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lib,src: make StatWatcher a HandleWrap
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Wrapping libuv handles is what `HandleWrap` is there for.
This allows a decent reduction of state tracking machinery
by moving active-ness tracking to JS, and removing all
interaction with garbage collection.

Refs: #21093

PR-URL: #21244
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
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@addaleax @targos
addaleax authored and targos committed Jun 14, 2018
1 parent dea3ac7 commit 740d9f1
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Showing 4 changed files with 67 additions and 141 deletions.
68 changes: 40 additions & 28 deletions lib/internal/fs/watchers.js
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Original file line number Diff line number Diff line change
Expand Up @@ -11,41 +11,42 @@ const {
getStatsFromBinding,
validatePath
} = require('internal/fs/utils');
const { defaultTriggerAsyncIdScope } = require('internal/async_hooks');
const { toNamespacedPath } = require('path');
const { validateUint32 } = require('internal/validators');
const { getPathFromURL } = require('internal/url');
const util = require('util');
const assert = require('assert');

const kOldStatus = Symbol('kOldStatus');
const kUseBigint = Symbol('kUseBigint');
const kOwner = Symbol('kOwner');

function emitStop(self) {
self.emit('stop');
}

function StatWatcher(bigint) {
EventEmitter.call(this);

this._handle = new _StatWatcher(bigint);

// uv_fs_poll is a little more powerful than ev_stat but we curb it for
// the sake of backwards compatibility
let oldStatus = -1;

this._handle.onchange = (newStatus, stats) => {
if (oldStatus === -1 &&
newStatus === -1 &&
stats[2/* new nlink */] === stats[16/* old nlink */]) return;

oldStatus = newStatus;
this.emit('change', getStatsFromBinding(stats),
getStatsFromBinding(stats, kFsStatsFieldsLength));
};

this._handle.onstop = () => {
process.nextTick(emitStop, this);
};
this._handle = null;
this[kOldStatus] = -1;
this[kUseBigint] = bigint;
}
util.inherits(StatWatcher, EventEmitter);

function onchange(newStatus, stats) {
const self = this[kOwner];
if (self[kOldStatus] === -1 &&
newStatus === -1 &&
stats[2/* new nlink */] === stats[16/* old nlink */]) {
return;
}

self[kOldStatus] = newStatus;
self.emit('change', getStatsFromBinding(stats),
getStatsFromBinding(stats, kFsStatsFieldsLength));
}

// FIXME(joyeecheung): this method is not documented.
// At the moment if filename is undefined, we
Expand All @@ -54,16 +55,23 @@ util.inherits(StatWatcher, EventEmitter);
// on a valid filename and the wrap has been initialized
// This method is a noop if the watcher has already been started.
StatWatcher.prototype.start = function(filename, persistent, interval) {
assert(this._handle instanceof _StatWatcher, 'handle must be a StatWatcher');
if (this._handle.isActive) {
if (this._handle !== null)
return;
}

this._handle = new _StatWatcher(this[kUseBigint]);
this._handle[kOwner] = this;
this._handle.onchange = onchange;
if (!persistent)
this._handle.unref();

// uv_fs_poll is a little more powerful than ev_stat but we curb it for
// the sake of backwards compatibility
this[kOldStatus] = -1;

filename = getPathFromURL(filename);
validatePath(filename, 'filename');
validateUint32(interval, 'interval');
const err = this._handle.start(toNamespacedPath(filename),
persistent, interval);
const err = this._handle.start(toNamespacedPath(filename), interval);
if (err) {
const error = errors.uvException({
errno: err,
Expand All @@ -80,11 +88,15 @@ StatWatcher.prototype.start = function(filename, persistent, interval) {
// FSWatcher is .close()
// This method is a noop if the watcher has not been started.
StatWatcher.prototype.stop = function() {
assert(this._handle instanceof _StatWatcher, 'handle must be a StatWatcher');
if (!this._handle.isActive) {
if (this._handle === null)
return;
}
this._handle.stop();

defaultTriggerAsyncIdScope(this._handle.getAsyncId(),
process.nextTick,
emitStop,
this);
this._handle.close();
this._handle = null;
};


