Add POSIX functions to list directory entries on supported platforms

Add `atomvm:posix_opendir/1`, `atomvm:posix_closedir/1` and
`atomvm:posix_readdir/1` functions.

Signed-off-by: Davide Bettio <[email protected]>

CHANGELOG.md

@@ -34,6 +34,8 @@ also non string parameters (e.g. `Enum.join([1, 2], ",")`
 - Support for Elixir `IO.chardata_to_string/1`
 - Support for Elixir `List.duplicate/2`
 - Support for `binary:copy/1,2`
+- Support for directory listing using POSIX APIs: (`atomvm:posix_opendir/1`,
+`atomvm:posix_readdir/1`, `atomvm:posix_closedir/1`).
 
 ### Changed
 

libs/eavmlib/src/atomvm.erl

@@ -40,12 +40,16 @@
     posix_close/1,
     posix_read/2,
     posix_write/2,
-    posix_clock_settime/2
+    posix_clock_settime/2,
+    posix_opendir/1,
+    posix_closedir/1,
+    posix_readdir/1
 ]).
 
 -export_type([
     posix_fd/0,
-    posix_open_flag/0
+    posix_open_flag/0,
+    posix_dir/0
 ]).
 
 -deprecated([
@@ -84,6 +88,8 @@
     atom()
     | integer().
 
+-opaque posix_dir() :: binary().
+
 %%-----------------------------------------------------------------------------
 %% @returns The platform name.
 %% @doc     Return the platform moniker.
@@ -295,3 +301,37 @@ posix_write(_File, _Data) ->
     ok | {error, Reason :: posix_error()}.
 posix_clock_settime(_ClockId, _Time) ->
     erlang:nif_error(undefined).
+
+%%-----------------------------------------------------------------------------
+%% @param   Path    Path to the directory to open
+%% @returns A tuple with a directory descriptor or an error tuple.
+%% @doc     Open a file (on platforms that have `opendir(3)').
+%% @end
+%%-----------------------------------------------------------------------------
+-spec posix_opendir(Path :: iodata()) ->
+    {ok, posix_dir()} | {error, posix_error()}.
+posix_opendir(_Path) ->
+    erlang:nif_error(undefined).
+
+%%-----------------------------------------------------------------------------
+%% @param   Dir    Descriptor to a directory to close
+%% @returns `ok' or an error tuple
+%% @doc     Close a directory that was opened with `posix_opendir/1'
+%% @end
+%%-----------------------------------------------------------------------------
+-spec posix_closedir(Dir :: posix_dir()) -> ok | {error, posix_error()}.
+posix_closedir(_Dir) ->
+    erlang:nif_error(undefined).
+
+%%-----------------------------------------------------------------------------
+%% @param   Dir    Descriptor to an open directory
+%% @returns a `{dirent, InodeNo, Name}' tuple, `eof' or an error tuple
+%% @doc     Read a directory entry
+%% `eof' is returned if no more data can be read because the directory cursor
+%% reached the end.
+%% @end
+%%-----------------------------------------------------------------------------
+-spec posix_readdir(Dir :: posix_dir()) ->
+    {ok, {dirent, Inode :: integer(), Name :: binary()}} | eof | {error, posix_error()}.
+posix_readdir(_Dir) ->
+    erlang:nif_error(undefined).

src/libAtomVM/CMakeLists.txt

@@ -187,10 +187,13 @@ if (NOT ATOMIC_POINTER_LOCK_FREE_IS_TWO AND NOT (HAVE_PLATFORM_ATOMIC_H OR (AVM_
 endif()
 
 include(DefineIfExists)
-# HAVE_OPEN & HAVE_CLOSE are used in globalcontext.h
+# HAVE_OPEN, HAVE_OPENDIR, HAVE_CLOSE HAVE_CLOSEDIR, HAVE_READDIR are used in globalcontext.h
 define_if_function_exists(libAtomVM open "fcntl.h" PUBLIC HAVE_OPEN)
+define_if_function_exists(libAtomVM opendir "dirent.h" PUBLIC HAVE_OPENDIR)
 define_if_function_exists(libAtomVM close "unistd.h" PUBLIC HAVE_CLOSE)
+define_if_function_exists(libAtomVM closedir "dirent.h" PUBLIC HAVE_CLOSEDIR)
 define_if_function_exists(libAtomVM mkfifo "sys/stat.h" PRIVATE HAVE_MKFIFO)
+define_if_function_exists(libAtomVM readdir "dirent.h" PUBLIC HAVE_READDIR)
 define_if_function_exists(libAtomVM unlink "unistd.h" PRIVATE HAVE_UNLINK)
 define_if_symbol_exists(libAtomVM O_CLOEXEC "fcntl.h" PRIVATE HAVE_O_CLOEXEC)
 define_if_symbol_exists(libAtomVM O_DIRECTORY "fcntl.h" PRIVATE HAVE_O_DIRECTORY)

