feat: wrap cgo Handles with Erlang Resources (#17)

* Add Option_type resource type

* Use resource in functions

* Add resources for each type

* Use resources on stream handler

* Fix destructor not being called

NIFs keep a reference to the allocated resource by default on allocation.
We need to release that reference before returning, otherwise it will never be GC'd.

* Use reference instead of integer for typespec

* Unify function naming in Go

* Explicitly ignore autogenerated header only

* Add "dirty NIF" flags to IO calls

Author: MegaRedHand

.gitignore

@@ -36,8 +36,8 @@ lambda_ethereum_consensus-*.tar
 # Compiled artifacts.
 *.o
 *.a
-*.h
 *.so
+native/libp2p_nif/main.h
 
 # VSCode configuration dir.
 .vscode/

lib/lambda_ethereum_consensus/libp2p.ex

@@ -13,37 +13,37 @@ defmodule Libp2p do
   @typedoc """
   A handle to a Go resource.
   """
-  @type handle :: integer
+  @opaque handle :: reference
 
   @typedoc """
   A handle to a host.Host.
   """
-  @type host :: handle
+  @opaque host :: handle
 
   @typedoc """
   A handle to a peerstore.Peerstore.
   """
-  @type peerstore :: handle
+  @opaque peerstore :: handle
 
   @typedoc """
   A handle to a peer.ID.
   """
-  @type peer_id :: handle
+  @opaque peer_id :: handle
 
   @typedoc """
   A handle to a []multiaddr.MultiAddr.
   """
-  @type addrs :: handle
+  @opaque addrs :: handle
 
   @typedoc """
   A handle to a stream.
   """
-  @type stream :: handle
+  @opaque stream :: handle
 
   @typedoc """
   A handle to an Option.
   """
-  @type option :: handle
+  @opaque option :: handle
 
   @typedoc """
   An error returned by this module.

native/libp2p_nif/libp2p.c

@@ -1,16 +1,17 @@
 #include "main.h"
 #include "utils.h"
+#include <stdbool.h>
 #include <erl_nif.h>
 
 #define ERL_FUNCTION(FUNCTION_NAME) static ERL_NIF_TERM FUNCTION_NAME(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
 
-#define ERL_FUNCTION_GETTER(NAME, GETTER)                       \
-    ERL_FUNCTION(NAME)                                          \
-    {                                                           \
-        uintptr_t _handle = get_handle_from_term(env, argv[0]); \
-        IF_ERROR(_handle == 0, "invalid first argument");       \
-        uintptr_t _res = GETTER(_handle);                       \
-        return get_handle_result(env, _res);                    \
+#define ERL_FUNCTION_GETTER(NAME, RECV_TYPE, ATTR_TYPE, GETTER)            \
+    ERL_FUNCTION(NAME)                                                     \
+    {                                                                      \
+        uintptr_t _handle = get_handle_from_term(env, RECV_TYPE, argv[0]); \
+        IF_ERROR(_handle == 0, "invalid first argument");                  \
+        uintptr_t _res = GETTER(_handle);                                  \
+        return get_handle_result(env, ATTR_TYPE, _res);                    \
     }
 
 #define IF_ERROR(COND, MSG)                \
@@ -19,29 +20,72 @@
         return make_error_msg(env, (MSG)); \
     }
 
-#define GET_HANDLE(TERM, NAME)                                 \
-    ({                                                         \
-        uintptr_t _handle = get_handle_from_term(env, (TERM)); \
-        IF_ERROR(_handle == 0, "invalid " NAME);               \
-        _handle;                                               \
+#define GET_HANDLE(TERM, TYPE)                                         \
+    ({                                                                 \
+        uintptr_t _handle = get_handle_from_term(env, (TYPE), (TERM)); \
+        IF_ERROR(_handle == 0, "invalid " #TYPE);                      \
+        _handle;                                                       \
     })
 
-#define NIF_ENTRY(FUNCTION_NAME, ARITY)      \
-    {                                        \
-        #FUNCTION_NAME, ARITY, FUNCTION_NAME \
+#define NIF_ENTRY(FUNCTION_NAME, ARITY, ...)              \
+    {                                                     \
+        #FUNCTION_NAME, ARITY, FUNCTION_NAME, __VA_ARGS__ \
     }
 
-const uint64_t PID_LENGTH = 1024;
 const uint64_t BUFFER_SIZE = 4096;
 
