CRC校驗(yàn)實(shí)驗(yàn)報(bào)告

1、實(shí)驗(yàn)三 CRC校驗(yàn)一、CRC校驗(yàn)碼的基本原理編碼過程：CRC校驗(yàn)碼的編碼方法是用待發(fā)送的二進(jìn)制數(shù)據(jù)t(x)除以生成多項(xiàng)式g(x)，將最后的余數(shù)作為CRC校驗(yàn)碼。其實(shí)現(xiàn)步驟如下： 1 設(shè)待發(fā)送的數(shù)據(jù)塊是m位的二進(jìn)制多項(xiàng)式t(x)，生成多項(xiàng)式 為r階的g(x)。在數(shù)據(jù)塊的末尾添加r個(gè)0，數(shù)據(jù)塊的長(zhǎng)度增 加到m+r位。 2 用生成多項(xiàng)式g（x）去除 ，求得余數(shù)為階數(shù)為r-1的二進(jìn)制 多項(xiàng)式y(tǒng)(x)。此二進(jìn)制多項(xiàng)式y(tǒng)(x)就是t(x)經(jīng)過生成多項(xiàng)式 g(x)編碼的CRC校驗(yàn)碼。 3 將y(x)的尾部加上校驗(yàn)碼，得到二進(jìn)制多項(xiàng)式 。 就是包含 了CRC校驗(yàn)碼的待發(fā)送字符串。解碼過程： 從CRC的編碼規(guī)則

2、可以看出，CRC編碼實(shí)際上是將代發(fā)送的m位二進(jìn)制多項(xiàng)式t(x)轉(zhuǎn)換成了可以被g(x)除盡的m+r位二進(jìn)制多項(xiàng)式所以解碼時(shí)可以用接收到的數(shù)據(jù)去除g（x），如果余數(shù)位零，則表示傳輸過程沒有錯(cuò)誤；如果余數(shù)不為零，則在傳輸過程中肯定存在錯(cuò)誤。許多CRC的硬件解碼電路就是按這種方式進(jìn)行檢錯(cuò)的。同時(shí),可以看做是由t（x）和CRC校驗(yàn)碼的組合，所以解碼時(shí)將接收到的二進(jìn)制數(shù)據(jù)去掉尾部的r位數(shù)據(jù)，得到的就是原始數(shù)據(jù)。解碼過程示例：運(yùn)行結(jié)果：附錄（實(shí)現(xiàn)代碼）：using System;using System.Collections.Generic;using System.Text;namespace CRC

3、public abstract class Change / <summary> / 字節(jié)數(shù)組轉(zhuǎn)進(jìn)制 / </summary> / <param name="bytes">字節(jié)數(shù)組</param> / <param name="b1">字節(jié)數(shù)組長(zhǎng)度</param> public static string ByteToHex(byte bytes, int b1) string returnStr = "" if (bytes != null) for (int

4、i = 0; i < b1; i+) returnStr += bytesi.ToString("x2").ToUpper(); return returnStr; / <summary> / 16進(jìn)制轉(zhuǎn)字節(jié)數(shù)組 / </summary> / <param name="hexStr">16進(jìn)制數(shù)</param> public static byte HexToByte(string hexStr) hexStr = hexStr.Replace(" ", "")

5、; if (hexStr.Length % 2) != 0) hexStr += " "/空格 byte bytes = new bytehexStr.Length / 2; for (int i = 0; i < bytes.Length; i+) bytesi = Convert.ToByte(hexStr.Substring(i * 2, 2), 16); return bytes; / <summary> / 字符串轉(zhuǎn)進(jìn)制 / </summary> / <param name="str">字符串</

6、param> / <returns></returns> public static string StrToHex(string str) if (str = "") return "" byte bTemp = System.Text.Encoding.Default.GetBytes(str); return ByteToHex(bTemp, bTemp.Length); / <summary> / 16進(jìn)制轉(zhuǎn)字符串 / </summary> / <param name="str

7、">16進(jìn)制</param> / <returns></returns> public static string HexToStr(string str) byte bytes = new bytestr.Length; bytes = HexToByte(str); return Encoding.Default.GetString(bytes); namespace CRC /哈夫曼樹 150 / 結(jié)點(diǎn)類Node的定義如下： public class Node private int weight; /結(jié)點(diǎn)權(quán)值 private int

8、lChild; /左孩子結(jié)點(diǎn) private int rChild; /右孩子結(jié)點(diǎn) private int parent; /父結(jié)點(diǎn) /結(jié)點(diǎn)權(quán)值屬性 public int Weight get return weight; set weight = value; /左孩子結(jié)點(diǎn)屬性 public int LChild get return lChild; set lChild = value; /右孩子結(jié)點(diǎn)屬性 public int RChild get return rChild; set rChild = value; /父結(jié)點(diǎn)屬性 public int Parent get return

9、parent; set parent = value; /構(gòu)造器 public Node() weight = 0;lChild = -1; rChild = -1; parent = -1; /構(gòu)造器 public Node(int w, int lc, int rc, int p) weight = w; lChild = lc; rChild = rc; parent = p; public class HuffmanTree private List<Node> data = new List<Node>(); /結(jié)點(diǎn)數(shù)組 private int leafNum

10、; /葉子結(jié)點(diǎn)數(shù)目 /索引器 public Node thisint index get return dataindex; set dataindex = value; /葉子結(jié)點(diǎn)數(shù)目屬性public int LeafNum public int LeafNum get return leafNum; set leafNum = value; /構(gòu)造器 public HuffmanTree() public HuffmanTree(List<NumKindchar> m_NumKind) leafNum = m_NumKind.Count; for (int j = 0; j &

11、lt; 2 * m_NumKind.Count - 1; j+)/n中字符共需要2n-1個(gè)節(jié)點(diǎn) Node databuff = new Node(); if (j < this.leafNum) databuff.Weight = m_NumKindj.num; data.Add(databuff);/每創(chuàng)建一個(gè)節(jié)點(diǎn)將節(jié)點(diǎn)加入節(jié)點(diǎn)數(shù)組data當(dāng)中 public List<Node> Create() int max1, max2, tmp1, tmp2; /處理n個(gè)葉子結(jié)點(diǎn)，建立哈夫曼樹 for (int i = 0; i < this.leafNum - 1; +i)

12、 max1 = max2 = Int32.MaxValue; tmp1 = tmp2 = 0; /在全部結(jié)點(diǎn)中找權(quán)值最小的兩個(gè)結(jié)點(diǎn) for (int j = 0; j < this.leafNum + i; +j) if (dataj.Weight < max1) && (dataj.Parent = -1) max2 = max1; tmp2 = tmp1; tmp1 = j; max1 = dataj.Weight; else if (dataj.Weight < max2) && (dataj.Parent = -1) max2 = dataj.Weight; tmp2 = j; datatmp1.Parent = this.leafNum + i; datatmp2.Parent = this.leafNum + i; datathis.leafNum + i.Weight = datatmp1.Weight + datatmp2.Weight; datathis.leafNum + i.LChild = tmp1; datathis.leafNum + i.RChild = tmp2; return data; public class NumKindchar public char let