Erlang external term format

Kent Boortz <>
Thu Feb 26 01:31:11 CET 2004


Carsten Schultz <> writes:
> > look into erts/emulator/internal_doc in the sources.
> 
> That was very helpful, thanks again.  I have written a (partial)
> implementation of it in Haskell, it works and it is fun.  Now, the
> Haskell programs my Yaws script call can send back Erlang terms :-)
> (The FLOAT_EXT part could use some clarification.)

Nice. Yes the document needs some improvements. Note that it is in
some cases possible to encode the same term in different ways. For
example an Erlang integer is not necessarily encoded into the most
compact external representation. An INTEGER_EXT can hold a 32 bit
integer but currently the emulator and erl_interface only use it for
encoding integers that fits into 28 bits (for historical reasons I
think).

> Is the atom cache described in the above document used anywhere?  Not
> in binary_to_term, it seems, at least if I understand it correctly.
> It's a pity, it looked like a good idea.

It is used encoding terms in the distribution protocol between two
nodes that agree on using it. Look in

  erts/emulator/beam/dist.c
  erts/emulator/beam/external.c

kent

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