+/*************/
+/* NIF Setup */
+/*************/
+
+ErlNifResourceType *Option;
+ErlNifResourceType *Host;
+ErlNifResourceType *Peerstore;
+ErlNifResourceType *peer_ID;
+ErlNifResourceType *Multiaddr_arr;
+ErlNifResourceType *Stream;
+
+// Resource type helpers
+void handle_cleanup(ErlNifEnv *env, void *obj)
+{
+    uintptr_t *handle = obj;
+    DeleteHandle(*handle);
+}
+
+#define OPEN_RESOURCE_TYPE(NAME) ((NAME) = enif_open_resource_type(env, NULL, (#NAME), handle_cleanup, flags, NULL))
+
+static int open_resource_types(ErlNifEnv *env, ErlNifResourceFlags flags)
+{
+    int failed = false;
+    failed |= NULL == OPEN_RESOURCE_TYPE(Option);
+    failed |= NULL == OPEN_RESOURCE_TYPE(Host);
+    failed |= NULL == OPEN_RESOURCE_TYPE(Peerstore);
+    failed |= NULL == OPEN_RESOURCE_TYPE(peer_ID);
+    failed |= NULL == OPEN_RESOURCE_TYPE(Multiaddr_arr);
+    failed |= NULL == OPEN_RESOURCE_TYPE(Stream);
+    return failed;
+}
+
+static int load(ErlNifEnv *env, void **priv_data, ERL_NIF_TERM load_info)
+{
+    return open_resource_types(env, ERL_NIF_RT_CREATE | ERL_NIF_RT_TAKEOVER);
+}
+
+static int upgrade(ErlNifEnv *env, void **priv_data, void **old_priv_data,
+                   ERL_NIF_TERM load_info)
+{
+    return open_resource_types(env, ERL_NIF_RT_TAKEOVER);
+}
+
 /***********/
 /* Helpers */
 /***********/
 
-static uintptr_t get_handle_from_term(ErlNifEnv *env, ERL_NIF_TERM term)
+static uintptr_t get_handle_from_term(ErlNifEnv *env, ErlNifResourceType *type, ERL_NIF_TERM term)
 {
-    uintptr_t handle;
-    return enif_get_uint64(env, term, &handle) ? handle : 0;
+    uintptr_t *obj;
+    int result = enif_get_resource(env, term, type, (void **)&obj);
+    return (!result || obj == NULL) ? 0 : *obj;
 }
 
 static ERL_NIF_TERM _make_error_msg(ErlNifEnv *env, uint len, const char *msg)
@@ -62,10 +106,32 @@ static ERL_NIF_TERM make_ok_tuple2(ErlNifEnv *env, ERL_NIF_TERM term)
     return enif_make_tuple2(env, enif_make_atom(env, "ok"), term);
 }
 
-static ERL_NIF_TERM get_handle_result(ErlNifEnv *env, uintptr_t handle)
+static ERL_NIF_TERM get_handle_result(ErlNifEnv *env, ErlNifResourceType *type, uintptr_t handle)
 {
     IF_ERROR(handle == 0, "invalid handle returned");
-    return make_ok_tuple2(env, enif_make_uint64(env, handle));
+    uintptr_t *obj = enif_alloc_resource(type, sizeof(uintptr_t));
+    IF_ERROR(obj == NULL, "couldn't create resource");
+    *obj = handle;
+    ERL_NIF_TERM term = enif_make_resource(env, obj);
+    // NOTE: we need to release our reference, so it can be GC'd
+    enif_release_resource(obj);
+    return make_ok_tuple2(env, term);
+}
+
+void send_message(erl_pid_t _pid, uintptr_t stream_handle)
+{
+    // Passed as void* to avoid including erl_nif.h in the header.
+    ErlNifPid *pid = (ErlNifPid *)_pid;
+    ErlNifEnv *env = enif_alloc_env();
+
+    ERL_NIF_TERM message = get_handle_result(env, Stream, stream_handle);
+
+    int result = enif_send(NULL, pid, env, message);
+    // On error, the env isn't freed by the function.
+    if (!result)
+    {
+        enif_free_env(env);
+    }
 }
 
 /*********/
@@ -80,7 +146,7 @@ ERL_FUNCTION(listen_addr_strings)
 
     uintptr_t handle = ListenAddrStrings(listen_addr);
 
-    return get_handle_result(env, handle);
+    return get_handle_result(env, Option, handle);
 }
 
 /****************/
@@ -97,23 +163,24 @@ ERL_FUNCTION(host_new)
     while (!enif_is_empty_list(env, tail) && i < MAX_OPTIONS)
     {
         enif_get_list_cell(env, tail, &head, &tail);
-        options[i++] = GET_HANDLE(head, "option");
+        uintptr_t handle = GET_HANDLE(head, Option);
+        options[i++] = handle;
     }
     GoSlice go_options = {options, i, MAX_OPTIONS};
     uintptr_t result = HostNew(go_options);
-    return get_handle_result(env, result);
+    return get_handle_result(env, Host, result);
 }
 
 ERL_FUNCTION(host_close)
 {
-    uintptr_t host = GET_HANDLE(argv[0], "host");
+    uintptr_t host = GET_HANDLE(argv[0], Host);
     HostClose(host);
     return enif_make_atom(env, "ok");
 }
 
 ERL_FUNCTION(host_set_stream_handler)
 {
-    uintptr_t host = GET_HANDLE(argv[0], "host");
+    uintptr_t host = GET_HANDLE(argv[0], Host);
 
     ErlNifBinary bin;
     IF_ERROR(!enif_inspect_binary(env, argv[1], &bin), "invalid protocol ID");
@@ -124,41 +191,41 @@ ERL_FUNCTION(host_set_stream_handler)
 
     IF_ERROR(!enif_self(env, pid), "failed to get pid");
 
