bencoding编码的解析器

1、BT客户端开始一个下载首先要处理的就是torrent文件.而torrent文件使用bencoding编码.所以实现bencoding编码的解析器，就是第一步工作.Bencoding is done as follows:Strings are length-prefixed base ten followed by a colon and the string. For example 4:spam corresponds to spam.Integers are represented by an i followed by the number in base 10 followed by

2、 an e. For example i3e corresponds to 3 and i-3e corresponds to -3. Integers have no size limitation. i-0e is invalid. All encodings with a leading zero, such as i03e, are invalid, other than i0e, which of course corresponds to 0.Lists are encoded as an l followed by their elements (also bencoded) f

3、ollowed by an e. For example l4:spam4:eggse corresponds to spam, eggs.Dictionaries are encoded as a d followed by a list of alternating keys and their corresponding values followed by an e. For example, d3:cow3:moo4:spam4:eggse corresponds to cow: moo, spam: eggs and d4:spaml1:a1:bee corresponds to

4、spam: a, b . Keys must be strings and appear in sorted order (sorted as raw strings, not alphanumerics).下面是实现的bencoding解码器的VC+源代码：/ BEncode.h: interface for the CBEncode class./#if !defined(AFX_BENCODE_H_4D0BB462_2AE0_45B3_8BE8_19D51B2DBB2E_INCLU DED_)#defineAFX_BENCODE_H_4D0BB462_2AE0_45B3_8BE8_19D

5、51B2DBB2E_INCLUDED_ #if _MSC_VER 1000#pragma once#endif / _MSC_VER 1000#pragma warning( disable : 4786 )#pragma warning( disable : 4355 )#include #include #include #include using namespace std;enum BEncodeParserErrorCodeenm_BEncodeErr_noerr = 0,/没有错误enm_BEncodeErr_errString,/错误的字符串enm_BEncodeErr_err

6、Int,/错 误的整型数据enm_BEncodeErr_errList,/错 误的歹。表enm_BEncodeErr_errDict,/错误的词典结构enm_BEncodeErr_End,/文 本结束enm_BEncodeErr_unknown/未 知错误；enum BEncodeObjectTypeenum_BEncodeType_Objectbase = 0,enum_BEncodeType_String,enum_BEncodeType_Int,enum_BEncodeType_List,enum_BEncodeType_Dict,；class CBEncodeObjectBasepub

7、lic:CBEncodeObjectBase(BEncodeObjectTypetype=enum_BEncodeType_Objectbase)m_type = type;clear();virtual CBEncodeObjectBase();void clear()szPos = NULL;m_error = enm_BEncodeErr_noerr;public:BEncodeObjectType m_type; /对象类型char * szPos; 对象在字符串中的位置int ilen;/对象的数据长度BEncodeParserErrorCode m_error;/错误值;class

8、 CBEncodeInt : public CBEncodeObjectBasepublic:CBEncodeInt() : CBEncodeObjectBase(enum_BEncodeType_Int) virtual CBEncodeInt()public:int m_iValue;/整型对象的值;class CBEncodeString : public CBEncodeObjectBasepublic:CBEncodeString() : CBEncodeObjectBase(enum_BEncodeType_String) m_szData =NULL;virtual CBEnco

9、deString()public:bool getstring(string & strValue)if(m_error = enm_BEncodeErr_noerr & m_szData)strValue.assign(m_szData,m_ilen); return true;return false;char * m_szData;int m_ilen;class CBEncodeList : public CBEncodeObjectBasepublic:CBEncodeList() : CBEncodeObjectBase(enum_BEncodeType_List) virtual

10、 CBEncodeList()clear(); void clear() list:iterator it;for(it = m_listObj.begin();it!=m_listObj.end();+it) delete (*it);m_listObj.clear();public:list m_listObj;class CBEncodeDict : public CBEncodeObjectBasepublic:CBEncodeDict() : CBEncodeObjectBase(enum_BEncodeType_Dict) virtual CBEncodeDict()clear()

11、;CBEncodeObjectBase* getvalue(const char * szName) map:iterator it = m_mapObj.find(szName); if(it != m_mapObj.end()return it-second;return NULL;void clear()list:iterator it;for(it = m_listObj.begin();it!=m_listObj.end();+it) delete (*it);m_listObj.clear();m_mapObj.clear();public:map m_mapObj;/list m

12、_listObj;/真正的对象保存在 list 中,list 是一个 name 对象一 个value对象.map只是一个映射表，引用了指针而已 ;class CBEncodepublic:bool readint(char *szCurPos,int & iendpos,list & listObj);bool readstring(char *szCurPos,int & iendpos,list & listObj);bool readlist(char *szCurPos,int & iendpos,list & listObj);bool readdict(char *szCurPos

13、,int & iendpos,list & listObj);bool parse(const char * szData);CBEncode();virtual CBEncode();void clear()listvCBEncodeObjectBase *:iterator it;for(it = m_listObj.begin();it!=m_listObj.end();+it) delete (*it);m_listObj.clear();public:listvCBEncodeObjectBase*m_listObj;CBEncodeObjectBase* m_plastObj ;/

