标签：The ++ erro nat private cat bytes style syntax
来源 https://wangye.org/blog/archives/5/
可能很多人听说过Base64编码，很少有人听说过Base24编码，Base24编码主要应用在序列号生成上，其实基本的算法思想都是一样的，只是编码的模式有点变化。
Base64所对应的编码表是
ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=
共计64位。
而Base24所对应的编码表是
BCDFGHJKMPQRTVWXY2346789
共计24位，这里主要去掉了一些对于序列号来说不容易识别和容易混淆的字符。
具体算法网上都有介绍我就不再赘述，下面直接谈怎么编码实现吧:-)
对于Base64算法的C语言实现，大家可以参考Bob Trower的经典开源项目b64.c，网址是http://base64.sourceforge.net/。
在这里我要谈的是如何用ASP进行Base64编码，网上搜索出的一大堆算法不是太复杂就是运行不准确，其实ASP的Base64编码可以很简单，当然要用到服务器的一个COM组件XmlDom，具体思路是这样的，首先创建个临时的节点tmp，然后给结点tmp，设置datatype = “bin.base64″，这样就可以进行相应的编解码了，对于文本字符串的编解码还要用ADODB.Stream进行一次编码转换。
Base64的ASP实现：
Class CBase64 Private objXmlDom Private objXmlNode ‘ GetObjectParam() 这个函数实现参考了开源项目PJBlog Private Function GetObjectParam() On Error Resume Next Dim Temp GetObjectParam = "Microsoft.XMLDOM" Err = 0 Dim TmpObj Set TmpObj = Server.CreateObject(GetObjectParam) Temp = Err.Number If Temp = 1 Or Temp = -2147221005 Then GetObjectParam = "Msxml2.DOMDocument.5.0" End If Err.Clear Set TmpObj = Nothing Err = 0 End Function Private Sub Class_Initialize() Set objXmlDom = Server.CreateObject(GetObjectParam()) End Sub Private Sub Class_Terminate() Set objXmlDom = Nothing End Sub Public Function encode(AnsiCode) encode = "" Set objXmlNode = objXmlDom.createElement("tmp") objXmlNode.datatype = "bin.base64" objXmlNode.nodeTypedvalue = AnsiCode encode = objXmlNode.Text Set objXmlNode = Nothing End Function Public Function decode(base64Code) On Error Resume Next decode = "" Set objXmlNode = objXmlDom.createElement("tmp") objXmlNode.datatype = "bin.base64" objXmlNode.Text = base64Code decode = objXmlNode.nodeTypedvalue Set objXmlNode = Nothing If Err Then Err.Clear End If End Function ‘ 以下函数编码字符串 Public Function encodeText(ByVal str) On Error Resume Next Dim ado, r: r = "" If str <> "" Then Set ado = Server.CreateObject("ADODB.Stream") With ado .Charset = "gb2312" .Type = 2 If .State = 0 Then .Open .WriteText str .Position = 0 .Type = 1 r = encode(.Read(-1)) .Close End With Set ado = Nothing End If If Err Then Err.Clear: r = "" encodeText = r End Function ‘ 以下函数解码字符串 Public Function decodeText(ByVal str) On Error Resume Next Dim ado, r: r = "" If str <> "" Then Set ado = Server.CreateObject("ADODB.Stream") With ado .Charset = "gb2312" .Type = 1 If .State = 0 Then .Open .Write (decode(str)) .Position = 0 .Type = 2 r = .ReadText(-1) .Close End With Set ado = Nothing End If If Err Then Err.Clear: r = "" decodeText = r End Function End Class
写到这里想起以前项目里改写过一段Base64和16进制互转的代码，在这里与大家分享下。
‘ Base64转16进制 Function B64ToHex(ByVal strContent) Dim i,strReturned, b64pad, _ b64map, chTemp, intLocate, k , slop strReturned = "" : k = 0 b64map="ABCDEFGHIJKLMNOPQRSTUVWXYZ" &_ "abcdefghijklmnopqrstuvwxyz0123456789+/" b64pad="=" For i=0 To Len(strContent)-1 chTemp = Mid(strContent, i+1, 1) If chTemp = b64pad Then Exit For intLocate = InStr(1, b64map, chTemp, 0)-1 If intLocate > -1 Then Select Case K Case 0 strReturned = strReturned &_ Int2Char(Int(intLocate / 4)) slop = intLocate And 3 : k = 1 Case 