README.md
1# cJSON
2
3Ultralightweight JSON parser in ANSI C.
4
5## Table of contents
6* [License](#license)
7* [Usage](#usage)
8 * [Welcome to cJSON](#welcome-to-cjson)
9 * [Building](#building)
10 * [Copying the source](#copying-the-source)
11 * [CMake](#cmake)
12 * [Makefile](#makefile)
13 * [Meson](#meson)
14 * [Vcpkg](#Vcpkg)
15 * [Including cJSON](#including-cjson)
16 * [Data Structure](#data-structure)
17 * [Working with the data structure](#working-with-the-data-structure)
18 * [Basic types](#basic-types)
19 * [Arrays](#arrays)
20 * [Objects](#objects)
21 * [Parsing JSON](#parsing-json)
22 * [Printing JSON](#printing-json)
23 * [Example](#example)
24 * [Printing](#printing)
25 * [Parsing](#parsing)
26 * [Caveats](#caveats)
27 * [Zero Character](#zero-character)
28 * [Character Encoding](#character-encoding)
29 * [C Standard](#c-standard)
30 * [Floating Point Numbers](#floating-point-numbers)
31 * [Deep Nesting Of Arrays And Objects](#deep-nesting-of-arrays-and-objects)
32 * [Thread Safety](#thread-safety)
33 * [Case Sensitivity](#case-sensitivity)
34 * [Duplicate Object Members](#duplicate-object-members)
35 * [Enjoy cJSON!](#enjoy-cjson)
36
37## License
38
39MIT License
40
41> Copyright (c) 2009-2017 Dave Gamble and cJSON contributors
42>
43> Permission is hereby granted, free of charge, to any person obtaining a copy
44> of this software and associated documentation files (the "Software"), to deal
45> in the Software without restriction, including without limitation the rights
46> to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
47> copies of the Software, and to permit persons to whom the Software is
48> furnished to do so, subject to the following conditions:
49>
50> The above copyright notice and this permission notice shall be included in
51> all copies or substantial portions of the Software.
52>
53> THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
54> IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
55> FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
56> AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
57> LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
58> OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
59> THE SOFTWARE.
60
61## Usage
62
63### Welcome to cJSON.
64
65cJSON aims to be the dumbest possible parser that you can get your job done with.
66It's a single file of C, and a single header file.
67
68JSON is described best here: http://www.json.org/
69It's like XML, but fat-free. You use it to move data around, store things, or just
70generally represent your program's state.
71
72As a library, cJSON exists to take away as much legwork as it can, but not get in your way.
73As a point of pragmatism (i.e. ignoring the truth), I'm going to say that you can use it
74in one of two modes: Auto and Manual. Let's have a quick run-through.
75
76I lifted some JSON from this page: http://www.json.org/fatfree.html
77That page inspired me to write cJSON, which is a parser that tries to share the same
78philosophy as JSON itself. Simple, dumb, out of the way.
79
80### Building
81
82There are several ways to incorporate cJSON into your project.
83
84#### copying the source
85
86Because 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.
87
88cJSON is written in ANSI C (C89) in order to support as many platforms and compilers as possible.
89
90#### CMake
91
92With CMake, cJSON supports a full blown build system. This way you get the most features. CMake with an equal or higher version than 2.8.5 is supported. With CMake it is recommended to do an out of tree build, meaning the compiled files are put in a directory separate from the source files. So in order to build cJSON with CMake on a Unix platform, make a `build` directory and run CMake inside it.
93
94```
95mkdir build
96cd build
97cmake ..
98```
99
100This will create a Makefile and a bunch of other files. You can then compile it:
101
102```
103make
104```
105
106And install it with `make install` if you want. By default it installs the headers `/usr/local/include/cjson` and the libraries to `/usr/local/lib`. It also installs files for pkg-config to make it easier to detect and use an existing installation of CMake. And it installs CMake config files, that can be used by other CMake based projects to discover the library.
