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moving KBucket library to floSupernode tag

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sairajzero 2019-12-19 20:27:21 +05:30
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commit 8f3ef66d15
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standard_Operations.html
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@ -6274,6 +6274,406 @@
} }
} }
/**Kademlia DHT K-bucket implementation as a binary tree.
* Implementation of a Kademlia DHT k-bucket used for storing
* contact (peer node) information.
*
* @extends EventEmitter
*/
function BuildKBucket(options = {}) {
/**
* `options`:
* `distance`: Function
* `function (firstId, secondId) { return distance }` An optional
* `distance` function that gets two `id` Uint8Arrays
* and return distance (as number) between them.
* `arbiter`: Function (Default: vectorClock arbiter)
* `function (incumbent, candidate) { return contact; }` An optional
* `arbiter` function that givent two `contact` objects with the same `id`
* returns the desired object to be used for updating the k-bucket. For
* more details, see [arbiter function](#arbiter-function).
* `localNodeId`: Uint8Array An optional Uint8Array representing the local node id.
* If not provided, a local node id will be created via `randomBytes(20)`.
* `metadata`: Object (Default: {}) Optional satellite data to include
* with the k-bucket. `metadata` property is guaranteed not be altered by,
* it is provided as an explicit container for users of k-bucket to store
* implementation-specific data.
* `numberOfNodesPerKBucket`: Integer (Default: 20) The number of nodes
* that a k-bucket can contain before being full or split.
* `numberOfNodesToPing`: Integer (Default: 3) The number of nodes to
* ping when a bucket that should not be split becomes full. KBucket will
* emit a `ping` event that contains `numberOfNodesToPing` nodes that have
* not been contacted the longest.
*
* @param {Object=} options optional
*/
this.localNodeId = options.localNodeId || window.crypto.getRandomValues(new Uint8Array(20))
this.numberOfNodesPerKBucket = options.numberOfNodesPerKBucket || 20
this.numberOfNodesToPing = options.numberOfNodesToPing || 3
this.distance = options.distance || this.distance
// use an arbiter from options or vectorClock arbiter by default
this.arbiter = options.arbiter || this.arbiter
this.metadata = Object.assign({}, options.metadata)
this.createNode = function () {
return {
contacts: [],
dontSplit: false,
left: null,
right: null
}
}
this.ensureInt8 = function (name, val) {
if (!(val instanceof Uint8Array)) {
throw new TypeError(name + ' is not a Uint8Array')
}
}
/**
* @param {Uint8Array} array1
* @param {Uint8Array} array2
* @return {Boolean}
*/
this.arrayEquals = function (array1, array2) {
if (array1 === array2) {
return true
}
if (array1.length !== array2.length) {
return false
}
for (let i = 0, length = array1.length; i < length; ++i) {
if (array1[i] !== array2[i]) {
return false
}
}
return true
}
this.ensureInt8('option.localNodeId as parameter 1', this.localNodeId)
this.root = this.createNode()
/**
* Default arbiter function for contacts with the same id. Uses
* contact.vectorClock to select which contact to update the k-bucket with.
* Contact with larger vectorClock field will be selected. If vectorClock is
* the same, candidat will be selected.
*
* @param {Object} incumbent Contact currently stored in the k-bucket.
* @param {Object} candidate Contact being added to the k-bucket.
* @return {Object} Contact to updated the k-bucket with.
*/
this.arbiter = function (incumbent, candidate) {
return incumbent.vectorClock > candidate.vectorClock ? incumbent : candidate
}
/**
* Default distance function. Finds the XOR
* distance between firstId and secondId.
*
* @param {Uint8Array} firstId Uint8Array containing first id.
* @param {Uint8Array} secondId Uint8Array containing second id.
* @return {Number} Integer The XOR distance between firstId
* and secondId.
*/
this.distance = function (firstId, secondId) {
let distance = 0
let i = 0
const min = Math.min(firstId.length, secondId.length)
const max = Math.max(firstId.length, secondId.length)
for (; i < min; ++i) {
distance = distance * 256 + (firstId[i] ^ secondId[i])
}
for (; i < max; ++i) distance = distance * 256 + 255
return distance
}
/**
* Adds a contact to the k-bucket.
