Amount Compression for Ruby

bc_amount_compression.rb

#!/usr/bin/env ruby

# Bitcoin Core Amount compression
# https://github.com/bitcoin/bitcoin/blob/v0.16.3/src/compressor.cpp#L133

def compress_amount(n)
  if n == 0
    return 0
  end
  e = 0
  while (n % 10 == 0) and e < 9 do
    n /= 10
    e += 1
  end
  if e < 9
    d = n % 10
    n /= 10
    return 1 + (n * 9 + d - 1) * 10 + e
  else
    return 1 + (n - 1) * 10 + 9
  end
end

def decompress_amount(x)
  if x == 0
    return 0
  end
  x -= 1
  e = x % 10
  x /= 10
  n = 0
  if e < 9
    d = (x % 9) + 1
    x /= 9
    n = x * 10 + d
  else
    n = x + 1
  end
  while e > 0 do
    n *= 10
    e -= 1
  end
  return n
end