JsonParser.h

00001 /*
00002  * (c) Copyright 2012 EVRYTHNG Ltd London / Zurich
00003  * www.evrythng.com
00004  *
00005  * --- DISCLAIMER ---
00006  *
00007  * EVRYTHNG provides this source code "as is" and without warranty of any kind,
00008  * and hereby disclaims all express or implied warranties, including without
00009  * limitation warranties of merchantability, fitness for a particular purpose,
00010  * performance, accuracy, reliability, and non-infringement.
00011  *
00012  * Author: Michel Yerly
00013  *
00014  */
00015 #ifndef JSONPARSER_H
00016 #define JSONPARSER_H
00017 
00018 #include <vector>
00019 #include <map>
00020 #include <string>
00021 
00022 /*
00023  * Possible JSON value types
00024  */
00025 enum ValueType {
00026 
00027     VT_DOUBLE,   // Number
00028     VT_CHAR_PTR, // String
00029     VT_VEC_PTR,  // Array
00030     VT_MAP_PTR,  // Object
00031     VT_CST_NULL, // Null
00032     VT_CST_TRUE, // True
00033     VT_CST_FALSE // False
00034 };
00035 
00036 /*
00037  * Class to hold a JSON value. A JSON value may be composed of other JSON
00038  * values.
00039  */
00040 class JsonValue
00041 {
00042 public:
00043 
00044     /*
00045      * Creates a new string JSON value. The string is copied into the object.
00046      * WARNING: a new object is created. The caller is responsible of deleting
00047      * it.
00048      * buffer: the string to read from.
00049      * len: the number of characters to read.
00050      */
00051     static JsonValue* createString(const char* buffer, int len);
00052     
00053     /* Creates a new number JSON value.
00054      * WARNING: a new object is created. The caller is responsible of deleting
00055      * it.
00056      */
00057     static JsonValue* createDouble(double d);
00058 
00059     /* Creates a new object JSON value.
00060      * WARNING: a new object is created. The caller is responsible of deleting
00061      * it.
00062      */
00063     static JsonValue* createMap();
00064 
00065     /* Creates a new array JSON value.
00066      * WARNING: a new object is created. The caller is responsible of deleting
00067      * it.
00068      */
00069     static JsonValue* createVector();
00070     
00071     /* Creates a new true or false JSON value, depending on b.
00072      * WARNING: a new object is created. The caller is responsible of deleting
00073      * it.
00074      */
00075     static JsonValue* createBoolean(bool b);
00076     
00077     /* Creates a new null JSON value.
00078      * WARNING: a new object is created. The caller is responsible of deleting
00079      * it.
00080      */
00081     static JsonValue* createNull();
00082 
00083     /* 
00084      * Destructor.
00085      * The destructor also deletes nested JsonValues if any.
00086      */
00087     virtual ~JsonValue();
00088 
00089     /*
00090      * Gets a JSON value given a path.
00091      * If the path is NULL or an empty string the method returns this.
00092      * If there is an error, the method returns NULL.
00093      * The path is composed of strings (object keys) and numbers (array 
00094      * indices) separated by '/'.
00095      *
00096      * Example:
00097      *   JSON: {"xy":34,"ab":[{"r":true},{"s":false}]}
00098      *   Path: ab/1/s
00099      *   Returns: a JsonValue representing false.
00100      */
00101     JsonValue* get(const char* path);
00102     
00103     /*
00104      * Gets a pointer to a double given a path (see get()).
00105      * If there is an error, the method returns NULL.
00106      */
00107     const double* getDouble(const char* path);
00108     
00109     /*
00110      * Gets a pointer to a string given a path (see get()).
00111      * If there is an error, the method returns NULL.
00112      */
00113     const char* getString(const char* path);
00114     
00115     /*
00116      * Gets a pointer to an array given a path (see get()).
00117      * If there is an error, the method returns NULL.
00118      */
00119     const std::vector<JsonValue*>* getVector(const char* path);
00120 
00121     /*
00122      * Gets a pointer to a map given a path (see get()).
00123      * If there is an error, the method returns NULL.
00124      */
00125     const std::map<std::string,JsonValue*>* getMap(const char* path);
00126 
00127     /*
00128      * Gets a pointer to a boolean given a path (see get()).
00129      * If there is an error, the method returns NULL.
00130      */
00131     const bool* getBoolean(const char* path);
00132 
00133     /*
00134      * Determines if the value at the path (see get()) is null.
00135      * Return true if and only if the value is explicitely null.
00136      */
00137     bool isNull(const char* path);
00138 
00139     /*
00140      * Debug function.
00141      */
00142     void print();
00143 
00144     friend class JsonParser;
00145 
00146 private:
00147 
00148     /*
00149      * Constructor that creates a string JSON value. The string is copied into
00150      * the object.
00151      * buffer: the string to read from.
00152      * len: the number of characters to read.
00153      */
00154     JsonValue(const char* buffer, int len);
00155     
00156     /*
00157      * Constructor that creates a number JSON value.
00158      */
00159     JsonValue(double d);
00160     
00161     /*
00162      * Constructor that creates either a True or a False JSON value.
00163      */
00164     JsonValue(bool b);
00165     
00166     /*
00167      * Constructor that creates a JSON value without specifying the type.
00168      */
00169     JsonValue();
00170     
00171     ValueType type;
00172     union {
00173         double d;
00174         char* s;
00175         std::vector<JsonValue*>* vec;
00176         std::map<std::string,JsonValue*>* map;
00177     } value;
00178 
00179 };
00180 
00181 enum TokenType {
00182     TOKEN_EOS,
00183     TOKEN_NUMBER,
00184     TOKEN_STRING,
00185     TOKEN_DELIMITER,
00186     TOKEN_TRUE,
00187     TOKEN_FALSE,
00188     TOKEN_NULL
00189 };
00190 
00191 /*
00192  * Class to parse a JSON string.
00193  *
00194  * NOTE: The current implementation does only support ASCII encoding.
00195  */
00196 class JsonParser
00197 {
00198 public:
00199 
00200     /*
00201      * Constructor.
00202      */
00203     JsonParser();
00204     
00205     /*
00206      * Destructor.
00207      * The destructor also deletes the parsed document (the one you get with
00208      * getDocument().
00209      */
00210     virtual ~JsonParser();
00211     
00212     /*
00213      * Parses the json string.
00214      * json: String that contains the json to parse.
00215      * Returns 0 on success, or -1 on error.
00216      *
00217      * NOTE: This method deletes the previously parsed document.
00218      */
00219     int parse(const char* json);
00220     
00221     /*
00222      * Returns the parsed document, or NULL if the json is not parsed.
00223      */
00224     JsonValue* getDocument();
00225 
00226 private:
00227     const char* json;
00228     int json_len;
00229     TokenType ct;
00230     int ctPos;
00231     int ctLen;
00232     double ctNumberVal;
00233     JsonValue* pDocument;
00234 
00235     int goToNextToken();
00236 
00237     int parseObject(JsonValue** object);
00238     int parseValue(JsonValue** value);
00239     int parseArray(JsonValue** array);
00240 };
00241 
00242 #endif