Files: 8b3b6ad9bccab11efb8cdb0f5a71e03b011e8ee0 / index.js
6876 bytesRaw
1 | const Graph = require('ipld-graph-builder') |
2 | const Uint1Array = require('uint1array') |
3 | const TextEncoder = require('text-encoding').TextEncoder |
4 | const DAG = require('./dag.js') |
5 | const treeNode = require('./treeNode.js') |
6 | |
7 | const encoder = new TextEncoder('utf-8') |
8 | |
9 | module.exports = class RadixTree { |
10 | /** |
11 | * @param opts |
12 | * @param opts.root {object} a merkle root to a radix tree. If none, RadixTree will create an new root. |
13 | * @param opts.graph {object} an instance of [ipld-graph-builder](https://github.com/ipld/js-ipld-graph-builder) alternitvly `opts.dag` can be used |
14 | * @param opts.dag {object} an instance if [ipfs.dag](https://github.com/ipfs/js-ipfs#dag). If there is no `opts.graph` this will be used to create a new graph instance. |
15 | */ |
16 | constructor (opts) { |
17 | this.root = opts.root || { |
18 | '/': RadixTree.emptyTreeState |
19 | } |
20 | |
21 | this.dag = opts.dag || new DAG(opts.db) |
22 | this.graph = opts.graph || new Graph(this.dag) |
23 | } |
24 | |
25 | /** |
26 | * returns the state of an empty tree |
27 | */ |
28 | static get emptyTreeState () { |
29 | return [null, null, null] |
30 | } |
31 | |
32 | /** |
33 | * returns an Uint1Array constructir which is used to repersent keys |
34 | * @returns {object} |
35 | */ |
36 | static get ArrayConstructor () { |
37 | return Uint1Array |
38 | } |
39 | |
40 | async _get (key) { |
41 | let index = 0 |
42 | let root = this.root |
43 | let parent |
44 | |
45 | while (1) { |
46 | // load the root |
47 | const exNode = await this.graph.get(root, treeNode.EXTENSION, true) |
48 | if (exNode) { |
49 | let subKey = key.subarray(index) |
50 | |
51 | const {extensionIndex, extensionLen, extension} = findMatchBits(subKey, root) |
52 | index += extensionIndex |
53 | // check if we compelete travered the extension |
54 | if (extensionIndex !== extensionLen) { |
55 | return { |
56 | index: index, |
57 | root: root, |
58 | extension: extension, |
59 | extensionIndex: extensionIndex |
60 | } |
61 | } |
62 | } |
63 | |
64 | let keySegment = key[index] |
65 | if (keySegment !== undefined) { |
66 | const branch = treeNode.getBranch(root) |
67 | await this.graph.get(branch, keySegment, true) |
68 | // preseves the '/' |
69 | const nextRoot = branch[keySegment] |
70 | if (!nextRoot) { |
71 | return { |
72 | root: root, |
73 | index: index |
74 | } |
75 | } else { |
76 | parent = root |
77 | root = nextRoot |
78 | } |
79 | } else { |
80 | break |
81 | } |
82 | |
83 | index++ |
84 | } |
85 | |
86 | const value = treeNode.getValue(root) |
87 | |
88 | return { |
89 | value: value, |
90 | root: root, |
91 | parent: parent, |
92 | index: index |
93 | } |
94 | } |
95 | |
96 | /** |
97 | * gets a value given a key |
98 | * @param {*} key |
99 | * @return {Promise} |
100 | */ |
101 | async get (key) { |
102 | key = RadixTree.formatKey(key) |
103 | const result = await this._get(key) |
104 | return result.value |
105 | } |
106 | |
107 | /** |
108 | * stores a value at a given key |
109 | * @param {*} key |
110 | * @return {Promise} |
111 | */ |
112 | async set (key, value) { |
113 | key = RadixTree.formatKey(key) |
114 | |
115 | if (treeNode.isEmpty(this.root)) { |
116 | this.root['/'] = createNode(key, [null, null], value)['/'] |
117 | } else { |
118 | let {root, extensionIndex, extension, index, value: rValue} = await this._get(key) |
119 | |
120 | if (rValue) { |
121 | treeNode.setValue(root, value) |
122 | } else { |
123 | if (extensionIndex !== undefined) { |
124 | // split the extension node in two |
125 | const extensionKey = extension[extensionIndex] |
126 | const remExtension = extension.subarray(extensionIndex + 1) |
127 | extension = extension.subarray(0, extensionIndex) |
128 | |