107
108You can change the build process with a list of different options that you can pass to CMake. Turn them on with `On` and off with `Off`:
109
110* `-DENABLE_CJSON_TEST=On`: Enable building the tests. (on by default)
111* `-DENABLE_CJSON_UTILS=On`: Enable building cJSON_Utils. (off by default)
112* `-DENABLE_TARGET_EXPORT=On`: Enable the export of CMake targets. Turn off if it makes problems. (on by default)
113* `-DENABLE_CUSTOM_COMPILER_FLAGS=On`: Enable custom compiler flags (currently for Clang, GCC and MSVC). Turn off if it makes problems. (on by default)
114* `-DENABLE_VALGRIND=On`: Run tests with [valgrind](http://valgrind.org). (off by default)
115* `-DENABLE_SANITIZERS=On`: Compile cJSON with [AddressSanitizer](https://github.com/google/sanitizers/wiki/AddressSanitizer) and [UndefinedBehaviorSanitizer](https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html) enabled (if possible). (off by default)
116* `-DENABLE_SAFE_STACK`: Enable the [SafeStack](https://clang.llvm.org/docs/SafeStack.html) instrumentation pass. Currently only works with the Clang compiler. (off by default)
117* `-DBUILD_SHARED_LIBS=On`: Build the shared libraries. (on by default)
118* `-DBUILD_SHARED_AND_STATIC_LIBS=On`: Build both shared and static libraries. (off by default)
119* `-DCMAKE_INSTALL_PREFIX=/usr`: Set a prefix for the installation.
120* `-DENABLE_LOCALES=On`: Enable the usage of localeconv method. ( on by default )
121* `-DCJSON_OVERRIDE_BUILD_SHARED_LIBS=On`: Enable overriding the value of `BUILD_SHARED_LIBS` with `-DCJSON_BUILD_SHARED_LIBS`.
122* `-DENABLE_CJSON_VERSION_SO`: Enable cJSON so version. ( on by default )
123
124If you are packaging cJSON for a distribution of Linux, you would probably take these steps for example:
125```
126mkdir build
127cd build
128cmake .. -DENABLE_CJSON_UTILS=On -DENABLE_CJSON_TEST=Off -DCMAKE_INSTALL_PREFIX=/usr
129make
130make DESTDIR=$pkgdir install
131```
132
133On Windows CMake is usually used to create a Visual Studio solution file by running it inside the Developer Command Prompt for Visual Studio, for exact steps follow the official documentation from CMake and Microsoft and use the online search engine of your choice. The descriptions of the the options above still generally apply, although not all of them work on Windows.
134
135#### Makefile
136
137**NOTE:** This Method is deprecated. Use CMake if at all possible. Makefile support is limited to fixing bugs.
138
139If you don't have CMake available, but still have GNU make. You can use the makefile to build cJSON:
140
141Run this command in the directory with the source code and it will automatically compile static and shared libraries and a little test program (not the full test suite).
142
143```
144make all
145```
146
147If you want, you can install the compiled library to your system using `make install`. By default it will install the headers in `/usr/local/include/cjson` and the libraries in `/usr/local/lib`. But you can change this behavior by setting the `PREFIX` and `DESTDIR` variables: `make PREFIX=/usr DESTDIR=temp install`. And uninstall them with: `make PREFIX=/usr DESTDIR=temp uninstall`.
148
149#### Meson
150
151To make cjson work in a project using meson, the libcjson dependency has to be included:
152
153```meson
154project('c-json-example', 'c')
155
156cjson = dependency('libcjson')
157
158example = executable(
159 'example',
160 'example.c',
161 dependencies: [cjson],
162)
163```
164
165
166#### Vcpkg
167
168You can download and install cJSON using the [vcpkg](https://github.com/Microsoft/vcpkg) dependency manager:
169```
170git clone https://github.com/Microsoft/vcpkg.git
171cd vcpkg
172./bootstrap-vcpkg.sh
173./vcpkg integrate install
174vcpkg install cjson
175```
176
177The cJSON port in vcpkg is kept up to date by Microsoft team members and community contributors. If the version is out of date, please [create an issue or pull request](https://github.com/Microsoft/vcpkg) on the vcpkg repository.
