JSON Library Tutorial from scratch (I): starting to learn and organize notes

Original website ： From scratch JSON Library Tutorial - You know

 JSON What is it? ？

JSON（JavaScript Object Notation） Is a text format for data exchange .

JSON It's a tree structure , Contains only 6 Type of data ：

• null: Expressed as null
• boolean: Expressed as true or false
• number: General representation of floating point numbers , Explain in detail in the next module
• string: Expressed as "..."
• array: Expressed as [ ... ]
• object: Expressed as { ... }

What we want to achieve JSON library , Mainly completed 3 A need ：

1. hold JSON The text is parsed into a tree data structure （parse）.
2. Provide an interface to access the data structure （access）.
3. Convert the data structure into JSON Text （stringify）.

JSON There is 6 Type of data , If you put true and false As two types, they are 7 Kind of , We declare an enumeration type for this （enumeration type）：

typedef enum {   
                 LEPT_NULL, 
                 LEPT_FALSE, 
                 LEPT_TRUE, 
                 LEPT_NUMBER,
                 LEPT_STRING, 
                 LEPT_ARRAY, 
                 LEPT_OBJECT 
             } lept_type;

JSON It's a tree structure , We finally need to implement a tree data structure , Each node uses lept_value The structure represents , We'll call it a JSON value （JSON value）.

typedef struct {
    lept_type type;
}lept_value;

We only need two now API function , One is parsing JSON：

int lept_parse(lept_value* v, const char* json);

The return values are the following enumerated values , No error will be returned LEPT_PARSE_OK.

enum {
    LEPT_PARSE_OK = 0,
    LEPT_PARSE_EXPECT_VALUE,
    LEPT_PARSE_INVALID_VALUE,
    LEPT_PARSE_ROOT_NOT_SINGULAR
};

• If one JSON Contains only white space , Send back LEPT_PARSE_EXPECT_VALUE.
• If after a value , There are other characters after whitespace , Send back LEPT_PARSE_ROOT_NOT_SINGULAR.
• If the value is not the three literal values , Send back LEPT_PARSE_INVALID_VALUE.

Now we only need a function to access the result , Is to get its type ：

lept_type lept_get_type(const lept_value* v);

To reduce the number of arguments passed between analytic functions , We put json Put all the data into one lept_context Structure ：

typedef struct {
    const char* json;
}lept_context;