cJSON

mirror of Dave's cJSON
git clone git://git.thc420.xyz/cJSON
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commit ebba183f1e95765e4d12dc4de2e2901221463ce8
parent 4cc55858fd5d1a1cce59a231b76286ad41708005
Author: Kevin Branigan <kbranigan@gmail.com>
Date:   Mon, 22 Aug 2011 00:47:25 -0400

updated README markdown, gitignore, added the Makefile and fixed weird comments in test.c

Diffstat:
A.gitignore | 4++++
AMakefile | 4++++
MREADME.md | 193++++++++++++++++++++++++++++++++++++++++---------------------------------------
Mtest.c | 4++--
4 files changed, 107 insertions(+), 98 deletions(-)

diff --git a/.gitignore b/.gitignore @@ -0,0 +1,3 @@ +a.out +.svn +*.o+ \ No newline at end of file diff --git a/Makefile b/Makefile @@ -0,0 +1,3 @@ +all: cJSON.o + cc -Wall cJSON.c -c -o cJSON.o + cc -Wall cJSON.o test.c -lm+ \ No newline at end of file diff --git a/README.md b/README.md @@ -21,6 +21,7 @@ */ 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. @@ -29,68 +30,68 @@ 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 - + 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 +---------- + + { + "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); + + 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; + 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; - + cJSON_GetObjectItem(format,"frame rate")->valueint=25; + Back to disk? - char *rendered=cJSON_Print(root); + char *rendered=cJSON_Print(root); Finished? Delete the root (this takes care of everything else). - cJSON_Delete(root); + 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); + 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 @@ -111,18 +112,20 @@ Sibling hs 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; +--------------------- + + 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. @@ -146,59 +149,59 @@ 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); - } -} + 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; -} + 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. - } -} + 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; - } -} + 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. @@ -212,20 +215,20 @@ 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; -} - + 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. @@ -235,7 +238,6 @@ 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[]. @@ -243,5 +245,4 @@ which are more complex than I'd care to try and stash into a const char array[]. Enjoy cJSON! - - Dave Gamble, Aug 2009 diff --git a/test.c b/test.c @@ -69,7 +69,7 @@ void create_objects() cJSON_AddFalseToObject (fmt,"interlace"); cJSON_AddNumberToObject(fmt,"frame rate", 24); - out=cJSON_Print(root); cJSON_Delete(root); printf("%s\n",out); free(out); /* Print to text, Delete the cJSON, print it, release the string. + out=cJSON_Print(root); cJSON_Delete(root); printf("%s\n",out); free(out); /* Print to text, Delete the cJSON, print it, release the string. */ /* Our "days of the week" array: */ const char *strings[7]={"Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday"}; @@ -142,7 +142,7 @@ int main (int argc, const char * argv[]) { doit(text4); doit(text5); - /* Parse standard testfiles: + /* Parse standard testfiles: */ /* dofile("../../tests/test1"); */ /* dofile("../../tests/test2"); */ /* dofile("../../tests/test3"); */