CopyEncoder.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 / CopyEncoder.cs / 1305376 / CopyEncoder.cs
                        

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

    internal class CopyEncoder { 

        // padding for copy encoder formatting 
        //  - 1 byte for header 
        //  - 4 bytes for len, nlen
        private const int PaddingSize = 5; 

        // max uncompressed deflate block size is 64K.
        private const int MaxUncompressedBlockSize = 65536;
 

        // null input means write an empty payload with formatting info. This is needed for the final block. 
        public void GetBlock(DeflateInput input, OutputBuffer output, bool isFinal) { 
            Debug.Assert(output != null);
            Debug.Assert(output.FreeBytes >= PaddingSize); 

            // determine number of bytes to write
            int count = 0;
            if (input != null) { 

                // allow space for padding and bits not yet flushed to buffer 
                count = Math.Min(input.Count, output.FreeBytes - PaddingSize - output.BitsInBuffer); 

                // we don't expect the output buffer to ever be this big (currently 4K), but we'll check this 
                // just in case that changes.
                if (count > MaxUncompressedBlockSize - PaddingSize) {
                    count = MaxUncompressedBlockSize - PaddingSize;
                } 
            }
 
            // write header and flush bits 
            if (isFinal) {
                output.WriteBits(FastEncoderStatics.BFinalNoCompressionHeaderBitCount, 
                                        FastEncoderStatics.BFinalNoCompressionHeader);
            }
            else {
                output.WriteBits(FastEncoderStatics.NoCompressionHeaderBitCount, 
                                        FastEncoderStatics.NoCompressionHeader);
            } 
 
            // now we're aligned
            output.FlushBits(); 

            // write len, nlen
            WriteLenNLen((ushort)count, output);
 
            // write uncompressed bytes
            if (input != null && count > 0) { 
                output.WriteBytes(input.Buffer, input.StartIndex, count); 
                input.ConsumeBytes(count);
            } 

        }

        private void WriteLenNLen(ushort len, OutputBuffer output) { 

            // len 
            output.WriteUInt16(len); 

            // nlen 
            ushort onesComp = (ushort)(~(ushort)len);
            output.WriteUInt16(onesComp);
        }
    } 
}

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

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