1 strReturned = strReturned &_ Int2Char( (slop * 4) Or (Int(intLocate / 16)) ) slop = intLocate And &h0f : k = 2 Case 2 strReturned = strReturned &_ Int2Char(slop) & Int2Char(Int(intLocate / 4)) slop = intLocate And 3 : k=3 Case Else strReturned = strReturned &_ Int2Char( (slop * 4) Or (Int(intLocate / 16)) ) &_ Int2Char(intLocate And &h0f) k = 0 End Select End If Next If k=1 Then strReturned = strReturned & Int2Char(slop * 4) B64ToHex = strReturned End Function ‘ 16进制转Base64 Function HexToB64(ByVal strContent) Dim i, c, strReturned, b64map, b64pad, intLen b64map="ABCDEFGHIJKLMNOPQRSTUVWXYZ" &_ "abcdefghijklmnopqrstuvwxyz0123456789+/" b64pad="=" intLen = Len(strContent) For i=0 To intLen-3 Step 3 c=Clng("&h" & Mid(strContent,i+1,3)) strReturned = strReturned &_ Mid(b64map, Int(c / 64 +1), 1) &_ Mid(b64map, (c And 63)+1, 1) Next If i+1=intLen Then c =Clng("&h" & Mid(strContent,i+1,1)) strReturned = strReturned & Mid(b64map, c * 4 + 1, 1) ElseIf i+2=intLen Then c =Clng("&h" & Mid(strContent,i+1,2)) strReturned = strReturned & Mid(b64map, Int(c / 4) + 1, 1) &_ Mid(b64map, (c And 3)*16+1, 1) End If While (Len(strReturned) And 3) >0 strReturned = strReturned & b64pad Wend HexToB64 = strReturned End Function
有关Base24的代码实现网上也有很多，这里给出两种不同程序语言的实现供参考。
Base24的C语言实现
static const char sel[] = { ‘B‘,‘C‘,‘D‘,‘F‘,‘G‘, ‘H‘,‘J‘,‘K‘,‘M‘,‘P‘, ‘Q‘,‘R‘,‘T‘,‘V‘,‘W‘, ‘X‘,‘Y‘,‘2‘,‘3‘,‘4‘, ‘6‘,‘7‘,‘8‘,‘9‘, ‘\0‘}; char *b24e(char *buf, unsigned char *byst, size_t sizeOfBytes) { int i = 0; unsigned char *p = byst; while ((size_t)(i = (p-byst)) < sizeOfBytes) { buf[2*i] = sel[((*p) >> 4)]; buf[(2*i)+1] = sel[23 - ((*p) & 0x0f)]; p++; } buf[(2*i)+1] = ‘\0‘; return buf; } unsigned char *b24d(unsigned char *buf, char *str, size_t countOfChars) { size_t i; char *p = str; char *loc[2]; unsigned char n[2]; if (countOfChars % 2) return NULL; for (i = 0; i < (countOfChars>>1); i++) { loc[0] = strchr( sel, str[2*i] ); loc[1] = strchr( sel, str[ ( 2*i ) + 1 ] ); if (loc[0] == NULL || loc[1] == NULL) return NULL; n[0] = (unsigned char)( loc[0] - sel ); n[1] = 23 - (unsigned char)( loc[1] - sel ); buf[i] = (unsigned char)((n[0] << 4) | n[1]); } return buf; }
后来由于项目需要，我特地改写了C#版。
public static class Base24 { private static string sel = "BCDFGHJKMPQRTVWXY2346789"; public static string Encode(string Text) { int i = 0; int Pos = 0; char []Buf = new char[Text.Length<<1]; while ((i = Pos) < Text.Length) { Buf[i<<1] = sel[(Text[Pos]) >> 4]; Buf[(i<<1) + 1] = sel[23 - (Text[Pos] & 0x0F)]; Pos++; } return new string(Buf); } public static string Decode(string Text) { if (Text.Length % 2 != 0) return null; int [] NPos = new int[2]; char[] N = new char[2]; char[] Buf = new char[Text.Length >> 1]; for (int i = 0; i < (Text.Length >> 1); i++) { NPos[0] = sel.IndexOf(Text[ i<<1 ]); NPos[1] = 23 - sel.IndexOf(Text[(i<<1) + 1]); if (NPos[0] < 0 || NPos[1] < 0) { return null; } Buf[i] = ((char)((NPos[0] << 4) | NPos[1])); } return new string(Buf); } }
标签：The ++ erro nat private cat bytes style syntax
原文地址：https://www.cnblogs.com/lsgxeva/p/12021597.html