Expand Down
108 changes: 21 additions & 87 deletions src/node_stat_watcher.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -31,17 +31,12 @@
namespace node {

using v8::Context;
using v8::DontDelete;
using v8::DontEnum;
using v8::FunctionCallbackInfo;
using v8::FunctionTemplate;
using v8::HandleScope;
using v8::Integer;
using v8::Local;
using v8::Object;
using v8::PropertyAttribute;
using v8::ReadOnly;
using v8::Signature;
using v8::String;
using v8::Uint32;
using v8::Value;
Expand All @@ -58,43 +53,32 @@ void StatWatcher::Initialize(Environment* env, Local<Object> target) {

AsyncWrap::AddWrapMethods(env, t);
env->SetProtoMethod(t, "start", StatWatcher::Start);
env->SetProtoMethod(t, "stop", StatWatcher::Stop);

Local<FunctionTemplate> is_active_templ =
FunctionTemplate::New(env->isolate(),
IsActive,
env->as_external(),
Signature::New(env->isolate(), t));
t->PrototypeTemplate()->SetAccessorProperty(
FIXED_ONE_BYTE_STRING(env->isolate(), "isActive"),
is_active_templ,
Local<FunctionTemplate>(),
static_cast<PropertyAttribute>(ReadOnly | DontDelete | DontEnum));
env->SetProtoMethod(t, "close", HandleWrap::Close);
env->SetProtoMethod(t, "ref", HandleWrap::Ref);
env->SetProtoMethod(t, "unref", HandleWrap::Unref);
env->SetProtoMethod(t, "hasRef", HandleWrap::HasRef);

target->Set(statWatcherString, t->GetFunction());
}


StatWatcher::StatWatcher(Environment* env, Local<Object> wrap, bool use_bigint)
: AsyncWrap(env, wrap, AsyncWrap::PROVIDER_STATWATCHER),
watcher_(nullptr),
StatWatcher::StatWatcher(Environment* env,
Local<Object> wrap,
bool use_bigint)
: HandleWrap(env,
wrap,
reinterpret_cast<uv_handle_t*>(&watcher_),
AsyncWrap::PROVIDER_STATWATCHER),
use_bigint_(use_bigint) {
MakeWeak();
}


StatWatcher::~StatWatcher() {
if (IsActive())
Stop();
CHECK_EQ(0, uv_fs_poll_init(env->event_loop(), &watcher_));
}


void StatWatcher::Callback(uv_fs_poll_t* handle,
int status,
const uv_stat_t* prev,
const uv_stat_t* curr) {
StatWatcher* wrap = static_cast<StatWatcher*>(handle->data);
CHECK_EQ(wrap->watcher_, handle);
StatWatcher* wrap = ContainerOf(&StatWatcher::watcher_, handle);
Environment* env = wrap->env();
HandleScope handle_scope(env->isolate());
Context::Scope context_scope(env->context());
Expand All @@ -118,78 +102,28 @@ void StatWatcher::New(const FunctionCallbackInfo<Value>& args) {
new StatWatcher(env, args.This(), args[0]->IsTrue());
}

bool StatWatcher::IsActive() {
return watcher_ != nullptr;
}

void StatWatcher::IsActive(const v8::FunctionCallbackInfo<v8::Value>& args) {
StatWatcher* wrap = Unwrap<StatWatcher>(args.This());
CHECK_NOT_NULL(wrap);
args.GetReturnValue().Set(wrap->IsActive());
}

// wrap.start(filename, persistent, interval)
// wrap.start(filename, interval)
void StatWatcher::Start(const FunctionCallbackInfo<Value>& args) {
CHECK_EQ(args.Length(), 3);
CHECK_EQ(args.Length(), 2);

