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Commit 8d222d4

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addaleaxMylesBorins
addaleax
authored and
MylesBorins
committed
n-api: add helper for addons to get the event loop
Add a utility functions for addons to use when they need a reference to the current event loop. While the libuv API is not directly part of N-API, it provides a quite stable C API as well, and is tightly integrated with Node itself. As a particular use case, without access to the event loop it is hard to do something interesting from inside a N-API finalizer function, since calls into JS and therefore virtually all other N-API functions are not allowed. PR-URL: #17109 Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl> Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
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‎doc/api/n-api.md‎

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+17Lines changed: 17 additions & 0 deletions
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Original file line numberDiff line numberDiff line change
@@ -3686,6 +3686,23 @@ NAPI_EXTERN napi_status napi_run_script(napi_env env,
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- `[in] script`: A JavaScript string containing the script to execute.
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- `[out] result`: The value resulting from having executed the script.
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## libuv event loop
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N-API provides a function for getting the current event loop associated with
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a specific `napi_env`.
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### napi_get_uv_event_loop
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<!-- YAML
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added: REPLACEME
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-->
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```C
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NAPI_EXTERN napi_status napi_get_uv_event_loop(napi_env env,
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uv_loop_t** loop);
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```
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- `[in] env`: The environment that the API is invoked under.
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- `[out] loop`: The current libuv loop instance.
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[Promises]: #n_api_promises
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[Simple Asynchronous Operations]: #n_api_simple_asynchronous_operations
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[Custom Asynchronous Operations]: #n_api_custom_asynchronous_operations
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‎src/node_api.cc‎

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+19-9Lines changed: 19 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -18,7 +18,7 @@
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#include "node_api.h"
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#include "node_internals.h"
2020

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#define NAPI_VERSION 1
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#define NAPI_VERSION 2
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static
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napi_status napi_set_last_error(napi_env env, napi_status error_code,
@@ -28,8 +28,10 @@ static
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napi_status napi_clear_last_error(napi_env env);
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struct napi_env__ {
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explicit napi_env__(v8::Isolate* _isolate): isolate(_isolate),
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last_error() {}
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explicit napi_env__(v8::Isolate* _isolate, uv_loop_t* _loop)
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: isolate(_isolate),
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last_error(),
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loop(_loop) {}
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~napi_env__() {
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last_exception.Reset();
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wrap_template.Reset();
@@ -43,6 +45,7 @@ struct napi_env__ {
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v8::Persistent<v8::ObjectTemplate> accessor_data_template;
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napi_extended_error_info last_error;
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int open_handle_scopes = 0;
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uv_loop_t* loop = nullptr;
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};
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#define ENV_OBJECT_TEMPLATE(env, prefix, destination, field_count) \
@@ -771,7 +774,7 @@ napi_env GetEnv(v8::Local<v8::Context> context) {
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if (value->IsExternal()) {
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result = static_cast<napi_env>(value.As<v8::External>()->Value());
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} else {
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result = new napi_env__(isolate);
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result = new napi_env__(isolate, node::GetCurrentEventLoop(isolate));
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auto external = v8::External::New(isolate, result);
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// We must also stop hard if the result of assigning the env to the global
@@ -3401,15 +3404,22 @@ napi_status napi_delete_async_work(napi_env env, napi_async_work work) {
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return napi_clear_last_error(env);
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}
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napi_status napi_get_uv_event_loop(napi_env env, uv_loop_t** loop) {
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CHECK_ENV(env);
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CHECK_ARG(env, loop);
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*loop = env->loop;
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return napi_clear_last_error(env);
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}
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napi_status napi_queue_async_work(napi_env env, napi_async_work work) {
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CHECK_ENV(env);
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CHECK_ARG(env, work);
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// Consider: Encapsulate the uv_loop_t into an opaque pointer parameter.
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// Currently the environment event loop is the same as the UV default loop.
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// Someday (if node ever supports multiple isolates), it may be better to get
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// the loop from node::Environment::GetCurrent(env->isolate)->event_loop();
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uv_loop_t* event_loop = uv_default_loop();
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napi_status status;
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uv_loop_t* event_loop = nullptr;
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status = napi_get_uv_event_loop(env, &event_loop);
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if (status != napi_ok)
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return napi_set_last_error(env, status);
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uvimpl::Work* w = reinterpret_cast<uvimpl::Work*>(work);
34153425