178
179### Including cJSON
180
181If you installed it via CMake or the Makefile, you can include cJSON like this:
182
183```c
184#include <cjson/cJSON.h>
185```
186
187### Data Structure
188
189cJSON represents JSON data using the `cJSON` struct data type:
190
191```c
192/* The cJSON structure: */
193typedef struct cJSON
194{
195 struct cJSON *next;
196 struct cJSON *prev;
197 struct cJSON *child;
198 int type;
199 char *valuestring;
200 /* writing to valueint is DEPRECATED, use cJSON_SetNumberValue instead */
201 int valueint;
202 double valuedouble;
203 char *string;
204} cJSON;
205```
206
207An item of this type represents a JSON value. The type is stored in `type` as a bit-flag (**this means that you cannot find out the type by just comparing the value of `type`**).
208
209To check the type of an item, use the corresponding `cJSON_Is...` function. It does a `NULL` check followed by a type check and returns a boolean value if the item is of this type.
210
211The type can be one of the following:
212
213* `cJSON_Invalid` (check with `cJSON_IsInvalid`): Represents an invalid item that doesn't contain any value. You automatically have this type if you set the item to all zero bytes.
214* `cJSON_False` (check with `cJSON_IsFalse`): Represents a `false` boolean value. You can also check for boolean values in general with `cJSON_IsBool`.
215* `cJSON_True` (check with `cJSON_IsTrue`): Represents a `true` boolean value. You can also check for boolean values in general with `cJSON_IsBool`.
216* `cJSON_NULL` (check with `cJSON_IsNull`): Represents a `null` value.
217* `cJSON_Number` (check with `cJSON_IsNumber`): Represents a number value. The value is stored as a double in `valuedouble` and also in `valueint`. If the number is outside of the range of an integer, `INT_MAX` or `INT_MIN` are used for `valueint`.
218* `cJSON_String` (check with `cJSON_IsString`): Represents a string value. It is stored in the form of a zero terminated string in `valuestring`.
219* `cJSON_Array` (check with `cJSON_IsArray`): Represent an array value. This is implemented by pointing `child` to a linked list of `cJSON` items that represent the values in the array. The elements are linked together using `next` and `prev`, where the first element has `prev.next == NULL` and the last element `next == NULL`.
220* `cJSON_Object` (check with `cJSON_IsObject`): Represents an object value. Objects are stored same way as an array, the only difference is that the items in the object store their keys in `string`.
221* `cJSON_Raw` (check with `cJSON_IsRaw`): Represents any kind of JSON that is stored as a zero terminated array of characters in `valuestring`. This can be used, for example, to avoid printing the same static JSON over and over again to save performance. cJSON will never create this type when parsing. Also note that cJSON doesn't check if it is valid JSON.
222
223Additionally there are the following two flags:
224
225* `cJSON_IsReference`: Specifies that the item that `child` points to and/or `valuestring` is not owned by this item, it is only a reference. So `cJSON_Delete` and other functions will only deallocate this item, not its `child`/`valuestring`.
226* `cJSON_StringIsConst`: This means that `string` points to a constant string. This means that `cJSON_Delete` and other functions will not try to deallocate `string`.
227
228### Working with the data structure
229
230For every value type there is a `cJSON_Create...` function that can be used to create an item of that type.
231All of these will allocate a `cJSON` struct that can later be deleted with `cJSON_Delete`.
232Note that you have to delete them at some point, otherwise you will get a memory leak.
233**Important**: If you have added an item to an array or an object already, you **mustn't** delete it with `cJSON_Delete`. Adding it to an array or object transfers its ownership so that when that array or object is deleted,
234it gets deleted as well. You also could use `cJSON_SetValuestring` to change a `cJSON_String`'s `valuestring`, and you needn't to free the previous `valuestring` manually.
