bst refactor. comments.
This commit is contained in:
Christopher Jeffrey
parent
4d823742c3
commit
135fca806c
197
lib/bcoin/bst.js
197
lib/bcoin/bst.js
@ -1,7 +1,6 @@
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/*!
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* bst.js - iterative binary search tree for bcoin
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* Copyright (c) 2014-2015, Fedor Indutny (MIT License)
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* Copyright (c) 2014-2016, Christopher Jeffrey (MIT License).
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* Copyright (c) 2016, Christopher Jeffrey (MIT License).
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* https://github.com/bcoin-org/bcoin
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*/
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@ -12,8 +11,10 @@ var assert = utils.assert;
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var DUMMY = new Buffer([0]);
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/**
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* An iterative in-memory binary search tree. Used for the mempool.
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* Many of its options, parameters and methods mimic the leveldown interface.
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* An iterative binary search tree.
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* Used for the mempool. Many of its
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* options, parameters, and methods
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* mimic the leveldown interface.
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* @exports BST
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* @constructor
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* @param {String?} location - Phony location.
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@ -35,7 +36,7 @@ function BST(location, options) {
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/**
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* Do a key lookup.
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* @param {String|Buffer} key
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* @param {Buffer|String} key
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* @returns {Buffer?} value
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*/
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@ -59,14 +60,14 @@ BST.prototype.search = function search(key) {
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/**
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* Insert a record.
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* @param {String|Buffer} key
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* @param {Buffer|String} key
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* @param {Buffer} value
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*/
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BST.prototype.insert = function insert(key, value) {
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var current = this.root;
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var left = false;
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var parent, cmp;
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var parent, cmp, node;
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if (typeof key === 'string')
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key = new Buffer(key, 'ascii');
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@ -93,15 +94,17 @@ BST.prototype.insert = function insert(key, value) {
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}
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}
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node = new BSTNode(key, value);
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if (!parent) {
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this.root = { key: key, value: value };
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this.root = node;
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return;
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}
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if (left)
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parent.left = { key: key, value: value };
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parent.left = node;
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else
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parent.right = { key: key, value: value };
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parent.right = node;
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};
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/**
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@ -191,7 +194,7 @@ BST.prototype.remove = function remove(key) {
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/**
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* Take a snapshot and return a cloned root node.
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* @return {Object}
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* @returns {BSTNode}
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*/
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BST.prototype.snapshot = function snapshot() {
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@ -203,13 +206,13 @@ BST.prototype.snapshot = function snapshot() {
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for (;;) {
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if (current) {
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if (left) {
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copy = clone(current);
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copy = current.clone();
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if (parent)
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parent.left = copy;
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else
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snapshot = copy;
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} else {
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copy = clone(current);
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copy = current.clone();
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if (parent)
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parent.right = copy;
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else
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@ -237,7 +240,7 @@ BST.prototype.snapshot = function snapshot() {
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/**
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* Traverse the key and filter records.
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* @param {Function} test
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* @returns {Object[]} Matched records.
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* @returns {BSTNode[]} Records.
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*/
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BST.prototype.traverse = function traverse(test) {
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@ -247,12 +250,8 @@ BST.prototype.traverse = function traverse(test) {
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for (;;) {
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if (current) {
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if (test(current)) {
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items.push({
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key: current.key,
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value: current.value
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});
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}
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if (test(current))
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items.push(current.copy());
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stack.push(current);
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current = current.left;
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continue;
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@ -270,7 +269,7 @@ BST.prototype.traverse = function traverse(test) {
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/**
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* Dump all records.
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* @returns {Object[]} Records.
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* @returns {BSTNode[]} Records.
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*/
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BST.prototype.dump = function dump() {
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@ -281,7 +280,7 @@ BST.prototype.dump = function dump() {
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* Traverse between a range of keys and collect records.
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* @param {Buffer} gte
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* @param {Buffer} lte
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* @returns {Object[]} records
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* @returns {BSTNode[]} Records.
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*/
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BST.prototype.range = function range(gte, lte) {
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@ -300,10 +299,7 @@ BST.prototype.range = function range(gte, lte) {
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if (current) {
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cmp = this.rangeCompare(current.key, gte, lte);
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if (cmp === 0) {
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items.push({
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key: current.key,
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value: current.value
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});
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items.push(current.copy());
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stack.push(current);
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}
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if (cmp <= 0)
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@ -513,15 +509,22 @@ BST.prototype.getProperty = function getProperty(name) {
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/**
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* Calculate approximate database size (leveldown method).
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* @param {String} start - Start key.
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* @param {String} end - End key.
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* @param {Buffer|String} start - Start key.
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* @param {Buffer|String} end - End key.
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* @param {Function} callback - Returns [Error, Number].
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*/
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BST.prototype.approximateSize = function approximateSize(start, end, callback) {
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var size = this.range(start, end).reduce(function(total, item) {
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return total + item.key.length + item.value.length;
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}, 0);
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var items = this.range(start, end);
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var size = 0;
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var i, item;
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for (i = 0; i < items.length; i++) {
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item = items[i];
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size += item.key.length;
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size += item.value.length;
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}
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return utils.asyncify(callback)(null, size);
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};
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@ -545,8 +548,52 @@ BST.repair = function repair(location, callback) {
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return utils.nextTick(callback);
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};
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/*
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/**
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* BST Node
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* @constructor
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* @private
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* @param {Buffer} key
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* @param {Buffer} value
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* @property {Buffer} key
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* @property {Buffer} value
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* @property {BSTNode|null} left
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* @property {BSTNode|null} right
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*/
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function BSTNode(key, value) {
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this.key = key;
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this.value = value;
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this.left = null;
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this.right = null;
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}
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/**
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* Clone the node.