src/libAtomVM/globalcontext.c

@@ -135,6 +135,21 @@ GlobalContext *globalcontext_new()
     }
 #endif
 
+#if HAVE_OPENDIR && HAVE_READDIR && HAVE_CLOSEDIR
+    ErlNifEnv dir_env;
+    erl_nif_env_partial_init_from_globalcontext(&dir_env, glb);
+    glb->posix_dir_resource_type = enif_init_resource_type(&env, "posix_dir", &posix_dir_resource_type_init, ERL_NIF_RT_CREATE, NULL);
+    if (IS_NULL_PTR(glb->posix_dir_resource_type)) {
+#ifndef AVM_NO_SMP
+        smp_rwlock_destroy(glb->modules_lock);
+#endif
+        free(glb->modules_table);
+        atom_table_destroy(glb->atom_table);
+        free(glb);
+        return NULL;
+    }
+#endif
+
     sys_init_platform(glb);
 
 #ifndef AVM_NO_SMP

src/libAtomVM/globalcontext.h

@@ -152,6 +152,10 @@ struct GlobalContext
     ErlNifResourceType *posix_fd_resource_type;
 #endif
 
+#if HAVE_OPENDIR && HAVE_READDIR && HAVE_CLOSEDIR
+    ErlNifResourceType *posix_dir_resource_type;
+#endif
+
     void *platform_data;
 };
 

src/libAtomVM/nifs.c

@@ -794,6 +794,11 @@ DEFINE_MATH_NIF(tanh)
 #else
 #define IF_HAVE_CLOCK_SETTIME_OR_SETTIMEOFDAY(expr) NULL
 #endif
+#if HAVE_OPENDIR && HAVE_READDIR && HAVE_CLOSEDIR
+#define IF_HAVE_OPENDIR_READDIR_CLOSEDIR(expr) (expr)
+#else
+#define IF_HAVE_OPENDIR_READDIR_CLOSEDIR(expr) NULL
+#endif
 
 //Ignore warning caused by gperf generated code
 #pragma GCC diagnostic push

src/libAtomVM/nifs.gperf

@@ -141,6 +141,9 @@ atomvm:posix_select_stop/1, IF_HAVE_OPEN_CLOSE(&atomvm_posix_select_stop_nif)
 atomvm:posix_mkfifo/2, IF_HAVE_MKFIFO(&atomvm_posix_mkfifo_nif)
 atomvm:posix_unlink/1, IF_HAVE_UNLINK(&atomvm_posix_unlink_nif)
 atomvm:posix_clock_settime/2, IF_HAVE_CLOCK_SETTIME_OR_SETTIMEOFDAY(&atomvm_posix_clock_settime_nif)
+atomvm:posix_opendir/1, IF_HAVE_OPENDIR_READDIR_CLOSEDIR(&atomvm_posix_opendir_nif)
+atomvm:posix_closedir/1, IF_HAVE_OPENDIR_READDIR_CLOSEDIR(&atomvm_posix_closedir_nif)
+atomvm:posix_readdir/1, IF_HAVE_OPENDIR_READDIR_CLOSEDIR(&atomvm_posix_readdir_nif)
 code:load_abs/1, &code_load_abs_nif
 code:load_binary/3, &code_load_binary_nif
 code:ensure_loaded/1, &code_ensure_loaded_nif

src/libAtomVM/posix_nifs.c

@@ -38,10 +38,15 @@
 #include <sys/time.h>
 #endif
 
-#if HAVE_OPEN && HAVE_CLOSE || defined(HAVE_CLOCK_SETTIME) || defined(HAVE_SETTIMEOFDAY)
+#if HAVE_OPEN && HAVE_CLOSE || defined(HAVE_CLOCK_SETTIME) || defined(HAVE_SETTIMEOFDAY) \
+    || HAVE_OPENDIR && HAVE_READDIR && HAVE_CLOSEDIR
 #include <errno.h>
 #endif
 
+#if HAVE_OPENDIR && HAVE_READDIR && HAVE_CLOSEDIR
+#include <dirent.h>
+#endif
+
 #include "defaultatoms.h"
 #include "erl_nif_priv.h"
 #include "globalcontext.h"
@@ -602,6 +607,172 @@ static term nif_atomvm_posix_clock_settime(Context *ctx, int argc, term argv[])
 }
 #endif
 