235
236#### Basic types
237
238* **null** is created with `cJSON_CreateNull`
239* **booleans** are created with `cJSON_CreateTrue`, `cJSON_CreateFalse` or `cJSON_CreateBool`
240* **numbers** are created with `cJSON_CreateNumber`. This will set both `valuedouble` and `valueint`. If the number is outside of the range of an integer, `INT_MAX` or `INT_MIN` are used for `valueint`
241* **strings** are created with `cJSON_CreateString` (copies the string) or with `cJSON_CreateStringReference` (directly points to the string. This means that `valuestring` won't be deleted by `cJSON_Delete` and you are responsible for its lifetime, useful for constants)
242
243#### Arrays
244
245You can create an empty array with `cJSON_CreateArray`. `cJSON_CreateArrayReference` can be used to create an array that doesn't "own" its content, so its content doesn't get deleted by `cJSON_Delete`.
246
247To add items to an array, use `cJSON_AddItemToArray` to append items to the end.
248Using `cJSON_AddItemReferenceToArray` an element can be added as a reference to another item, array or string. This means that `cJSON_Delete` will not delete that items `child` or `valuestring` properties, so no double frees are occurring if they are already used elsewhere.
249To insert items in the middle, use `cJSON_InsertItemInArray`. It will insert an item at the given 0 based index and shift all the existing items to the right.
250
251If you want to take an item out of an array at a given index and continue using it, use `cJSON_DetachItemFromArray`, it will return the detached item, so be sure to assign it to a pointer, otherwise you will have a memory leak.
252
253Deleting items is done with `cJSON_DeleteItemFromArray`. It works like `cJSON_DetachItemFromArray`, but deletes the detached item via `cJSON_Delete`.
254
255You can also replace an item in an array in place. Either with `cJSON_ReplaceItemInArray` using an index or with `cJSON_ReplaceItemViaPointer` given a pointer to an element. `cJSON_ReplaceItemViaPointer` will return `0` if it fails. What this does internally is to detach the old item, delete it and insert the new item in its place.
256
257To get the size of an array, use `cJSON_GetArraySize`. Use `cJSON_GetArrayItem` to get an element at a given index.
258
259Because an array is stored as a linked list, iterating it via index is inefficient (`O(n²)`), so you can iterate over an array using the `cJSON_ArrayForEach` macro in `O(n)` time complexity.
260
261#### Objects
262
263You can create an empty object with `cJSON_CreateObject`. `cJSON_CreateObjectReference` can be used to create an object that doesn't "own" its content, so its content doesn't get deleted by `cJSON_Delete`.
264
265To add items to an object, use `cJSON_AddItemToObject`. Use `cJSON_AddItemToObjectCS` to add an item to an object with a name that is a constant or reference (key of the item, `string` in the `cJSON` struct), so that it doesn't get freed by `cJSON_Delete`.
266Using `cJSON_AddItemReferenceToArray` an element can be added as a reference to another object, array or string. This means that `cJSON_Delete` will not delete that items `child` or `valuestring` properties, so no double frees are occurring if they are already used elsewhere.
267
268If you want to take an item out of an object, use `cJSON_DetachItemFromObjectCaseSensitive`, it will return the detached item, so be sure to assign it to a pointer, otherwise you will have a memory leak.
269
270Deleting items is done with `cJSON_DeleteItemFromObjectCaseSensitive`. It works like `cJSON_DetachItemFromObjectCaseSensitive` followed by `cJSON_Delete`.
271
272You can also replace an item in an object in place. Either with `cJSON_ReplaceItemInObjectCaseSensitive` using a key or with `cJSON_ReplaceItemViaPointer` given a pointer to an element. `cJSON_ReplaceItemViaPointer` will return `0` if it fails. What this does internally is to detach the old item, delete it and insert the new item in its place.
273
274To get the size of an object, you can use `cJSON_GetArraySize`, this works because internally objects are stored as arrays.
275
276If you want to access an item in an object, use `cJSON_GetObjectItemCaseSensitive`.
277
278To iterate over an object, you can use the `cJSON_ArrayForEach` macro the same way as for arrays.
