在 stream流和 byte[] 中查找(搜索)指定字符串

约定不等于承诺〃 2024-02-17 23:22 30阅读 0赞

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