Module: StrokeDB::ChainSync

Included in:
Store
Defined in:
lib/strokedb/sync/chain_sync.rb

Overview

You may mix-in this into specific sync implementations

Defined Under Namespace

Classes: NonMatchingChains

Instance Method Summary collapse

Instance Method Details

#sync_chains(from, to) ⇒ Object

We have 2 chains as an input: our chain (“to”) and a foreign chain (“from”). We’re going to calculate the difference between those chains to know how to implement synchronization.

There’re two cases: 1) from is a subset of to -> nothing to sync 2) to is a subset of from -> fast-forward merge 3) else: merge case: return base, head_from & head_to

Raises:



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# File 'lib/strokedb/sync/chain_sync.rb', line 13

def sync_chains(from, to)
  common = from & to
  raise NonMatchingChains, "no common element found" if common.empty?
  base = common[common.size - 1]
  ifrom = from.index(base)
  ito   = to.index(base)
  
  # from:  -------------base
  # to:    -----base----head
  if ifrom == from.size - 1
    :up_to_date
  
  # from:  -----base----head
  # to:    -------------base
  elsif ito == to.size - 1
    [ :fast_forward, from[ifrom..-1] ]
  
  # from:  -----base--------head
  # to:    --------base-----head
  else
    [ :merge, from[ifrom..-1], to[ito..-1] ]
  end
end