279
280cJSON also provides convenient helper functions for quickly creating a new item and adding it to an object, like `cJSON_AddNullToObject`. They return a pointer to the new item or `NULL` if they failed.
281
282### Parsing JSON
283
284Given some JSON in a zero terminated string, you can parse it with `cJSON_Parse`.
285
286```c
287cJSON *json = cJSON_Parse(string);
288```
289
290Given some JSON in a string (whether zero terminated or not), you can parse it with `cJSON_ParseWithLength`.
291
292```c
293cJSON *json = cJSON_ParseWithLength(string, buffer_length);
294```
295
296It will parse the JSON and allocate a tree of `cJSON` items that represents it. Once it returns, you are fully responsible for deallocating it after use with `cJSON_Delete`.
297
298The allocator used by `cJSON_Parse` is `malloc` and `free` by default but can be changed (globally) with `cJSON_InitHooks`.
299
300If an error occurs a pointer to the position of the error in the input string can be accessed using `cJSON_GetErrorPtr`. Note though that this can produce race conditions in multithreading scenarios, in that case it is better to use `cJSON_ParseWithOpts` with `return_parse_end`.
301By default, characters in the input string that follow the parsed JSON will not be considered as an error.
302
303If you want more options, use `cJSON_ParseWithOpts(const char *value, const char **return_parse_end, cJSON_bool require_null_terminated)`.
304`return_parse_end` returns a pointer to the end of the JSON in the input string or the position that an error occurs at (thereby replacing `cJSON_GetErrorPtr` in a thread safe way). `require_null_terminated`, if set to `1` will make it an error if the input string contains data after the JSON.
305
306If you want more options giving buffer length, use `cJSON_ParseWithLengthOpts(const char *value, size_t buffer_length, const char **return_parse_end, cJSON_bool require_null_terminated)`.
307
308### Printing JSON
309
310Given a tree of `cJSON` items, you can print them as a string using `cJSON_Print`.
311
312```c
313char *string = cJSON_Print(json);
314```
315
316It will allocate a string and print a JSON representation of the tree into it. Once it returns, you are fully responsible for deallocating it after use with your allocator. (usually `free`, depends on what has been set with `cJSON_InitHooks`).
317
318`cJSON_Print` will print with whitespace for formatting. If you want to print without formatting, use `cJSON_PrintUnformatted`.
319
320If you have a rough idea of how big your resulting string will be, you can use `cJSON_PrintBuffered(const cJSON *item, int prebuffer, cJSON_bool fmt)`. `fmt` is a boolean to turn formatting with whitespace on and off. `prebuffer` specifies the first buffer size to use for printing. `cJSON_Print` currently uses 256 bytes for its first buffer size. Once printing runs out of space, a new buffer is allocated and the old gets copied over before printing is continued.
321
322These dynamic buffer allocations can be completely avoided by using `cJSON_PrintPreallocated(cJSON *item, char *buffer, const int length, const cJSON_bool format)`. It takes a buffer to a pointer to print to and its length. If the length is reached, printing will fail and it returns `0`. In case of success, `1` is returned. Note that you should provide 5 bytes more than is actually needed, because cJSON is not 100% accurate in estimating if the provided memory is enough.
323
324### Example
325
326In this example we want to build and parse the following JSON:
327
328```json
329{
330 "name": "Awesome 4K",
331 "resolutions": [
332 {
333 "width": 1280,
334 "height": 720
335 },
336 {
337 "width": 1920,
338 "height": 1080
339 },
340 {
341 "width": 3840,
342 "height": 2160
343 }
344 ]
345}
346```
347
348#### Printing
349
350Let's build the above JSON and print it to a string:
351
352```c
353//create a monitor with a list of supported resolutions
354//NOTE: Returns a heap allocated string, you are required to free it after use.
