轻量级的C++解析Json：TinyJson

小咪咪 2022-05-17 05:46 343阅读 0赞

只要这一个头文件即可，的确是轻量级的，而且跨平台。地址：[https://github.com/button-chen/tinyjson][https_github.com_button-chen_tinyjson]

/** tinyjson.h */
    /**
    *
    *	tiny::TinyJson library
    *	Copyright 2017 Button
    *
    */
    
    #ifndef TINY_JSON_H_
    #define TINY_JSON_H_
    
    #include <string>
    #include <sstream>
    #include <map>
    #include <vector>
    #include <algorithm>
    #include <iostream>
    
    namespace tiny {
    
    	/**
    	* 无类型，解析时确认
    	*
    	*/
    	class Value
    	{
    	public:
    		Value() 
    		{
    			value_.clear();
    			nokey_ = false;
    		}
    		Value(std::string val) : value_(val) 
    		{
    			if (value_ == "") 
    			{
    				value_.clear();
    				nokey_ = true;
    			}
    			else 
    			{
    				nokey_ = false;
    			}
    		}
    		~Value() {}
    
    	public:
    		std::string value() 
    		{ 
    			return value_; 
    		}
    		template<typename R> 
    		R GetAs() 
    		{
    			std::istringstream iss(value_);
    			R v;
    			iss >> v;
    			return v;
    		}
    
    
    		template<typename V> 
    		void Set(V v) 
    		{
    			std::ostringstream oss;
    			if (nokey_) 
    			{
    				oss << v;
    			}
    			else 
    			{
    				oss << "\"" << value_ << "\"" << ":" << v;
    			}
    			value_ = oss.str();
    		}
    
    		template<typename T>
    		void Push(T& v) 
    		{
    			std::ostringstream oss;
    			if (v.get_nokey()) 
    			{
                    oss << v.WriteJson(0);
    			}
    			else 
    			{
                    oss << v.WriteJson(1);
    			}
    			value_ = oss.str();
    		}
    
    	private:
    		std::string value_;
    		bool nokey_;
    	};
    
            template<> bool Value::GetAs() 
    		{ 
    			return value_ == "true" ? true : false; 
    		}
            template<> std::string Value::GetAs() 
    		{ 
    			return value_; 
    		}
            template<>
            void Value::Set(std::string v) 
    		{
                    std::ostringstream oss;
                    if (nokey_) 
    				{
                            oss << "\"" << v << "\"";
                    }
                    else 
    				{
                            oss << "\"" << value_ << "\"" << ":" << "\"" << v << "\"";
                    }
                    value_ = oss.str();
            }
    
            template<>
            void Value::Set(const char* v) 
    		{
                    Set(std::string(v));
            }
    
            template<>
            void Value::Set(bool v) 
    		{
                    std::ostringstream oss;
                    std::string val = v == true ? "true" : "false";
                    if (nokey_) 
    				{
                            oss << val;
                    }
                    else 
    				{
                            oss << "\"" << value_ << "\"" << ":" << val;
                    }
                    value_ = oss.str();
            }
    
    	/**
    	* 此模板类处理json键对应的值是一个嵌套对象或者数组的情况
    	* 
    	*/
    	template<typename T>
    	class ValueArray : public T
    	{
    	public:
    		ValueArray() {}
    		ValueArray(std::vector<std::string> vo) 
    		{ 
    			vo_ = vo; 
    		}
    
    		bool Enter(int i) 
    		{
    			std::string obj = vo_[i];
                return this->ReadJson(obj);
    		}
    
    		int Count() 
    		{ 
    			return vo_.size(); 
    		}
    
    	private:
    		std::vector<std::string> vo_;
    	};
    
    	/**
    	* 解析json字符串保存为键值的顺序存储，解析是按一层一层的进行
    	* 解析时把json看做是对象'{}' 与 数组'[]' 的组合
    	*
    	*/
    	class ParseJson
    	{
    	public:
            ParseJson() {}
            ~ParseJson() {}
    
    	public:
    		bool ParseArray(std::string json, std::vector<std::string>& vo);
    		bool ParseObj(std::string json);
    		std::vector<std::string> GetKeyVal() 
    		{
    			return keyval_;
    		}
    
    	protected:
    		std::string Trims(std::string s, char lc, char rc);
    		int GetFirstNotSpaceChar(std::string& s, int cur);
    		std::string FetchArrayStr(std::string inputstr, int inpos, int& offset);
    		std::string FetchObjStr(std::string inputstr, int inpos, int& offset);
    		std::string FetchStrStr(std::string inputstr, int inpos, int& offset);
    		std::string FetchNumStr(std::string inputstr, int inpos, int& offset);
    
    	private:
    		std::vector<char> token_;
    		std::vector<std::string> keyval_;
    	};
    
