Code:
/ DotNET / DotNET / 8.0 / 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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