Merge pull request #1474 from pguyot/w02/add-epmd

Add support for formatting ports

Add support for io_lib (and io, etc...) to format ports.
Adds port_to_list/1 to erlang module exports to keep dialyzer happy.
Adds a missing clause to handle port terms in `memory_estimate_usage(term)`
function that is necessary for formatting ports for io or other purposes.

This is a continuation of #1473.

These changes are made under both the "Apache 2.0" and the "GNU Lesser General
Public License 2.1 or later" license terms (dual license).

SPDX-License-Identifier: Apache-2.0 OR LGPL-2.1-or-later

Author: bettio

libs/estdlib/src/erlang.erl

@@ -74,6 +74,7 @@
     integer_to_list/2,
     fun_to_list/1,
     pid_to_list/1,
+    port_to_list/1,
     ref_to_list/1,
     register/2,
     unregister/1,
@@ -853,6 +854,16 @@ fun_to_list(_Fun) ->
 pid_to_list(_Pid) ->
     erlang:nif_error(undefined).
 
+%%-----------------------------------------------------------------------------
+%% @param   Port     port to convert to a string
+%% @returns a string representation of the port
+%% @doc     Create a string representing a port.
+%% @end
+%%-----------------------------------------------------------------------------
+-spec port_to_list(Port :: port()) -> string().
+port_to_list(_Port) ->
+    erlang:nif_error(undefined).
+
 %%-----------------------------------------------------------------------------
 %% @param   Ref     reference to convert to a string
 %% @returns a string representation of the reference

libs/estdlib/src/io_lib.erl

@@ -292,6 +292,8 @@ format_spw(_Format, T) when is_float(T) ->
     erlang:float_to_list(T);
 format_spw(_Format, T) when is_pid(T) ->
     erlang:pid_to_list(T);
+format_spw(_Format, T) when is_port(T) ->
+    erlang:port_to_list(T);
 format_spw(_Format, T) when is_reference(T) ->
     erlang:ref_to_list(T);
 format_spw(_Format, T) when is_function(T) ->

src/libAtomVM/memory.c

@@ -594,6 +594,10 @@ static void memory_scan_and_copy(HeapFragment *old_fragment, term *mem_start, co
             TRACE("Found PID (%" TERM_X_FMT ")\n", t);
             ptr++;
 
+        } else if (term_is_local_port(t)) {
+            TRACE("Found port (%" TERM_X_FMT ")\n", t);
+            ptr++;
+
         } else if ((t & 0x3) == 0x0) {
             TRACE("Found boxed header (%" TERM_X_FMT ")\n", t);
 

tests/erlang_tests/CMakeLists.txt

@@ -162,6 +162,7 @@ compile_erlang(test_concat_badarg)
 compile_erlang(register_and_whereis_badarg)
 compile_erlang(test_send)
 compile_erlang(test_open_port_badargs)
+compile_erlang(test_port_to_list)
 compile_erlang(echo)
 compile_erlang(pingpong)
 compile_erlang(prime_ext)
@@ -641,6 +642,7 @@ add_custom_target(erlang_test_modules DEPENDS
     register_and_whereis_badarg.beam
     test_send.beam
     test_open_port_badargs.beam
+    test_port_to_list.beam
     echo.beam
     pingpong.beam
     prime_ext.beam

tests/erlang_tests/test_port_to_list.erl

@@ -0,0 +1,71 @@
+%%
+%% This file is part of AtomVM.
+%%
+%% Copyright (c) 2025 <winford@object.stream>
+%% All rights reserved.
+%%
+%% Licensed under the Apache License, Version 2.0 (the "License");
+%% you may not use this file except in compliance with the License.
+%% You may obtain a copy of the License at
+%%
+%%     http://www.apache.org/licenses/LICENSE-2.0
+%%
+%% Unless required by applicable law or agreed to in writing, software
+%% distributed under the License is distributed on an "AS IS" BASIS,
+%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+%% See the License for the specific language governing permissions and
+%% limitations under the License.
+%%
+%%
+%% SPDX-License-Identifier: Apache-2.0 OR LGPL-2.1-or-later
+%%
+-module(test_port_to_list).
+
+-export([start/0, test_echo_port_to_list/0]).
+
+-define(PORTBEGIN, "#Port<0.").
+-define(PORTEND, ">").
+
+start() ->
+    test_echo_port_to_list().
+
+test_echo_port_to_list() ->
+    Port = open_port({spawn, "echo"}, []),
+    validate_port_fmt(Port).
+
+%% internal
+validate_port_fmt(Port) ->
+    case get_valid_portchars(Port) of
+        {ok, PortChars} ->
+            Res = port_to_list(Port) =:= flatten([?PORTBEGIN, PortChars, ?PORTEND], []),
+            case Res of
+                true -> 0;
+                _ -> 2
+            end;
+        {invalid_format, Port} ->
+            1
+    end.
+
+get_valid_portchars(Port) ->
+    PList = port_to_list(Port),
+    Bin = list_to_binary(PList),
+    [_, Portend] = binary:split(Bin, <<?PORTBEGIN>>),
+    [PortNum, _] = binary:split(Portend, <<?PORTEND>>),
+    try binary_to_integer(PortNum) of
+        Num when is_integer(Num) ->
+            {ok, binary_to_list(PortNum)};
+        _ ->
+            {invalid_format, Port}
+    catch
+        _:_ ->
+            {invalid_format, Port}
+    end.
+
+flatten([], Accum) ->
+    Accum;
+flatten([H | T], Accum) when is_list(H) ->
+    FlattenedT = flatten(T, Accum),
+    flatten(H, FlattenedT);
+flatten([H | T], Accum) ->
+    FlattenedT = flatten(T, Accum),
+    [H | FlattenedT].

tests/test.c

@@ -208,6 +208,7 @@ struct Test tests[] = {
     TEST_CASE_EXPECTED(register_and_whereis_badarg, 333),
     TEST_CASE(test_send),
     TEST_CASE_EXPECTED(test_open_port_badargs, -21),
+    TEST_CASE(test_port_to_list),
     TEST_CASE_EXPECTED(prime_ext, 1999),
     TEST_CASE_EXPECTED(test_try_case_end, 256),
     TEST_CASE(test_exception_classes),