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cson

Transformation between json string and struct.

The transformation between string to JSON objects (e.g. json_t in Jansson) is implemented by a third-party library (Jansson or cJSON. Refer to Dependence). What cson really implements is the transformation between JSON object and structure.

Compilation

Compile static library

$ git clone https://github.com/sunchb/cson.git
$ cd cson
$ make

Compile demo

$ cd demo
$ make
$ ./test

How to use

Define the data structure for JSON.
Define the property description table for data structure.
Call cson api to decode or encode.

Dependence

https://github.com/akheron/jansson.git https://github.com/DaveGamble/cJSON.git

Demo

Here is a JSON with various data types. eg. Interger, String, Real, Boolean, Object, and Array. We're going to decode and encode it by cson.

{
    "name":"jay zhou",
    "creater":"dahuaxia",
    "songNum":2,
    "songList":[
        {
            "songName":"qilixiang",
            "signerName":"jay zhou",
            "albumName":"qilixiang",
            "url":"www.kugou.com",
            "duration":200,
            "paid":false,
            "price":6.6600000000000001,
            "lyricNum":2,
            "lyric":[
                {
                    "time":1,
                    "text":"Sparrow outside the window"
                },
                {
                    "time":10,
                    "text":"Multi mouth on the pole"
                }
            ]
        },
        {
            "songName":"dongfengpo",
            "signerName":"jay zhou",
            "albumName":"dongfengpo",
            "url":"music.qq.com",
            "duration":180,
            "paid":true,
            "price":0.88,
            "lyricNum":2,
            "lyric":[
                {
                    "time":10,
                    "text":"A sad parting, standing alone in the window"
                },
                {
                    "time":20,
                    "text":"I'm behind the door pretending you're not gone"
                }
            ]
        }
    ],
    "extData":{
        "a":999,
        "b":1.05
    }
}

1. Define the data structure for JSON.

Even if you don't use cson, you usually need to do like this.

Attention

String must be declared as char*.
Array must be declared as pointer.
Declare additional properties to hold the array size for every array property.
The structure property name must be the same as the JSON field name.

typedef struct {
    int         time;
    char*       text;         /* String must be declared as char* */
} Lyric;

typedef struct {
    char*       songName;
    char*       signerName;
    char*       albumName;
    char*       url;
    int         duration;
    int         paid;
    double      price;
    size_t      lyricNum;     /* Declare additional properties to hold the array size */
    Lyric*      lyric;        /* Array must be declared as pointer */
} SongInfo;

typedef struct {
    int         a;
    double      b;
} ExtData;

typedef struct {
    char*       name;
    char*       creater;
    size_t      songNum;
    SongInfo*   songList;
    ExtData     extData;
} PlayList;

2. Define the property description table for data structure.

Use following definitions to help you describe the structure.

_property_int(type, field)
_property_real(type, field)
_property_bool(type, field)
_property_string(type, field)
_property_obj(type, field, tbl)
_property_array_object(type, field, tbl, arrayType, countfild) # I know it's a little cumbersome, I'm trying to simplify it.
_property_array_int(type, field, arrayType, countfild)
_property_array_string(type, field, arrayType, countfild)
_property_array_real(type, field, arrayType, countfild)
_property_array_bool(type, field, arrayType, countfild)

Args notes:

type: type of data structure
field: property name
tbl: description table of the property type. use when object or object array
arrayType: type of the array (Used to calculate size when dynamically get array memory)
countfild: property to save array size

You can also use macro definitions with extended parameters, the range of args is _ex_args_nullable, _ex_args_exclude_decode, _ex_args_exclude_encode and thire combinations.

#define _ex_args_nullable (0x01) //continue parse or encode when the field exception occurred. Default is "ON".
#define _ex_args_exclude_decode (0x02) //do not parse the field.
#define _ex_args_exclude_encode (0x04) //do not encode the field.
#define _ex_args_all (_ex_args_nullable | _ex_args_exclude_decode | _ex_args_exclude_encode)
_property_int_ex(type, field, args)
_property_real_ex(type, field, args)
_property_bool_ex(type, field, args)
_property_string_ex(type, field, args)
_property_obj_ex(type, field, tbl, args)
_property_array_ex(type, field, tbl, subType, count, args)
_property_array_object_ex(type, field, tbl, subType, count, args)
_property_array_int_ex(type, field, subType, count, args)
_property_array_string_ex(type, field, subType, count, args)
_property_array_real_ex(type, field, subType, count, args)
_property_array_bool_ex(type, field, subType, count, args)

/* description for Lyric */
reflect_item_t lyric_ref_tbl[] = {
    _property_int(Lyric, time),
    _property_string(Lyric, text),
    _property_end()
};

/* description for SongInfo */
reflect_item_t song_ref_tbl[] = {
    _property_string(SongInfo, songName),
    _property_string(SongInfo, signerName),
    _property_string(SongInfo, albumName),
    _property_string(SongInfo, url),
    _property_int(SongInfo, duration),
    _property_bool(SongInfo, paid),
    _property_real(SongInfo, price),
    _property_int(SongInfo, lyricNum),          
    _property_array(SongInfo, lyric, lyric_ref_tbl, Lyric, lyricNum),   /* Lyric: type of array; lyricNum: property to save array size */
    _property_end()
};

/* description for ExtData */
reflect_item_t ext_data_ref_tbl[] = {
    _property_int(ExtData, a),
    _property_real(ExtData, b),
    _property_end()
};

/* description for PlayList */
reflect_item_t play_list_ref_tbl[] = {
    _property_string(PlayList, name),
    _property_string(PlayList, creater),
    _property_int(PlayList, songNum),
    _property_array(PlayList, songList, song_ref_tbl, SongInfo, songNum),
    _property_obj(PlayList, extData, ext_data_ref_tbl),
    _property_end()
};

3. Call cson api to decode or encode.

PlayList playList;

/* Decode */
csonJsonStr2Struct(jStr, &playList, play_list_ref_tbl);

/* Encode */
char* jstrOutput;
csonStruct2JsonStr(&jstrOutput, &playList, play_list_ref_tbl);

Restrict

Multidimensional arrays are not supported.
Cjson is used by default. If you want to use jannson or other json lib, please modify $(JSON_LIB) in makefile.

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