base on A super-fast, compact, JSON-equivalent binary data format  # Fleece __Fleece__ is a binary encoding for semi-structured data. Its data model is a superset of JSON, adding support for binary values. It is designed to be: * **Very fast to read:** No parsing is needed, and the data can be navigated and read without any heap allocation. Fleece objects are internal pointers into the raw data. Arrays and dictionaries can be random-accessed. Performance on real-world-scale data has been clocked at 20x that of JSON. (Want proof? See the [benchmark](Performance.md).) * **Compact:** Simple values will be about the same size as JSON. Complex ones may be much smaller, since repeated values, especially strings, only need to be stored once. * **Efficient to convert into native objects:** Numbers are binary, strings are raw UTF-8 without quoting, binary data is not base64-encoded. Storing repeated values once means they only need to be converted into native objects once. * **Appendable:** Fleece is what's known as a [persistent data structure](https://en.wikipedia.org/wiki/Persistent_data_structure). A Fleece document can be mutated by appending data to it. The mutation is in effect a delta, so it's usually much smaller than the original document. And the original document is unchanged, which is great for concurrency as well as (simple) version control. ## What You Get * Documentation, including * **High-level API guide "[Using Fleece](https://github.com/couchbaselabs/fleece/wiki/Using-Fleece)"** * The [design document](Fleece.md), with details on the data format and other internals * An [example](Example.md) showing the details of the encoding of a specific data structure, and a walkthrough of what happens when a program works with the resulting Fleece objects * A C++ reference implementation, including: * Encoder and decoder/accessors * Extensions for converting JSON directly to Fleece or vice versa * Extensions for encoding from and decoding to Objective-C (Foundation) object trees * Extensions for mutable values, making it easy to modify Fleece documents and then save them again * Extensions for delta compression * Unit tests * Some simple performance benchmarks * C++ and C APIs * A command-line tool, `fleece`, that can convert JSON to Fleece or vice versa, or dump Fleece data in a human-readable form that shows the internal structure * Some experimental stuff: * A [Hash-Array-Mapped Trie](https://en.wikipedia.org/wiki/Hash_array_mapped_trie) implementation for building highly scaleable persistent hash tables in Fleece * At the other extreme, an extremely compact binary tree of strings that might find a use someday ## FAQ **Q: Why does the world need yet another binary JSON encoding?** A: Excellent question, sock puppet! Fleece is different from [BSON](http://bsonspec.org), [PSON](https://github.com/dcodeIO/PSON), etc. in that it's been carefully designed to not need parsing or heap allocation. In performance tests with other binary formats I found that, while they were faster to parse than JSON, the total time was still dominated by allocating and freeing the resulting objects, as well as the conversion from UTF-8 data to platform strings. (I was using Objective-C, but similar issues would arise if using STL or GLib or other collection frameworks.) The way around this is to structure the encoded data more like a memory dump, with "pointers" (relative byte offsets) and fixed-width random-accessible arrays. That's what Fleece does. As a result, it's many times faster to work with than JSON; [literally _20x faster_](Performance.md) in the included benchmark run on a Macbook Pro. **Q: Can I use it in \$LANGUAGE?** [where \$LANGUAGE not in ("C++", "C")] A: Not currently. It would be very nice to more bindings, and the C API should make that fairly straightforward since it's easy to call from other languages. (But any real API should follow the language's idioms, instead of being a direct translation!) **Q: Why didn't you write this in \$NEW_LANGUAGE instead of crufty C++?** A: I probably should have! \$NEW_LANGUAGE is deservedly attracting a lot of attention for its combination of safety, readable syntax, and support for modern programming paradigms. I've been trying out \$NEW_LANGUAGE and want to write more code in it. But for this I chose C++ because it's supported on all platforms, lots of people know how to use it, and it still supports high-level abstractions (unlike C.) **Q: Why the name "Fleece"?