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|
require 'dl/import'
module POC
module FEC
extend DL::Importable
dlload "./libfec.so"
# misc
# FIXME: hier korrekter type und rausfinden
# wie NULL Pointer in libfec_init uebergeben werden
extern "void libfec_init(void *, void *) "
extern "void libfec_close()"
# IO
extern "int libfec_read_adu(unsigned char *, unsigned int)"
extern "void libfec_write_adu(unsigned char *, unsigned int)"
# decoding
extern "fec_decode_t *libfec_new_group(unsigned char,
unsigned char,
unsigned long)"
extern "void libfec_add_pkt(fec_decode_t *,
unsigned char,
unsigned long,
unsigned char*)"
extern "unsigned int libfec_decode(fec_decode_t *,
unsigned char *,
unsigned int,
unsigned int)"
extern "void libfec_delete_group(fec_decode_t *)"
#encoding
extern "fec_encode_t *libfec_new_encode(unsigned char,
unsigned char)"
extern "int libfec_add_adu(fec_encode_t *,
unsigned long,
unsigned char *)"
extern "unsigned int libfec_max_length(fec_encode_t *)"
extern "unsigned int libfec_encode(fec_encode_t *,
unsigned char *,
unsigned int,
unsigned int)"
extern "void libfec_delete_encode(fec_encode_t *)"
class Error < Exception
end
class Encoder
def initialize(n, k)
@group = FEC::libfec_new_encode(n, k)
raise Error.new("cannot allocate new FEC group") unless @group
if block_given?
begin
yield self
ensure
close
end
end
end
def add(data)
success = FEC::libfec_add_adu(@group, data.size, data) == 1
raise Error.new("cannot add ADU to FEC group") unless success
end
def maxlen
FEC::libfec_max_length(@group)
end
def encode(idx)
bufferlen = maxlen
buffer = (" " * bufferlen).to_ptr
encoded = FEC::libfec_encode(@group, buffer, idx, bufferlen)
buffer.to_s(encoded)
end
def close
FEC::libfec_delete_encode(@group)
end
end
class Decoder
def initialize(n, k, len)
@group = FEC::libfec_new_group(n, k, len)
@maxlen = len
raise Error.new("cannot allocate new FEC group") unless @group
if block_given?
begin
yield self
ensure
close
end
end
end
def add(seq, data)
FEC::libfec_add_pkt(@group, seq, data.size, data)
end
def decode(idx)
buffer = (" " * @maxlen).to_ptr
decoded = FEC::libfec_decode(@group, buffer, idx, @maxlen)
return nil if decoded == 0
buffer.to_s(decoded)
end
def close
FEC::libfec_delete_group(@group)
end
end
def encode(pkts, k)
raise Error.new("#pkts (#{pkts.size}) > k (#{k})") if pkts.size > k
res = []
maxlen = 0
Encoder.new(pkts.size, k) do |encoder|
pkts.each do |pkt|
encoder.add(pkt)
end
k.times do |idx|
res << encoder.encode(idx)
end
maxlen = encoder.maxlen
end
[maxlen, res]
end
# ... [pkt, nil, pkt, pkt, ...]
def decode(pkts, n)
maxlen = pkts.map{ |pkt| pkt ? pkt.size : 0 }.max
res = []
Decoder.new(n, pkts.size, maxlen) do |decoder|
pkts.each_with_index do |pkt, idx|
next unless pkt
decoder.add(idx, pkt)
end
n.times do |idx|
res << decoder.decode(idx)
end
end
res
end
module_function :decode, :encode
def readAdu
buffer = (" " * 4000).to_ptr
len = FEC::libfec_read_adu(buffer, 4000)
return nil if len == -1
buffer.to_s(len)
end
def writeAdu(adu)
FEC::libfec_write_adu(adu, adu.size)
end
module_function :readAdu, :writeAdu
def init(infile = nil, outfile = nil)
libfec_init(infile, outfile)
end
module_function :init
end
end
=begin
POC::FEC::init("-", "-")
while adu = POC::FEC::readAdu
POC::FEC::writeAdu(adu)
end
=end
if __FILE__ == $0
POC::FEC::init
# 3 Datenpakete ...
data = ["foooo", "bl0rg", "baaaz"]
p data
# ... aufblasen auf 5 (n = 3, k = 5)
maxlen, encoded = POC::FEC::encode(data, 5)
p encoded
# Paket 1 und 2 gehen vorloren
encoded[1] = nil
encoded[2] = nil
# die 3 original Pakete zurueckholen
decoded = POC::FEC::decode(encoded, 3)
p decoded
end
|