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‎src/node_api.h‎

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+6Lines changed: 6 additions & 0 deletions
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@@ -14,6 +14,8 @@
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#include <stdbool.h>
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#include "node_api_types.h"
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struct uv_loop_s; // Forward declaration.
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#ifdef _WIN32
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#ifdef BUILDING_NODE_EXTENSION
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#ifdef EXTERNAL_NAPI
@@ -581,6 +583,10 @@ NAPI_EXTERN napi_status napi_run_script(napi_env env,
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napi_value script,
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napi_value* result);
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// Return the current libuv event loop for a given environment
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NAPI_EXTERN napi_status napi_get_uv_event_loop(napi_env env,
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struct uv_loop_s** loop);
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EXTERN_C_END
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#endif // SRC_NODE_API_H_
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‎test/addons-napi/test_general/test.js‎

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+1-1Lines changed: 1 addition & 1 deletion
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@@ -34,7 +34,7 @@ assert.ok(test_general.testGetPrototype(baseObject) !==
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// test version management functions
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// expected version is currently 1
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assert.strictEqual(test_general.testGetVersion(), 1);
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assert.strictEqual(test_general.testGetVersion(), 2);
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const [ major, minor, patch, release ] = test_general.testGetNodeVersion();
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assert.strictEqual(process.version.split('-')[0],
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‎test/addons-napi/test_uv_loop/binding.gyp‎

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@@ -0,0 +1,8 @@
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{
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"targets": [
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{
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"target_name": "test_uv_loop",
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"sources": [ "test_uv_loop.cc" ]
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}
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]
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}
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‎test/addons-napi/test_uv_loop/test.js‎

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@@ -0,0 +1,5 @@
1+
'use strict';
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const common = require('../../common');
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const { SetImmediate } = require(`./build/${common.buildType}/test_uv_loop`);
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SetImmediate(common.mustCall());
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‎test/addons-napi/test_uv_loop/test_uv_loop.cc‎

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+78Lines changed: 78 additions & 0 deletions
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@@ -0,0 +1,78 @@
1+
#include <node_api.h>
2+
#include <uv.h>
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#include <utility>
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#include <memory>
5+
#include <assert.h>
6+
#include "../common.h"
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8+
template <typename T>
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void* SetImmediate(napi_env env, T&& cb) {
10+
T* ptr = new T(std::move(cb));
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uv_loop_t* loop = nullptr;
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uv_check_t* check = new uv_check_t;
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check->data = ptr;
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NAPI_ASSERT(env,
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napi_get_uv_event_loop(env, &loop) == napi_ok,
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"can get event loop");
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uv_check_init(loop, check);
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uv_check_start(check, [](uv_check_t* check) {
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std::unique_ptr<T> ptr {static_cast<T*>(check->data)};
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T cb = std::move(*ptr);
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uv_close(reinterpret_cast<uv_handle_t*>(check), [](uv_handle_t* handle) {
22+
delete reinterpret_cast<uv_check_t*>(handle);
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});
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assert(cb() != nullptr);
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});
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return nullptr;
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}
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static char dummy;
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napi_value SetImmediateBinding(napi_env env, napi_callback_info info) {
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size_t argc = 1;
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napi_value argv[1];
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napi_value _this;
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void* data;
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NAPI_CALL(env,
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napi_get_cb_info(env, info, &argc, argv, &_this, &data));
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NAPI_ASSERT(env, argc >= 1, "Not enough arguments, expected 1.");
40+
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napi_valuetype t;
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NAPI_CALL(env, napi_typeof(env, argv[0], &t));
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NAPI_ASSERT(env, t == napi_function,
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"Wrong first argument, function expected.");
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napi_ref cbref;
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NAPI_CALL(env,
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napi_create_reference(env, argv[0], 1, &cbref));
49+
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SetImmediate(env, [=]() -> char* {
51+
napi_value undefined;
52+
napi_value callback;
53+
napi_handle_scope scope;
54+
NAPI_CALL(env, napi_open_handle_scope(env, &scope));
55+
NAPI_CALL(env, napi_get_undefined(env, &undefined));
56+
NAPI_CALL(env, napi_get_reference_value(env, cbref, &callback));
57+
NAPI_CALL(env, napi_delete_reference(env, cbref));
58+
NAPI_CALL(env,
59+
napi_call_function(env, undefined, callback, 0, nullptr, nullptr));
60+
NAPI_CALL(env, napi_close_handle_scope(env, scope));
61+
return &dummy;
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});
63+
64+
return nullptr;
65+
}
66+
67+
napi_value Init(napi_env env, napi_value exports) {
68+
napi_property_descriptor properties[] = {
69+
DECLARE_NAPI_PROPERTY("SetImmediate", SetImmediateBinding)
70+
};
71+
72+
NAPI_CALL(env, napi_define_properties(
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env, exports, sizeof(properties) / sizeof(*properties), properties));
74+
75+
return exports;
76+
}
77+
78+
NAPI_MODULE(NODE_GYP_MODULE_NAME, Init)

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