class BBS::Gateway::AsciiBridge

The translation a gateway puts on the line when a PETSCII caller (a Commodore 64) dials a board made for ASCII and ANSI terminals. The board’s bytes go down as PETSCII: text in UTF-8, or CP437 from the first bytes that are not UTF-8 on, through a Petscii::Encoder, so letters swap case, ANSI colours and cursor moves become C64 control codes and line drawing the nearest glyph. The C64’s keys go up as an ANSI terminal sends them.

bridge = BBS::Gateway::AsciiBridge.new
bridge.down("Hello\r\n")   # PETSCII bytes for the C64
bridge.up("\x91".b)        # => "\e[A" (CRSR up)

Constants

IAC: The telnet IAC byte, doubled in what goes down so the caller’s telnet client takes it as data.
KEYS: The C64’s special keys (BBS::Petscii.key) as an ANSI terminal sends them; a key not listed (F1-F8) is not sent.
SIGNS: Signs the C64 has a key for and ASCII has not, as their ASCII stand-in.
UTF8_LEADS: The first byte of a UTF-8 sequence of two, three and four bytes.

Public Class Methods

new ()

Source

# File lib/bbs/gateway/ascii_bridge.rb, line 30
def initialize
  @encoder = Petscii::Encoder.new
  @pending = +''.b
  @cp437   = false
end

Creates a bridge with a fresh encoder and no partial character.

Public Instance Methods

down (bytes)

Source

# File lib/bbs/gateway/ascii_bridge.rb, line 40
def down(bytes)
  data     = @pending + bytes.b
  @pending = @cp437 ? +''.b : cut_character(data)
  whole    = data.byteslice(0, data.bytesize - @pending.bytesize)
  @encoder.encode(text(whole)).gsub(IAC, IAC + IAC)
end

Returns the PETSCII bytes for bytes the board sent (telnet commands already taken out). While the board writes UTF-8, a character cut at the end of bytes waits for the next call; the encoder’s column and colour carry over too.

up (bytes)

Source

# File lib/bbs/gateway/ascii_bridge.rb, line 50
def up(bytes) = bytes.b.each_byte.filter_map { |byte| key(Petscii.key(byte)) }.join.b

Returns the bytes an ANSI terminal would send for bytes, the keys the C64 sent: letters in ASCII case, RETURN as CR, DEL as backspace, the cursor keys as ANSI sequences, RUN/STOP as ESC.