leveldb/lib/leveldb/batch.js

Bindings for using LevelDB through node.

// Generated by CoffeeScript 1.3.3
var Batch, binding, noop;

binding = require('../../build/Release/leveldb.node');

noop = function() {};

/*

    A batch holds a sequence of put/delete operations to atomically write to
    the database.

    Usage:

        var leveldb = require('leveldb');

        var db, db2, batch, batch2 = new leveldb.Batch, writes = 2;

        leveldb.open('/tmp/test.db', onOpen);

        function onOpen(err, handle) {
          db = handle;
          batch = db.batch();
          batch
            .put('foo', 'bar')
            .del('baz')
            .put('pass', 'xyzzy')
            .write(afterWrite);
        }

        function afterWrite(err) {
          leveldb.open('/tmp/test2.db', onOpen2);
        }

        function onOpen2(err, handle) {
          db2 = handle;
          batch2
            .put('foo', 'coconut')
            .del('pass');

          db.write(batch2, afterWrite2);
          db2.write(batch2, afterWrite2);
        }

        function afterWrite2(err) {
          writes -= 1;
          if (writes <= 0) {
            // batch2 has not been cleared to allow for reuse.
            batch2.clear();

            // works because the batch is cleared after committing when using
            // batch.commit()
            batch
              .put('hello', 'world')
              .put('goodbye', 'world');

            db.write(batch);
            db2.write(batch);
          }
        }
*/


exports.Batch = Batch = (function() {
  /*
  
        Constructor.
  
        @param {leveldb.Handle} [handle] Pass a database handle to use with
          `batch.write()` or `batch.writeSync()`.
  */

  function Batch(handle) {
    this.handle = handle;
    this.self = new binding.Batch;
    this.readLock_ = 0;
  }

  /*
  
        Add a put operation to the batch.
  
        @param {String|Buffer} key The key to put.
        @param {String|Buffer} val The value to put.
  */


  Batch.prototype.put = function(key, val) {
    if (this.readLock_ > 0) {
      throw 'Read locked';
    }
    if (!Buffer.isBuffer(key)) {
      key = new Buffer(key);
    }
    if (!Buffer.isBuffer(val)) {
      val = new Buffer(val);
    }
    this.self.put(key, val);
    return this;
  };

  /*
  
        Add a delete operation to the batch.
  
        @param {String|Buffer} key The key to delete.
  */


  Batch.prototype.del = function(key) {
    if (this.readLock_ > 0) {
      throw 'Read locked';
    }
    if (!Buffer.isBuffer(key)) {
      key = new Buffer(key);
    }
    this.self.del(key);
    return this;
  };

  /*
  
        Commit the batch operations to disk.
        See `Handle.write()`.
  */


  Batch.prototype.write = function(options, callback) {
    var _this = this;
    if (!this.handle) {
      throw new Error('No handle');
    }
    ++this.readLock_;
    if (typeof options === 'function') {
      callback = options;
      options = null;
    }
    callback || (callback = noop);
    return this.handle.write(this.self, options, function(err) {
      --_this.readLock_;
      if (!err) {
        _this.self.clear();
      }
      return callback(err);
    });
  };

  /*
  
        Reset this batch instance by removing all pending operations.
  */


  Batch.prototype.clear = function() {
    if (this.readLock_ > 0) {
      throw 'Read locked';
    }
    this.self.clear();
    return this;
  };

  return Batch;

})();