cJSON: Lightweight JSON parser

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cJSON is one of the simplest possible parser that you can get your job done with. It's a single file of C, and a single header file.

JSON is described best here: http://www.json.org/ It's like XML, but fat-free. You use it to move data around, store things, or just generally represent your program's state.

As a library, cJSON exists to take away as much legwork as it can, but not get in your way. 

There are several ways to incorporate cJSON into your project, one of them is just copying the source.

Because the entire library is only one C file and one header file, you can just copy cJSON.h and cJSON.c to your projects source and start using it.

cJSON is written in ANSI C (C89) in order to support as many platforms and compilers as possible.

Some JSON:

{
"name": "Jack (\"Bee\") Nimble",
"format": {
"type": "rect",
"width": 1920,
"height": 1080,
"interlace": false,
"frame rate": 24
}
}
Assume that you got this from a file, a webserver, or magic JSON elves, whatever, you have a char * to it. Everything is a cJSON struct. Get it parsed:

cJSON * root = cJSON_Parse(my_json_string);
This is an object. We're in C. We don't have objects. But we do have structs. What's the framerate?

cJSON *format = cJSON_GetObjectItemCaseSensitive(root, "format");
cJSON *framerate_item = cJSON_GetObjectItemCaseSensitive(format, "frame rate");
double framerate = 0;
if (cJSON_IsNumber(framerate_item))
{
framerate = framerate_item->valuedouble;
}
Want to change the framerate?

cJSON *framerate_item = cJSON_GetObjectItemCaseSensitive(format, "frame rate");
cJSON_SetNumberValue(framerate_item, 25);
Back to disk?

char *rendered = cJSON_Print(root);
Finished? Delete the root (this takes care of everything else).

cJSON_Delete(root);
That's AUTO mode. If you're going to use Auto mode, you really ought to check pointers before you dereference them. If you want to see how you'd build this struct in code?

cJSON *root;
cJSON *fmt;
root = cJSON_CreateObject();
cJSON_AddItemToObject(root, "name", cJSON_CreateString("Jack (\"Bee\") Nimble"));
cJSON_AddItemToObject(root, "format", fmt = cJSON_CreateObject());
cJSON_AddStringToObject(fmt, "type", "rect");
cJSON_AddNumberToObject(fmt, "width", 1920);
cJSON_AddNumberToObject(fmt, "height", 1080);
cJSON_AddFalseToObject (fmt, "interlace");
cJSON_AddNumberToObject(fmt, "frame rate", 24);
Hopefully we can agree that's not a lot of code? There's no overhead, no unnecessary setup. Look at test.c for a bunch of nice examples, mostly all ripped off the json.org site, and a few from elsewhere.

 

Source: https://github.com/DaveGamble/cJSON

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