level-objectify

level-objectify

Compile the contents of a leveldb read stream into an object and create a patch for changes as a batch update.

Example

level = require('level-test')()
objectify = require('../')

db = level 'level-objectify-test', {valueEncoding: 'json'}

var c1 = {
  person: {
    gaius: {name: 'Gaius Baltar'},
    six: {name: 'Six'}
  }
}

// {depth: 1} = use the first layer of keys as a prefix to their children
var batch = objectify({depth: 1}).computeBatch({}, c1)
// returns a valid leveldb batch of operations.
// [
//   { key: 'personÿgaius', type: 'put', value: { name: 'Gaius Baltar' } },
//   { key: 'personÿsix', type: 'put', value: { name: 'Six' } }
// ]

db.batch(batch)

// with data already in the db, the contents can be objectified
db.readStream().pipe(objectify({depth: 1}).compile(function (err, result) {
  if (err) return console.log('problem', err)

  // `result` matches the object we started with!
  assert.deepEqual(c1, result)
  // see the tests for more examples.
}))

Usage

var obj = objectify(opts={})

options

• opts.depth = 0 the depth of key that should be used as a prefix for each property
• opts.separator = '\xff' the string to use to separate sections of the prefix.

Methods

obj.compile(callback(err, result))

Returns a writable stream that expects data in the format {key: ..., value: ...} (like the data emitted by level.readStream()). When the stream ends, callback is called with any error and the compiled result.

obj.computeBatch(prev, next)

Returns a batch operations array (compatible with leveldb) that will patch the database in the state prev to match the state of next.

Note: you will lose any information about the object's state that stops short of that opts.depth. The default depth is 0.

// in the database used with objectify({depth: 2}), this is one document.
// {key: 'aÿbÿc', value: {d: 'e'}}
var prev = { a: { b: { c: {d: 'e'} } } }
var next = { a: {} }

var batch = objectify({depth: 2}).computeBatch(prev, next)
// this will simply delete the one document. {a: {}} will be lost.
// [{type: 'del', key: 'aÿbÿc'}]

obj.computePatch(prev, next)

Exports computePatch() from patcher.

Contributing

Please make any changes to the .coffee source files and npm build before sending a pull request.

License

MIT