Bitcoin Core Base128 Serializer by Ruby

bc_b128.rb

#!/usr/bin/env ruby

# Bitcoin Core Base128 Serializer
# https://github.com/bitcoin/bitcoin/blob/v0.16.3/src/serialize.h#L317

def b128_encode( n )
  puts (n).to_s(2)
  tmp = []
  while true do
    tmp.push( ((n & 0x7F) | (tmp.length>0 ? 0x80 : 0x00) ).chr )
    if n <= 0x7F
      break
    end
    n = (n >> 7) - 1
  end
  tmp.reverse.join
end

def b128_decode( bytes , offset = 0)
  bytes = bytes[offset..-1]
  n = 0
  bytes.each_byte {|b|
    offset += 1
    n = ( n << 7 ) | ( b.ord & 0x7F )
    if b.ord & 0x80 == 128
      n += 1
    else
      return n, offset
    end
  }
end