+#if HAVE_OPENDIR && HAVE_READDIR && HAVE_CLOSEDIR
+struct PosixDir
+{
+    DIR *dir;
+};
+
+static void posix_dir_dtor(ErlNifEnv *caller_env, void *obj)
+{
+    UNUSED(caller_env);
+
+    struct PosixDir *dir_obj = (struct PosixDir *) obj;
+    if (dir_obj->dir) {
+        closedir(dir_obj->dir);
+        dir_obj->dir = NULL;
+    }
+}
+
+const ErlNifResourceTypeInit posix_dir_resource_type_init = {
+    .members = 1,
+    .dtor = posix_dir_dtor
+};
+
+static term errno_to_error_tuple_maybe_gc(Context *ctx)
+{
+    if (UNLIKELY(memory_ensure_free_opt(ctx, TUPLE_SIZE(2), MEMORY_CAN_SHRINK) != MEMORY_GC_OK)) {
+        RAISE_ERROR(OUT_OF_MEMORY_ATOM);
+    }
+
+    term result = term_alloc_tuple(2, &ctx->heap);
+    term_put_tuple_element(result, 0, ERROR_ATOM);
+    term_put_tuple_element(result, 1, posix_errno_to_term(errno, ctx->global));
+
+    return result;
+}
+
+static term nif_atomvm_posix_opendir(Context *ctx, int argc, term argv[])
+{
+    UNUSED(argc);
+
+    GlobalContext *glb = ctx->global;
+
+    term path_term = argv[0];
+
+    int ok;
+    char *path = interop_term_to_string(path_term, &ok);
+    if (UNLIKELY(!ok)) {
+        RAISE_ERROR(BADARG_ATOM);
+    }
+
+    term result;
+    DIR *dir = opendir(path);
+    free(path);
+
+    if (IS_NULL_PTR(dir)) {
+        return errno_to_error_tuple_maybe_gc(ctx);
+    } else {
+        // Return a resource object
+        struct PosixDir *dir_obj
+            = enif_alloc_resource(glb->posix_dir_resource_type, sizeof(struct PosixDir));
+        if (IS_NULL_PTR(dir_obj)) {
+            RAISE_ERROR(OUT_OF_MEMORY_ATOM);
+        }
+        dir_obj->dir = dir;
+        if (UNLIKELY(memory_ensure_free_opt(
+                         ctx, TUPLE_SIZE(2) + TERM_BOXED_RESOURCE_SIZE, MEMORY_CAN_SHRINK)
+                != MEMORY_GC_OK)) {
+            RAISE_ERROR(OUT_OF_MEMORY_ATOM);
+        }
+        term obj = term_from_resource(dir_obj, &ctx->heap);
+        result = term_alloc_tuple(2, &ctx->heap);
+        term_put_tuple_element(result, 0, OK_ATOM);
+        term_put_tuple_element(result, 1, obj);
+    }
+
+    return result;
+}
+
+static term nif_atomvm_posix_closedir(Context *ctx, int argc, term argv[])
+{
+    UNUSED(argc);
+
+    term result = OK_ATOM;
+
+    void *dir_obj_ptr;
+    if (UNLIKELY(!enif_get_resource(erl_nif_env_from_context(ctx), argv[0],
+            ctx->global->posix_dir_resource_type, &dir_obj_ptr))) {
+        RAISE_ERROR(BADARG_ATOM);
+    }
+    struct PosixDir *dir_obj = (struct PosixDir *) dir_obj_ptr;
+    if (dir_obj->dir != NULL) {
+        if (UNLIKELY(closedir(dir_obj->dir) < 0)) {
+            dir_obj->dir = NULL; // even if bad things happen, do not close twice.
+            return errno_to_error_tuple_maybe_gc(ctx);
+        }
+        dir_obj->dir = NULL;
+    }
+
+    return result;
+}
+
+// This function main purpose is to avoid warnings, such as:
+// warning: comparison is always true due to limited range of data type [-Wtype-limits]
+static inline term to_boxed_safe(uint64_t value, Context *ctx)
+{
+    if (value <= INT64_MAX) {
+        return term_make_maybe_boxed_int64(value, &ctx->heap);
+    } else {
+        return UNDEFINED_ATOM;
+    }
+}
+
+static term nif_atomvm_posix_readdir(Context *ctx, int argc, term argv[])
+{
+    UNUSED(argc);
+
+    GlobalContext *glb = ctx->global;
+
+    void *dir_obj_ptr;
+    if (UNLIKELY(!enif_get_resource(
+            erl_nif_env_from_context(ctx), argv[0], glb->posix_dir_resource_type, &dir_obj_ptr))) {
+        RAISE_ERROR(BADARG_ATOM);
+    }
+    struct PosixDir *dir_obj = (struct PosixDir *) dir_obj_ptr;
+
+    errno = 0;
+    struct dirent *dir_result = readdir(dir_obj->dir);
+    if (dir_result == NULL) {
+        if (UNLIKELY(errno != 0)) {
+            return errno_to_error_tuple_maybe_gc(ctx);
+        }
+
+        return globalcontext_make_atom(glb, ATOM_STR("\x3", "eof"));
+    }
+
+    size_t name_len = strlen(dir_result->d_name);
+    if (UNLIKELY(
+            memory_ensure_free_opt(ctx,
+                BOXED_INT64_SIZE + term_binary_heap_size(name_len) + TUPLE_SIZE(3) + TUPLE_SIZE(2),
+                MEMORY_CAN_SHRINK)
+            != MEMORY_GC_OK)) {
+        RAISE_ERROR(OUT_OF_MEMORY_ATOM);
+    }
+
+    term ino_no = to_boxed_safe(dir_result->d_ino, ctx);
+
+    term name_term = term_create_uninitialized_binary(name_len, &ctx->heap, glb);
+    memcpy((void *) term_binary_data(name_term), dir_result->d_name, name_len);
+
+    term dirent_atom = globalcontext_make_atom(glb, ATOM_STR("\x6", "dirent"));
+
+    // {dirent, Inode, Name}
+    term dirent_term = term_alloc_tuple(3, &ctx->heap);
+    term_put_tuple_element(dirent_term, 0, dirent_atom);
+    term_put_tuple_element(dirent_term, 1, ino_no);
+    term_put_tuple_element(dirent_term, 2, name_term);
+
+    // {ok, DirentTuple}
+    term result = term_alloc_tuple(2, &ctx->heap);
+    term_put_tuple_element(result, 0, OK_ATOM);
+    term_put_tuple_element(result, 1, dirent_term);
+
+    return result;
+}
+
+#endif
+
 #if HAVE_OPEN && HAVE_CLOSE
 const struct Nif atomvm_posix_open_nif = {
     .base.type = NIFFunctionType,
@@ -650,3 +821,17 @@ const struct Nif atomvm_posix_clock_settime_nif = {
     .nif_ptr = nif_atomvm_posix_clock_settime
 };
 #endif
+#if HAVE_OPENDIR && HAVE_READDIR && HAVE_CLOSEDIR
+const struct Nif atomvm_posix_opendir_nif = {
+    .base.type = NIFFunctionType,
+    .nif_ptr = nif_atomvm_posix_opendir
+};
+const struct Nif atomvm_posix_closedir_nif = {
+    .base.type = NIFFunctionType,
+    .nif_ptr = nif_atomvm_posix_closedir
+};
+const struct Nif atomvm_posix_readdir_nif = {
+    .base.type = NIFFunctionType,
+    .nif_ptr = nif_atomvm_posix_readdir
+};
+#endif

