fcoin/lib/db/lowlevelup.js

/*!
 * lowlevelup.js - low level levelup
 * Copyright (c) 2014-2015, Fedor Indutny (MIT License)
 * Copyright (c) 2014-2016, Christopher Jeffrey (MIT License).
 * https://github.com/bcoin-org/bcoin
 */

'use strict';

var utils = require('../utils/utils');
var assert = utils.assert;
var AsyncObject = require('../utils/async');
var spawn = require('../utils/spawn');
var co = spawn.co;
var wrap = spawn.wrap;
var VERSION_ERROR;

/**
 * Extremely low-level version of levelup.
 * The only levelup feature it provides is
 * error-wrapping. It gives a nice recallable
 * `open()` method and event. It assumes ascii
 * keys and binary values.
 *
 * This avoids pulling in extra deps and
 * lowers memory usage.
 *
 * @expose LowlevelUp
 * @constructor
 * @param {String} file - Location.
 * @param {Object} options - Leveldown options.
 */

function LowlevelUp(file, options) {
  if (!(this instanceof LowlevelUp))
    return new LowlevelUp(file, options);

  AsyncObject.call(this);

  this.options = options;
  this.backend = options.db;
  this.location = file;
  this.bufferKeys = options.bufferKeys === true;

  this.db = new options.db(file);

  // Stay as close to the metal as possible.
  // We want to make calls to C++ directly.
  while (this.db.db && this.db.db.put && this.db.db !== this.db)
    this.db = this.db.db;

  this.binding = this.db;

  if (this.db.binding)
    this.binding = this.db.binding;
}

utils.inherits(LowlevelUp, AsyncObject);

/**
 * Open the database (recallable).
 * @alias LowlevelUp#open
 * @param {Function} callback
 */

LowlevelUp.prototype._open = function open() {
  var self = this;
  return new Promise(function(resolve, reject) {
    self.binding.open(self.options, wrap(resolve, reject));
  });
};

/**
 * Close the database (recallable).
 * @alias LowlevelUp#close
 * @param {Function} callback
 */

LowlevelUp.prototype._close = function close() {
  var self = this;
  return new Promise(function(resolve, reject) {
    self.binding.close(wrap(resolve, reject));
  });
};

/**
 * Destroy the database.
 * @param {Function} callback
 */

LowlevelUp.prototype.destroy = function destroy() {
  var self = this;

  assert(!this.loading);
  assert(!this.closing);
  assert(!this.loaded);

  return new Promise(function(resolve, reject) {
    if (!self.backend.destroy)
      return reject(new Error('Cannot destroy.'));
    self.backend.destroy(self.location, wrap(resolve, reject));
  });
};

/**
 * Repair the database.
 * @param {Function} callback
 */

LowlevelUp.prototype.repair = function repair() {
  var self = this;

  assert(!this.loading);
  assert(!this.closing);
  assert(!this.loaded);

  return new Promise(function(resolve, reject) {
    if (!self.backend.repair)
      return reject(new Error('Cannot repair.'));
    self.backend.repair(self.location, wrap(resolve, reject));
  });
};

/**
 * Backup the database.
 * @param {String} path
 * @param {Function} callback
 */

LowlevelUp.prototype.backup = function backup(path) {
  var self = this;

  assert(!this.loading);
  assert(!this.closing);
  assert(this.loaded);

  if (!this.binding.backup)
    return this.clone(path);

  return new Promise(function(resolve, reject) {
    self.binding.backup(path, wrap(resolve, reject));
  });
};

/**
 * Retrieve a record from the database.
 * @param {String} key
 * @param {Object?} options
 * @param {Function} callback - Returns [Error, Buffer].
 */

LowlevelUp.prototype.get = function get(key, options) {
  var self = this;

  assert(this.loaded, 'Cannot use database before it is loaded.');

  return new Promise(function(resolve, reject) {
    self.binding.get(key, options || {}, function(err, result) {
      if (err) {
        if (isNotFound(err))
          return resolve();
        return reject(err);
      }
      return resolve(result);
    });
  });
};

/**
 * Store a record in the database.
 * @param {String} key
 * @param {Buffer} value
 * @param {Object?} options
 * @param {Function} callback
 */

LowlevelUp.prototype.put = function put(key, value, options) {
  var self = this;
  assert(this.loaded, 'Cannot use database before it is loaded.');
  return new Promise(function(resolve, reject) {
    self.binding.put(key, value, options || {}, wrap(resolve, reject));
  });
};

/**
 * Remove a record from the database.
 * @param {String} key
 * @param {Object?} options
 * @param {Function} callback
 */

LowlevelUp.prototype.del = function del(key, options) {
  var self = this;
  assert(this.loaded, 'Cannot use database before it is loaded.');
  return new Promise(function(resolve, reject) {
    self.binding.del(key, options || {}, wrap(resolve, reject));
  });
};

/**
 * Create an atomic batch.
 * @param {Array?} ops
 * @param {Object?} options
 * @param {Function} callback
 * @returns {Leveldown.Batch}
 */

LowlevelUp.prototype.batch = function batch(ops, options) {
  var self = this;

  assert(this.loaded, 'Cannot use database before it is loaded.');

  if (!ops)
    return new Batch(this);

  return new Promise(function(resolve, reject) {
    self.binding.batch(ops, options || {}, wrap(resolve, reject));
  });
};

/**
 * Create an iterator.
 * @param {Object} options
 * @returns {Leveldown.Iterator}
 */

LowlevelUp.prototype.iterator = function iterator(options) {
  assert(this.loaded, 'Cannot use database before it is loaded.');

  var opt = {
    gte: options.gte,
    lte: options.lte,
    keys: options.keys !== false,
    values: options.values || false,
    fillCache: options.fillCache || false,
    keyAsBuffer: this.bufferKeys,
    valueAsBuffer: true,
    reverse: options.reverse || false
  };

