131 lines
4.3 KiB
Markdown
131 lines
4.3 KiB
Markdown
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# json-c d'accord library (libjsoncdac)
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jsonc-daccord is a lightweight JSON Schema validation library written in C, and is taking advantage of the libjson-c library.
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## Design Goals
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The goal is to have a lightweight JSON Schema validation implementation in C using json-c. json-c is popular in OpenWRT communities. Initially I just wanted it to support a small subset of JSON Schema to suit a need to validate simple json files. See the minimum build supports below. However to suit a broader audience, supporting more JSON Schema is important.
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Currently the footprint of libjsoncdac.so is 8KB. The keep the footprint from bloating out, new features should be selectable using CMake options.
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Minimal build supports:
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- all: type, enum, required, properties, const.
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- objects:
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- strings: minLength, maxLength.
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- integers and doubles: minimum, maximum.
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- arrays: minItems, maxItems, uniqeItems, items.
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## Example Use
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Public headers:
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See [jsoncdaccord.h](include/jsoncdaccord.h)
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```C
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int jdac_validate_file(const char *jsonfile, const char *jsonschemafile);
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int jdac_validate(json_object *jobj, json_object *jschema);
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int jdac_ref_set_localpath(const char *_localpath);
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const char* jdac_errorstr(unsigned int jdac_errors);
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```
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Link your binary to: `-ljsoncdac -ljson-c`
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Use the #include header: `#include <jsoncdaccord.h>`
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Example C code:
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```C
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#include <stdio.h>
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#include <json-c/json.h>
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#include <jsoncdaccord.h>
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int main(int argc, char *argv[])
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{
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char *json_file = "test.json";
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char *schema_file = "schema.json";
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// optional: load referenced schema files from filesystem
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char *localpath = "/my/path/to_json_files/";
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jdac_ref_set_localpath(localpath);
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printf("validating %s with %s\n", json_file, schema_file);
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int err = jdac_validate_file(json_file, schema_file);
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if (err==JDAC_ERR_VALID) {
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printf("validation ok\n");
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} else {
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printf("validate failed %d: %s\n", err, jdac_errorstr(err));
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}
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return err;
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}
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```
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See [jdac-cli.c](libjsoncdac/jdac-cli.c) as well.
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## Install
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Building from source:
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Install json-c and libcmocka-dev (used in the debug builds).
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- Release version:
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```
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git clone --branch libjsoncdac-0.2 https://github.com/domoslabs/jsonc-daccord &&\
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cd jsonc-daccord && mkdir build && cd build &&\
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cmake .. -DCMAKE_BUILD_TYPE=Release && make && sudo make install
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```
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- Debug version:
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```
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git clone --branch libjsoncdac-0.2 https://github.com/domoslabs/jsonc-daccord &&\
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cd jsonc-daccord && mkdir build && cd build &&\
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cmake .. -DCMAKE_BUILD_TYPE=Debug && make && sudo make install
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```
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Note: After install you might need to run `sudo ldconfig`.
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## CMake Options
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build options:
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| option | description |
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| :------------------------- | :------------------------------------------------------- |
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| CMAKE_BUILD_TYPE | Build as Release or Debug. Default: Release. |
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| RUN_TEST_SUITE | Run JSON Schema test suite (CMAKE_BUILD_TYPE=Debug Only) |
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| BUILD_PATTERN | Support *pattern*. |
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| BUILD_PATTERNPROPERTIES | Support *patternProperties* |
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| BUILD_ADDITIONALPROPERTIES | Support *additionalProperties* |
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| BUILD_PROPERTYNAMES | Support *propertyNames* |
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| BUILD_SUBSCHEMALOGIC | Support *allOf*, *anyOf*, *oneOf*, *not*, *if-then-else* |
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| BUILD_CONTAINS | Support *contains*, *minContains*, and *maxContains* |
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| BUILD_DOWNLOAD | Support downloading referenced schema files |
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| BUILD_STORE | Support build a list of schema uri, id, and anchors |
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| BUILD_REF | Support *$ref* keyword. load schemas by file. |
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Note: All BUILD_* options are selected by default
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## Run tests
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For debug builds:
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```
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ctest
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ctest -V # to see output of tests
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```
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Running test suites are currently optional, and are select with `RUN_TEST_SUITE=ON` in the cmake options.
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## Command Line Interface
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You can try the library with the jdac-cli command.
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```/tmp/domos/domosqos-sta_statistics_json
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jdac-cli -h
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```
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## To do
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- prevent infinite recursion
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## Related links
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- https://json-schema.org/specification.html
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- https://github.com/json-schema-org/JSON-Schema-Test-Suite
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- https://github.com/json-c/json-c
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