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index.js
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index.js
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const bounds = require('binary-search-bounds')
const Long = require('long')
class MultiValue {
constructor (...values) {
this.values = values
}
}
// Extract the common key prefix from an array of values
function commonPrefix (arr, options) {
if (arr.length === 0) {
return options.emptyPrefix
} else if (arr.length === 1) {
return options.getKey(arr[0])
}
const first = options.getKey(arr[0])
const last = options.getKey(arr[arr.length - 1])
const n = options.match(first, last)
return options.prefix(first, n)
}
function assign (newVal, oldVal, options) {
if (options.uniqueKeys || oldVal === undefined) {
return newVal
} else if (oldVal instanceof MultiValue) {
oldVal.values.push(newVal)
return oldVal
}
let mv = new MultiValue(oldVal, newVal)
mv = options.setKey(mv, options.getKey(newVal))
return mv
}
function coerceArray (arr) {
const n = arr.length
return (n === 0) ? undefined : ((n === 1) ? arr[0] : arr)
}
const find = (node, key, options, cb) => {
let prev = null
while (true) {
const n = options.match(key, node.skip)
// If no prefix match, then return
if (n !== node.skip.length) {
return cb(node, prev, false)
}
// If this is a terminal node, stop
if (!node.edges) {
return cb(node, prev, true)
}
// If the internal value matches this key, stop
if (n === key.length) {
return cb(node, prev, true)
}
// Traverse the jump table
const x = key.charAt(node.skip.length)
const child = node.edges[x]
if (!child) {
return cb(node, prev, false)
}
prev = node
node = child
}
}
class Node {
// Values must be sorted by key
constructor (values, options) {
this.skip = commonPrefix(values, options)
this.edges = undefined
this.values = values
this.dirty = false
this._explode(options)
}
// Add a value
add (key, value, options) {
// If this is a terminal node, simply add the value
if (!this.edges) {
this._insert(key, value, options)
this._explode(options)
return
}
// Check if we have a prefix match
const n = options.match(key, this.skip)
if (n === this.skip.length) {
if (n === key.length) {
// Value belongs on this node
this.values = assign(value, this.values, options)
return
}
// Traverse the jump table
const x = key.charAt(this.skip.length)
const node = this.edges[x]
if (node) {
node.add(key, value, options)
} else {
this.edges[x] = new Node([value], options)
}
return
}
// It is necessary to split this node apart, start by splitting skip
const prefix = options.prefix(this.skip, n)
const cx = this.skip.charAt(prefix.length)
// Create the new child node, which will inherit everything on this node
const child = new Node([], options)
child.skip = this.skip
child.edges = this.edges
child.values = this.values
this.skip = prefix
this.edges = []
this.edges[cx] = child
this.values = undefined
// Now we can call add on this node again
this.add(key, value, options)
}
// Insert value into a terminal node's bin of values
_insert (key, value, options) {
// Update skip value
const n = options.match(key, this.skip)
if (n !== this.skip.length) {
this.skip = options.prefix(this.skip, n)
}
// Update dirty flag
const count = this.values.length
if (count && options.comparator(this.values[count - 1], value) >= 0) {
this.dirty = true
}
this.values.push(value)
}
// Search for a value by it's key
get (key, options) {
return find(this, key, options, (node, parent, matched) => {
if (!matched) {
return undefined
} else if (node.edges) {
return node.values // Match was on internal value
} else {
return node._search(key, options) // Binary search the values list
}
})
}
// Binary search a terminal node's values list for a key
_search (key, options) {
this._sortValues(options)
const needle = options.setKey({}, key) // Create a dummy value for searching
const idx = bounds.eq(this.values, needle, options.comparator)
