cJSON

mirror of Dave's cJSON
git clone git://git.thc420.xyz/cJSON
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commit 25b65feb362d96acb28ca0a5f039c6197918a3de
parent 1dff6f160fc944c8f7bf9d70f6580913d31c1cd6
Author: Max Bruckner <max@maxbruckner.de>
Date:   Fri,  4 Nov 2016 20:41:17 +0700

Remove old readme. It was replaced by README.md

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DREADME | 247-------------------------------------------------------------------------------
1 file changed, 0 insertions(+), 247 deletions(-)

diff --git a/README b/README @@ -1,247 +0,0 @@ -/* - Copyright (c) 2009 Dave Gamble - - Permission is hereby granted, free of charge, to any person obtaining a copy - of this software and associated documentation files (the "Software"), to deal - in the Software without restriction, including without limitation the rights - to use, copy, modify, merge, publish, distribute, sublicense, and/or sell - copies of the Software, and to permit persons to whom the Software is - furnished to do so, subject to the following conditions: - - The above copyright notice and this permission notice shall be included in - all copies or substantial portions of the Software. - - THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR - IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, - FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE - AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER - LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, - OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN - THE SOFTWARE. -*/ - -Welcome to cJSON. - -cJSON aims to be the dumbest 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. - - -First up, how do I build? -Add cJSON.c to your project, and put cJSON.h somewhere in the header search path. -For example, to build the test app: - -gcc cJSON.c test.c -o test -lm -./test - - -As a library, cJSON exists to take away as much legwork as it can, but not get in your way. -As a point of pragmatism (i.e. ignoring the truth), I'm going to say that you can use it -in one of two modes: Auto and Manual. Let's have a quick run-through. - - -I lifted some JSON from this page: http://www.json.org/fatfree.html -That page inspired me to write cJSON, which is a parser that tries to share the same -philosophy as JSON itself. Simple, dumb, out of the way. - -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_GetObjectItem(root,"format"); - int framerate = cJSON_GetObjectItem(format,"frame rate")->valueint; - - -Want to change the framerate? - cJSON_GetObjectItem(format,"frame rate")->valueint=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,*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. - -What about manual mode? First up you need some detail. -Let's cover how the cJSON objects represent the JSON data. -cJSON doesn't distinguish arrays from objects in handling; just type. -Each cJSON has, potentially, a child, siblings, value, a name. - -The root object has: Object Type and a Child -The Child has name "name", with value "Jack ("Bee") Nimble", and a sibling: -Sibling has type Object, name "format", and a child. -That child has type String, name "type", value "rect", and a sibling: -Sibling has type Number, name "width", value 1920, and a sibling: -Sibling has type Number, name "height", value 1080, and a sibling: -Sibling has type False, name "interlace", and a sibling: -Sibling has type Number, name "frame rate", value 24 - -Here's the structure: -typedef struct cJSON { - struct cJSON *next,*prev; - struct cJSON *child; - - int type; - - char *valuestring; - int valueint; - double valuedouble; - - char *string; -} cJSON; - -By default all values are 0 unless set by virtue of being meaningful. - -next/prev is a doubly linked list of siblings. next takes you to your sibling, -prev takes you back from your sibling to you. -Only objects and arrays have a "child", and it's the head of the doubly linked list. -A "child" entry will have prev==0, but next potentially points on. The last sibling has next=0. -The type expresses Null/True/False/Number/String/Array/Object, all of which are #defined in -cJSON.h - -A Number has valueint and valuedouble. If you're expecting an int, read valueint, if not read -valuedouble. - -Any entry which is in the linked list which is the child of an object will have a "string" -which is the "name" of the entry. When I said "name" in the above example, that's "string". -"string" is the JSON name for the 'variable name' if you will. - -Now you can trivially walk the lists, recursively, and parse as you please. -You can invoke cJSON_Parse to get cJSON to parse for you, and then you can take -the root object, and traverse the structure (which is, formally, an N-tree), -and tokenise as you please. If you wanted to build a callback style parser, this is how -you'd do it (just an example, since these things are very specific): - -void parse_and_callback(cJSON *item,const char *prefix) -{ - while (item) - { - char *newprefix=malloc(strlen(prefix)+strlen(item->name)+2); - sprintf(newprefix,"%s/%s",prefix,item->name); - int dorecurse=callback(newprefix, item->type, item); - if (item->child && dorecurse) parse_and_callback(item->child,newprefix); - item=item->next; - free(newprefix); - } -} - -The prefix process will build you a separated list, to simplify your callback handling. -The 'dorecurse' flag would let the callback decide to handle sub-arrays on it's own, or -let you invoke it per-item. For the item above, your callback might look like this: - -int callback(const char *name,int type,cJSON *item) -{ - if (!strcmp(name,"name")) { /* populate name */ } - else if (!strcmp(name,"format/type") { /* handle "rect" */ } - else if (!strcmp(name,"format/width") { /* 800 */ } - else if (!strcmp(name,"format/height") { /* 600 */ } - else if (!strcmp(name,"format/interlace") { /* false */ } - else if (!strcmp(name,"format/frame rate") { /* 24 */ } - return 1; -} - -Alternatively, you might like to parse iteratively. -You'd use: - -void parse_object(cJSON *item) -{ - int i; for (i=0;i<cJSON_GetArraySize(item);i++) - { - cJSON *subitem=cJSON_GetArrayItem(item,i); - // handle subitem. - } -} - -Or, for PROPER manual mode: - -void parse_object(cJSON *item) -{ - cJSON *subitem=item->child; - while (subitem) - { - // handle subitem - if (subitem->child) parse_object(subitem->child); - - subitem=subitem->next; - } -} - -Of course, this should look familiar, since this is just a stripped-down version -of the callback-parser. - -This should cover most uses you'll find for parsing. The rest should be possible -to infer.. and if in doubt, read the source! There's not a lot of it! ;) - - -In terms of constructing JSON data, the example code above is the right way to do it. -You can, of course, hand your sub-objects to other functions to populate. -Also, if you find a use for it, you can manually build the objects. -For instance, suppose you wanted to build an array of objects? - -cJSON *objects[24]; - -cJSON *Create_array_of_anything(cJSON **items,int num) -{ - int i;cJSON *prev, *root=cJSON_CreateArray(); - for (i=0;i<24;i++) - { - if (!i) root->child=objects[i]; - else prev->next=objects[i], objects[i]->prev=prev; - prev=objects[i]; - } - return root; -} - -and simply: Create_array_of_anything(objects,24); - -cJSON doesn't make any assumptions about what order you create things in. -You can attach the objects, as above, and later add children to each -of those objects. - -As soon as you call cJSON_Print, it renders the structure to text. - - - -The test.c code shows how to handle a bunch of typical cases. If you uncomment -the code, it'll load, parse and print a bunch of test files, also from json.org, -which are more complex than I'd care to try and stash into a const char array[]. - - -Enjoy cJSON! - - -- Dave Gamble, Aug 2009