From 348f3f2ee2d2707e30658c3600e05309ad0e72bf Mon Sep 17 00:00:00 2001
From: Lukas Larsson <lukas.larsson@erlang-solutions.com>
Date: Thu, 10 Dec 2015 10:59:34 +0100
Subject: erts: Add enif_is_process/port_alive

---
 erts/emulator/beam/erl_nif.c           | 70 +++++++++++++++++++++++++++++++++-
 erts/emulator/beam/erl_nif.h           |  7 +++-
 erts/emulator/beam/erl_nif_api_funcs.h |  6 +++
 3 files changed, 81 insertions(+), 2 deletions(-)

(limited to 'erts/emulator/beam')

diff --git a/erts/emulator/beam/erl_nif.c b/erts/emulator/beam/erl_nif.c
index 703c96777a..8440fd26b5 100644
--- a/erts/emulator/beam/erl_nif.c
+++ b/erts/emulator/beam/erl_nif.c
@@ -404,12 +404,28 @@ static int is_offheap(const ErlOffHeap* oh)
 
 ErlNifPid* enif_self(ErlNifEnv* caller_env, ErlNifPid* pid)
 {
+    if (caller_env->proc->common.id == ERTS_INVALID_PID)
+        return NULL;
     pid->pid = caller_env->proc->common.id;
     return pid;
 }
+
 int enif_get_local_pid(ErlNifEnv* env, ERL_NIF_TERM term, ErlNifPid* pid)
 {
-    return is_internal_pid(term) ? (pid->pid=term, 1) : 0;
+    if (is_internal_pid(term)) {
+        pid->pid=term;
+        return 1;
+    }
+    return 0;
+}
+
+int enif_get_local_port(ErlNifEnv* env, ERL_NIF_TERM term, ErlNifPort* port)
+{
+    if (is_internal_port(term)) {
+        port->port_id=term;
+        return 1;
+    }
+    return 0;
 }
 
 int enif_is_atom(ErlNifEnv* env, ERL_NIF_TERM term)
@@ -1158,6 +1174,58 @@ int enif_make_reverse_list(ErlNifEnv* env, ERL_NIF_TERM term, ERL_NIF_TERM *list
     return 1;
 }
 
+int enif_is_process_alive(ErlNifEnv* env, ErlNifPid *proc)
+{
+    ErtsProcLocks rp_locks = 0; /* We don't need any locks,
+                                   just to check if it is alive */
+    Eterm target = proc->pid;
+    Process* rp;
+    Process* c_p;
+    int scheduler = erts_get_scheduler_id() != 0;
+
+    if (env != NULL) {
+	c_p = env->proc;
+	if (target == c_p->common.id) {
+            /* We are alive! */
+	    return 1;
+	}
+    }
+    else {
+#ifdef ERTS_SMP
+	c_p = NULL;
+#else
+	erts_exit(ERTS_ABORT_EXIT,"enif_is_process_alive: "
+                  "env==NULL on non-SMP VM");
+#endif
+    }
+
+    rp = (scheduler
+	  ? erts_proc_lookup(target)
+	  : erts_pid2proc_opt(c_p, ERTS_PROC_LOCK_MAIN,
+			      target, rp_locks, ERTS_P2P_FLG_INC_REFC));
+    if (rp == NULL) {
+        ASSERT(env == NULL || target != c_p->common.id);
+	return 0;
+    } else {
+        if (!scheduler)
+            erts_proc_dec_refc(rp);
+        return 1;
+    }
+}
+
+int enif_is_port_alive(ErlNifEnv *env, ErlNifPort *port)
+{
+    /* only allowed if called from scheduler */
+    if (erts_get_scheduler_id() == 0)
+        erts_exit(ERTS_ABORT_EXIT,"enif_is_port_alive: called from non-scheduler");
+
+    return erts_port_lookup(
+        port->port_id,
+        (erts_port_synchronous_ops
+         ? ERTS_PORT_SFLGS_INVALID_DRIVER_LOOKUP
+         : ERTS_PORT_SFLGS_INVALID_LOOKUP)) != NULL;
+}
+
 ERL_NIF_TERM
 enif_now_time(ErlNifEnv *env)
 {
diff --git a/erts/emulator/beam/erl_nif.h b/erts/emulator/beam/erl_nif.h
index 959fcb5412..6ee22a693c 100644
--- a/erts/emulator/beam/erl_nif.h
+++ b/erts/emulator/beam/erl_nif.h
@@ -150,7 +150,12 @@ typedef enum
 typedef struct
 {
     ERL_NIF_TERM pid;  /* internal, may change */
-}ErlNifPid;
+} ErlNifPid;
+
+typedef struct
+{
+    ERL_NIF_TERM port_id;  /* internal, may change */
+}ErlNifPort;
 
 typedef ErlDrvSysInfo ErlNifSysInfo;
 
diff --git a/erts/emulator/beam/erl_nif_api_funcs.h b/erts/emulator/beam/erl_nif_api_funcs.h
index 3fe60e3df8..21864c8b35 100644
--- a/erts/emulator/beam/erl_nif_api_funcs.h
+++ b/erts/emulator/beam/erl_nif_api_funcs.h
@@ -166,6 +166,9 @@ ERL_NIF_API_FUNC_DECL(ErlNifTime, enif_convert_time_unit, (ErlNifTime, ErlNifTim
 ERL_NIF_API_FUNC_DECL(ERL_NIF_TERM, enif_now_time, (ErlNifEnv *env));
 ERL_NIF_API_FUNC_DECL(ERL_NIF_TERM, enif_cpu_time, (ErlNifEnv *env));
 ERL_NIF_API_FUNC_DECL(ERL_NIF_TERM, enif_make_unique_integer, (ErlNifEnv *env, ErlNifUniqueInteger properties));
+ERL_NIF_API_FUNC_DECL(int, enif_is_process_alive, (ErlNifEnv *env, ErlNifPid *pid));
+ERL_NIF_API_FUNC_DECL(int, enif_is_port_alive, (ErlNifEnv *env, ErlNifPort *port_id));
+ERL_NIF_API_FUNC_DECL(int, enif_get_local_port, (ErlNifEnv* env, ERL_NIF_TERM, ErlNifPort* port_id));
 
 /*
 ** ADD NEW ENTRIES HERE (before this comment) !!!
@@ -324,6 +327,9 @@ ERL_NIF_API_FUNC_DECL(int,enif_is_on_dirty_scheduler,(ErlNifEnv*));
 #  define enif_now_time ERL_NIF_API_FUNC_MACRO(enif_now_time)
 #  define enif_cpu_time ERL_NIF_API_FUNC_MACRO(enif_cpu_time)
 #  define enif_make_unique_integer ERL_NIF_API_FUNC_MACRO(enif_make_unique_integer)
+#  define enif_is_process_alive ERL_NIF_API_FUNC_MACRO(enif_is_process_alive)
+#  define enif_is_port_alive ERL_NIF_API_FUNC_MACRO(enif_is_port_alive)
+#  define enif_get_local_port ERL_NIF_API_FUNC_MACRO(enif_get_local_port)
 
 /*
 ** ADD NEW ENTRIES HERE (before this comment)
-- 
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