module FDB::Tuple

def self.decode(v, pos)
  code = v.getbyte(pos)
  if code == @@NULL_CODE
    [nil, pos+1]
  elsif code == @@BYTES_CODE
    epos = find_terminator(v, pos+1)
    [v.slice(pos+1, epos-pos-1).gsub("\x00\xFF", "\x00"), epos+1]
  elsif code == @@STRING_CODE
    epos = find_terminator(v, pos+1)
    [v.slice(pos+1, epos-pos-1).gsub("\x00\xFF", "\x00").force_encoding("UTF-8"), epos+1]
  elsif code >= @@INT_ZERO_CODE && code < @@POS_INT_END
    n = code - @@INT_ZERO_CODE
    [("\x00" * (8-n) + v.slice(pos+1, n)).unpack("Q>")[0], pos+n+1]
  elsif code > @@NEG_INT_START and code < @@INT_ZERO_CODE
    n = @@INT_ZERO_CODE - code
    [("\x00" * (8-n) + v.slice(pos+1, n)).unpack("Q>")[0]-@@size_limits[n], pos+n+1]
  elsif code == @@POS_INT_END
    length = v.getbyte(pos+1)
    val = 0
    length.times do |i|
      val = val << 8
      val += v.getbyte(pos+2+i)
    end
    [val, pos+length+2]
  elsif code == @@NEG_INT_START
    length = v.getbyte(pos+1) ^ 0xff
    val = 0
    length.times do |i|
      val = val << 8
      val += v.getbyte(pos+2+i)
    end
    [val - (1 << (length*8)) + 1, pos+length+2]
  elsif code == @@FALSE_CODE
    [false, pos+1]
  elsif code == @@TRUE_CODE
    [true, pos+1]
  elsif code == @@FLOAT_CODE
    [SingleFloat.new(float_adjust(v, pos+1, 4, false).unpack("g")[0]), pos+5]
  elsif code == @@DOUBLE_CODE
    [float_adjust(v, pos+1, 8, false).unpack("G")[0], pos+9]
  elsif code == @@UUID_CODE
    [UUID.new(v.slice(pos+1, 16)), pos+17]
  elsif code == @@NESTED_CODE
    epos = pos+1
    nested = []
    while epos < v.length
      if v.getbyte(epos) == @@NULL_CODE 
        if epos+1 < v.length and v.getbyte(epos+1) == 0xFF
          nested << nil
          epos += 2
        else
          break
        end
      else
        r, epos = decode(v, epos)
        nested << r
      end
    end
    [nested, epos+1]
  else
    raise "Unknown data type in DB: " + code.ord.to_s
  end
end