src/libAtomVM/posix_nifs.h

@@ -53,6 +53,12 @@ extern const struct Nif atomvm_posix_unlink_nif;
 #if defined(HAVE_CLOCK_SETTIME) || defined(HAVE_SETTIMEOFDAY)
 extern const struct Nif atomvm_posix_clock_settime_nif;
 #endif
+#if HAVE_OPENDIR && HAVE_READDIR && HAVE_CLOSEDIR
+extern const ErlNifResourceTypeInit posix_dir_resource_type_init;
+extern const struct Nif atomvm_posix_opendir_nif;
+extern const struct Nif atomvm_posix_readdir_nif;
+extern const struct Nif atomvm_posix_closedir_nif;
+#endif
 
 /**
  * @brief Convenient function to return posix errors as atom.

src/platforms/esp32/CMakeLists.txt

@@ -31,6 +31,12 @@ set(HAVE_MKFIFO "" CACHE INTERNAL "Have symbol mkfifo" FORCE)
 # in CMAKE_REQUIRED_INCLUDES as lwip includes freetos and many esp system components
 set(HAVE_SOCKET 1 CACHE INTERNAL "Have symbol socket" FORCE)
 
+# opendir, closedir and readdir functions are not detected
+# but they are available
+set(HAVE_OPENDIR 1 CACHE INTERNAL "Have symbol opendir" FORCE)
+set(HAVE_CLOSEDIR 1 CACHE INTERNAL "Have symbol closedir" FORCE)
+set(HAVE_READDIR 1 CACHE INTERNAL "Have symbol readdir" FORCE)
+
 list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/../../../CMakeModules")
 
 # Disable SMP with esp32 socs that have only one core

tests/libs/eavmlib/CMakeLists.txt

@@ -23,6 +23,7 @@ project(test_eavmlib)
 include(BuildErlang)
 
 set(ERLANG_MODULES
+    test_dir
     test_file
     test_ahttp_client
     test_port