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etfpp

A simple C++ library that helps you build and encode Erlang structures (ETF).

support

  • Version
  • SmallInteger
  • Integer
  • Float
  • Atom
  • SmallTuple
  • LargeTuple
  • Map
  • Nil
  • String
  • List
  • Binary
  • SmallBig
  • LargeBig
  • SmallAtom
  • BitBinary
  • NewFloat
  • AtomUtf8
  • SmallAtomUtf8

probably will not support

Not sure I really want to support these for what I'm doing right now, but maybe in the future.

  • AtomCacheRef
  • Fun
  • NewFun
  • Export
  • NewReference
  • Reference
  • Port
  • Pid

building

bazel build ...
bazel test ...

If you want to run a quick check (bazel build is a prereq):

./tools/run_codec.sh

sample output

This is what you get when you run the sample binary built with bazel. It will generate a bunch of etf files that you can then parse using file:read_file(...), and then converting the binary with term_to_binary(...) in Erlang.

psyomn$ ./tools/run_codec.sh
file-0.etf: [{}]
file-1.etf: [123.123]
file-2.etf: [<<"hello world this is a binary">>]
file-3.etf: [{1,2,3,<<"hello">>}]
file-4.etf: [one,two,three,ÿapple]
file-5.etf: [<<170,187,204,110:7>>]
file-6.etf: ['\x{1F00}\x{3BC}\x{3BC}\x{3BF}\x{3C5}\x{3B4}\x{3B9}\x{1F72}\x{3C2}']
file-7.etf: ['\x{394}\x{3B9}\x{3BF}\x{3B3}\x{3AD}\x{3BD}\x{3B7}\x{3C2}']
file-8.etf: [123.123]
file-9.etf: [#{1 => 2}]
psyomn$ cat ./tools/run_codec.sh
#!/usr/bin/env bash
./bazel-bin/bin/example-encode
./test/data/binary_file_to_term.erl *.etf

The weirdness you see above in file 6, and file 7, are utf8 encoded atoms. They don't render well when printing but if you read file files from the interpreter, you get:

1> {ok, C1} = file:read_file("file-6.etf").
{ok,<<131,108,0,0,0,1,118,0,20,225,188,128,206,188,206,
      188,206,191,207,133,206,180,206,185,225,189,178,...>>}
2> binary_to_term(C1).
['ἀμμουδιὲς']
3> {ok, C2} = file:read_file("file-7.etf").
{ok,<<131,108,0,0,0,1,119,16,206,148,206,185,206,191,206,
      179,206,173,206,189,206,183,207,130,106>>}
4> binary_to_term(C2).
['Διογένης']

testing

You'll notice I hand craft some of the binary payloads. That's purposeful, and I want tests to fail in case tags change (which won't but I sleep with one eye open so...)

plan

  • Add a builder to make usage of lib a little more ergonomic
  • Write extern C stuff to make it C portable

licensing

Apache v2. See LICENSE.