129 | treeNode.setExtension(root, remExtension) |
130 | const branch = [null, null] |
131 | branch[extensionKey] = {'/': root['/']} |
132 | root['/'] = createNode(extension, branch)['/'] |
133 | } |
134 | |
135 | // if there are remaning key segments create an extension node |
136 | if (index < key.length) { |
137 | const keySegment = key[index] |
138 | const extension = key.subarray(index + 1, key.length) |
139 | const newNode = createNode(extension, [null, null], value) |
140 | const rootBranch = treeNode.getBranch(root) |
141 | rootBranch[keySegment] = newNode |
142 | treeNode.setBranch(root, rootBranch) |
143 | } else { |
144 | treeNode.setValue(root, value) |
145 | } |
146 | } |
147 | } |
148 | } |
149 | |
150 | /** |
151 | * deletes a value at a given key |
152 | * @param {*} key |
153 | * @return {Promise} |
154 | */ |
155 | async delete (key) { |
156 | key = RadixTree.formatKey(key) |
157 | const results = await this._get(key) |
158 | if (results.value !== undefined) { |
159 | const root = results.root |
160 | const parent = results.parent |
161 | |
162 | treeNode.deleteValue(root) |
163 | |
164 | const branch = treeNode.getBranch(root) |
165 | if (branch.some(el => el !== null)) { |
166 | joinNodes(root) |
167 | } else { |
168 | if (!parent) { |
169 | root['/'] = RadixTree.emptyTreeState |
170 | } else { |
171 | let branch = treeNode.getBranch(parent) |
172 | branch = branch.map(node => node === root ? null : node) |
173 | treeNode.setBranch(parent, branch) |
174 | await this.graph.tree(parent, 2) |
175 | |
176 | joinNodes(parent) |
177 | } |
178 | } |
179 | } |
180 | |
181 | function joinNodes (root) { |
182 | if (treeNode.getValue(root) === undefined) { |
183 | let index |
184 | const branch = treeNode.getBranch(root) |
185 | const nodes = branch.filter((node, i) => { |
186 | if (node) { |
187 | index = i |
188 | return true |
189 | } |
190 | }) |
191 | |
192 | if (nodes.length === 1) { |
193 | const child = nodes[0] |
194 | const pExtension = treeNode.getExtension(root) |
195 | const childExtension = treeNode.getExtension(child) |
196 | const newExtension = new RadixTree.ArrayConstructor(pExtension.length + childExtension.length + 1) |
197 | |
198 | newExtension.set(pExtension) |
199 | newExtension[pExtension.length] = index |
200 | newExtension.set(childExtension, pExtension.length + 1) |
201 | |
202 | treeNode.setExtension(child, newExtension) |
203 | root['/'] = child['/'] |
204 | } |
205 | } |
206 | } |
207 | } |
208 | |
209 | /** |
210 | * creates a merkle root for the current tree and stores the data perstantly |
211 | * @returns {Promise} |
212 | */ |
213 | flush () { |
214 | return this.graph.flush(this.root) |
215 | } |
216 | |
217 | static formatKey (key) { |
218 | if (typeof key === 'string') { |
219 | key = encoder.encode(key) |
220 | } |
221 | |
222 | if (key.constructor !== RadixTree.ArrayConstructor) { |
223 | return new RadixTree.ArrayConstructor(key.buffer) |
224 | } else { |
225 | return key |
226 | } |
227 | } |
228 | } |
229 | |
230 | function createNode (ex, branch, value) { |
231 | const node = { |
232 | '/': [] |
233 | } |
234 | |
235 | treeNode.setValue(node, value) |
236 | treeNode.setExtension(node, ex) |
237 | treeNode.setBranch(node, branch) |
238 | |
239 | return node |
240 | } |
241 | |
242 | function findMatchBits (key, node) { |
243 | let extensionIndex = 0 |
244 | const extension = treeNode.getExtension(node) |
245 | const extensionLen = extension.length |
246 | |
247 | // checks the extension against the key |
248 | while (extensionIndex < extensionLen && extension[extensionIndex] === key[extensionIndex]) { |
249 | extensionIndex++ |
250 | } |
251 | |
252 | return { |
253 | extensionIndex: extensionIndex, |
254 | extensionLen: extensionLen, |
255 | extension: extension |
256 | } |
257 | } |
258 |
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