-    SetStreamHandler(host, proto_id, (void *)pid);
+    HostSetStreamHandler(host, proto_id, (void *)pid, send_message);
 
     return enif_make_atom(env, "ok");
 }
 
 ERL_FUNCTION(host_new_stream)
 {
-    uintptr_t host = GET_HANDLE(argv[0], "host");
-    uintptr_t id = GET_HANDLE(argv[1], "peer id");
+    uintptr_t host = GET_HANDLE(argv[0], Host);
+    uintptr_t id = GET_HANDLE(argv[1], peer_ID);
 
     ErlNifBinary bin;
     IF_ERROR(!enif_inspect_binary(env, argv[2], &bin), "invalid protocol ID");
     GoString proto_id = {(const char *)bin.data, bin.size};
 
-    int result = NewStream(host, id, proto_id);
-    return get_handle_result(env, result);
+    uintptr_t result = HostNewStream(host, id, proto_id);
+    return get_handle_result(env, Stream, result);
 }
 
-ERL_FUNCTION_GETTER(host_peerstore, Peerstore)
-ERL_FUNCTION_GETTER(host_id, ID)
-ERL_FUNCTION_GETTER(host_addrs, Addrs)
+ERL_FUNCTION_GETTER(host_peerstore, Host, Peerstore, HostPeerstore)
+ERL_FUNCTION_GETTER(host_id, Host, peer_ID, HostID)
+ERL_FUNCTION_GETTER(host_addrs, Host, Multiaddr_arr, HostAddrs)
 
 /*********************/
 /* Peerstore methods */
 /*********************/
 
 ERL_FUNCTION(peerstore_add_addrs)
 {
-    uintptr_t ps = GET_HANDLE(argv[0], "peerstore");
-    uintptr_t id = GET_HANDLE(argv[1], "peer id");
-    uintptr_t addrs = GET_HANDLE(argv[2], "addrs");
+    uintptr_t ps = GET_HANDLE(argv[0], Peerstore);
+    uintptr_t id = GET_HANDLE(argv[1], peer_ID);
+    uintptr_t addrs = GET_HANDLE(argv[2], Multiaddr_arr);
     u_long ttl;
     IF_ERROR(!enif_get_uint64(env, argv[3], &ttl), "invalid TTL");
 
-    AddAddrs(ps, id, addrs, ttl);
+    PeerstoreAddAddrs(ps, id, addrs, ttl);
     return enif_make_atom(env, "ok");
 }
 
@@ -168,7 +235,7 @@ ERL_FUNCTION(peerstore_add_addrs)
 
 ERL_FUNCTION(stream_read)
 {
-    uintptr_t stream = GET_HANDLE(argv[0], "stream");
+    uintptr_t stream = GET_HANDLE(argv[0], Stream);
 
     char buffer[BUFFER_SIZE];
     GoSlice go_buffer = {buffer, BUFFER_SIZE, BUFFER_SIZE};
@@ -185,7 +252,7 @@ ERL_FUNCTION(stream_read)
 
 ERL_FUNCTION(stream_write)
 {
-    uintptr_t stream = GET_HANDLE(argv[0], "stream");
+    uintptr_t stream = GET_HANDLE(argv[0], Stream);
 
     ErlNifBinary bin;
     IF_ERROR(!enif_inspect_binary(env, argv[1], &bin), "invalid data");
@@ -199,7 +266,7 @@ ERL_FUNCTION(stream_write)
 
 ERL_FUNCTION(stream_close)
 {
-    uintptr_t stream = GET_HANDLE(argv[0], "stream");
+    uintptr_t stream = GET_HANDLE(argv[0], Stream);
     StreamClose(stream);
     return enif_make_atom(env, "ok");
 }
@@ -209,14 +276,15 @@ static ErlNifFunc nif_funcs[] = {
     NIF_ENTRY(host_new, 1),
     NIF_ENTRY(host_close, 1),
     NIF_ENTRY(host_set_stream_handler, 2),
-    NIF_ENTRY(host_new_stream, 3),
+    // TODO: check if host_new_stream is truly dirty
+    NIF_ENTRY(host_new_stream, 3, ERL_NIF_DIRTY_JOB_IO_BOUND), // blocks negotiating protocol
     NIF_ENTRY(host_peerstore, 1),
     NIF_ENTRY(host_id, 1),
     NIF_ENTRY(host_addrs, 1),
     NIF_ENTRY(peerstore_add_addrs, 4),
-    NIF_ENTRY(stream_read, 1),
-    NIF_ENTRY(stream_write, 2),
+    NIF_ENTRY(stream_read, 1, ERL_NIF_DIRTY_JOB_IO_BOUND),  // blocks until reading
+    NIF_ENTRY(stream_write, 2, ERL_NIF_DIRTY_JOB_IO_BOUND), // blocks when buffer is full
     NIF_ENTRY(stream_close, 1),
 };
 
-ERL_NIF_INIT(Elixir.Libp2p, nif_funcs, NULL, NULL, NULL, NULL)
+ERL_NIF_INIT(Elixir.Libp2p, nif_funcs, load, NULL, upgrade, NULL)