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/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#include "mongo/platform/basic.h"
#include "mongo/scripting/mozjs/countdownlatch.h"
#include <cmath>
#include "mongo/platform/mutex.h"
#include "mongo/scripting/mozjs/implscope.h"
#include "mongo/scripting/mozjs/objectwrapper.h"
#include "mongo/scripting/mozjs/valuewriter.h"
#include "mongo/stdx/condition_variable.h"
#include "mongo/stdx/unordered_map.h"
namespace mongo {
namespace mozjs {
const char* const CountDownLatchInfo::className = "CountDownLatch";
const JSFunctionSpec CountDownLatchInfo::methods[5] = {
MONGO_ATTACH_JS_FUNCTION(_new),
MONGO_ATTACH_JS_FUNCTION(_await),
MONGO_ATTACH_JS_FUNCTION(_countDown),
MONGO_ATTACH_JS_FUNCTION(_getCount),
JS_FS_END,
};
/**
* The global CountDownLatch holder.
*
* Provides an interface for communicating between JSThread's
*/
class CountDownLatchHolder {
public:
CountDownLatchHolder() : _counter(0) {}
int32_t make(int32_t count) {
uassert(ErrorCodes::JSInterpreterFailure, "argument must be >= 0", count >= 0);
stdx::lock_guard<Latch> lock(_mutex);
int32_t desc = ++_counter;
_latches.insert(std::make_pair(desc, std::make_shared<CountDownLatch>(count)));
return desc;
}
void await(int32_t desc) {
auto latch = get(desc);
stdx::unique_lock<Latch> lock(latch->mutex);
while (latch->count != 0) {
latch->cv.wait(lock);
}
}
void countDown(int32_t desc) {
auto latch = get(desc);
stdx::unique_lock<Latch> lock(latch->mutex);
if (latch->count > 0)
latch->count--;
if (latch->count == 0)
latch->cv.notify_all();
}
int32_t getCount(int32_t desc) {
auto latch = get(desc);
stdx::unique_lock<Latch> lock(latch->mutex);
return latch->count;
}
private:
/**
* Latches for communication between threads
*/
struct CountDownLatch {
CountDownLatch(int32_t count) : count(count) {}
Mutex mutex = MONGO_MAKE_LATCH("Latch::mutex");
stdx::condition_variable cv;
int32_t count;
};
std::shared_ptr<CountDownLatch> get(int32_t desc) {
stdx::lock_guard<Latch> lock(_mutex);
auto iter = _latches.find(desc);
uassert(ErrorCodes::JSInterpreterFailure,
"not a valid CountDownLatch descriptor",
iter != _latches.end());
return iter->second;
}
using Map = stdx::unordered_map<int32_t, std::shared_ptr<CountDownLatch>>;
Mutex _mutex = MONGO_MAKE_LATCH("CountDownLatchHolder::_mutex");
Map _latches;
int32_t _counter;
};
namespace {
CountDownLatchHolder globalCountDownLatchHolder;
} // namespace
/**
* The argument for _new is a count value. We restrict it to be a 32 bit integer.
*
* The argument for _await/_countDown/_getCount is an id for CountDownLatch instance returned from
* _new call. It must be a 32 bit integer.
*/
auto uassertGet(JS::CallArgs args, unsigned int i) {
uassert(ErrorCodes::JSInterpreterFailure, "need exactly one argument", args.length() == 1);
auto int32Arg = args.get(i);
if (int32Arg.isDouble()) {
uassert(ErrorCodes::JSInterpreterFailure,
"argument must not be an NaN",
!int32Arg.isDouble() || !std::isnan(int32Arg.toDouble()));
auto val = int32Arg.toDouble();
uassert(ErrorCodes::JSInterpreterFailure,
"argument must be a 32 bit integer",
INT_MIN <= val && val <= INT_MAX);
return static_cast<int32_t>(val);
}
uassert(
ErrorCodes::JSInterpreterFailure, "argument must be a 32 bit integer", int32Arg.isInt32());
return int32Arg.toInt32();
}
void CountDownLatchInfo::Functions::_new::call(JSContext* cx, JS::CallArgs args) {
args.rval().setInt32(globalCountDownLatchHolder.make(uassertGet(args, 0)));
}
void CountDownLatchInfo::Functions::_await::call(JSContext* cx, JS::CallArgs args) {
globalCountDownLatchHolder.await(uassertGet(args, 0));
args.rval().setUndefined();
}
void CountDownLatchInfo::Functions::_countDown::call(JSContext* cx, JS::CallArgs args) {
globalCountDownLatchHolder.countDown(uassertGet(args, 0));
args.rval().setUndefined();
}
void CountDownLatchInfo::Functions::_getCount::call(JSContext* cx, JS::CallArgs args) {
args.rval().setInt32(globalCountDownLatchHolder.getCount(uassertGet(args, 0)));
}
/**
* We have to do this odd dance here because we need the methods from
* CountDownLatch to be installed in a plain object as enumerable properties.
* This is due to the way CountDownLatch is invoked, specifically after being
* transmitted across our js fork(). So we can't inherit and can't rely on the
* type. Practically, we also end up wrapping up all of these functions in pure
* js variants that call down, which makes them bson <-> js safe.
*/
void CountDownLatchInfo::postInstall(JSContext* cx,
JS::HandleObject global,
JS::HandleObject proto) {
auto objPtr = JS_NewPlainObject(cx);
uassert(ErrorCodes::JSInterpreterFailure, "Failed to JS_NewPlainObject", objPtr);
JS::RootedObject obj(cx, objPtr);
ObjectWrapper objWrapper(cx, obj);
ObjectWrapper protoWrapper(cx, proto);
JS::RootedValue val(cx);
for (auto iter = methods; iter->name; ++iter) {
invariant(!iter->name.isSymbol());
ObjectWrapper::Key key(iter->name.string());
protoWrapper.getValue(key, &val);
objWrapper.setValue(key, val);
}
val.setObjectOrNull(obj);
ObjectWrapper(cx, global).setValue("CountDownLatch", val);
}
} // namespace mozjs
} // namespace mongo
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