Commit 9a567d9d by Niels

- tidied code

- added more documentation
parent 52c2cb8c
...@@ -12,9 +12,9 @@ There are myriads of [JSON](http://json.org) libraries out there, and each may e ...@@ -12,9 +12,9 @@ There are myriads of [JSON](http://json.org) libraries out there, and each may e
Other aspects were not so important to us: Other aspects were not so important to us:
- **Memory efficiency**. Each JSON object has an overhead of one pointer and one enumeration element (1 byte). We use the following C++ data types: `std::string` for strings, `int` or `double` for numbers, `std::map` for objects, `std::vector` for arrays, and `bool` for Booleans. We know that there are more efficient ways to store the values, but we are happy enough right now. And by the way: [Valgrind](http://valgrind.org) says our code is free of leaks. - **Memory efficiency**. Each JSON object has an overhead of one pointer (the maximal size of a union) and one enumeration element (1 byte). We use the following C++ data types: `std::string` for strings, `int` or `double` for numbers, `std::map` for objects, `std::vector` for arrays, and `bool` for Booleans. We know that there are more efficient ways to store the values, but we are happy enough right now. And by the way: [Valgrind](http://valgrind.org) says our code is free of leaks.
- **Speed**. We currently implement the parser as naive [recursive descent parser](http://en.wikipedia.org/wiki/Recursive_descent_parser) with hand coded string handling. It is fast enough, but a [LALR-parser](http://en.wikipedia.org/wiki/LALR_parser) with a decent regular expression processor should be even faster. - **Speed**. We currently implement the parser as naive [recursive descent parser](http://en.wikipedia.org/wiki/Recursive_descent_parser) with hand coded string handling. It is fast enough, but a [LALR-parser](http://en.wikipedia.org/wiki/LALR_parser) with a decent regular expression processor should be even faster (but would consist of more files which makes the integration harder).
- **Rigourous standard compliance**. We followed the [specification](http://json.org) as close as possible, but did not invest too much in a 100% compliance with respect to Unicode support. As a result, there might be edge cases of false positives and false negatives, but as long as we have a hand-written parser, we won't invest too much to be fully compliant. - **Rigourous standard compliance**. We followed the [specification](http://json.org) as close as possible, but did not invest too much in a 100% compliance with respect to Unicode support. As a result, there might be edge cases of false positives and false negatives, but as long as we have a hand-written parser, we won't invest too much to be fully compliant.
...@@ -48,7 +48,7 @@ j["name"] = "Niels"; ...@@ -48,7 +48,7 @@ j["name"] = "Niels";
// add an object inside the object // add an object inside the object
j["further"]["entry"] = 42; j["further"]["entry"] = 42;
// add an array that is stored as std::vector // add an array that is stored as std::vector (C++11)
j["list"] = { 1, 0, 2 }; j["list"] = { 1, 0, 2 };
``` ```
...@@ -63,6 +63,8 @@ j << "{ \"pi\": 3.141, \"happy\": true }"; ...@@ -63,6 +63,8 @@ j << "{ \"pi\": 3.141, \"happy\": true }";
std::cout << j; std::cout << j;
``` ```
These operators work for any subclases of `std::istream` or `std::ostream`.
### STL-like access ### STL-like access
```cpp ```cpp
...@@ -77,6 +79,11 @@ for (JSON::iterator it = j.begin(); it != j.end(); ++it) { ...@@ -77,6 +79,11 @@ for (JSON::iterator it = j.begin(); it != j.end(); ++it) {
std::cout << *it << '\n'; std::cout << *it << '\n';
} }
// C++11 style
for (auto element : j) {
std::cout << element << '\n';
}
// getter/setter // getter/setter
std::string tmp = j[0]; std::string tmp = j[0];
j[1] = 42; j[1] = 42;
...@@ -85,4 +92,42 @@ j[1] = 42; ...@@ -85,4 +92,42 @@ j[1] = 42;
j.size(); // 3 j.size(); // 3
j.empty(); // false j.empty(); // false
j.type(); // JSON::array j.type(); // JSON::array
// create an object
JSON o;
o["foo"] = 23;
o["bar"] = false;
o["baz"] = 3.141;
// find an entry
if (o.find("foo") != o.end()) {
// there is an entry with key "foo"
}
// iterate the object
for (JSON::iterator it = o.begin(); it != o.end(); ++it) {
std::cout << it.key() << ':' << it.value() << '\n';
}
``` ```
### Implicit conversions
The type of the JSON object is determined automatically by the expression to store. Likewise, the stored value is implicitly converted
```cpp
/// strings
std::string s1 = "Hello, world!";
JSON js = s;
std::string s2 = j;
// Booleans
bool b1 = true;
JSON jb = b1;
bool b2 = jb;
// numbers
int i = 42;
JSON jn = i;
double f = jn;
```
...@@ -5,17 +5,12 @@ ...@@ -5,17 +5,12 @@
#define __cplusplus11 #define __cplusplus11
#endif #endif
// allow us to use "nullptr" everywhere // STL containers
#include <cstddef>
#ifndef nullptr
#define nullptr NULL
#endif
#include <string> #include <string>
#include <vector> #include <vector>
#include <map> #include <map>
// additional C++11 header // additional C++11 headers
#ifdef __cplusplus11 #ifdef __cplusplus11
#include <mutex> #include <mutex>
#include <initializer_list> #include <initializer_list>
...@@ -27,8 +22,8 @@ class JSON { ...@@ -27,8 +22,8 @@ class JSON {
class iterator; class iterator;
class const_iterator; class const_iterator;
private:
#ifdef __cplusplus11 #ifdef __cplusplus11
private:
/// mutex to guard payload /// mutex to guard payload
static std::mutex _token; static std::mutex _token;
#endif #endif
...@@ -55,19 +50,32 @@ class JSON { ...@@ -55,19 +50,32 @@ class JSON {
/// a JSON value /// a JSON value
union value { union value {
/// array as pointer to array_t
array_t* array; array_t* array;
/// object as pointer to object_t
object_t* object; object_t* object;