*
* @param {Object} contact the contact object to add
*/
this.add = function (contact) {
this.ensureInt8('contact.id', (contact || {}).id)
let bitIndex = 0
let node = this.root
while (node.contacts === null) {
// this is not a leaf node but an inner node with 'low' and 'high'
// branches; we will check the appropriate bit of the identifier and
// delegate to the appropriate node for further processing
node = this._determineNode(node, contact.id, bitIndex++)
}
// check if the contact already exists
const index = this._indexOf(node, contact.id)
if (index >= 0) {
this._update(node, index, contact)
return this
}
if (node.contacts.length < this.numberOfNodesPerKBucket) {
node.contacts.push(contact)
return this
}
// the bucket is full
if (node.dontSplit) {
// we are not allowed to split the bucket
// we need to ping the first this.numberOfNodesToPing
// in order to determine if they are alive
// only if one of the pinged nodes does not respond, can the new contact
// be added (this prevents DoS flodding with new invalid contacts)
return this
}
this._split(node, bitIndex)
return this.add(contact)
}
/**
* Get the n closest contacts to the provided node id. "Closest" here means:
* closest according to the XOR metric of the contact node id.
*
* @param {Uint8Array} id Contact node id
* @param {Number=} n Integer (Default: Infinity) The maximum number of
* closest contacts to return
* @return {Array} Array Maximum of n closest contacts to the node id
*/
this.closest = function (id, n = Infinity) {
this.ensureInt8('id', id)
if ((!Number.isInteger(n) && n !== Infinity) || n <= 0) {
throw new TypeError('n is not positive number')
}
let contacts = []
for (let nodes = [this.root], bitIndex = 0; nodes.length > 0 && contacts.length < n;) {
const node = nodes.pop()
if (node.contacts === null) {
const detNode = this._determineNode(node, id, bitIndex++)
nodes.push(node.left === detNode ? node.right : node.left)
nodes.push(detNode)
} else {
contacts = contacts.concat(node.contacts)
}
}
return contacts
.map(a => [this.distance(a.id, id), a])
.sort((a, b) => a[0] - b[0])
.slice(0, n)
.map(a => a[1])
}
/**
* Counts the total number of contacts in the tree.
*
* @return {Number} The number of contacts held in the tree
*/
this.count = function () {
// return this.toArray().length
let count = 0
for (const nodes = [this.root]; nodes.length > 0;) {
const node = nodes.pop()
if (node.contacts === null) nodes.push(node.right, node.left)
else count += node.contacts.length
}
return count
}
/**
* Determines whether the id at the bitIndex is 0 or 1.
* Return left leaf if `id` at `bitIndex` is 0, right leaf otherwise
*
* @param {Object} node internal object that has 2 leafs: left and right
* @param {Uint8Array} id Id to compare localNodeId with.
* @param {Number} bitIndex Integer (Default: 0) The bit index to which bit
* to check in the id Uint8Array.
* @return {Object} left leaf if id at bitIndex is 0, right leaf otherwise.
*/
this._determineNode = function (node, id, bitIndex) {
// *NOTE* remember that id is a Uint8Array and has granularity of
// bytes (8 bits), whereas the bitIndex is the bit index (not byte)
// id's that are too short are put in low bucket (1 byte = 8 bits)
// (bitIndex >> 3) finds how many bytes the bitIndex describes
// bitIndex % 8 checks if we have extra bits beyond byte multiples
// if number of bytes is <= no. of bytes described by bitIndex and there
// are extra bits to consider, this means id has less bits than what
// bitIndex describes, id therefore is too short, and will be put in low
// bucket
const bytesDescribedByBitIndex = bitIndex >> 3
const bitIndexWithinByte = bitIndex % 8
if ((id.length <= bytesDescribedByBitIndex) && (bitIndexWithinByte !== 0)) {
return node.left
}
const byteUnderConsideration = id[bytesDescribedByBitIndex]
// byteUnderConsideration is an integer from 0 to 255 represented by 8 bits
// where 255 is 11111111 and 0 is 00000000
// in order to find out whether the bit at bitIndexWithinByte is set
// we construct (1 << (7 - bitIndexWithinByte)) which will consist
// of all bits being 0, with only one bit set to 1
// for example, if bitIndexWithinByte is 3, we will construct 00010000 by
// (1 << (7 - 3)) -> (1 << 4) -> 16
if (byteUnderConsideration & (1 << (7 - bitIndexWithinByte))) {
return node.right
}
return node.left
}
/**
* Get a contact by its exact ID.