  // Workaround for a leveldown
  // bug I haven't fixed yet.
  if (options.limit != null)
    opt.limit = options.limit;

  if (options.keyAsBuffer != null)
    opt.keyAsBuffer = options.keyAsBuffer;

  assert(opt.keys || opt.values, 'Keys and/or values must be chosen.');

  return new Iterator(this, opt);
};

/**
 * Get a database property.
 * @param {String} name - Property name.
 * @returns {String}
 */

LowlevelUp.prototype.getProperty = function getProperty(name) {
  assert(this.loaded, 'Cannot use database before it is loaded.');

  if (!this.binding.getProperty)
    return '';

  return this.binding.getProperty(name);
};

/**
 * Calculate approximate database size.
 * @param {String} start - Start key.
 * @param {String} end - End key.
 * @param {Function} callback - Returns [Error, Number].
 */

LowlevelUp.prototype.approximateSize = function approximateSize(start, end) {
  var self = this;
  assert(this.loaded, 'Cannot use database before it is loaded.');

  return new Promise(function(resolve, reject) {
    if (!self.binding.approximateSize)
      return reject(new Error('Cannot get size.'));

    self.binding.approximateSize(start, end, wrap(resolve, reject));
  });
};

/**
 * Test whether a key exists.
 * @param {String} key
 * @param {Function} callback - Returns [Error, Boolean].
 */

LowlevelUp.prototype.has = co(function* has(key) {
  var value = yield this.get(key);
  return value != null;
});

/**
 * Collect all keys from iterator options.
 * @param {Object} options - Iterator options.
 * @param {Function} callback - Returns [Error, Array].
 */

LowlevelUp.prototype.iterate = co(function* iterate(options) {
  var items = [];
  var parse = options.parse;
  var iter, result, data;

  assert(typeof parse === 'function', 'Parse must be a function.');

  iter = this.iterator(options);

  for (;;) {
    result = yield iter.next();

    if (!result)
      return items;

    data = parse(result.key, result.value);

    if (data)
      items.push(data);
  }

  return items;
});

/**
 * Write and assert a version number for the database.
 * @param {Number} version
 * @param {Function} callback
 */

LowlevelUp.prototype.checkVersion = co(function* checkVersion(key, version) {
  var data = yield this.get(key);

  if (!data) {
    data = new Buffer(4);
    data.writeUInt32LE(version, 0, true);
    yield this.put(key, data);
    return;
  }

  data = data.readUInt32LE(0, true);

  if (data !== version)
    throw new Error(VERSION_ERROR);
});

/**
 * Clone the database.
 * @param {String} path
 * @param {Function} callback
 */

LowlevelUp.prototype.clone = co(function* clone(path) {
  var opt = { keys: true, values: true };
  var options = utils.merge({}, this.options);
  var hwm = 256 << 20;
  var total = 0;
  var tmp, batch, iter, items, key, value;

  assert(!this.loading);
  assert(!this.closing);
  assert(this.loaded);

  options.createIfMissing = true;
  options.errorIfExists = true;

  tmp = new LowlevelUp(path, options);

  yield tmp.open();

  batch = tmp.batch();
  iter = this.iterator(opt);

  for (;;) {
    items = yield iter.next();

    if (!items) {
      try {
        yield batch.write();
      } catch (e) {
        yield tmp.close();
        throw e;
      }
      return;
    }

    key = items[0];
    value = items[0];

    batch.put(key, value);
    total += value.length;

    if (total >= hwm) {
      total = 0;
      try {
        yield batch.write();
      } catch (e) {
        yield tmp.close();
        throw e;
      }
      batch = tmp.batch();
    }
  }
});

function Batch(db) {
  this.db = db;
  this.batch = db.binding.batch();
}

Batch.prototype.put = function(key, value) {
  this.batch.put(key, value);
  return this;
};

Batch.prototype.del = function del(key) {
  this.batch.del(key);
  return this;
};

Batch.prototype.write = function write() {
  var self = this;
  return new Promise(function(resolve, reject) {
    self.batch.write(wrap(resolve, reject));
  });
};

Batch.prototype.clear = function clear() {
  this.batch.clear();
  return this;
};

function Iterator(db, options) {
  this.db = db;
  this.iter = db.db.iterator(options);
}

Iterator.prototype.next = function() {
  var self = this;
  return new Promise(function(resolve, reject) {
    self.iter.next(function(err, key, value) {
      if (err) {
        self.iter.end(function() {
          reject(err);
        });
        return;
      }

      if (key === undefined && value === undefined) {
        self.iter.end(wrap(resolve, reject));
        return;
      }

      resolve(new KeyValue(key, value));
    });
  });
};

Iterator.prototype.seek = function seek(key) {
  this.iter.seek(key);
};

Iterator.prototype.end = function end() {
  var self = this;
  return new Promise(function(resolve, reject) {
    self.iter.end(wrap(resolve, reject));
  });
};

/*
 * Helpers
 */

function KeyValue(key, value) {
  this.key = key;
  this.value = value;
}

function isNotFound(err) {
  if (!err)
    return false;

  return err.notFound
    || err.type === 'NotFoundError'
    || /not\s*found/i.test(err.message);
}

VERSION_ERROR = 'Warning:'
  + ' Your database does not match the current database version.'
  + ' This is likely because the database layout or serialization'
  + ' format has changed drastically. If you want to dump your'
  + ' data, downgrade to your previous version first. If you do'
  + ' not think you should be seeing this error, post an issue on'
  + ' the repo.';

/*
 * Expose
 */

module.exports = LowlevelUp;