/// string as pointer to string_t
string_t* string; string_t* string;
/// Boolean
boolean_t boolean; boolean_t boolean;
/// number (integer)
number_t number; number_t number;
/// number (float)
number_float_t number_float; number_float_t number_float;
/// default constructor
value() {} value() {}
/// constructor for arrays
value(array_t* array): array(array) {} value(array_t* array): array(array) {}
/// constructor for objects
value(object_t* object): object(object) {} value(object_t* object): object(object) {}
/// constructor for strings
value(string_t* string): string(string) {} value(string_t* string): string(string) {}
/// constructor for Booleans
value(boolean_t boolean) : boolean(boolean) {} value(boolean_t boolean) : boolean(boolean) {}
/// constructor for numbers (integer)
value(number_t number) : number(number) {} value(number_t number) : number(number) {}
/// constructor for numbers (float)
value(number_float_t number_float) : number_float(number_float) {} value(number_float_t number_float) : number_float(number_float) {}
}; };
...@@ -84,15 +92,15 @@ class JSON { ...@@ -84,15 +92,15 @@ class JSON {
#endif #endif
public: public:
/// create an empty (null) object /// create a null object
JSON(); JSON();
/// create an empty object according to given type /// create an object according to given type
JSON(json_t); JSON(json_t);
/// create a string object from C++ string /// create a string object from a C++ string
JSON(const std::string&); JSON(const std::string&);
/// create a string object from C string /// create a string object from a C string
JSON(char*); JSON(char*);
/// create a string object from C string /// create a string object from a C string
JSON(const char*); JSON(const char*);
/// create a Boolean object /// create a Boolean object
JSON(const bool); JSON(const bool);
...@@ -135,13 +143,16 @@ class JSON { ...@@ -135,13 +143,16 @@ class JSON {
operator double() const; operator double() const;
/// implicit conversion to Boolean (only for Booleans) /// implicit conversion to Boolean (only for Booleans)
operator bool() const; operator bool() const;
/// implicit conversion to JSON vector (not for objects)
operator std::vector<JSON>() const;
/// implicit conversion to JSON map (only for objects)
operator std::map<std::string, JSON>() const;
/// write to stream /// write to stream
friend std::ostream& operator<<(std::ostream& o, const JSON& j) { friend std::ostream& operator<<(std::ostream& o, const JSON& j) {
o << j.toString(); o << j.toString();
return o; return o;
} }
/// write to stream /// write to stream
friend std::ostream& operator>>(const JSON& j, std::ostream& o) { friend std::ostream& operator>>(const JSON& j, std::ostream& o) {
o << j.toString(); o << j.toString();
...@@ -153,7 +164,6 @@ class JSON { ...@@ -153,7 +164,6 @@ class JSON {
parser(i).parse(j); parser(i).parse(j);
return i; return i;
} }
/// read from stream /// read from stream
friend std::istream& operator<<(JSON& j, std::istream& i) { friend std::istream& operator<<(JSON& j, std::istream& i) {
parser(i).parse(j); parser(i).parse(j);
...@@ -211,8 +221,11 @@ class JSON { ...@@ -211,8 +221,11 @@ class JSON {
/// find an element in an object (returns end() iterator otherwise) /// find an element in an object (returns end() iterator otherwise)
iterator find(const std::string&); iterator find(const std::string&);
/// find an element in an object (returns end() iterator otherwise)
const_iterator find(const std::string&) const; const_iterator find(const std::string&) const;
/// find an element in an object (returns end() iterator otherwise)
iterator find(const char*); iterator find(const char*);
/// find an element in an object (returns end() iterator otherwise)
const_iterator find(const char*) const; const_iterator find(const char*) const;
/// direct access to the underlying payload /// direct access to the underlying payload
...@@ -222,6 +235,8 @@ class JSON { ...@@ -222,6 +235,8 @@ class JSON {
/// lexicographically compares the values /// lexicographically compares the values
bool operator==(const JSON&) const; bool operator==(const JSON&) const;
/// lexicographically compares the values
bool operator!=(const JSON&) const;
private: private:
/// return the type as string /// return the type as string
...@@ -299,26 +314,43 @@ class JSON { ...@@ -299,26 +314,43 @@ class JSON {
const_iterator cend() const; const_iterator cend() const;
private: private:
/// a helper class to parse a JSON object
class parser { class parser {
public: public:
/// a parser reading from a C string
parser(char*); parser(char*);
/// a parser reading from a C++ string
parser(std::string&); parser(std::string&);
/// a parser reading from an input stream
parser(std::istream&); parser(std::istream&);
/// destructor of the parser
~parser(); ~parser();
/// parse into a given JSON object
void parse(JSON&); void parse(JSON&);
private: private:
/// read the next character, stripping whitespace
bool next(); bool next();
void error(std::string = "") __attribute__((noreturn)); /// raise an exception with an error message
void error(std::string) __attribute__((noreturn));
/// parse a quoted string
std::string parseString(); std::string parseString();
/// parse a Boolean "true"
void parseTrue(); void parseTrue();
/// parse a Boolean "false"
void parseFalse(); void parseFalse();
/// parse a null object
void parseNull(); void parseNull();
/// a helper function to expect a certain character
void expect(char); void expect(char);
/// the current character
char _current; char _current;
/// a buffer of the input
char* _buffer; char* _buffer;
/// the position inside the input buffer
size_t _pos; size_t _pos;
/// the length of the input buffer
size_t _length; size_t _length;
}; };
}; };
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