Implement enif_select and add select and mkfifo to file functions

`enif_select` is an API that allows nifs to use `select(2)` or equivalent,
paving the way for nif-based drivers.

`enif_select` depends on platform implementations and this PR only implements
it on generic_unix platform, using `sys_poll_event` select-like function,
namely `kqueue(2)` or `poll(2)`. As a result, `enif_select` does not exactly
behaves like `select(2)` and this is documented.

For testing, add `mkfifo` and `select` to POSIX file functions.

Signed-off-by: Paul Guyot <[email protected]>

src/libAtomVM/CMakeLists.txt

@@ -173,6 +173,7 @@ endfunction()
 test_function_exists(open "fcntl.h" PUBLIC HAVE_OPEN)
 test_function_exists(close "unistd.h" PUBLIC HAVE_CLOSE)
 test_function_exists(unlink "unistd.h" PRIVATE HAVE_UNLINK)
+test_function_exists(mkfifo "sys/stat.h" PRIVATE HAVE_MKFIFO)
 test_symbol_exists(O_CLOEXEC "fcntl.h" PRIVATE HAVE_O_CLOEXEC)
 test_symbol_exists(O_DIRECTORY "fcntl.h" PRIVATE HAVE_O_DIRECTORY)
 test_symbol_exists(O_DSYNC "fcntl.h" PRIVATE HAVE_O_DSYNC)

src/libAtomVM/defaultatoms.c

@@ -135,6 +135,10 @@ static const char *const info_atom = "\x4" "info";
 
 static const char *const module_atom = "\x06" "module";
 
+static const char *const select_atom = "\x6" "select";
+static const char *const ready_input_atom = "\xB" "ready_input";
+static const char *const ready_output_atom = "\xC" "ready_output";
+
 void defaultatoms_init(GlobalContext *glb)
 {
     int ok = 1;
@@ -254,6 +258,10 @@ void defaultatoms_init(GlobalContext *glb)
 
     ok &= globalcontext_insert_atom(glb, module_atom) == MODULE_ATOM_INDEX;
 
+    ok &= globalcontext_insert_atom(glb, select_atom) == SELECT_ATOM_INDEX;
+    ok &= globalcontext_insert_atom(glb, ready_input_atom) == READY_INPUT_ATOM_INDEX;
+    ok &= globalcontext_insert_atom(glb, ready_output_atom) == READY_OUTPUT_ATOM_INDEX;
+
     if (!ok) {
         AVM_ABORT();
     }