    	inline bool ParseJson::ParseArray(std::string json, std::vector<std::string>& vo) 
    	{
    		json = Trims(json, '[', ']');
    		std::string tokens;
    		size_t i = 0;
    		for (; i < json.size(); ++i) 
    		{
    			char c = json[i];
    			if (isspace(c) || c == '\"') 
    				continue;
    			if (c == ':' || c == ',' || c == '{') 
    			{
    				if (!tokens.empty()) 
    				{
    					vo.push_back(tokens);
    					tokens.clear();
    				}
    				if (c == ',') 
    					continue;
    				int offset = 0;
    				char nextc = c;
    				for (; c != '{';) 
    				{
    					nextc = json[++i];
    					if (isspace(nextc)) 
    						continue;
    					break;
    				}
    				if (nextc == '{') 
    				{
    					tokens = FetchObjStr(json, i, offset);
    				}
    				else if (nextc == '[') 
    				{
    					tokens = FetchArrayStr(json, i, offset);
    				}
    				i += offset;
    				continue;
    			}
    			tokens.push_back(c);
    		}
    		if (!tokens.empty()) 
    		{
    			vo.push_back(tokens);
    		}
    		return true;
    	}
    
    	// 解析为 key-value 调用一次解析一个层次
    	inline bool ParseJson::ParseObj(std::string json) 
    	{
    		auto LastValidChar = [&](int index)->char
    		{
    			for (int i = index-1; i >= 0; --i)
    			{
    				if (isspace(json[i])) 
    					continue;
    				char tmp = json[i];
    				return tmp;
    			}
    			return '\0';
    		};
    
    		json = Trims(json, '{', '}');
    		size_t i = 0;
    		for (; i < json.size(); ++i) 
    		{
    			char nextc = json[i];
    			if (isspace(nextc)) 
    				continue;
    
    			std::string tokens;
    			int offset = 0;
    			if (nextc == '{') 
    			{
    				tokens = FetchObjStr(json, i, offset);
    			}
    			else if (nextc == '[') 
    			{
    				tokens = FetchArrayStr(json, i, offset);
    			}
    			else if (nextc == '\"')
    			{
    				tokens = FetchStrStr(json, i, offset);
    			}
    			else if (isdigit(nextc) && LastValidChar(i) == ':')
    			{
    				tokens = FetchNumStr(json, i, offset);
    			}
    			else 
    			{
    				continue;
    			}
    			keyval_.push_back(tokens);
    			i += offset;
    		}
    		if (keyval_.size() == 0)
    		{
    			keyval_.push_back(json);
    		}
    		return true;
    	}
    
    	inline std::string ParseJson::Trims(std::string s, char lc, char rc)
    	{
    		std::string ss = s;
    		if (s.find(lc) != std::string::npos && s.find(rc) != std::string::npos) 
    		{
    			size_t b = s.find_first_of(lc);
    			size_t e = s.find_last_of(rc);
    			ss = s.substr(b + 1, e - b - 1);
    		}
    		return ss;
    	}
    
    	inline int ParseJson::GetFirstNotSpaceChar( std::string& s, int cur )
    	{
    		for (size_t i = cur; i < s.size(); i++)
    		{
    			if (isspace(s[i])) continue;
    			return i - cur;
    		}
    		return 0;
    	}
    
    	inline std::string ParseJson::FetchArrayStr(std::string inputstr, int inpos, int& offset)
    	{
    		int tokencount = 0;
    		std::string objstr;
    		size_t i = inpos + GetFirstNotSpaceChar(inputstr, inpos);
    		for (; i < inputstr.size(); i++) 
    		{
    			char c = inputstr[i];
    			if (c == '[') 
    			{
    				++tokencount;
    			}
    			if (c == ']') 
    			{
    				--tokencount;
    			}
    			objstr.push_back(c);
    			if (tokencount == 0) 
    			{
    				break;
    			}
    		}
    		offset = i - inpos;
    		return objstr;
    	}
    
    	inline std::string ParseJson::FetchObjStr(std::string inputstr, int inpos, int& offset)
    	{
    		int tokencount = 0;
    		std::string objstr;
    		size_t i = inpos + GetFirstNotSpaceChar(inputstr, inpos);
    		for (; i < inputstr.size(); i++) 
    		{
    			char c = inputstr[i];
    			if (c == '{') 
    			{
    				++tokencount;
    			}
    			if (c == '}') 
    			{
    				--tokencount;
    			}
    			objstr.push_back(c);
    			if (tokencount == 0) 
    			{
    				break;
    			}
    		}
    		offset = i - inpos;
    		return objstr;
    	}
    
