cache.js

// cache osm nodes and ways in leveldb

var osmium = require('osmium');
    levelup = require('levelup');

if (process.argv[2] === undefined) {
    return console.log('specify a file: `node osmium.js [file]');
}

var db = levelup('./' + (process.argv[3] || 'test.ldb'));
var nodes = levelup('./nodes.ldb');
var ways = [];

var reader = new osmium.Reader(process.argv[2], {
    'node': true,
    'way': true
});

function nextBuffer() {
    var buffer = reader.read();
    if (!buffer) return pushBatch(batch);

    while (object = buffer.next()) {
        console.log(object);
        var type = ('nodes_count' in object) ? 'w' : 'n';
        var details;
        var tags = object.tags();

        details.version = object.version;
        details.user = object.user;
        details.changeset = object.changeset;
        if (tags.length) details.tags = tags;

        if (type === 'n') {
            details.lat = object.lat;
            details.lon = object.lon;
            nodes.push({
                type: 'put',
                key: 'n' + object.id,
                value: JSON.stringify(details)
            });
        }

        if (type === 'w') {
            ways.push({
                type: 'put',
                key: type + object.id,
                value: JSON.stringify(details)
            });
        }
    }

    pushBatch(batch, nextBuffer);
}

function pushBatch(array, callback) {
    db.batch(array, function(err) {
        if (err) return console.log(err);
        batch = [];
        return callback ? callback() : false;
    });
}

nextBuffer();