Files: 3d628f57a11eceed9c7d6369490decbdade51afd / index.js
8733 bytesRaw
1 | const Graph = require('ipld-graph-builder') |
2 | const Uint1Array = require('uint1array') |
3 | const TextEncoder = require('text-encoding').TextEncoder |
4 | const DataStore = require('./datastore.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.db {object} a level db instance alternitly `opts.graph` can be used |
14 | * @param opts.graph {object} an instance of [ipld-graph-builder](https://github.com/ipld/js-ipld-graph-builder) alternitvly `opts.dag` can be used |
15 | * @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. |
16 | */ |
17 | constructor (opts) { |
18 | this.root = opts.root || { |
19 | '/': RadixTree.emptyTreeState |
20 | } |
21 | |
22 | this.dag = opts.dag || new DataStore(opts.db) |
23 | this.graph = opts.graph || new Graph(this.dag) |
24 | this._setting = Promise.resolve() |
25 | this.appendKeyToRoot = opts.appendKeyToRoot |
26 | } |
27 | |
28 | /** |
29 | * creates a new instance of RadixTree that is the subTree of the given key |
30 | * @param {*} key |
31 | * @return {Promise} resolve to the new instance of RadixTree |
32 | */ |
33 | async getSubTree (key, decode) { |
34 | const {root} = await this.get(key, decode) |
35 | return new RadixTree({dag: this.dag, root: root, appendKeyToRoot: true}) |
36 | } |
37 | |
38 | /** |
39 | * gets a value given a key. The promise resolves with an object containing |
40 | * `node` the node in the merkle tree and `value` the value of the that the |
41 | * node contains |
42 | * @param {*} key |
43 | * @return {Promise} |
44 | */ |
45 | async get (key, decode) { |
46 | key = this.formatKey(key) |
47 | await this.done() |
48 | return this._get(key) |
49 | } |
50 | |
51 | async _get (key) { |
52 | let index = 0 |
53 | let root = this.root |
54 | let parent |
55 | |
56 | while (1) { |
57 | // load the root |
58 | const exNode = await this.graph.get(root, treeNode.EXTENSION, true) |
59 | if (exNode) { |
60 | let subKey = key.subarray(index) |
61 | |
62 | const {extensionIndex, extensionLen, extension} = findMatchBits(subKey, root) |
63 | index += extensionIndex |
64 | // check if we compelete travered the extension |
65 | if (extensionIndex !== extensionLen) { |
66 | return { |
67 | index, |
68 | root, |
69 | extension, |
70 | extensionIndex |
71 | } |
72 | } |
73 | } |
74 | |
75 | let keySegment = key[index] |
76 | if (keySegment !== undefined) { |
77 | const branch = treeNode.getBranch(root) |
78 | await this.graph.get(branch, keySegment, true) |
79 | // preseves the '/' |
80 | const nextRoot = branch[keySegment] |
81 | if (!nextRoot) { |
82 | return { |
83 | root: root, |
84 | index: index |
85 | } |
86 | } else { |
87 | parent = root |
88 | root = nextRoot |
89 | } |
90 | } else { |
91 | break |
92 | } |
93 | |
94 | index++ |
95 | } |
96 | |
97 | const value = treeNode.getValue(root) |
98 | |
99 | return { |
100 | value, |
101 | root, |
102 | parent, |
103 | index |
104 | } |
105 | } |
106 | |
107 | /** |
108 | * stores a value at a given key |
109 | * @param {*} key |
110 | * @return {Promise} |
111 | */ |
112 | set (key, value) { |
113 | key = this.formatKey(key) |
114 | return this._mutationLock(this._set.bind(this, key, value)) |
115 | } |
116 | |
117 | async _set (key, value) { |
118 | if (treeNode.isEmpty(this.root)) { |
119 | this.root['/'] = createNode(key, [null, null], value)['/'] |
120 | } else { |
121 | let {root, extensionIndex, extension, index, value: rValue} = await this._get(key) |
122 | |
123 | if (rValue) { |
124 | treeNode.setValue(root, value) |
125 | } else { |
126 | if (extensionIndex !== undefined) { |
127 | // split the extension node in two |
128 | const extensionKey = extension[extensionIndex] |
129 | const remExtension = extension.subarray(extensionIndex + 1) |
130 | extension = extension.subarray(0, extensionIndex) |
131 | |
132 | treeNode.setExtension(root, remExtension) |
133 | const branch = [null, null] |
134 | branch[extensionKey] = { |
135 | '/': root['/'] |
136 | } |
