class BBS::Zmodem::Output

The Sender’s side of the line: headers and data subpackets framed, escaped and checked with a CRC-16, or a CRC-32 once the receiver said it can (crc32=), and 0xFF doubled as telnet IAC on a telnet line.

Attributes

crc32 [W]

Whether frames carry a CRC-32 instead of a CRC-16.

Public Class Methods

new (session, telnet:)

Source

# File lib/bbs/zmodem/output.rb, line 14
def initialize(session, telnet:)
  @session = session
  @telnet  = telnet
  @crc32   = false
end

Writes to session (anything with write_raw); telnet doubles 0xFF.

Public Instance Methods

bin_header (type, bytes)

Source

# File lib/bbs/zmodem/output.rb, line 29
def bin_header(type, bytes)
  frame = [type, *bytes].pack('C*')
  emit(BIN_HEADER + (@crc32 ? ZBIN32 : ZBIN).chr + Zmodem.escape(frame + crc(frame)))
end

Writes a binary header of type with the four bytes.

emit (bytes)

Source

# File lib/bbs/zmodem/output.rb, line 54
def emit(bytes)
  @session.write_raw(@telnet ? bytes.b.gsub(TELNET_IAC, TELNET_IAC * 2) : bytes)
end

Writes bytes as they are (IAC doubled on a telnet line).

hex_header (type, bytes)

Source

# File lib/bbs/zmodem/output.rb, line 21
def hex_header(type, bytes)
  frame = [type, *bytes].pack('C*')
  hex   = (frame + [Zmodem.crc16(frame)].pack('n')).unpack1('H*')
  tail  = [ZFIN, ZACK].include?(type) ? '' : XON.chr
  emit("#{HEX_HEADER}#{hex}#{Ansi::CRLF}#{tail}".b)
end

Writes a hex header of type with the four bytes.

offer (info)

Source

# File lib/bbs/zmodem/output.rb, line 40
def offer(info)
  bin_header(ZFILE, [0, 0, 0, ZCBIN])
  subpacket(info, ZCRCW)
end

Offers a file: a ZFILE header and its info subpacket (name, size, time, mode and what is left of the batch).

position_header (type, pos)

Source

# File lib/bbs/zmodem/output.rb, line 36
def position_header(type, pos) = bin_header(type, [pos].pack('V').bytes)

Writes a binary header of type whose data is the file position pos.

subpacket (data, frameend)

Source

# File lib/bbs/zmodem/output.rb, line 47
def subpacket(data, frameend)
  out = Zmodem.escape(data) << ZDLE << frameend << Zmodem.escape(crc(data + frameend.chr))
  out << XON if frameend == ZCRCW
  emit(out)
end

Writes data as a subpacket ending in frameend (ZCRCE, ZCRCG or ZCRCW, which wants an XON after it).