scripting/mozjs/bson.cpp

/**
 *    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/bson.h"

#include <boost/optional.hpp>
#include <set>

#include "mongo/scripting/mozjs/idwrapper.h"
#include "mongo/scripting/mozjs/implscope.h"
#include "mongo/scripting/mozjs/internedstring.h"
#include "mongo/scripting/mozjs/objectwrapper.h"
#include "mongo/scripting/mozjs/valuereader.h"
#include "mongo/scripting/mozjs/valuewriter.h"
#include "mongo/util/string_map.h"

namespace mongo {
namespace mozjs {

const char* const BSONInfo::className = "BSON";

const JSFunctionSpec BSONInfo::freeFunctions[3] = {
    MONGO_ATTACH_JS_FUNCTION(bsonWoCompare), MONGO_ATTACH_JS_FUNCTION(bsonBinaryEqual), JS_FS_END,
};

namespace {

/**
 * Holder for bson objects which tracks state for the js wrapper
 *
 * Basically, we have read only and read/write variants, and a need to manage
 * the appearance of mutable state on the read/write versions.
 */
struct BSONHolder {
    BSONHolder(const BSONObj& obj, const BSONObj* parent, const MozJSImplScope* scope, bool ro)
        : _obj(obj),
          _generation(scope->getGeneration()),
          _isOwned(obj.isOwned() || (parent && parent->isOwned())),
          _resolved(false),
          _readOnly(ro),
          _altered(false) {
        uassert(
            ErrorCodes::BadValue,
            "Attempt to bind an unowned BSON Object to a JS scope marked as requiring ownership",
            _isOwned || (!scope->requiresOwnedObjects()));
        if (parent) {
            _parent.emplace(*parent);
        }
    }

    const BSONObj& getOwner() const {
        return _parent ? *(_parent) : _obj;
    }

    void uassertValid(JSContext* cx) const {
        if (!_isOwned && getScope(cx)->getGeneration() != _generation)
            uasserted(ErrorCodes::BadValue,
                      "Attempt to access an invalidated BSON Object in JS scope");
    }

    BSONObj _obj;
    boost::optional<BSONObj> _parent;
    std::size_t _generation;
    bool _isOwned;
    bool _resolved;
    bool _readOnly;
    bool _altered;
    StringMap<bool> _removed;
};

BSONHolder* getValidHolder(JSContext* cx, JSObject* obj) {
    auto holder = static_cast<BSONHolder*>(JS_GetPrivate(obj));

    if (holder)
        holder->uassertValid(cx);

    return holder;
}

}  // namespace

void BSONInfo::make(
    JSContext* cx, JS::MutableHandleObject obj, BSONObj bson, const BSONObj* parent, bool ro) {
    auto scope = getScope(cx);

    scope->getProto<BSONInfo>().newObject(obj);
    JS_SetPrivate(obj, scope->trackedNew<BSONHolder>(bson, parent, scope, ro));
}

void BSONInfo::finalize(JSFreeOp* fop, JSObject* obj) {
    auto holder = static_cast<BSONHolder*>(JS_GetPrivate(obj));

    if (!holder)
        return;

    getScope(fop)->trackedDelete(holder);
}

void BSONInfo::enumerate(JSContext* cx,
                         JS::HandleObject obj,
                         JS::AutoIdVector& properties,
                         bool enumerableOnly) {
    auto holder = getValidHolder(cx, obj);

    if (!holder)
        return;

    BSONObjIterator i(holder->_obj);

    ObjectWrapper o(cx, obj);
    JS::RootedValue val(cx);
    JS::RootedId id(cx);

    while (i.more()) {
        BSONElement e = i.next();

        // TODO: when we get heterogenous set lookup, switch to StringData
        // rather than involving the temporary string
        if (holder->_removed.find(e.fieldName()) != holder->_removed.end())
            continue;

