C++判断JSON字符串的合法性

写了一些，被证明有点非时间，不太符合业务的需求，留贴纪念吧。

json-format-check.h

#ifndef JSON_FORMAT_CHECK#define JSON_FORMAT_CHECK#include <iostream>#include <string>using namespace std;class JsonString{public:typedef const char* Location;JsonString();/* 检测json字符串格式是否合法 */bool CheckFormat(const char *begin, const char *end);private:enum TokenType{tokenEndOfStream = 0,tokenObjectBegin,tokenObjectEnd,tokenArrayBegin,tokenArrayEnd,tokenString,tokenNumber,tokenTrue,tokenFalse,tokenNull,tokenArraySeparator,tokenMemberSeparator,tokenError};class Token{public:TokenType type_;};private:void SkipSpace();char GetNextChar();bool Match(Location pattern, int patternLength);bool ReadToken(Token &token);bool ReadString();void ReadNumber();bool ReadValue();bool ReadObject(Token &token);bool ReadArray(Token &token);private:Location begin_;Location end_;Location current_;/* 用于记录对象的数量 */int objnum;};#endif//JSON_FORMAT_CHECK

json-format-check.cpp

#include "json-format-check.h"JsonString::JsonString(){objnum = 0;}/* 验证json字符串的合法性 */bool JsonString::CheckFormat(const char* strbegin, const char *strend){begin_   = strbegin;end_     = strend;current_ = begin_;bool succssful = ReadValue();if(objnum == 0){return false;}return succssful;}/* 跳过空白字符 */void JsonString::SkipSpace(){while(current_ != end_){char c = *current_;if(c == ' ' || c == '\t' || c == '\r' || c == '\n'){++current_;}else{break;}}}/* 获得下一个字符 */char JsonString::GetNextChar(){if(current_ == end_){return 0;}return *current_++;}/* 字符串匹配 */bool JsonString::Match(Location pattern, int patternlength){if((end_ - current_) < patternlength ){return false;}int index = patternlength;while(index --){if(current_[index] != pattern[index] ){return false;}}current_ += patternlength;return true;}/* 读取字符串 */bool JsonString::ReadString(){char c = 0;while(current_ != end_){c= GetNextChar();if( c == '\\'){c = GetNextChar();}else if( c == '"'){break;}}return (c == '"');}/* */void JsonString::ReadNumber(){while(current_ != end_){if(!(*current_ >= '0' && *current_ <= '9')&& !(*current_ == '.' || *current_ == 'e'|| *current_ == 'E' || *current_ == '+'|| *current_ == '-')){break;}++current_;}}bool JsonString::ReadToken( Token &token){SkipSpace();char c = GetNextChar();SkipSpace();if(c == ',' && *current_ == '}'){return false;}bool ok = true;switch(c){case '{':token.type_ = tokenObjectBegin;break;case '}':token.type_ = tokenObjectEnd;break;case '[':token.type_ = tokenArrayBegin;break;case ']':token.type_ = tokenArrayEnd;break;case '"':token.type_ = tokenString;ok = ReadString();break;case '0':case '1':case '2':case '3':case '4':case '5':case '6':case '7':case '8':case '9':case '-':token.type_ = tokenNumber;ReadNumber();break;case 't':token.type_ = tokenTrue;ok = Match( "rue", 3 );break;case 'f':token.type_ = tokenFalse;ok = Match( "alse", 4 );break;case 'n':token.type_ = tokenNull;ok = Match( "ull", 3 );break;case ',':token.type_ = tokenArraySeparator;break;case ':':token.type_ = tokenMemberSeparator;break;case 0:token.type_ = tokenEndOfStream;break;default:ok = false;break;}if ( !ok )token.type_ = tokenError;return true;}bool JsonString::ReadObject(Token &tokenstart){Token tokenname;while(ReadToken(tokenname)){if(tokenname.type_ == tokenObjectEnd){return true;}if(tokenname.type_ != tokenString){break;}Token colon;if(!ReadToken(colon) || colon.type_ != tokenMemberSeparator){return false;}bool ok = ReadValue();if(!ok){return false;}Token comma;if(!ReadToken(comma) ||(comma.type_  != tokenObjectEnd && comma.type_ != tokenArraySeparator)){return false;}if(comma.type_ == tokenObjectEnd){return true;}}return false;}bool JsonString::ReadArray(Token &tokenstart){SkipSpace();if(*current_ == ']'){Token endArray;ReadToken(endArray);return true;}int index = 0;while(true){bool ok = ReadValue();if(!ok){return false;}Token token;ok = ReadToken(token);bool badTokentype = (token.type_ == tokenArraySeparator&& token.type_ == tokenArrayEnd);if( !ok & badTokentype){return false;}if(token.type_ == tokenArrayEnd){break;}}return true;}bool JsonString::ReadValue(){Token token;ReadToken(token);bool successful = true;switch(token.type_){case tokenObjectBegin:objnum++;successful = ReadObject(token);break;case tokenArrayBegin:successful = ReadArray(token);break;case tokenNumber:case tokenString:case tokenTrue:case tokenFalse:case tokenNull:break;default:return false;}return successful;}