diff --git a/README.md b/README.md index 7bc1b12..d642b04 100644 --- a/README.md +++ b/README.md @@ -1,27 +1,40 @@ +# cJSON - Copyright (c) 2009 Dave Gamble +Ultralightweight JSON parser in ANSI C. - 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: +## Table of contents +* [License](#license) +* [Usage](#usage) + * [Welcome to cJSON](#welcome-to-cjson) + * [Some JSON](#some-json) + * [Here's the structure](#heres-the-structure) + * [Enjoy cJSON!](#enjoy-cjson) - The above copyright notice and this permission notice shall be included in - all copies or substantial portions of the Software. +## License - 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. +> Copyright (c) 2009-2016 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. +## Usage -Welcome to cJSON. ------------------ +### 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. @@ -34,8 +47,10 @@ 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 +``` +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 @@ -45,56 +60,69 @@ 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: ----------- +### Some JSON: - { - "name": "Jack (\"Bee\") Nimble", - "format": { - "type": "rect", - "width": 1920, - "height": 1080, - "interlace": false, - "frame rate": 24 - } +```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); +```c +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; +```c +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; +```c +cJSON_GetObjectItem(format,"frame rate")->valueint = 25; +``` Back to disk? - char * rendered = cJSON_Print(root); +```c +char * rendered = cJSON_Print(root); +``` Finished? Delete the root (this takes care of everything else). - cJSON_Delete(root); +```c +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); +```c +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 @@ -114,21 +142,22 @@ 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: ---------------------- +# Here's the structure: - typedef struct cJSON { - struct cJSON *next,*prev; - struct cJSON *child; +```c +typedef struct cJSON { + struct cJSON *next,*prev; + struct cJSON *child; - int type; + int type; - char *valuestring; - int valueint; - double valuedouble; + char *valuestring; + int valueint; + double valuedouble; - char *string; - } cJSON; + char *string; +} cJSON; +``` By default all values are 0 unless set by virtue of being meaningful. @@ -152,23 +181,26 @@ 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); - } - } +```c +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: +```c int callback(const char *name,int type,cJSON *item) { if (!strcmp(name,"name")) { /* populate name */ } @@ -179,33 +211,38 @@ let you invoke it per-item. For the item above, your callback might look like th 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. - } - } +```c +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; - } - } +```c +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. @@ -218,22 +255,24 @@ 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]; +```c +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 * 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 @@ -245,7 +284,6 @@ 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! ------------------------ +# Enjoy cJSON! - Dave Gamble, Aug 2009