The blockchain class can effectively now be shallow,
we can have a list of blockheaders of, for instance, the last year
alone. It builds on top of a known checkpoint (hardcoded block data)
and as long as we do not access block info that is unavailable, things
just work like normal.
We throw at the request of a blockheader that is too old.
This change makes it so that we rely less on the downloaded
blockheader data being only in memory and us saving it when
the client shuts down.
Instead, we save more regularly and we save smaller files
instead of always overwriting the complete downloaded headers.
Having less to save at shutdown is then a happy side-effect.
What we did previously is load a static chain which was to avoid lots of
work by simply memory-mapping the data instead of inserting it in a
vector.
This improves upon that by also having a metadata file which holds the
block-hashes directly readable. This avoids us having to iterate over
the blockheaders and hashing them.
Additionally we now have a single chain-work field that is the total
amount added work for the headers. This saves us from doing 256-bit
divisions and work for each blockheader as well.
Result is that we make the statup mostly about memory moving and remove
all CPU intensive stuff. Going from 1450ms to 400ms on desktop.
I expect an even greater gain on mobile CPUs.
The NetworkManager usage was mostly for low connection counts and this
made defaults selection easy.
With more usages it is important to allow the NWM-connection to be more
configurable about memory usage and leaner in general.
This changes the headers-buffers (used to create envelopes) to not be per
connection anymore but per thread using the tread_local keyword.
This changes the ring-buffers to become configurable using
NetworkConnections::setMessageQueueSizes().
Also removing some include statements where they were not really needed
in the P2PNet lib.
We reuse the NetworkManager lower level code in order to connect
to the Bitcoin P2P network.
This implements the basics for anyone wanting to be a player on
this network.
tomFlowee
TomZ