src/libAtomVM/defaultatoms.gperf

@@ -0,0 +1,114 @@
+/*
+ * This file is part of AtomVM.
+ *
+ * Copyright 2023 Paul Guyot <[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
+ */
+
+%readonly-tables
+%define lookup-function-name defaultatom_in_word_set
+%pic
+
+%{
+#include <defaultatom.h>
+%}
+%%
+"\005false", FALSE_ATOM_INDEX
+"\004true", TRUE_ATOM_INDEX
+"\002ok", OK_ATOM_INDEX
+"\005error", ERROR_ATOM_INDEX
+"\011undefined", UNDEFINED_ATOM_INDEX
+"\006badarg", BADARG_ATOM_INDEX
+"\010badarith", BADARITH_ATOM_INDEX
+"\010badarity", BADARITY_ATOM_INDEX
+"\006badfun", BADFUN_ATOM_INDEX
+"\014system_limit", SYSTEM_LIMIT_ATOM_INDEX
+"\017function_clause", FUNCTION_CLAUSE_ATOM_INDEX
+"\012try_clause", TRY_CLAUSE_ATOM_INDEX
+"\015out_of_memory", OUT_OF_MEMORY_ATOM_INDEX
+"\010overflow", OVERFLOW_ATOM_INDEX
+"\005flush", FLUSH_ATOM_INDEX
+"\011heap_size", HEAP_SIZE_ATOM_INDEX
+"\006latin1", LATIN1_ATOM_INDEX
+"\015max_heap_size", MAX_HEAP_SIZE_ATOM_INDEX
+"\006memory", MEMORY_ATOM_INDEX
+"\021message_queue_len", MESSAGE_QUEUE_LEN_ATOM_INDEX
+"\004puts", PUTS_ATOM_INDEX
+"\012stack_size", STACK_SIZE_ATOM_INDEX
+"\015min_heap_size", MIN_HEAP_SIZE_ATOM_INDEX
+"\015process_count", PROCESS_COUNT_ATOM_INDEX
+"\012port_count", PORT_COUNT_ATOM_INDEX
+"\012atom_count", ATOM_COUNT_ATOM_INDEX
+"\023system_architecture", SYSTEM_ARCHITECTURE_ATOM_INDEX
+"\010wordsize", WORDSIZE_ATOM_INDEX
+"\010decimals", DECIMALS_ATOM_INDEX
+"\012scientific", SCIENTIFIC_ATOM_INDEX
+"\007compact", COMPACT_ATOM_INDEX
+"\010badmatch", BADMATCH_ATOM_INDEX
+"\013case_clause", CASE_CLAUSE_ATOM_INDEX
+"\011if_clause", IF_CLAUSE_ATOM_INDEX
+"\005throw", THROW_ATOM_INDEX
+"\013low_entropy", LOW_ENTROPY_ATOM_INDEX
+"\013unsupported", UNSUPPORTED_ATOM_INDEX
+"\004used", USED_ATOM_INDEX
+"\003all", ALL_ATOM_INDEX
+"\005start", START_ATOM_INDEX
+"\005undef", UNDEF_ATOM_INDEX
+"\010vm_abort", VM_ABORT_ATOM_INDEX
+"\004link", LINK_ATOM_INDEX
+"\007monitor", MONITOR_ATOM_INDEX
+"\006normal", NORMAL_ATOM_INDEX
+"\004DOWN", DOWN_ATOM_INDEX
+"\007process", PROCESS_ATOM_INDEX
+"\007nocatch", NOCATCH_ATOM_INDEX
+"\020refc_binary_info", REFC_BINARY_INFO_ATOM_INDEX
+"\006noproc", NOPROC_ATOM_INDEX
+"\011trap_exit", TRAP_EXIT_ATOM_INDEX
+"\004EXIT", EXIT_ATOM_INDEX
+"\006badmap", BADMAP_ATOM_INDEX
+"\006badkey", BADKEY_ATOM_INDEX
+"\004none", NONE_ATOM_INDEX
+"\012io_request", IO_REQUEST_ATOM_INDEX
+"\010io_reply", IO_REPLY_ATOM_INDEX
+"\011put_chars", PUT_CHARS_ATOM_INDEX
+"\004exit", LOWERCASE_EXIT_ATOM_INDEX
+"\016atomvm_version", ATOMVM_VERSION_ATOM_INDEX
+"\006second", SECOND_ATOM_INDEX
+"\013millisecond", MILLISECOND_ATOM_INDEX
+"\013microsecond", MICROSECOND_ATOM_INDEX
+"\010infinity", INFINITY_ATOM_INDEX
+"\015timeout_value", TIMEOUT_VALUE_ATOM_INDEX
+"\007machine", MACHINE_ATOM_INDEX
+"\015avm_floatsize", AVM_FLOATSIZE_ATOM_INDEX
+"\006append", APPEND_ATOM_INDEX
+"\016private_append", PRIVATE_APPEND_ATOM_INDEX
+"\006binary", BINARY_ATOM_INDEX
+"\007integer", INTEGER_ATOM_INDEX
+"\006little", LITTLE_ATOM_INDEX
+"\006native", NATIVE_ATOM_INDEX
+"\006string", STRING_ATOM_INDEX
+"\004utf8", UTF8_ATOM_INDEX
+"\005utf16", UTF16_ATOM_INDEX
+"\005utf32", UTF32_ATOM_INDEX
+"\011badrecord", BADRECORD_ATOM_INDEX
+"\004copy", COPY_ATOM_INDEX
+"\005reuse", REUSE_ATOM_INDEX
+"\017ensure_at_least", ENSURE_AT_LEAST_ATOM_INDEX
+"\016ensure_exactly", ENSURE_EXACTLY_ATOM_INDEX
+"\004skip", SKIP_ATOM_INDEX
+"\010get_tail", GET_TAIL_ATOM_INDEX
+"\003=:=", EQUAL_COLON_EQUAL_ATOM_INDEX
+"\006signed", SIGNED_ATOM_INDEX

src/libAtomVM/defaultatoms.h

@@ -144,7 +144,11 @@ extern "C" {
 
 #define MODULE_ATOM_INDEX 92
 
-#define PLATFORM_ATOMS_BASE_INDEX 93
+#define SELECT_ATOM_INDEX 93
+#define READY_INPUT_ATOM_INDEX 94
+#define READY_OUTPUT_ATOM_INDEX 95
+
+#define PLATFORM_ATOMS_BASE_INDEX 96
 
 #define FALSE_ATOM TERM_FROM_ATOM_INDEX(FALSE_ATOM_INDEX)
 #define TRUE_ATOM TERM_FROM_ATOM_INDEX(TRUE_ATOM_INDEX)
@@ -263,6 +267,10 @@ extern "C" {
 
 #define MODULE_ATOM TERM_FROM_ATOM_INDEX(MODULE_ATOM_INDEX)
 
+#define SELECT_ATOM TERM_FROM_ATOM_INDEX(SELECT_ATOM_INDEX)
+#define READY_INPUT_ATOM TERM_FROM_ATOM_INDEX(READY_INPUT_ATOM_INDEX)
+#define READY_OUTPUT_ATOM TERM_FROM_ATOM_INDEX(READY_OUTPUT_ATOM_INDEX)
+
 void defaultatoms_init(GlobalContext *glb);
 
 void platform_defaultatoms_init(GlobalContext *glb);

src/libAtomVM/erl_nif.h

@@ -63,15 +63,21 @@ typedef int ErlNifEvent;
  */
 typedef void ErlNifResourceDtor(ErlNifEnv *caller_env, void *obj);
 