return (idx < 0) ? undefined : this.values[idx]
}
_sortValues (options) {
if (this.dirty) {
const arr = this.values
arr.sort(options.comparator)
this.dirty = false
// Collapse multiple values with same key into a single value
const n = arr.length
if (n > 1) {
let i = 0
for (let j = 1; j < n; j++) {
if (options.comparator(arr[i], arr[j]) === 0) {
arr[i] = assign(arr[j], arr[i], options)
} else {
i++
arr[i] = arr[j]
}
}
arr.splice(i + 1)
}
}
}
// Remove a value from the trie by key
delete (key, options, filter) {
// If no prefix match, then return
const n = options.match(key, this.skip)
if (n !== this.skip.length) {
return undefined
}
// If this is a terminal node, binary search for the key
if (!this.edges) {
this._sortValues(options)
const needle = options.setKey({}, key) // Create a dummy value for searching
const idx = bounds.eq(this.values, needle, options.comparator)
if (idx >= 0) {
const [ keep, removed ] = this._delete(this.values[idx], filter)
if (keep === undefined) {
this.values.splice(idx, 1)
}
return removed
}
return undefined
}
// Check if the internal value matches this key
if (n === key.length) {
const [ keep, removed ] = this._delete(this.values, filter)
this.values = keep
return removed
}
// Traverse the jump table
const x = key.charAt(this.skip.length)
const child = this.edges[x]
if (child) {
// Call delete recursively
const ret = child.delete(key, options, filter)
if (ret !== undefined) {
this._compact(x, child) // Compact if we actually removed something
}
return ret
}
return undefined
}
_delete (val, filter) {
// Handle multi-value case first
if (val instanceof MultiValue) {
let keep = []
let removed = []
val.values.forEach(x => {
if (filter === undefined || filter(x)) {
removed.push(x)
} else {
keep.push(x)
}
})
val.values = keep
keep = (keep.length > 1) ? val : coerceArray(keep)
removed = coerceArray(removed)
return [keep, removed]
}
// Handle simple value case
if (filter === undefined || filter(val)) {
return [undefined, val]
} else {
return [val, undefined]
}
}
_compact (path, child) {
// Check if child is an empty terminal node
if (!child.edges && !child.values.length) {
delete this.edges[path]
// Count how many edges we have left
let edgeCount = 0
for (const node of this.edges) {
child = node
edgeCount++
}
// Try to compact this node
if (edgeCount === 0) {
// No edges left, convert back to terminal node
this.edges = undefined
this.values = this.values ? [this.values] : []
this.dirty = false
} else if (edgeCount === 1 && this.values === undefined) {
// Single edge and no internal value, redundant node
this.skip = child.skip
this.edges = child.edges
this.values = child.values
this.dirty = child.dirty
}
}
}
// Convert from a terminal node to node with branches
_explode (options) {
// Check if we're big enough
if (this.values.length <= options.binSize) {
return
}
// Make sure values are sorted, and combine duplicate keys
this._sortValues(options)
// Are we still big enough?
if (this.values.length <= options.binSize) {
return
}
// Update internal state
const values = this.values
this.skip = commonPrefix(values, options)
this.edges = []
this.values = undefined
const prefixLen = this.skip.length
// For each value, get it's corresponding character in the jump table
const nextChars = values.map(v => {
const k = options.getKey(v)
return k.length === prefixLen ? undefined : k.charAt(prefixLen)
})
const count = nextChars.length
// Set internal value (exact key match), if one exists
let i = 0
if (nextChars[0] === undefined) {
this.values = values[0]
i++
}
// Populate edges
while (i < count) {
const x = nextChars[i]
let j = i + 1
while (j < count) {
if (x !== nextChars[j]) {
break
}
j++
}
// Populate edge
this.edges[x] = new Node(values.slice(i, j), options)
i = j
}
}
}
const DEFAULT_OPTS = {
uniqueKeys: true,
binSize: 256
}
function cmp (a, b) {
if (a === b) {
return 8
}
let n = 0