** A: It's a reference to the mythical [Golden Fleece](https://en.wikipedia.org/wiki/Golden_Fleece), the treasure sought by Jason and the Argonauts. **Q: Who wrote this?** [Jens Alfke](https://github.com/snej), with design input from [Volker Mische](https://github.com/vmx) and [Dave Rigby](https://github.com/daverigby), and much help with portability and bug-fixing from [Jim Borden](https://github.com/borrrden). (And thanks to Mark Nunberg for the excellent [jsonsl](https://github.com/mnunberg/jsonsl) parser.) ## Status Fleece is in active use and development. It is a core component of Couchbase Lite, via the [LiteCore](https://github.com/couchbase/couchbase-lite-core) library. ## Requirements / Compatibility * Fleece builds with Xcode, Clang, GCC and MSVC. Most of the code is C++17, but some newer parts need C++20. (Yes, there are some Objective-C++ source files (`.mm`), but those are only used to provide Objective-C glue and Mac/iOS specific benchmarks. You can ignore them on other platforms.) * There are no dependencies on any external libraries, other than the standard C library and the C++ STL. * It _should_ work correctly, and create interoperable data, on both little-endian and big-endian CPUs, but admittedly we are not currently testing or using Fleece on any big-endian platforms. We use GitHub CI, covering Clang, GCC, Xcode and MSVC on macOS, Linux and Windows. If you encounter portability problems, please file an issue and we'll fix it. ## License Couchbase Business Source License ", Assign "at most 3 tags" to the expected json: {"id":"5752","tags":[]} "only from the tags list I provide: [{"id":77,"name":"3d"},{"id":89,"name":"agent"},{"id":17,"name":"ai"},{"id":54,"name":"algorithm"},{"id":24,"name":"api"},{"id":44,"name":"authentication"},{"id":3,"name":"aws"},{"id":27,"name":"backend"},{"id":60,"name":"benchmark"},{"id":72,"name":"best-practices"},{"id":39,"name":"bitcoin"},{"id":37,"name":"blockchain"},{"id":1,"name":"blog"},{"id":45,"name":"bundler"},{"id":58,"name":"cache"},{"id":21,"name":"chat"},{"id":49,"name":"cicd"},{"id":4,"name":"cli"},{"id":64,"name":"cloud-native"},{"id":48,"name":"cms"},{"id":61,"name":"compiler"},{"id":68,"name":"containerization"},{"id":92,"name":"crm"},{"id":34,"name":"data"},{"id":47,"name":"database"},{"id":8,"name":"declarative-gui "},{"id":9,"name":"deploy-tool"},{"id":53,"name":"desktop-app"},{"id":6,"name":"dev-exp-lib"},{"id":59,"name":"dev-tool"},{"id":13,"name":"ecommerce"},{"id":26,"name":"editor"},{"id":66,"name":"emulator"},{"id":62,"name":"filesystem"},{"id":80,"name":"finance"},{"id":15,"name":"firmware"},{"id":73,"name":"for-fun"},{"id":2,"name":"framework"},{"id":11,"name":"frontend"},{"id":22,"name":"game"},{"id":81,"name":"game-engine "},{"id":23,"name":"graphql"},{"id":84,"name":"gui"},{"id":91,"name":"http"},{"id":5,"name":"http-client"},{"id":51,"name":"iac"},{"id":30,"name":"ide"},{"id":78,"name":"iot"},{"id":40,"name":"json"},{"id":83,"name":"julian"},{"id":38,"name":"k8s"},{"id":31,"name":"language"},{"id":10,"name":"learning-resource"},{"id":33,"name":"lib"},{"id":41,"name":"linter"},{"id":28,"name":"lms"},{"id":16,"name":"logging"},{"id":76,"name":"low-code"},{"id":90,"name":"message-queue"},{"id":42,"name":"mobile-app"},{"id":18,"name":"monitoring"},{"id":36,"name":"networking"},{"id":7,"name":"node-version"},{"id":55,"name":"nosql"},{"id":57,"name":"observability"},{"id":46,"name":"orm"},{"id":52,"name":"os"},{"id":14,"name":"parser"},{"id":74,"name":"react"},{"id":82,"name":"real-time"},{"id":56,"name":"robot"},{"id":65,"name":"runtime"},{"id":32,"name":"sdk"},{"id":71,"name":"search"},{"id":63,"name":"secrets"},{"id":25,"name":"security"},{"id":85,"name":"server"},{"id":86,"name":"serverless"},{"id":70,"name":"storage"},{"id":75,"name":"system-design"},{"id":79,"name":"terminal"},{"id":29,"name":"testing"},{"id":12,"name":"ui"},{"id":50,"name":"ux"},{"id":88,"name":"video"},{"id":20,"name":"web-app"},{"id":35,"name":"web-server"},{"id":43,"name":"webassembly"},{"id":69,"name":"workflow"},{"id":87,"name":"yaml"}]" returns me the "expected json"