Twinson
Simple and lightweight JSON decoder for TwinCAT and CODESYS.
State of the implementation
- Continuous integration
- Parser
- Strings
- Numbers
- Boolean
- Null
- Objects (including nested objects)
- Arrays (including mixed array and nested arrays)
- Basic element access
- Monadic element access
- Unittests
- Performance improvements for accessing elements, use tree to store data instead of array
- Performance tuning
- Node access for "cached" element access
Comparison to Tc3_Json
Twinson is lightweight alternative to Beckhoff's Tc3_Json.FB_JsonDomParser. When comparing Twinson with the Tc3_Json (TC 3.1.4024.25), I discovered issues with Tc3_Json that might be addressed by Beckhoff in the future.
null, as specified by the JSON format, is not parsed correctly.- Parsing nested arrays is cumbersome, because there is no way (at least I didn't find any documented) to access an array element directly.
Benchmark
Twinson includes a seperate PLC for benchmarking the library against Tc3_Json. The benchmark uses several examples with increasing JSON complexity (In terms of how many "levels" the JSON objects have). We measure the duration it takes for parsing a JSON document and assigning all members of the JSON document to TwinCAT variables with direct element access.
- Example 1: Object with 3 key/value pairs
- Example 2: Object with 10 key/value pairs
- Example 3: Object with 3 arrays, each containing 10 strings
- Example 4: Object with 3 arrays, each containing 3 objects and each object has 10 key/value pairs
- Example 5: Nested object with 10 levels object1.object2.(...).object9.string1...string10)
