What is narcs?

narcs is an encoder combinator library, essential the reverse of the decoder combinators provided by scran.

Examples

For a 16 bit big endian unsigned length encoded string of “abc”, returning iodata:

1> (narcs_bytes:length_encoded(narcs_number:u(big, 16)))(<<"abc">>).
[<<0,3>>,<<"abc">>]

For the same string to be null terminated:

1> (narcs_bytes:null_terminated())(<<"abc">>).
[<<"abc">>,0].

Using a map of parameters, to encode some flags (32 bit integer), followed by some null terminated bytes:

1> (narcs_sequence:sequence(
      [narcs_combinator:v(flags, narcs_number:u(big, 32)),
       narcs_combinator:v(bytes, narcs_bytes:null_terminated())]))
         (#{flags => 128, bytes => <<"hello world!">>}).
[<<0,0,0,128>>,[<<"hello world!">>,0]]

Using a map of parameters, write each key as null terminated bytes and each value as a 16 bit numeric value:

1> KV = (narcs_sequence:sequence(
         %% keys are atoms encoded as null terminated bytes:
         narcs_combinator:map_result(
             narcs_bytes:from_atom(),
             narcs_bytes:null_terminated()),

         %% values are 16 bit big endian:
         narcs_number:u(big, 16))).

#Fun<narcs_sequence.1.53547035>

2> KV(#{a => 1, b => 2, c => 3}).

[[<<"b">>,0],
 <<0,2>>,
 [<<"a">>,0],
 <<0,1>>,
 [<<"c">>,0],
 <<0,3>>]