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* @returns {BSTNode}
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*/
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BSTNode.prototype.clone = function clone() {
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var node = new BSTNode(this.key, this.value);
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node.left = this.left;
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node.right = this.right;
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return node;
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};
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/**
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* Clone the node (key/value only).
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* @returns {BSTNode}
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*/
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BSTNode.prototype.copy = function copy() {
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return new BSTNode(this.key, this.value);
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};
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/**
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* Batch
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* @constructor
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* @private
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* @param {BST} tree
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* @param {Object?} options
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*/
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function Batch(tree, options) {
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@ -555,32 +602,49 @@ function Batch(tree, options) {
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this.tree = tree;
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}
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/**
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* Insert a record.
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* @param {Buffer|String} key
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* @param {Buffer} value
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*/
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Batch.prototype.put = function(key, value) {
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assert(this.tree, 'Already written.');
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this.ops.push({ type: 'put', key: key, value: value });
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return this;
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};
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/**
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* Remove a record.
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* @param {Buffer|String} key
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*/
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Batch.prototype.del = function del(key) {
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assert(this.tree, 'Already written.');
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this.ops.push({ type: 'del', key: key });
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return this;
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};
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/**
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* Commit the batch.
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* @param {Function} callback
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*/
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Batch.prototype.write = function write(callback) {
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var self = this;
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var i, op;
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if (!this.tree)
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return utils.asyncify(callback)(new Error('Already written.'));
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return callback(new Error('Already written.'));
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this.ops.forEach(function(op) {
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for (i = 0; i < this.ops.length; i++) {
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op = this.ops[i];
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if (op.type === 'put')
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self.tree.insert(op.key, op.value);
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this.tree.insert(op.key, op.value);
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else if (op.type === 'del')
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self.tree.remove(op.key);
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this.tree.remove(op.key);
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else
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assert(false);
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});
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}
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this.ops.length = 0;
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this.ops = null;
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@ -592,14 +656,22 @@ Batch.prototype.write = function write(callback) {
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return this;
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};
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/**
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* Clear batch of all ops.
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*/
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Batch.prototype.clear = function clear() {
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assert(this.tree, 'Already written.');
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this.ops.length = 0;
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return this;
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};
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/*
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/**
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* Iterator
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* @constructor
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* @private
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* @param {BST} tree
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* @param {Object?} options
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*/
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function Iterator(tree, options) {
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@ -622,11 +694,16 @@ function Iterator(tree, options) {
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this.tree = tree;
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this.ended = false;
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this.items = this.tree.range(this.options.gte, this.options.lte);
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this.index = this.options.reverse ? this.items.length - 1 : 0;
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this.snapshot = this.tree.range(this.options.gte, this.options.lte);
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this.index = this.options.reverse ? this.snapshot.length - 1 : 0;
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this.total = 0;
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}
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/**
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* Seek to the next key.
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* @param {Function} callback
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*/
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Iterator.prototype.next = function(callback) {
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var item, key, value;
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@ -634,9 +711,9 @@ Iterator.prototype.next = function(callback) {
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return utils.asyncify(callback)(new Error('Cannot call next after end.'));
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if (this.options.reverse)
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item = this.items[this.index--];
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item = this.snapshot[this.index--];
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else
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item = this.items[this.index++];
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item = this.snapshot[this.index++];
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if (this.options.limit != null) {
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if (this.total++ >= this.options.limit) {
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@ -668,6 +745,11 @@ Iterator.prototype.next = function(callback) {
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utils.asyncify(callback)(null, key, value);
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};
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/**
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* Seek to a key gte to `key`.
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* @param {String|Buffer} key
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*/
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Iterator.prototype.seek = function seek(key) {
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var self = this;
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@ -676,20 +758,30 @@ Iterator.prototype.seek = function seek(key) {
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if (typeof key === 'string')
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key = new Buffer(key, 'ascii');
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this.index = utils.binarySearch(this.items, key, function(a, b) {
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this.index = utils.binarySearch(this.snapshot, key, function(a, b) {
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return self.tree.compare(a.key, b);
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}, true);
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};
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/**
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* Clean up the iterator.
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* @private
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*/
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Iterator.prototype._end = function end() {
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if (!this.tree)
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return;
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this.tree = null;
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this.items.length = 0;
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this.items = null;
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this.snapshot.length = 0;
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this.snapshot = null;
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};
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/**
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* End the iterator. Free up snapshot.
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* @param {Buffer} callback
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*/
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Iterator.prototype.end = function end(callback) {
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if (this.ended)
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return utils.asyncify(callback)(new Error('Already ended.'));
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@ -700,19 +792,6 @@ Iterator.prototype.end = function end(callback) {
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return utils.nextTick(callback);
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};
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/*
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* Helpers
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*/
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function clone(node) {
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return {
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key: node.key,
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value: node.value,
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left: node.left,
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right: node.right
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};
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}
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/*
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* Expose
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*/
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