355char *create_monitor(void)
356{
357 const unsigned int resolution_numbers[3][2] = {
358 {1280, 720},
359 {1920, 1080},
360 {3840, 2160}
361 };
362 char *string = NULL;
363 cJSON *name = NULL;
364 cJSON *resolutions = NULL;
365 cJSON *resolution = NULL;
366 cJSON *width = NULL;
367 cJSON *height = NULL;
368 size_t index = 0;
369
370 cJSON *monitor = cJSON_CreateObject();
371 if (monitor == NULL)
372 {
373 goto end;
374 }
375
376 name = cJSON_CreateString("Awesome 4K");
377 if (name == NULL)
378 {
379 goto end;
380 }
381 /* after creation was successful, immediately add it to the monitor,
382 * thereby transferring ownership of the pointer to it */
383 cJSON_AddItemToObject(monitor, "name", name);
384
385 resolutions = cJSON_CreateArray();
386 if (resolutions == NULL)
387 {
388 goto end;
389 }
390 cJSON_AddItemToObject(monitor, "resolutions", resolutions);
391
392 for (index = 0; index < (sizeof(resolution_numbers) / (2 * sizeof(int))); ++index)
393 {
394 resolution = cJSON_CreateObject();
395 if (resolution == NULL)
396 {
397 goto end;
398 }
399 cJSON_AddItemToArray(resolutions, resolution);
400
401 width = cJSON_CreateNumber(resolution_numbers[index][0]);
402 if (width == NULL)
403 {
404 goto end;
405 }
406 cJSON_AddItemToObject(resolution, "width", width);
407
408 height = cJSON_CreateNumber(resolution_numbers[index][1]);
409 if (height == NULL)
410 {
411 goto end;
412 }
413 cJSON_AddItemToObject(resolution, "height", height);
414 }
415
416 string = cJSON_Print(monitor);
417 if (string == NULL)
418 {
419 fprintf(stderr, "Failed to print monitor.\n");
420 }
421
422end:
423 cJSON_Delete(monitor);
424 return string;
425}
426```
427
428Alternatively we can use the `cJSON_Add...ToObject` helper functions to make our lives a little easier:
429
430```c
431//NOTE: Returns a heap allocated string, you are required to free it after use.
432char *create_monitor_with_helpers(void)
433{
434 const unsigned int resolution_numbers[3][2] = {
435 {1280, 720},
436 {1920, 1080},
437 {3840, 2160}
438 };
439 char *string = NULL;
440 cJSON *resolutions = NULL;
441 size_t index = 0;
442
443 cJSON *monitor = cJSON_CreateObject();
444
445 if (cJSON_AddStringToObject(monitor, "name", "Awesome 4K") == NULL)
446 {
447 goto end;
448 }
449
450 resolutions = cJSON_AddArrayToObject(monitor, "resolutions");
451 if (resolutions == NULL)
452 {
453 goto end;
454 }
455
456 for (index = 0; index < (sizeof(resolution_numbers) / (2 * sizeof(int))); ++index)
457 {
458 cJSON *resolution = cJSON_CreateObject();
459
460 if (cJSON_AddNumberToObject(resolution, "width", resolution_numbers[index][0]) == NULL)
461 {
462 goto end;
463 }
464
465 if (cJSON_AddNumberToObject(resolution, "height", resolution_numbers[index][1]) == NULL)
466 {
467 goto end;
468 }
469
470 cJSON_AddItemToArray(resolutions, resolution);
471 }
472
473 string = cJSON_Print(monitor);
474 if (string == NULL)
475 {
476 fprintf(stderr, "Failed to print monitor.\n");
477 }
478
479end:
480 cJSON_Delete(monitor);
481 return string;
482}
483```
484
485#### Parsing
486
487In this example we will parse a JSON in the above format and check if the monitor supports a Full HD resolution while printing some diagnostic output:
488
489```c
490/* return 1 if the monitor supports full hd, 0 otherwise */
491int supports_full_hd(const char * const monitor)
492{
493 const cJSON *resolution = NULL;
494 const cJSON *resolutions = NULL;
495 const cJSON *name = NULL;
496 int status = 0;
497 cJSON *monitor_json = cJSON_Parse(monitor);
498 if (monitor_json == NULL)
499 {
500 const char *error_ptr = cJSON_GetErrorPtr();
501 if (error_ptr != NULL)
502 {
503 fprintf(stderr, "Error before: %s\n", error_ptr);
504 }
505 status = 0;
506 goto end;
507 }
508