+/**
+ * @brief Select stop callback
+ */
+typedef void ErlNifResourceStop(ErlNifEnv *caller_env, void *obj, ErlNifEvent event, int is_direct_call);
+
 /**
  * @brief Resource callbacks.
- * @details Members should be set to 0, 1 depending on provided callbacks.
+ * @details Members should be set to 0, 1 or 2 depending on provided callbacks.
  * Callbacks can also be NULL if not used.
  */
 typedef struct
 {
     int members;
     ErlNifResourceDtor *dtor;
+    ErlNifResourceStop *stop;
 } ErlNifResourceTypeInit;
 
 /**
@@ -83,6 +89,35 @@ typedef enum
     // ERL_NIF_RT_TAKEOVER is not supported yet
 } ErlNifResourceFlags;
 
+/**
+ * @brief enif_select mode flags
+ * @details ERL_NIF_SELECT_CANCEL which was introduced with OTP-22, is unimplemented.
+ */
+enum ErlNifSelectFlags
+{
+    ERL_NIF_SELECT_READ = 1,
+    ERL_NIF_SELECT_WRITE = 2,
+    ERL_NIF_SELECT_STOP = 4,
+    //  ERL_NIF_SELECT_CANCEL = 8,
+};
+
+/**
+ * @brief enif_select result flags
+ * @details ERL_NIF_SELECT_CANCEL which was introduced with OTP-22, is unimplemented.
+ */
+enum
+{
+    ERL_NIF_SELECT_STOP_CALLED = 1,
+    ERL_NIF_SELECT_STOP_SCHEDULED = 2,
+    //  ERL_NIF_SELECT_READ_CANCELLED = 4,
+    //  ERL_NIF_SELECT_WRITE_CANCELLED = 8,
+
+    ERL_NIF_SELECT_INVALID_EVENT = -1,
+    ERL_NIF_SELECT_FAILED = -2,
+
+    ERL_NIF_SELECT_BADARG = -3,
+};
+
 /**
  * @brief Create or take over (code upgrade) a resource type.
  * @param env the current environment
@@ -143,6 +178,30 @@ int enif_release_resource(void *resource);
  */
 ERL_NIF_TERM enif_make_resource(ErlNifEnv *env, void *obj);
 
+/**
+ * @brief Run a POSIX-like select on a given object (event) and send a message
+ * when the object is readable or writable.
+ *
+ * @details Actual implementation is platform dependent and platforms may not
+ * implement this feature.
+ *
+ * On `generic_unix`, this is currently implemented using what
+ * `sys_poll_events` uses, namely `kqueue(2)` (if available) or `poll(2)`.
+ * Please note that `kqueue(2)` and `poll(2)` behave differently for some
+ * objects, for example for vnodes and EOF.
+ *
+ * @param env current environment
+ * @param event event object (typically a file descriptor)
+ * @param mode select mode (`ERL_NIF_SELECT_READ` and/or `ERL_NIF_SELECT_WRITE`)
+ * optionally with `ERL_NIF_SELECT_CANCEL` to cancel, or `ERL_NIF_SELECT_STOP`
+ * to stop.
+ * @param obj resource object working as a container of the event object.
+ * @param pid process id to send a message to or NULL to use the current process (from `env`)
+ * @param ref reference object used in sent messages or `undefined` atom.
+ * @return a negative value on failure, 0 or flags on success.
+ */
+int enif_select(ErlNifEnv *env, ErlNifEvent event, enum ErlNifSelectFlags mode, void *obj, const ErlNifPid *pid, ERL_NIF_TERM ref);
+
 #ifdef __cplusplus
 }
 #endif

src/libAtomVM/globalcontext.c

@@ -84,6 +84,7 @@ GlobalContext *globalcontext_new()
     synclist_init(&glb->registered_processes);
     synclist_init(&glb->listeners);
     synclist_init(&glb->resource_types);
+    synclist_init(&glb->select_events);
 
     glb->last_process_id = 0;
 
@@ -212,6 +213,13 @@ COLD_FUNC void globalcontext_destroy(GlobalContext *glb)
     }
     synclist_destroy(&glb->resource_types);
 
+    struct ListHead *select_events = synclist_nolock(&glb->select_events);
+    MUTABLE_LIST_FOR_EACH (item, tmp, select_events) {
+        struct SelectEvent *select_event = GET_LIST_ENTRY(item, struct SelectEvent, head);
+        free((void *) select_event);
+    }
+    synclist_destroy(&glb->select_events);
+
     free(glb);
 }
 

src/libAtomVM/globalcontext.h

@@ -78,6 +78,7 @@ struct GlobalContext
     struct SyncList registered_processes;
     struct SyncList listeners;
     struct SyncList resource_types;
+    struct SyncList select_events;
 
     int32_t last_process_id;