StatWatcher* wrap = Unwrap<StatWatcher>(args.Holder());
CHECK_NOT_NULL(wrap);
if (wrap->IsActive()) {
return;
}
StatWatcher* wrap;
ASSIGN_OR_RETURN_UNWRAP(&wrap, args.Holder());
CHECK(!uv_is_active(wrap->GetHandle()));

const int argc = args.Length();
CHECK_GE(argc, 3);

node::Utf8Value path(args.GetIsolate(), args[0]);
CHECK_NOT_NULL(*path);

bool persistent = true;
if (args[1]->IsFalse()) {
persistent = false;
}

CHECK(args[2]->IsUint32());
const uint32_t interval = args[2].As<Uint32>()->Value();

wrap->watcher_ = new uv_fs_poll_t();
CHECK_EQ(0, uv_fs_poll_init(wrap->env()->event_loop(), wrap->watcher_));
wrap->watcher_->data = static_cast<void*>(wrap);
// Safe, uv_ref/uv_unref are idempotent.
if (persistent)
uv_ref(reinterpret_cast<uv_handle_t*>(wrap->watcher_));
else
uv_unref(reinterpret_cast<uv_handle_t*>(wrap->watcher_));
CHECK(args[1]->IsUint32());
const uint32_t interval = args[1].As<Uint32>()->Value();

// Note that uv_fs_poll_start does not return ENOENT, we are handling
// mostly memory errors here.
const int err = uv_fs_poll_start(wrap->watcher_, Callback, *path, interval);
const int err = uv_fs_poll_start(&wrap->watcher_, Callback, *path, interval);
if (err != 0) {
args.GetReturnValue().Set(err);
}
wrap->ClearWeak();
}


void StatWatcher::Stop(const FunctionCallbackInfo<Value>& args) {
StatWatcher* wrap = Unwrap<StatWatcher>(args.Holder());
CHECK_NOT_NULL(wrap);
if (!wrap->IsActive()) {
return;
}

Environment* env = wrap->env();
Context::Scope context_scope(env->context());
wrap->MakeCallback(env->onstop_string(), 0, nullptr);
wrap->Stop();
}


void StatWatcher::Stop() {
env()->CloseHandle(watcher_, [](uv_fs_poll_t* handle) { delete handle; });
watcher_ = nullptr;
MakeWeak();
}


} // namespace node
16 changes: 6 additions & 10 deletions src/node_stat_watcher.h
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Original file line number Diff line number Diff line change
Expand Up @@ -25,26 +25,24 @@
#if defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS

#include "node.h"
#include "async_wrap.h"
#include "handle_wrap.h"
#include "env.h"
#include "uv.h"
#include "v8.h"

namespace node {

class StatWatcher : public AsyncWrap {
class StatWatcher : public HandleWrap {
public:
~StatWatcher() override;

static void Initialize(Environment* env, v8::Local<v8::Object> target);

protected:
StatWatcher(Environment* env, v8::Local<v8::Object> wrap, bool use_bigint);
StatWatcher(Environment* env,
v8::Local<v8::Object> wrap,
bool use_bigint);

static void New(const v8::FunctionCallbackInfo<v8::Value>& args);
static void Start(const v8::FunctionCallbackInfo<v8::Value>& args);
static void Stop(const v8::FunctionCallbackInfo<v8::Value>& args);
static void IsActive(const v8::FunctionCallbackInfo<v8::Value>& args);

size_t self_size() const override { return sizeof(*this); }

Expand All @@ -53,10 +51,8 @@ class StatWatcher : public AsyncWrap {
int status,
const uv_stat_t* prev,
const uv_stat_t* curr);
void Stop();
bool IsActive();

uv_fs_poll_t* watcher_;
uv_fs_poll_t watcher_;
const bool use_bigint_;
};

Expand Down
16 changes: 0 additions & 16 deletions test/sequential/test-fs-watch.js
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Original file line number Diff line number Diff line change
Expand Up @@ -126,19 +126,3 @@ tmpdir.refresh();
});
oldhandle.close(); // clean up
}

{
let oldhandle;
assert.throws(() => {
const w = fs.watchFile(__filename,
{ persistent: false },
common.mustNotCall());
oldhandle = w._handle;
w._handle = { stop: w._handle.stop };
w.stop();
}, {
message: 'handle must be a StatWatcher',
code: 'ERR_ASSERTION'
});
oldhandle.stop(); // clean up
}

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