ConnectionManager now storages Request * (not generates ids for it),
Requests have control on their RequestState, RequestIdPair is now called
Response and storages Request * with some response together.
All related classes are changed to use it in more clean and
understandable way.
Request, RequestState and Response are carefully commented/documented.
Can be used with Callback<T> (means it's still type safe). It's used to
pass not only Request id to user's callback, but also a value user
wanted.
void *data field is removed from RequestInfo.
This commit also adds GlobalFunctionCallback, because it was needed in
order to replace plain C pointers to functions (which were used in
Request) into our object-oriented BaseCallback pointers.
These callbacks can call object's methods, not some global C functions.
DropboxStorage::info2() and DropboxStorage::infoMethodCallback()
demonstrate the idea.
Originally, I intended to add Storage API, StorageFile and StorageInfo
stubs. When I tried to implement a simple info() call, I ended up fixing
Request to contain some pointer field and all callbacks to have Request*
parameter. And, now I have to place callback pointer into Request. which
calls another callback.
And, eventually, these "simple" callbacks would again require another
pointer (to some caller class).
With ConnectionManager singleton one can start their Requests without
creating Storage instance. Moreover, Storage instance should contain
cloud API, not Requests-related handling and timer starting methods.
Thus, these methods were moved into ConnectionManager itself.
