This commit refactors the ValueGenerator class to be a template that can
work with any container type. Previously, one has to manually take care
of the used container by lazily iterating over it within a lambda. Now,
the `ValueGenerator` class itself takes care of all the iteration,
making it easier to use and less error-prone. The new base `Generator`
class is required to allow the `JsonEncoder` to handle generators in a
type-erased manner.
This commit intruduces a small helper class that wraps any writer and
provides a flush operation that performs the corresponding action if the
writer is an AsyncJsonWriter and does nothing otherwise.
Replacing invalid UTF-8 characters beforehand by our selves doesn't make
any sense, the serializer can literally perform the same replacement ops
with the exact same Unicode replacement character (U+FFFD) on its own.
So, why not just use it directly? Instead of wasting memory on a temporary
`String` object to always UTF-8 validate every and each value, we just
use the serializer to directly to dump the replaced char (if any) into
the output writer. No memory waste, no fuss!
This commit removes EmbeddedNamespaceValue and ConstEmbeddedNamespaceValue and
reduces NamespaceValue down to a simple struct without inheritance or member
functions. The code from these clases is inlined into the Namespace class. The
class hierarchy determining whether a value is const is moved to an attribute
of NamespaceValue.
This is done in preparation for changes to the locking in the Namespace class.
Currently, it relies on a recursive mutex. In the future, a shared mutex
(read/write lock) should be used instead, which cannot allow recursive locking
(without failing or risk deadlocking on lock upgrades). With this change, all
operations requiring a lock for one operation are within one function, no
recursive locking is not needed any more.
