【例程】OneOS启物开发板板级支持包(BSP)

# cJSON Ultralightweight JSON parser in ANSI C. ## Table of contents * [License](#license) * [Usage](#usage) * [Welcome to cJSON](#welcome-to-cjson) * [Building](#building) * [Copying the source](#copying-the-source) * [CMake](#cmake) * [Makefile](#makefile) * [Including cJSON](#including-cjson) * [Data Structure](#data-structure) * [Working with the data structure](#working-with-the-data-structure) * [Basic types](#basic-types) * [Arrays](#arrays) * [Objects](#objects) * [Parsing JSON](#parsing-json) * [Printing JSON](#printing-json) * [Example](#example) * [Printing](#printing) * [Parsing](#parsing) * [Caveats](#caveats) * [Zero Character](#zero-character) * [Character Encoding](#character-encoding) * [C Standard](#c-standard) * [Floating Point Numbers](#floating-point-numbers) * [Deep Nesting Of Arrays And Objects](#deep-nesting-of-arrays-and-objects) * [Thread Safety](#thread-safety) * [Case Sensitivity](#case-sensitivity) * [Duplicate Object Members](#duplicate-object-members) * [Enjoy cJSON!](#enjoy-cjson) ## License MIT License > Copyright (c) 2009-2017 Dave Gamble and cJSON contributors > > 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. 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. 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. ### Building There are several ways to incorporate cJSON into your project. #### copying the source Because 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. cJSON is written in ANSI C (C89) in order to support as many platforms and compilers as possible. #### CMake With 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. ``` mkdir build cd build cmake .. ``` This will create a Makefile and a bunch of other files. You can then compile it: ``` make ``` And 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. You 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`: * `-DENABLE_CJSON_TEST=On`: Enable building the tests. (on by default) * `-DENABLE_CJSON_UTILS=On`: Enable building cJSON_Utils. (off by default) * `-DENABLE_TARGET_EXPORT=On`: Enable the export of CMake targets. Turn off if it makes problems. (on by default) * `-DENABLE_CUSTOM_COMPILER_FLAGS=On`: Enable custom compiler flags (currently for Clang, GCC and MSVC). Turn off if it makes problems. (on by default) * `-DENABLE_VALGRIND=On`: Run tests with [valgrind](http://valgrind.org). (off by default) * `-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) * `-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) * `-DBUILD_SHARED_LIBS=On`: Build the shared libraries. (on by default) * `-DBUILD_SHARED_AND_STATIC_LIBS=On`: Build both shared and static libraries. (off by default) * `-DCMAKE_INSTALL_PREFIX=/usr`: Set a prefix for the installation. * `-DENABLE_LOCALES=On`: Enable the usage of localeconv method. ( on by default ) * `-DCJSON_OVERRIDE_BUILD_SHARED_LIBS=On`: Enable overriding the value of `BUILD_SHARED_LIBS` with `-DCJSON_BUILD_SHARED_LIBS`. If you are packaging cJSON for a distribution of Linux, you would probably take these steps for example: ``` mkdir build cd build cmake .. -DENABLE_CJSON_UTILS=On -DENABLE_CJSON_TEST=Off -DCMAKE_INSTALL_PREFIX=/usr make make DESTDIR=$pkgdir install ``` On 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. #### Makefile **NOTE:** This Method is deprecated. Use CMake if at all possible. Makefile support is limited to fixing bugs. If you don't have CMake available, but still have GNU make. You can use the makefile to build cJSON: Run 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). ``` make all ``` If 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`. ### Including cJSON If you installed it via CMake or the Makefile, you can include cJSON like this: ```c #include <cjson/cJSON.h> ``` ### Data Structure cJSON represents JSON data using the `cJSON` struct data type: ```c /* The cJSON structure: */ typedef struct cJSON { struct cJSON *next; struct cJSON *prev; struct cJSON *child; int type; char *valuestring; /* writing to valueint is DEPRECATED, use cJSON_SetNumberValue instead */ int valueint; double valuedouble; char *string; } cJSON; ``` An 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`**). To check the type of an item, use the correspo