[Development] QtCS 2018 - Serialisation session notes
thiago.macieira at intel.com
Mon Jun 11 13:17:00 CEST 2018
=== Binary JSON ===
* Was created for qtjsondb
* fast reading
* Deprecate soon (Qt 5.12?)
** Remove from QJsonDocument in Qt 6
** Provide compat API to read
*** BSJON → JSON → parse again
=== QJsonDocument ===
* Limited to 128 MB of RAM footprint (due to Binary JSON)
* Needs to be fixed before Qt 6
* Can use the same backend as QCborValue
* Complaint: updating in-place is not easy
** If you update an entry in a node, you have to update the chain leading to
** QCborValue has the same problem, as it was designed to have the same API
QJsonValue foo = ...;
foo["s"] = "value"; // does not compile
foo.toObject()["s"] = "value"; // updates the temporary!
// must write instead:
QJsonObject fooObject = foo.toObject();
fooObject["s"] = "value";
=== Common DOM API? ===
* Should we have a common API for manipulating trees of JSON-like values?
* QCborValue is a superset of QJsonValue
** But it would be confusing to users to use CBOR classes to manipulate JSON
** Generic name?
* What other uses would this API have?
** Replace QJSValue (QtQml)?
** Replace QVariantMap?
** Entry point for a Protobuf API?
* How to make sure people can't insert combinations not allowed in the output?
** For example, associative containers using integers as keys in JSON
** Do they do that? Maybe they won't write such code
*** They know what their content is used for
** We could use templates, specialising for CBOR, JSON, etc.
** We could have a wrapper class that has inlines and provides only the
* QCborValue integrated last Friday into QtCore 5.12
** Need to know in the next few weeks if we keep it for 5.12
** Can yank it out and move to a new module for Tech Preview
=== Serialising Qt state ===
* Needed by Qt Remote Objects
* Slightly different from CBOR and JSON purposes
** Not about a standardised representation of a data model
** More about transmitting state from two independent processes of the same
* Currently using QDataStream
** Has a lot of problems, can't really detect errors and not extensible enough
* Need more exploration, no conclusion
=== Protobuf ===
* Need volunteers to write a Proof of Concept
** plugin to protoc?
Thiago Macieira - thiago.macieira (AT) intel.com
Software Architect - Intel Open Source Technology Center
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