14、解析出来的最后一个对象char * m_szTxt;#endif/ !defined(AFX_BENCODE_H_4D0BB462_2AE0_45B3_8BE8_19D51B2DBB2E_INCLUD ED_)/ BEncode.cpp: implementation of the CBEncode class./#include stdafx.h#include BEncode.h/ Construction/Destruction/CBEncode:CBEncode()m_plastObj = NULL;m_szTxt = NULL;CBEncode:CBEncode()clear();b

15、ool CBEncode:parse(const char *szData)if(szData = NULL|*szData=NULL) return false;clear();m_szTxt = (char*)szData;char * szCurPos = (char*)szData;int iendpos;while(*szCurPos)if(*szCurPos= i)if(!readint(szCurPos,iendpos,m_listObj)breaW/遇到任何错误都终止整个解析 szCurPos+=iendpos;else if(*szCurPos= l)if(!readlist

16、(szCurPos,iendpos,m_listObj) break;szCurPos+=iendpos;else if(*szCurPos= d)if(!readdict(szCurPos,iendpos,m_listObj) break;szCurPos+=iendpos;elseif(!readstring(szCurPos,iendpos,m_listObj) break;szCurPos+=iendpos;if(*szCurPos=0&m_plastObj-m_error = enm_BEncodeErr_noerr) return true;return false;从当前位置读取

17、一个字符串bool CBEncode:readstring(char *szCurPos,int & iendpos,list & listObj) char * szTmp = szCurPos;CBEncodeString * pNewString = new CBEncodeString;pNewString-szPos = szCurPos;char szLen20;int i = 0;while(*szTmp=0&*szTmp0) pNewString-m_szData = +szTmp;pNewString-m_ilen = ilen;szTmp+=ilen;elsepNewStr

18、ing-m_error = enm_BEncodeErr_errString; elsepNewString-m_error = enm_BEncodeErr_errString;listObj.push_back(pNewString);iendpos = szTmp-szCurPos;m_plastObj = pNewString;m_plastObj-ilen = iendpos;return pNewString-m_error = enm_BEncodeErr_noerr?true:false;读取一个整型数据bool CBEncode:readint(char *szCurPos,

19、int & iendpos,list & listObj) char * szTmp = szCurPos;CBEncodeInt * pNewInt= new CBEncodeInt;pNewInt-szPos = szCurPos;if(*szTmp = i)szTmp+;char szLen20;int i = 0;while(*szTmp=0&*szTmpm_iValue = atoi(szLen);+szTmp;elsepNewInt-m_error = enm_BEncodeErr_errInt;elsepNewInt-m_error = enm_BEncodeErr_errInt

20、;listObj.push_back(pNewInt);iendpos = szTmp-szCurPos;m_plastObj = pNewInt;m_plastObj-ilen = iendpos;return pNewInt-m_error = enm_BEncodeErr_noerr?true:false;读取一个列表bool CBEncode:readlist(char *szCurPos,int & iendpos,list & listObj) char * szTmp = szCurPos;CBEncodeList * pNewList= new CBEncodeList;pNe

21、wList-szPos = szCurPos;if(*szTmp = l)szTmp+;int ilistendpos;while(*szTmp!=e)if(*szTmp= i)if(!readint(szTmp,ilistendpos,pNewList-m_listObj)break;/遇到任何错误都终止整个解析szTmp+=ilistendpos;else if(*szTmp= l)if(!readlist(szTmp,ilistendpos,pNewList-m_listObj) break;szTmp+=ilistendpos;else if(*szTmp= d)if(!readdic

22、t(szTmp,ilistendpos,pNewList-m_listObj) break;szTmp+=ilistendpos;elseif(!readstring(szTmp,ilistendpos,pNewList-m_listObj) break;szTmp+=ilistendpos;if(*szTmp!=e|m_plastObj-m_error != enm_BEncodeErr_noerr) pNewList-m_error = enm_BEncodeErr_errList;elseszTmp+;elsepNewList-m_error = enm_BEncodeErr_errLi

23、st;listObj.push_back(pNewList);iendpos = szTmp-szCurPos;m_plastObj = pNewList;m_plastObj-ilen = iendpos;return pNewList-m_error = enm_BEncodeErr_noerr?true:false;读取一个字典bool CBEncode:readdict(char *szCurPos,int & iendpos,list & listObj) char * szTmp = szCurPos;CBEncodeDict * pNewDict= new CBEncodeDic

24、t;pNewDict-szPos = szCurPos;if(*szTmp = d)szTmp+;int ilistendpos;string strname;while(*szTmp!=e)if(!readstring(szTmp,ilistendpos,pNewDict-m_listObj) break;if(m_plastObj-m_type !=enum_BEncodeType_String) break;strname.assign(CBEncodeString *)m_plastObj)-m_szData,(CBEncodeString *)m_plastObj)-m_ilen);szTmp+=ilistendpos;if(*szTmp= i)if(!readint(szTmp,ilistendpos,