Add prim_file:get_cwd/0 (#68)

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
Added nif implementation for getcwd.

Signed-off-by: Mateusz Front <[email protected]>

Author: TheSobkiewicz

libs/estdlib/src/CMakeLists.txt

@@ -55,6 +55,7 @@ set(ERLANG_MODULES
     maps
     math
     net
+    prim_file
     logger
     logger_std_h
     proplists

libs/estdlib/src/prim_file.erl

@@ -0,0 +1,25 @@
+%
+% This file is part of AtomVM.
+%
+% Copyright 2024 Tomasz Sobkiewicz <[email protected]>
+%
+% 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(prim_file).
+
+-export([get_cwd/0]).
+
+get_cwd() ->
+    erlang:nif_error(undefined).

src/libAtomVM/nifs.c

@@ -31,6 +31,8 @@
 #include <stdio.h>
 #include <string.h>
 #include <time.h>
+#include <unistd.h>
+#include <limits.h>
 
 #include "atom_table.h"
 #include "avm_version.h"
@@ -99,6 +101,7 @@ static term nif_binary_part_3(Context *ctx, int argc, term argv[]);
 static term nif_binary_split(Context *ctx, int argc, term argv[]);
 static term nif_binary_replace(Context *ctx, int argc, term argv[]);
 static term nif_binary_match(Context *ctx, int argc, term argv[]);
+static term nif_prim_file_get_cwd_0(Context *ctx, int argc, term argv[]);
 static term nif_calendar_system_time_to_universal_time_2(Context *ctx, int argc, term argv[]);
 static term nif_erlang_delete_element_2(Context *ctx, int argc, term argv[]);
 static term nif_erlang_atom_to_binary(Context *ctx, int argc, term argv[]);
@@ -277,6 +280,12 @@ static const struct Nif binary_match_nif =
     .nif_ptr = nif_binary_match
 };
 
+static const struct Nif prim_file_get_cwd_nif =
+{
+    .base.type = NIFFunctionType,
+    .nif_ptr = nif_prim_file_get_cwd_0
+};
+
 static const struct Nif make_ref_nif =
 {
     .base.type = NIFFunctionType,
@@ -5842,6 +5851,53 @@ static term nif_erlang_lists_subtract(Context *ctx, int argc, term argv[])
     return result;
 }
 
+
+static term nif_prim_file_get_cwd_0(Context *ctx, int argc, term argv[])
+{
+    UNUSED(argc)
+    UNUSED(argv)
+    char cwd[PATH_MAX];
+    if (UNLIKELY(IS_NULL_PTR(cwd))) {
+        RAISE_ERROR(OUT_OF_MEMORY_ATOM);
+    }
+
+    if (UNLIKELY(memory_ensure_free(ctx, TUPLE_SIZE(2)) != MEMORY_GC_OK)) {
+        RAISE_ERROR(OUT_OF_MEMORY_ATOM);
+    }
+    term result_tuple = term_alloc_tuple(2, &ctx->heap);
+
+    if (UNLIKELY(IS_NULL_PTR(getcwd(cwd, PATH_MAX)))) {
+        term reason = UNDEFINED_ATOM;
+        switch (errno) {
+            case EACCES:
+                reason = globalcontext_make_atom(ctx->global, ATOM_STR("\x11", "permission_denied"));
+                break;
+            case EINVAL:
+                reason = globalcontext_make_atom(ctx->global, ATOM_STR("\xD", "negative_size"));
+                break;
+            case ERANGE:
+                reason = globalcontext_make_atom(ctx->global, ATOM_STR("\x10", "buffer_too_small"));
+                break;
+            default:
+                reason = globalcontext_make_atom(ctx->global, ATOM_STR("\xD", "unknown_error"));
+                break;
+        }
+        term_put_tuple_element(result_tuple, 0, ERROR_ATOM);
+        term_put_tuple_element(result_tuple, 1, reason);
+        return result_tuple;
+    }
+
+    size_t cwd_length = strlen(cwd);
+    if (UNLIKELY(memory_ensure_free_with_roots(ctx, term_binary_heap_size(cwd_length), 1, &result_tuple, MEMORY_CAN_SHRINK) != MEMORY_GC_OK)) {
+        RAISE_ERROR(OUT_OF_MEMORY_ATOM);
+    }
+    term result = term_from_literal_binary(cwd, cwd_length, &ctx->heap, ctx->global);
+
+    term_put_tuple_element(result_tuple, 0, OK_ATOM);
+    term_put_tuple_element(result_tuple, 1, result);
+    return result_tuple;
+}
+
 #ifdef WITH_ZLIB
 static term nif_zlib_compress_1(Context *ctx, int argc, term argv[])
 {

src/libAtomVM/nifs.gperf

@@ -145,6 +145,7 @@ ets:insert/2, &ets_insert_nif
 ets:lookup/2, &ets_lookup_nif
 ets:lookup_element/3, &ets_lookup_element_nif
 ets:delete/1, &ets_delete_nif
+prim_file:get_cwd/0, &prim_file_get_cwd_nif
 ets:delete/2, &ets_delete_nif
 ets:update_counter/3, &ets_update_counter_nif
 ets:update_counter/4, &ets_update_counter_nif

tests/erlang_tests/CMakeLists.txt

@@ -298,6 +298,8 @@ compile_erlang(test_binary_match)
 
 compile_erlang(test_zlib_compress)
 
+compile_erlang(test_prim_file_getcwd)
+
 compile_erlang(plusone)
 compile_erlang(plusone2)
 compile_erlang(minusone)
@@ -816,6 +818,8 @@ add_custom_target(erlang_test_modules DEPENDS
 
     test_zlib_compress.beam
 
+    test_prim_file_getcwd.beam
+
     plusone.beam
     plusone2.beam
     minusone.beam

tests/erlang_tests/test_prim_file_getcwd.erl

@@ -0,0 +1,37 @@
+%
+% This file is part of AtomVM.
+%
+% Copyright 2024 Tomasz Sobkiewicz <[email protected]>
+%
+% 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_prim_file_getcwd).
+
+-export([start/0]).
+
+start() ->
+    ok = test_getcwd(),
+    0.
+
+test_getcwd() ->
+    {ok, Path} = prim_file:get_cwd(),
+    true = is_valid_path(Path),
+    ok.
+
+is_valid_path(<<"/", _/binary>>) ->
+    true;
+is_valid_path(_) ->
+    false.

tests/test.c

@@ -329,6 +329,7 @@ struct Test tests[] = {
     TEST_CASE(test_binary_match),
 
     TEST_CASE(test_zlib_compress),
+    TEST_CASE(test_prim_file_getcwd),
 
     TEST_CASE_COND(plusone, 134217728, LONG_MAX != 9223372036854775807),