/// <summary> /// ChunkHelper 帮助将序列分成若干块。 /// /// 如果 totalItemCount 是 11，chunkSize 是 5，则： /// chunk[0] 0, 1, 2, 3, 4 /// chunk[1] 5, 6, 7, 8, 9 /// chunk[2] 10 /// </summary> public class ChunkHelper { /// <summary> /// /// </summary> /// <param name="totalItemCount"> 项目总数 </param> /// <param name="chunkSize"> 块大小 </param> public ChunkHelper( int totalItemCount, int chunkSize) { if (totalItemCount < 0 ) { throw new ArgumentOutOfRangeException( " itemCount " , totalItemCount, " itemCount 不能小于 0 " ); } if (chunkSize < 1 ) { throw new ArgumentOutOfRangeException( " chunkSize " , chunkSize, " chunkSize 不能小于 1 " ); } this .TotalItemCount = totalItemCount; this .ChunkSize = chunkSize; int i = this .TotalItemCount % this .ChunkSize == 0 ? 0 : 1 ; this .ChunkCount = this .TotalItemCount / this .ChunkSize + i; } /// <summary> /// 获取项目总数。 /// </summary> public int TotalItemCount { get ; private set ;} /// <summary> /// 获取块大小。 /// </summary> public int ChunkSize { get ; private set ; } /// <summary> /// 指定项目索引，获取此项目所属的分块索引。 /// </summary> /// <param name="itemIndex"></param> /// <returns></returns> public int GetChunkIndex( int itemIndex) { if (itemIndex < 0 || itemIndex >= TotalItemCount) { throw new ArgumentOutOfRangeException(); } return itemIndex / ChunkSize; } /// <summary> /// 获取分块数量，如果 TotalItemCount 为 0， 则返回值为 0，而不是 1。 /// </summary> public int ChunkCount { get ; private set ;} /// <summary> /// 获取指定的分块信息。 /// </summary> /// <param name="chunkIndex"></param> /// <returns></returns> public Chunk GetChunk( int chunkIndex) { if (chunkIndex < 0 || chunkIndex >= ChunkCount) { throw new ArgumentOutOfRangeException(); } int startItemIndex = chunkIndex * ChunkSize; int itemCountInChunk = ChunkSize; // 如果大于项目总数，则是最后一块 if (startItemIndex + itemCountInChunk > TotalItemCount) { itemCountInChunk = TotalItemCount % ChunkSize; } return new Chunk(chunkIndex, startItemIndex, itemCountInChunk); } } /// <summary> /// Chunk 表示一个分块。 /// </summary> public struct Chunk { /// <summary> /// 本块的索引。 /// </summary> public int ChunkIndex { get ; private set ;} /// <summary> /// 本块第一个项目在整个序列中的索引。 /// </summary> public int FirstItemIndex{ get ; private set ;} /// <summary> /// 本块的项目数。 /// </summary> public int ItemCount { get ; private set ;} /// <summary> /// 实例化 Chunk /// </summary> /// <param name="chunkIndex"></param> /// <param name="firstItemIndex"></param> /// <param name="itemCountInChunk"></param> internal Chunk( int chunkIndex, int firstItemIndex, int itemCountInChunk) : this () { this .ChunkIndex = chunkIndex; this .FirstItemIndex = firstItemIndex; this .ItemCount = itemCountInChunk; } }