* If this is a leaf, loop through the bucket contents and return the correct
* contact if we have it or null if not. If this is an inner node, determine
* which branch of the tree to traverse and repeat.
*
* @param {Uint8Array} id The ID of the contact to fetch.
* @return {Object|Null} The contact if available, otherwise null
*/
this.get = function (id) {
this.ensureInt8('id', id)
let bitIndex = 0
let node = this.root
while (node.contacts === null) {
node = this._determineNode(node, id, bitIndex++)
}
// index of uses contact id for matching
const index = this._indexOf(node, id)
return index >= 0 ? node.contacts[index] : null
}
/**
* Returns the index of the contact with provided
* id if it exists, returns -1 otherwise.
*
* @param {Object} node internal object that has 2 leafs: left and right
* @param {Uint8Array} id Contact node id.
* @return {Number} Integer Index of contact with provided id if it
* exists, -1 otherwise.
*/
this._indexOf = function (node, id) {
for (let i = 0; i < node.contacts.length; ++i) {
if (this.arrayEquals(node.contacts[i].id, id)) return i
}
return -1
}
/**
* Removes contact with the provided id.
*
* @param {Uint8Array} id The ID of the contact to remove.
* @return {Object} The k-bucket itself.
*/
this.remove = function (id) {
this.ensureInt8('the id as parameter 1', id)
let bitIndex = 0
let node = this.root
while (node.contacts === null) {
node = this._determineNode(node, id, bitIndex++)
}
const index = this._indexOf(node, id)
if (index >= 0) {
const contact = node.contacts.splice(index, 1)[0]
}
return this
}
/**
* Splits the node, redistributes contacts to the new nodes, and marks the
* node that was split as an inner node of the binary tree of nodes by
* setting this.root.contacts = null
*
* @param {Object} node node for splitting
* @param {Number} bitIndex the bitIndex to which byte to check in the
* Uint8Array for navigating the binary tree
*/
this._split = function (node, bitIndex) {
node.left = this.createNode()
node.right = this.createNode()
// redistribute existing contacts amongst the two newly created nodes
for (const contact of node.contacts) {
this._determineNode(node, contact.id, bitIndex).contacts.push(contact)
}
node.contacts = null // mark as inner tree node
// don't split the "far away" node
// we check where the local node would end up and mark the other one as
// "dontSplit" (i.e. "far away")
const detNode = this._determineNode(node, this.localNodeId, bitIndex)
const otherNode = node.left === detNode ? node.right : node.left
otherNode.dontSplit = true
}
/**
* Returns all the contacts contained in the tree as an array.
* If this is a leaf, return a copy of the bucket. `slice` is used so that we
* don't accidentally leak an internal reference out that might be
* accidentally misused. If this is not a leaf, return the union of the low
* and high branches (themselves also as arrays).
*
* @return {Array} All of the contacts in the tree, as an array
*/
this.toArray = function () {
let result = []
for (const nodes = [this.root]; nodes.length > 0;) {
const node = nodes.pop()
if (node.contacts === null) nodes.push(node.right, node.left)
else result = result.concat(node.contacts)
}
return result
}
/**
* Updates the contact selected by the arbiter.
* If the selection is our old contact and the candidate is some new contact
* then the new contact is abandoned (not added).
* If the selection is our old contact and the candidate is our old contact
* then we are refreshing the contact and it is marked as most recently
* contacted (by being moved to the right/end of the bucket array).
* If the selection is our new contact, the old contact is removed and the new
* contact is marked as most recently contacted.
*
* @param {Object} node internal object that has 2 leafs: left and right
* @param {Number} index the index in the bucket where contact exists
* (index has already been computed in a previous
* calculation)
* @param {Object} contact The contact object to update.
*/
this._update = function (node, index, contact) {
// sanity check
if (!this.arrayEquals(node.contacts[index].id, contact.id)) {
throw new Error('wrong index for _update')
}
const incumbent = node.contacts[index]
const selection = this.arbiter(incumbent, contact)
// if the selection is our old contact and the candidate is some new
// contact, then there is nothing to do
if (selection === incumbent && incumbent !== contact) return
node.contacts.splice(index, 1) // remove old contact
node.contacts.push(selection) // add more recent contact version
}
}
</script> </script>
<script id="compactIDB"> <script id="compactIDB">
/* Compact IndexedDB operations */ /* Compact IndexedDB operations */