gistfile1.nim

import unsigned

type 
  TAddrKind = enum
    akByte,
    akWord,
    akPacked,
    akPackedRoutine,
    akPackedString
  TAddr = object
    case kind: TAddrKind
    of akByte: byteVal: uint16
    of akWord: wordVal: uint16
    of akPacked: packedVal: uint16
    of akPackedRoutine: routineVal: uint16
    of akPackedString:  stringVal: uint16


#1.1
var data = newseq[uint8]()
var version = 0
var filename = ""
var highmem = 0
var dynamicmem = 0
var staticmem = 0
var length = 0'u32

converter 


proc getaddr(a: TAddr): uint32 =
  case a.kind
  of akByte:
    if a.byteVal <= length:
      return a.byteVal
    else:
      raise EOutOfRange
  of akWord:
    let v = a.wordVal * 2
    if v < length:
      return v
    else:
      raise EOutOfRange
  of akPacked:
    case version 
    of 1, 2, 3:
      let v = a.packedVal * 2
    of 4, 5: 
      let v = a.packedVal * 4