This commit contains the entire btcchain repository along with several
changes needed to move all of the files into the blockchain directory in
order to prepare it for merging. This does NOT update btcd or any of the
other packages to use the new location as that will be done separately.
- All import paths in the old btcchain test files have been changed to
the new location
- All references to btcchain as the package name have been changed to
blockchain
This commit refactors the code to make use of the btcnet package for
network-specific parameters instead of switching on the specific network.
For example, the percentage of the network that needs to run version 2
blocks is different between testnet and mainnet. Previously the code was
using a switch to choose these values. With this refactor, those
parameters are part of the network parameters provided when creating a new
chain instance.
Another example is checkpoints, which have been moved to btcnet so they
can be specified by the caller instead of hard coded into this package.
As a result, the checkpoints for the standard networks are now specified
in the btcnet package.
This makes it easier to add new networks such as a testnet4 should it
become needed. It also allows callers to define their own custom network
parameters without having to modify the code of the package to add new
switch cases for the custom network.
This commit exports a new variant of the existing internal
calcNextRequiredDifficulty function which calculates and returns the next
required difficulty for a block after the end of the current best chain
based on the difficulty retarget rules.
In order to support the exported function the internal one was slightly
modified to accept the block timestamp instead of an entire block since
the timestamp is all that is needed and the caller of the exported
function might next have a full block yet.
Previously, the code was using big rational numbers for work values which
resulted in carrying way too much precision around (and ultimately a lot
of extra memory and computation to carry that precision). This commit
converts the work values to big integers and calculates them with integer
division. This is acceptable because the numerator is multiplied by 2^256
which is higher than the maximum possible proof of work. Therefore
anything after the decimal is superfluous precision for the purposes of
chain selection.
Also, add a check for negative difficulty values when calculating the work
value. Negative values won't occur in practice with valid blocks, but
it's possible an invalid block could trigger the code path, so be safe and
check for it.
Rather than converting the proof of work limit to its compact
representation multiple times during operation, do it once at package
initialization time and export it via the chain parameters.
This commit modifies the code to use params based on the active network
which paves the way for supporting the special rules and different genesis
blocks used by the test networks.