if ((a & 0xFFFF0000) === (b & 0xFFFF0000)) {
n += 4
} else {
a = a >> 16
b = b >> 16
}
if ((a & 0xFF00) === (b & 0xFF00)) {
n += 2
} else {
a = a >> 8
b = b >> 8
}
if ((a & 0xF0) === (b & 0xF0)) {
n++
}
return n
}
class NumericKey {
constructor (num, length = 16) {
this.value = Long.fromNumber(num)
this.length = length
}
charAt (pos) {
let y = 64 - (pos + 1) * 4
return this.value.shr_u(y).low & 0xF
}
match (other) {
const a = this.value
const b = other.value
if (this.length === other.length && a.high === b.high && a.low === b.low) {
return this.length
}
let n = Math.min(this.length, other.length)
if (n > 0) {
if (a.high === b.high) {
n = Math.min(n, cmp(a.low, b.low) + 8)
} else {
n = Math.min(n, cmp(a.high, b.high))
}
}
return n
}
prefix (n) {
let y = 64 - (n * 4)
let num = this.value.shr_u(y).shl(y).toNumber()
return new NumericKey(num, n)
}
toNumber () {
return this.value.toNumber()
}
}
const KEY_TYPES = {
string: {
createKey: (opts) => {
return x => x
},
getKey: (opts) => {
if (opts.attr) {
return x => x[opts.attr]
} else {
return x => (x instanceof MultiValue) ? x.key : x
}
},
setKey: (opts) => {
if (opts.attr) {
return (value, key) => { value[opts.attr] = key; return value }
} else {
return (value, key) => {
if (value instanceof MultiValue) {
value.key = key
return value
} else {
return key
}
}
}
},
comparator: (opts) => {
if (opts.attr) {
return (a, b) => {
a = a[opts.attr]
b = b[opts.attr]
return a < b ? -1 : (a > b ? 1 : 0)
}
} else {
return (a, b) => {
a = (a instanceof MultiValue) ? a.key : a
b = (b instanceof MultiValue) ? b.key : b
return (a, b) => a < b ? -1 : (a > b ? 1 : 0)
}
}
},
match: (opts) => {
return (a, b) => {
let i = 0
const n = Math.min(a.length, b.length)
while (i < n && a[i] === b[i]) {
i++
}
return i
}
},
prefix: (opts) => {
return (key, n) => key.substr(0, n)
},
emptyPrefix: ''
},
number: {
createKey: (opts) => {
return x => new NumericKey(x)
},
getKey: (opts) => {
if (opts.attr) {
return x => new NumericKey(x[opts.attr])
} else {
return x => new NumericKey((x instanceof MultiValue) ? x.key : x)
}
},
setKey: (opts) => {
if (opts.attr) {
return (value, key) => { value[opts.attr] = key.toNumber(); return value }
} else {
return (value, key) => {
key = key.value()
if (value instanceof MultiValue) {
value.key = key
return value
} else {
return key
}
}
}
},
comparator: (opts) => {
if (opts.attr) {
return (a, b) => a[opts.attr] - b[opts.attr]
} else {
return (a, b) => a - b
}
},
match: (opts) => {
return (a, b) => a.match(b)
},
prefix: (opts) => {
return (key, n) => key.prefix(n)
},
emptyPrefix: new NumericKey(0, 0)
}
}
class Trie {
constructor (options = {}) {
// Construct type options
const { type } = {type: 'string', ...options}
let typeOpts = KEY_TYPES[type]
if (typeOpts) {
typeOpts = {
createKey: typeOpts.createKey(options),
getKey: typeOpts.getKey(options),
setKey: typeOpts.setKey(options),
comparator: typeOpts.comparator(options),
match: typeOpts.match(options),
prefix: typeOpts.prefix(options),
emptyPrefix: typeOpts.emptyPrefix
}
}
this.options = {...DEFAULT_OPTS, ...typeOpts, ...options}
this.root = new Node([], this.options)
}
add (value) {
const { root, options } = this
return root.add(options.getKey(value), value, options)
}
get (key, filter = undefined) {
const { root, options } = this
let ret = root.get(options.createKey(key), options)
// Coerce MultiValue's into array, and apply filter (if supplied)
if (ret instanceof MultiValue) {
ret = ret.values
if (filter) {
ret = ret.filter(x => filter(x))
}
return coerceArray(ret)
} else {
return (filter === undefined || filter(ret)) ? ret : undefined
}
}
delete (key, filter = undefined) {
const { root, options } = this
const ret = root.delete(options.createKey(key), options, filter)
if (!root.edges && !root.values.length) {
root.skip = options.emptyPrefix // Root node needs to be reset if empty
}
return ret
}
}
module.exports = Trie