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Third Party CJSON
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前往新版Gitcode,体验更适合开发者的 AI 搜索 >>
提交
ebba183f
编写于
8月 22, 2011
作者:
K
Kevin Branigan
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操作
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电子邮件补丁
差异文件
updated README markdown, gitignore, added the Makefile and fixed weird comments in test.c
上级
4cc55858
变更
4
隐藏空白更改
内联
并排
Showing
4 changed file
with
105 addition
and
98 deletion
+105
-98
.gitignore
.gitignore
+3
-0
Makefile
Makefile
+3
-0
README.md
README.md
+97
-96
test.c
test.c
+2
-2
未找到文件。
.gitignore
0 → 100644
浏览文件 @
ebba183f
a.out
.svn
*.o
\ No newline at end of file
Makefile
0 → 100644
浏览文件 @
ebba183f
all
:
cJSON.o
cc
-Wall
cJSON.c
-c
-o
cJSON.o
cc
-Wall
cJSON.o test.c
-lm
\ No newline at end of file
README.md
浏览文件 @
ebba183f
...
...
@@ -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
test.c
浏览文件 @
ebba183f
...
...
@@ -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"); */
...
...
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