd06116u, 0x21b4f4b5u, 0x56b3c423u, 0xcfba9599u,
            0xb8bda50fu, 0x2802b89eu, 0x5f058808u, 0xc60cd9b2u, 0xb10be924u, 
            0x2f6f7c87u, 0x58684c11u, 0xc1611dabu, 0xb6662d3du, 0x76dc4190u,
            0x01db7106u, 0x98d220bcu, 0xefd5102au, 0x71b18589u, 0x06b6b51fu,
            0x9fbfe4a5u, 0xe8b8d433u, 0x7807c9a2u, 0x0f00f934u, 0x9609a88eu,
            0xe10e9818u, 0x7f6a0dbbu, 0x086d3d2du, 0x91646c97u, 0xe6635c01u, 
            0x6b6b51f4u, 0x1c6c6162u, 0x856530d8u, 0xf262004eu, 0x6c0695edu,
            0x1b01a57bu, 0x8208f4c1u, 0xf50fc457u, 0x65b0d9c6u, 0x12b7e950u, 
            0x8bbeb8eau, 0xfcb9887cu, 0x62dd1ddfu, 0x15da2d49u, 0x8cd37cf3u, 
            0xfbd44c65u, 0x4db26158u, 0x3ab551ceu, 0xa3bc0074u, 0xd4bb30e2u,
            0x4adfa541u, 0x3dd895d7u, 0xa4d1c46du, 0xd3d6f4fbu, 0x4369e96au, 
            0x346ed9fcu, 0xad678846u, 0xda60b8d0u, 0x44042d73u, 0x33031de5u,
            0xaa0a4c5fu, 0xdd0d7cc9u, 0x5005713cu, 0x270241aau, 0xbe0b1010u,
            0xc90c2086u, 0x5768b525u, 0x206f85b3u, 0xb966d409u, 0xce61e49fu,
            0x5edef90eu, 0x29d9c998u, 0xb0d09822u, 0xc7d7a8b4u, 0x59b33d17u, 
            0x2eb40d81u, 0xb7bd5c3bu, 0xc0ba6cadu, 0xedb88320u, 0x9abfb3b6u,
            0x03b6e20cu, 0x74b1d29au, 0xead54739u, 0x9dd277afu, 0x04db2615u, 
            0x73dc1683u, 0xe3630b12u, 0x94643b84u, 0x0d6d6a3eu, 0x7a6a5aa8u, 
            0xe40ecf0bu, 0x9309ff9du, 0x0a00ae27u, 0x7d079eb1u, 0xf00f9344u,
            0x8708a3d2u, 0x1e01f268u, 0x6906c2feu, 0xf762575du, 0x806567cbu, 
            0x196c3671u, 0x6e6b06e7u, 0xfed41b76u, 0x89d32be0u, 0x10da7a5au,
            0x67dd4accu, 0xf9b9df6fu, 0x8ebeeff9u, 0x17b7be43u, 0x60b08ed5u,
            0xd6d6a3e8u, 0xa1d1937eu, 0x38d8c2c4u, 0x4fdff252u, 0xd1bb67f1u,
            0xa6bc5767u, 0x3fb506ddu, 0x48b2364bu, 0xd80d2bdau, 0xaf0a1b4cu, 
            0x36034af6u, 0x41047a60u, 0xdf60efc3u, 0xa867df55u, 0x316e8eefu,
            0x4669be79u, 0xcb61b38cu, 0xbc66831au, 0x256fd2a0u, 0x5268e236u, 
            0xcc0c7795u, 0xbb0b4703u, 0x220216b9u, 0x5505262fu, 0xc5ba3bbeu, 
            0xb2bd0b28u, 0x2bb45a92u, 0x5cb36a04u, 0xc2d7ffa7u, 0xb5d0cf31u,
            0x2cd99e8bu, 0x5bdeae1du, 0x9b64c2b0u, 0xec63f226u, 0x756aa39cu, 
            0x026d930au, 0x9c0906a9u, 0xeb0e363fu, 0x72076785u, 0x05005713u,
            0x95bf4a82u, 0xe2b87a14u, 0x7bb12baeu, 0x0cb61b38u, 0x92d28e9bu,
            0xe5d5be0du, 0x7cdcefb7u, 0x0bdbdf21u, 0x86d3d2d4u, 0xf1d4e242u,
            0x68ddb3f8u, 0x1fda836eu, 0x81be16cdu, 0xf6b9265bu, 0x6fb077e1u, 
            0x18b74777u, 0x88085ae6u, 0xff0f6a70u, 0x66063bcau, 0x11010b5cu,
            0x8f659effu, 0xf862ae69u, 0x616bffd3u, 0x166ccf45u, 0xa00ae278u, 
            0xd70dd2eeu, 0x4e048354u, 0x3903b3c2u, 0xa7672661u, 0xd06016f7u, 
            0x4969474du, 0x3e6e77dbu, 0xaed16a4au, 0xd9d65adcu, 0x40df0b66u,
            0x37d83bf0u, 0xa9bcae53u, 0xdebb9ec5u, 0x47b2cf7fu, 0x30b5ffe9u, 
            0xbdbdf21cu, 0xcabac28au, 0x53b39330u, 0x24b4a3a6u, 0xbad03605u,
            0xcdd70693u, 0x54de5729u, 0x23d967bfu, 0xb3667a2eu, 0xc4614ab8u,
            0x5d681b02u, 0x2a6f2b94u, 0xb40bbe37u, 0xc30c8ea1u, 0x5a05df1bu,
            0x2d02ef8du 
        };
 
        // Calculate CRC based on the old CRC and the new bytes 
        // See RFC1952 for details.
        static public uint UpdateCrc32(uint crc32, byte[] buffer, int offset, int length) { 
            Debug.Assert((buffer != null) && (offset >= 0) && (length >= 0)
                          && (offset <= buffer.Length - length), "check the caller");

            crc32 ^= 0xffffffffU; 

            while (--length >= 0) { 
                crc32 = crcTable[(crc32 ^ buffer[offset++]) & 0xFF] ^ (crc32 >> 8); 
            }
 
            crc32 ^= 0xffffffffU;
            return crc32;
        }
 

    } 
 

 
}


// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.

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