在 stream流 和 byte[] 中查找(搜索)指定字符串
这里注重看的是两个 Search 的扩展方法，一个是 stream 类型的扩展，另一个是 byte[] 类型的扩展，
如果大家有更好的“算法”，请给回复，我们一起优化！
-- 常用扩展代码，需要这部分代码的支持！
using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.IO; using System.Drawing;
namespace Ims.Bll { /// <summary> /// stream 、 string 、byte[] 间的转换扩展方法类 /// </summary> public static class StreamExtend { #region Stream 扩展 /// <summary> /// Stream Stream 转换为 byte 数组 /// </summary> /// <returns></returns> public static byte[] ToByteArray(this Stream stream) { byte[] bytes = new byte[stream.Length]; stream.Read(bytes, 0, bytes.Length); // 设置当前流的位置为流的开始 stream.Seek(0, SeekOrigin.Begin); return bytes; } /// <summary> /// Stream 转换为 image 图片 /// </summary> /// <returns></returns> public static Image ToImage(this Stream stream) { Image img = new Bitmap(stream); return img; } /// <summary> /// Stream 转换为 string ,使用 Encoding.Default 编码 /// </summary> /// <returns></returns> public static string ToStr(this Stream stream) { return System.Text.Encoding.Default.GetString(stream.ToByteArray()); } /// <summary> /// 在当前流中搜索指定的 byte[] /// </summary> /// <param name="arr"></param> /// <param name="key">搜索关键字</param> /// <param name="beginPosition">搜索开始位置</param> /// <returns>如果存在则返回byte[]在流中首次出现的位置，否则返回 -1</returns> public static long Search(this Stream stream, long beginPosition, byte[] key) { if (stream == null || stream.Length <= beginPosition) return -1;
if (key == null || stream.Length < key.Length) return -1;
long i=-1; long j = -1; int currentByte = int.MinValue; for(i=beginPosition;i<stream.Length;i++) { if (stream.Length < key.Length + i) break;
stream.Seek(i, SeekOrigin.Begin); for (j = 0; j < key.Length; j++) { currentByte = stream.ReadByte(); if (currentByte != key[j]) break; } if (j == key.Length) return i;
if(currentByte == -1) break; } return -1; } #endregion
#region byte[] 扩展 /// <summary> /// byte[] 转换为 stream 流 /// </summary> /// <returns></returns> public static Stream ToStream(this byte[] arr) { Stream stream = new MemoryStream(arr); // 设置当前流的位置为流的开始 stream.Seek(0, SeekOrigin.Begin); return stream; } /// <summary> /// byte[] 转换为 Image /// </summary> /// <returns></returns> public static Image ToImage(this byte[] arr) { return Image.FromStream(arr.ToStream()); } /// <summary> /// 转换为 string，使用 Encoding.Default 编码 /// </summary> /// <returns></returns> public static string ToStr(this byte[] arr) { return System.Text.Encoding.Default.GetString(arr); } /// <summary> /// 搜索 /// </summary> /// <param name="arr"></param> /// <param name="key">搜索关键字</param> /// <param name="beginPos">搜索开始位置</param> /// <returns></returns> public static int Search(this byte[] arr, int beginPosition, byte[] key) { if (arr == null || arr.Length <= beginPosition) return -1;
if (key == null || arr.Length < key.Length) return -1;
int i = -1; int j = -1; for (i = beginPosition; i < arr.Length; i++) { if (arr.Length < key.Length + i) break;
for (j = 0; j < key.Length; j++) { if (arr[i+j] != key[j]) break; } if (j == key.Length) return i; } return -1; } #endregion
#region string 扩展 /// <summary> /// string 转换为 byte[] /// </summary> /// <returns></returns> public static byte[] ToByteArray(this string str) { return System.Text.Encoding.Default.GetBytes(str); } /// <summary> /// string 转换为 Stream /// </summary> /// <returns></returns> public static Stream ToStream(this string str) { Stream stream = new MemoryStream(str.ToByteArray()); // 设置当前流的位置为流的开始 stream.Seek(0, SeekOrigin.Begin); return stream; } #endregion } }
------------------------
-- 测试脚本
byte[] arr = "0123456789111".ToByteArray(); byte[] key1 = "123".ToByteArray(); byte[] key2 = "678".ToByteArray(); byte[] key3 = "911".ToByteArray(); byte[] key4 = "111".ToByteArray(); //流内搜索测试 Stream sm = arr.ToStream(); long index1 = sm.Search(0, key1); long index2 = sm.Search(0, key2); long index3 = sm.Search(0, key3); long index4 = sm.Search(0, key4); //byte[]内搜索测试 long index10 = arr.Search(0, key1); long index20 = arr.Search(0, key2); long index30 = arr.Search(0, key3); long index40 = arr.Search(0, key4);
-----
技术支持：http://blog.csdn.net/xxj_jing
转载于:https://www.cnblogs.com/xxj-jing/archive/2012/04/26/2890072.html