        ValueReader(cx, &val).fromStringData(e.fieldNameStringData());

        if (!JS_ValueToId(cx, val, &id))
            uasserted(ErrorCodes::JSInterpreterFailure, "Failed to invoke JS_ValueToId");

        properties.append(id);
    }
}

void BSONInfo::setProperty(JSContext* cx,
                           JS::HandleObject obj,
                           JS::HandleId id,
                           JS::MutableHandleValue vp,
                           JS::ObjectOpResult& result) {
    auto holder = getValidHolder(cx, obj);

    if (holder) {
        if (holder->_readOnly) {
            uasserted(ErrorCodes::BadValue, "Read only object");
            return;
        }

        auto iter = holder->_removed.find(IdWrapper(cx, id).toString());

        if (iter != holder->_removed.end()) {
            holder->_removed.erase(iter);
        }

        holder->_altered = true;
    }

    ObjectWrapper(cx, obj).defineProperty(id, vp, JSPROP_ENUMERATE);
    result.succeed();
}

void BSONInfo::delProperty(JSContext* cx,
                           JS::HandleObject obj,
                           JS::HandleId id,
                           JS::ObjectOpResult& result) {
    auto holder = getValidHolder(cx, obj);

    if (holder) {
        if (holder->_readOnly) {
            uasserted(ErrorCodes::BadValue, "Read only object");
            return;
        }

        holder->_altered = true;

        JSStringWrapper jsstr;
        holder->_removed[IdWrapper(cx, id).toStringData(&jsstr)] = true;
    }

    result.succeed();
}

void BSONInfo::resolve(JSContext* cx, JS::HandleObject obj, JS::HandleId id, bool* resolvedp) {
    auto holder = getValidHolder(cx, obj);

    *resolvedp = false;

    if (!holder) {
        return;
    }

    IdWrapper idw(cx, id);
    JSStringWrapper jsstr;

    auto sname = idw.toStringData(&jsstr);

    if (!holder->_readOnly && holder->_removed.find(sname.toString()) != holder->_removed.end()) {
        return;
    }

    ObjectWrapper o(cx, obj);

    if (holder->_obj.hasField(sname)) {
        auto elem = holder->_obj[sname];

        JS::RootedValue vp(cx);

        ValueReader(cx, &vp).fromBSONElement(elem, holder->getOwner(), holder->_readOnly);

        o.defineProperty(id, vp, JSPROP_ENUMERATE);

        if (!holder->_readOnly && (elem.type() == mongo::Object || elem.type() == mongo::Array)) {
            // if accessing a subobject, we have no way to know if
            // modifications are being made on writable objects

            holder->_altered = true;
        }

        *resolvedp = true;
    }
}

std::tuple<BSONObj*, bool> BSONInfo::originalBSON(JSContext* cx, JS::HandleObject obj) {
    std::tuple<BSONObj*, bool> out(nullptr, false);

    if (auto holder = getValidHolder(cx, obj))
        out = std::make_tuple(&holder->_obj, holder->_altered);

    return out;
}

void BSONInfo::Functions::bsonWoCompare::call(JSContext* cx, JS::CallArgs args) {
    if (args.length() != 2)
        uasserted(ErrorCodes::BadValue, "bsonWoCompare needs 2 arguments");

    if (!args.get(0).isObject())
        uasserted(ErrorCodes::BadValue, "first argument to bsonWoCompare must be an object");

    if (!args.get(1).isObject())
        uasserted(ErrorCodes::BadValue, "second argument to bsonWoCompare must be an object");

    BSONObj firstObject = ValueWriter(cx, args.get(0)).toBSON();
    BSONObj secondObject = ValueWriter(cx, args.get(1)).toBSON();

    args.rval().setInt32(firstObject.woCompare(secondObject));
}

void BSONInfo::Functions::bsonBinaryEqual::call(JSContext* cx, JS::CallArgs args) {
    if (args.length() != 2)
        uasserted(ErrorCodes::BadValue, "bsonBinaryEqual needs 2 arguments");

    if (!args.get(0).isObject())
        uasserted(ErrorCodes::BadValue, "first argument to bsonBinaryEqual must be an object");

    if (!args.get(1).isObject())
        uasserted(ErrorCodes::BadValue, "second argument to bsonBinaryEqual must be an object");

    BSONObj firstObject = ValueWriter(cx, args.get(0)).toBSON();
    BSONObj secondObject = ValueWriter(cx, args.get(1)).toBSON();

    args.rval().setBoolean(firstObject.binaryEqual(secondObject));
}

void BSONInfo::postInstall(JSContext* cx, JS::HandleObject global, JS::HandleObject proto) {
    JS::RootedValue value(cx);
    value.setBoolean(true);

    ObjectWrapper(cx, proto).defineProperty(InternedString::_bson, value, 0);
}

}  // namespace mozjs
}  // namespace mongo