From 6e931258872c15404aa1dfd5198f2b490452b30b Mon Sep 17 00:00:00 2001
From: Micael Karlberg <bmk@erlang.org>
Date: Fri, 5 Oct 2018 14:52:47 +0200
Subject: [socket-nif] Add *preliminary* new function supports/0,1

---
 erts/emulator/nifs/common/socket_nif.c | 37 +++++++++++++++++++++++++++++++---
 erts/preloaded/src/socket.erl          | 14 +++++++++++++
 2 files changed, 48 insertions(+), 3 deletions(-)

diff --git a/erts/emulator/nifs/common/socket_nif.c b/erts/emulator/nifs/common/socket_nif.c
index 0ef88162bc..4def45f869 100644
--- a/erts/emulator/nifs/common/socket_nif.c
+++ b/erts/emulator/nifs/common/socket_nif.c
@@ -860,6 +860,9 @@ typedef struct {
 static ERL_NIF_TERM nif_info(ErlNifEnv*         env,
                              int                argc,
                              const ERL_NIF_TERM argv[]);
+static ERL_NIF_TERM nif_supports(ErlNifEnv*         env,
+                                 int                argc,
+                                 const ERL_NIF_TERM argv[]);
 /*
 This is a *global* debug function (enable or disable for all
 operations and all sockets.
@@ -2536,6 +2539,7 @@ static SocketData data;
  * Utility and admin functions:
  * ----------------------------
  * nif_info/0
+ * nif_supports/1
  * (nif_debug/1)
  *
  * The "proper" socket functions:
@@ -2619,6 +2623,31 @@ ERL_NIF_TERM nif_info(ErlNifEnv*         env,
 }
 
 
+
+/* ----------------------------------------------------------------------
+ * nif_supports
+ *
+ * Description:
+ * This function is intended to answer the question: "Is X supported?"
+ * Currently only one key is "supported": options
+ * That results in a list of all *known options* (known by us) and if
+ * the platform supports (OS) it or not.
+ */
+
+static
+ERL_NIF_TERM nif_support(ErlNifEnv*         env,
+                         int                argc,
+                         const ERL_NIF_TERM argv[])
+{
+    if (argc != 1) {
+        return enif_make_badarg(env);
+    } else {
+        return MKEL(env); // PLACEHOLDER
+    }
+}
+
+
+
 /* ----------------------------------------------------------------------
  * nif_open
  *
@@ -15412,9 +15441,11 @@ void socket_down_reader(ErlNifEnv*        env,
 static
 ErlNifFunc socket_funcs[] =
 {
-    // Some utility functions
-    {"nif_info",      0, nif_info, 0},
-    // {"nif_debug",      1, nif_debug_, 0},
+    // Some utility and support functions
+    {"nif_info",                0, nif_info, 0},
+    {"nif_supports",            1, nif_supports, 0},
+    // {"nif_debug",               1, nif_debug, 0},
+    // {"nif_command",             1, nif_command, 0},
 
     // The proper "socket" interface
     // nif_open/1 is used when we already have a file descriptor
diff --git a/erts/preloaded/src/socket.erl b/erts/preloaded/src/socket.erl
index c388fc2849..147d074310 100644
--- a/erts/preloaded/src/socket.erl
+++ b/erts/preloaded/src/socket.erl
@@ -27,6 +27,7 @@
 -export([
 	 on_load/0, on_load/1,
 	 info/0,
+         supports/0, supports/1,
          ensure_sockaddr/1
         ]).
 
@@ -843,6 +844,16 @@ info() ->
     nif_info().
 
 
+-spec supports() -> list().
+
+supports() ->
+    [{options, supports(options)}].
+
+supports(options) ->
+    nif_supports(?SOCKET_SUPPORTS_OPTIONS);
+supports(_) ->
+    false.
+
 
 %% ===========================================================================
 %%
@@ -3417,6 +3428,9 @@ error(Reason) ->
 nif_info() ->
     erlang:nif_error(undef).
 
+nif_supports(_Key) ->
+    erlang:nif_error(undef).
+
 nif_open(_Domain, _Type, _Protocol, _Extra) ->
     erlang:nif_error(undef).
 
-- 
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