embedded_builder.h

// embedded_builder.h

/*    Copyright 2009 10gen Inc.
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */

#pragma once

namespace mongo {

// utility class for assembling hierarchical objects
class EmbeddedBuilder {
public:
    EmbeddedBuilder(BSONObjBuilder* b) {
        _builders.push_back(std::make_pair("", b));
    }
    // It is assumed that the calls to prepareContext will be made with the 'name'
    // parameter in lex ascending order.
    void prepareContext(std::string& name) {
        int i = 1, n = _builders.size();
        while (
            i < n && name.substr(0, _builders[i].first.length()) == _builders[i].first &&
            (name[_builders[i].first.length()] == '.' || name[_builders[i].first.length()] == 0)) {
            name = name.substr(_builders[i].first.length() + 1);
            ++i;
        }
        for (int j = n - 1; j >= i; --j) {
            popBuilder();
        }
        for (std::string next = splitDot(name); !next.empty(); next = splitDot(name)) {
            addBuilder(next);
        }
    }
    void appendAs(const BSONElement& e, std::string name) {
        if (e.type() == Object &&
            e.valuesize() == 5) {  // empty object -- this way we can add to it later
            std::string dummyName = name + ".foo";
            prepareContext(dummyName);
            return;
        }
        prepareContext(name);
        back()->appendAs(e, name);
    }
    BufBuilder& subarrayStartAs(std::string name) {
        prepareContext(name);
        return back()->subarrayStart(name);
    }
    void done() {
        while (!_builderStorage.empty())
            popBuilder();
    }

    static std::string splitDot(std::string& str) {
        size_t pos = str.find('.');
        if (pos == std::string::npos)
            return "";
        std::string ret = str.substr(0, pos);
        str = str.substr(pos + 1);
        return ret;
    }

private:
    void addBuilder(const std::string& name) {
        boost::shared_ptr<BSONObjBuilder> newBuilder(new BSONObjBuilder(back()->subobjStart(name)));
        _builders.push_back(std::make_pair(name, newBuilder.get()));
        _builderStorage.push_back(newBuilder);
    }
    void popBuilder() {
        back()->done();
        _builders.pop_back();
        _builderStorage.pop_back();
    }

    BSONObjBuilder* back() {
        return _builders.back().second;
    }

    std::vector<std::pair<std::string, BSONObjBuilder*> > _builders;
    std::vector<boost::shared_ptr<BSONObjBuilder> > _builderStorage;
};

}  // namespace mongo