_ScatterGatherBuffers.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / FX-1434 / FX-1434 / 1.0 / untmp / whidbey / REDBITS / ndp / fx / src / Net / System / Net / _ScatterGatherBuffers.cs / 1 / _ScatterGatherBuffers.cs
                        

                        
                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//----------------------------------------------------------------------------- 

namespace System.Net { 
    using System; 
    using System.Collections;
 
    internal class ScatterGatherBuffers {

        private MemoryChunk headChunk; // = null;
        private MemoryChunk currentChunk; // = null; 

        private int nextChunkLength = 1024; // this could be customized at construction time 
        private int totalLength; // = 0; 
        private int chunkCount; // = 0;
 
        internal ScatterGatherBuffers() {
        }

        internal ScatterGatherBuffers(long totalSize) 
        {
            // We know up front how much data is to be written. 
            if (totalSize > 0) 
            {
                currentChunk = AllocateMemoryChunk(totalSize > Int32.MaxValue ? Int32.MaxValue : (int) totalSize); 
            }
        }

        internal BufferOffsetSize[] GetBuffers() { 
            if (Empty) {
                return null; 
            } 
            GlobalLog.Print("ScatterGatherBuffers#" + ValidationHelper.HashString(this) + "::ToArray() chunkCount:" + chunkCount.ToString());
            BufferOffsetSize[] array = new BufferOffsetSize[chunkCount]; 
            int index = 0;
            MemoryChunk thisMemoryChunk = headChunk;
            while (thisMemoryChunk!=null) {
                GlobalLog.Print("ScatterGatherBuffers#" + ValidationHelper.HashString(this) + "::ToArray() index:" + index.ToString() + " size:" + thisMemoryChunk.FreeOffset); 
                //
                // buffer itself is referenced by the BufferOffsetSize struct, data is not copied 
                // 
                array[index] = new BufferOffsetSize(thisMemoryChunk.Buffer, 0, thisMemoryChunk.FreeOffset, false);
                index++; 
                thisMemoryChunk = thisMemoryChunk.Next;
            }
            return array;
        } 

        private bool Empty { 
            get { 
                return headChunk==null || chunkCount==0;
            } 
        }

        internal int Length {
            get { 
                return totalLength;
            } 
        } 

        internal void Write(byte[] buffer, int offset, int count) { 
            GlobalLog.Print("ScatterGatherBuffers#" + ValidationHelper.HashString(this) + "::Add() count:" + count.ToString());
            while (count > 0) {
                //
                // compute available space in current allocated buffer (0 if there's no buffer) 
                //
                int available = Empty ? 0 : currentChunk.Buffer.Length - currentChunk.FreeOffset; 
                GlobalLog.Assert(available >= 0, "ScatterGatherBuffers::Add()|available < 0"); 
                //
                // if the current chunk is is full, allocate a new one 
                //
                if (available==0) {
                    // ask for at least count bytes so that we need at most one allocation
                    MemoryChunk newChunk = AllocateMemoryChunk(count); 
                    if (currentChunk!=null) {
                        currentChunk.Next = newChunk; 
                    } 
                    //
                    // move ahead in the linked list (or at the beginning if this is the fist buffer) 
                    //
                    currentChunk = newChunk;
                }
                int copyCount = count < available ? count : available; 

                Buffer.BlockCopy( 
                    buffer,                     // src 
                    offset,                     // src index
                    currentChunk.Buffer,        // dest 
                    currentChunk.FreeOffset,    // dest index
                    copyCount );                // total size to copy

                // 
                // update offsets and counts
                // 
                offset += copyCount; 
                count -= copyCount;
                totalLength += copyCount; 
                currentChunk.FreeOffset += copyCount;
            }
            GlobalLog.Print("ScatterGatherBuffers#" + ValidationHelper.HashString(this) + "::Add() totalLength:" + totalLength.ToString());
        } 

        private MemoryChunk AllocateMemoryChunk(int newSize) { 
            if (newSize > nextChunkLength) { 
                nextChunkLength = newSize;
            } 
            MemoryChunk newChunk = new MemoryChunk(nextChunkLength);
            if (Empty) {
                headChunk = newChunk;
            } 
            //
            // next time allocate twice as much. check fot possible overflows 
            // 
            nextChunkLength *= 2;
            // 
            // update number of chunks in the linked list
            //
            chunkCount++;
            GlobalLog.Print("ScatterGatherBuffers#" + ValidationHelper.HashString(this) + "::AllocateMemoryChunk() chunkCount:" + chunkCount.ToString() + " nextChunkLength:" + nextChunkLength.ToString()); 
            return newChunk;
        } 
 
        private class MemoryChunk {
            internal byte[] Buffer; 
            internal int FreeOffset; // = 0
            internal MemoryChunk Next; // = null
            internal MemoryChunk(int bufferSize) {
                Buffer = new byte[bufferSize]; 
            }
        } 
 
    } // class ScatterGatherBuffers
 


} // namespace System.Net

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