509 name = cJSON_GetObjectItemCaseSensitive(monitor_json, "name");
510 if (cJSON_IsString(name) && (name->valuestring != NULL))
511 {
512 printf("Checking monitor \"%s\"\n", name->valuestring);
513 }
514
515 resolutions = cJSON_GetObjectItemCaseSensitive(monitor_json, "resolutions");
516 cJSON_ArrayForEach(resolution, resolutions)
517 {
518 cJSON *width = cJSON_GetObjectItemCaseSensitive(resolution, "width");
519 cJSON *height = cJSON_GetObjectItemCaseSensitive(resolution, "height");
520
521 if (!cJSON_IsNumber(width) || !cJSON_IsNumber(height))
522 {
523 status = 0;
524 goto end;
525 }
526
527 if ((width->valuedouble == 1920) && (height->valuedouble == 1080))
528 {
529 status = 1;
530 goto end;
531 }
532 }
533
534end:
535 cJSON_Delete(monitor_json);
536 return status;
537}
538```
539
540Note that there are no NULL checks except for the result of `cJSON_Parse` because `cJSON_GetObjectItemCaseSensitive` checks for `NULL` inputs already, so a `NULL` value is just propagated and `cJSON_IsNumber` and `cJSON_IsString` return `0` if the input is `NULL`.
541
542### Caveats
543
544#### Zero Character
545
546cJSON doesn't support strings that contain the zero character `'\0'` or `\u0000`. This is impossible with the current API because strings are zero terminated.
547
548#### Character Encoding
549
550cJSON only supports UTF-8 encoded input. In most cases it doesn't reject invalid UTF-8 as input though, it just propagates it through as is. As long as the input doesn't contain invalid UTF-8, the output will always be valid UTF-8.
551
552#### C Standard
553
554cJSON is written in ANSI C (or C89, C90). If your compiler or C library doesn't follow this standard, correct behavior is not guaranteed.
555
556NOTE: ANSI C is not C++ therefore it shouldn't be compiled with a C++ compiler. You can compile it with a C compiler and link it with your C++ code however. Although compiling with a C++ compiler might work, correct behavior is not guaranteed.
557
558#### Floating Point Numbers
559
560cJSON does not officially support any `double` implementations other than IEEE754 double precision floating point numbers. It might still work with other implementations but bugs with these will be considered invalid.
561
562The maximum length of a floating point literal that cJSON supports is currently 63 characters.
563
564#### Deep Nesting Of Arrays And Objects
565
566cJSON doesn't support arrays and objects that are nested too deeply because this would result in a stack overflow. To prevent this cJSON limits the depth to `CJSON_NESTING_LIMIT` which is 1000 by default but can be changed at compile time.
567
568#### Thread Safety
569
570In general cJSON is **not thread safe**.
571
572However it is thread safe under the following conditions:
573
574* `cJSON_GetErrorPtr` is never used (the `return_parse_end` parameter of `cJSON_ParseWithOpts` can be used instead)
575* `cJSON_InitHooks` is only ever called before using cJSON in any threads.
576* `setlocale` is never called before all calls to cJSON functions have returned.
577
578#### Case Sensitivity
579
580When cJSON was originally created, it didn't follow the JSON standard and didn't make a distinction between uppercase and lowercase letters. If you want the correct, standard compliant, behavior, you need to use the `CaseSensitive` functions where available.
581
582#### Duplicate Object Members
583
584cJSON supports parsing and printing JSON that contains objects that have multiple members with the same name. `cJSON_GetObjectItemCaseSensitive` however will always only return the first one.
585
586# Enjoy cJSON!
587
588- Dave Gamble (original author)
589- Max Bruckner and Alan Wang (current maintainer)
590- and the other [cJSON contributors](CONTRIBUTORS.md)
591