[erlang-questions] encoding packets a style+efficiency question

Anupam Kapoor anupam.kapoor@REDACTED
Tue Jul 26 09:36:05 CEST 2011

hi all,

i have been playing with an implementation of tftp
(rfc-1350). encoding/decoding tftp-pdu's is trivial with erlang's bit

there seem to be couple of approaches to encoding/decoding tftp-pdu's:

   1. use native "in-place" encode/decode
   2. have a 'generic' encode/decode routine which accepts
         - a list of pdu primitives e.g. 'byte'/'string' etc. and
         - a list of corresponding values
      and returns the binary packet.

      for example, encoding a tftp-data packet looks like this:
          | %% encode data packet
          | encode_data_pkt(BlkNum, Data) ->
          |     encode_packet([?BYTE, ?BYTE, ?RAW],
[?TFTP_OPCODE_DATA, BlkNum, Data]).

to me, approach #2 seems pretty close to rfc's packet-format
specification. for example, the data-packet is shown as

           2 bytes     2 bytes      n bytes
          | Opcode |   Block #  |   Data     |

can you please provide your suggestion on whether #2 might be a good
approach to follow for complicated protocols e.g. gtp-v2 which defines a
large number of messages ? also, are there better (increasing order of
readability, performance etc.) approaches for doing this ?

thank you
kind regards

ps: the attached file contains encoders for tftp messages...

In the beginning was the lambda, and the lambda was with Emacs, and
Emacs was the lambda.
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