    	inline std::string ParseJson::FetchStrStr( std::string inputstr, int inpos, int& offset )
    	{
    		int tokencount = 0;
    		std::string objstr;
    		size_t i = inpos + GetFirstNotSpaceChar(inputstr, inpos);
    		for (; i < inputstr.size(); i++) 
    		{
    			char c = inputstr[i];
    			if (c == '\"') 
    			{
    				++tokencount;
    			}
    			objstr.push_back(c);
    			if (tokencount % 2 == 0 && (c == ',' || c == ':')) 
    			{
    				break;
    			}
    		}
    		offset = i - inpos;
    
    		return Trims(objstr, '\"', '\"');
    	}
    
    	inline std::string ParseJson::FetchNumStr( std::string inputstr, int inpos, int& offset )
    	{
    		std::string objstr;
    		size_t i = inpos + GetFirstNotSpaceChar(inputstr, inpos);
    		for (; i < inputstr.size(); i++) 
    		{
    			char c = inputstr[i];
    			if (c == ',') 
    			{
    				break;
    			}
    			objstr.push_back(c);
    		}
    		offset = i - inpos;
    
    		return objstr;
    	}
    
    	/**
    	* 对外接口类
    	*
    	*/
    	class TinyJson;
    	typedef ValueArray<TinyJson> xarray;
    	typedef ValueArray<TinyJson> xobject;
    
    	class TinyJson
    	{
    		friend class ValueArray<TinyJson>;
    	public:
    		TinyJson() 
    		{
    			nokey_ = false;
    		}
            ~TinyJson() {}
    
    	public:
    		// read
    		bool ReadJson(std::string json) 
    		{
    			ParseJson p;
    			p.ParseObj(json);
    			KeyVal_ = p.GetKeyVal();
    			return true;
    		}
    
    		template<typename R>
    		R Get(std::string key, R defVal) 
    		{
    			auto itr = std::find(KeyVal_.begin(), KeyVal_.end(), key);
    			if (itr == KeyVal_.end()) 
    			{
    				return defVal;
    			}
    			return Value(*(++itr)).GetAs<R>();
    		}
    
    		template<typename R>
    		R Get(std::string key) 
    		{
    			return Get(key, R());
    		}
    
            template<typename R>
            R Get() 
    		{
                return Value(KeyVal_[0]).GetAs<R>();
            }
    
    		// write
    		Value& operator[](std::string k) 
    		{
    			Items_.push_back(Value(k));
    			Value& v = Items_[Items_.size() - 1];
    			if (k == "") 
    			{
    				nokey_ = true;
    			}
    			return v;
    		}
    
    		void Push(TinyJson item) 
    		{
    			Items_.push_back(Value(""));
    			Value& v = Items_[Items_.size() - 1];
    			nokey_ = true;
    			v.Push(item);
    			sub_type_ = 1;
    		}
    
    		bool get_nokey() 
    		{
    			return nokey_;
    		}
    
    		std::string WriteJson()
    		{
                return WriteJson(1);
    		}
    
            // 0: none  1: object  2: array
            std::string WriteJson(int type);
    
    	public:
    		int sub_type_;
    
    	private:
    		std::vector<std::string> KeyVal_;
    		std::vector<Value> Items_;
    		bool nokey_;
    	};
    
        template<>
        xarray TinyJson::Get(std::string key) 
    	{
            std::string val = Get<std::string>(key);
            ParseJson p;
            std::vector<std::string> vo;
            p.ParseArray(val, vo);
            xarray vals(vo);
            return vals;
        }
    
        std::ostream & operator << (std::ostream& os, TinyJson& ob)
    	{
    		os << ob.WriteJson();
    		return os;
    	}
    
        inline std::string TinyJson::WriteJson(int type)
    	{
            std::string prefix = type == 1 ? "{" : "[";
            std::string suffix = type == 1 ? "}" : "]";
            if (type == 0) 
    		{
    			prefix = "";
    			suffix = "";
    		}
    		std::ostringstream oss;
    		oss << prefix;
    		int i = 0;
    		int size = Items_.size();
    		std::string seq = ",";
    		for (; i < size; ++i) 
    		{
    			Value& v = Items_[i];
    			oss << v.value() << seq;
    		}
    		std::string jsonstring = oss.str();
    		if (jsonstring.back() == ',') 
    		{
    			jsonstring = jsonstring.substr(0, jsonstring.find_last_of(','));
    		}
    
    		jsonstring += suffix;
    		return jsonstring;
    	}
    
    	template<>
    	void Value::Set(TinyJson v) 
    	{
    		std::ostringstream oss;
    		if (v.sub_type_ == 1) 
    		{
                oss << "\"" << value_ << "\"" << ":" << v.WriteJson(2);
    		}
    		else 
    		{
    			if (nokey_) 
    			{
    				oss << v;
    			}
    			else 
    			{
    				oss << "\"" << value_ << "\"" << ":" << v;
    			}
    		}
    		value_ = oss.str();
    	}
    
    }  // end namesapce
    
    #endif  // TINY_JSON_H_

[https_github.com_button-chen_tinyjson]: https://github.com/button-chen/tinyjson