This repository has been archived by the owner on Dec 20, 2024. It is now read-only.
-
-
Notifications
You must be signed in to change notification settings - Fork 5
/
iterator.js
68 lines (56 loc) · 1.52 KB
/
iterator.js
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
const util = require('util')
const AbstractIterator = require('abstract-leveldown').AbstractIterator
function Iterator (db, options) {
AbstractIterator.call(this, db)
this.binding = db.binding.iterator(options)
this.cache = null
this.finished = false
this.fastFuture = require('fast-future')()
}
util.inherits(Iterator, AbstractIterator)
Iterator.prototype.seek = function (target) {
if (this._ended) {
throw new Error('cannot call seek() after end()')
}
if (this._nexting) {
throw new Error('cannot call seek() before next() has completed')
}
if (typeof target !== 'string' && !Buffer.isBuffer(target)) {
throw new Error('seek() requires a string or buffer key')
}
if (target.length === 0) {
throw new Error('cannot seek() to an empty key')
}
this.cache = null
this.binding.seek(target)
this.finished = false
}
Iterator.prototype._next = function (callback) {
var that = this
var key
var value
if (this.cache && this.cache.length) {
key = this.cache.pop()
value = this.cache.pop()
this.fastFuture(function () {
callback(null, key, value)
})
} else if (this.finished) {
this.fastFuture(function () {
callback()
})
} else {
this.binding.next(function (err, array, finished) {
if (err) return callback(err)
that.cache = array
that.finished = finished
that._next(callback)
})
}
return this
}
Iterator.prototype._end = function (callback) {
delete this.cache
this.binding.end(callback)
}
module.exports = Iterator