137 | root['/'] = createNode(extension, branch)['/'] |
138 | } |
139 | |
140 | // if there are remaning key segments create an extension node |
141 | if (index < key.length) { |
142 | const keySegment = key[index] |
143 | const extension = key.subarray(index + 1, key.length) |
144 | const newNode = createNode(extension, [null, null], value) |
145 | const rootBranch = treeNode.getBranch(root) |
146 | rootBranch[keySegment] = newNode |
147 | treeNode.setBranch(root, rootBranch) |
148 | } else { |
149 | treeNode.setValue(root, value) |
150 | } |
151 | } |
152 | } |
153 | } |
154 | |
155 | /** |
156 | * deletes a value at a given key |
157 | * @param {*} key |
158 | * @return {Promise} |
159 | */ |
160 | delete (key) { |
161 | key = this.formatKey(key) |
162 | return this._mutationLock(this._delete.bind(this, key)) |
163 | } |
164 | |
165 | async _delete (key) { |
166 | const results = await this._get(key) |
167 | if (results.value !== undefined) { |
168 | const root = results.root |
169 | const parent = results.parent |
170 | |
171 | treeNode.deleteValue(root) |
172 | |
173 | const branch = treeNode.getBranch(root) |
174 | if (branch.some(el => el !== null)) { |
175 | joinNodes(root) |
176 | } else { |
177 | if (!parent) { |
178 | root['/'] = RadixTree.emptyTreeState |
179 | } else { |
180 | let branch = treeNode.getBranch(parent) |
181 | branch = branch.map(node => node === root ? null : node) |
182 | treeNode.setBranch(parent, branch) |
183 | await this.graph.tree(parent, 2) |
184 | |
185 | joinNodes(parent) |
186 | } |
187 | } |
188 | } |
189 | |
190 | function joinNodes (root) { |
191 | if (treeNode.getValue(root) === undefined) { |
192 | let index |
193 | const branch = treeNode.getBranch(root) |
194 | const nodes = branch.filter((node, i) => { |
195 | if (node) { |
196 | index = i |
197 | return true |
198 | } |
199 | }) |
200 | |
201 | if (nodes.length === 1) { |
202 | const child = nodes[0] |
203 | const pExtension = treeNode.getExtension(root) |
204 | const childExtension = treeNode.getExtension(child) |
205 | const newExtension = new RadixTree.ArrayConstructor(pExtension.length + childExtension.length + 1) |
206 | |
207 | newExtension.set(pExtension) |
208 | newExtension[pExtension.length] = index |
209 | newExtension.set(childExtension, pExtension.length + 1) |
210 | |
211 | treeNode.setExtension(child, newExtension) |
212 | root['/'] = child['/'] |
213 | } |
214 | } |
215 | } |
216 | } |
217 | |
218 | /** |
219 | * returns a promise that resolve when the tree is done with all of its writes |
220 | * @returns {Promise} |
221 | */ |
222 | async done () { |
223 | let setting |
224 | while (this._setting !== setting) { |
225 | setting = this._setting |
226 | await setting |
227 | } |
228 | } |
229 | |
230 | _mutationLock (func) { |
231 | const setting = this._setting |
232 | this._setting = new Promise((resolve, reject) => { |
233 | return setting.then(() => { |
234 | return func().then(resolve).catch(reject) |
235 | }) |
236 | }) |
237 | return this._setting |
238 | } |
239 | |
240 | /** |
241 | * creates a merkle root for the current tree and stores the data perstantly |
242 | * @returns {Promise} |
243 | */ |
244 | async flush () { |
245 | await this.done() |
246 | return this.graph.flush(this.root) |
247 | } |
248 | |
249 | formatKey (key) { |
250 | key = RadixTree.formatKey(key) |
251 | if (this.appendKeyToRoot) { |
252 | key = treeNode.getExtension(this.root).toJSON().concat(key.toJSON()) |
253 | key = new RadixTree.ArrayConstructor(key) |
254 | } |
255 | return key |
256 | } |
257 | |
258 | static formatKey (key) { |
259 | if (typeof key === 'string') { |
260 | key = encoder.encode(key) |
261 | } |
262 | |
263 | if (key.constructor !== RadixTree.ArrayConstructor) { |
264 | if (Buffer.isBuffer(key)) { |
265 | return new RadixTree.ArrayConstructor(new Uint8Array(key).buffer) |
266 | } else { |
267 | return new RadixTree.ArrayConstructor(key.buffer) |
268 | } |
269 | } else { |
270 | return key |
271 | } |
272 | } |
273 | |
274 | /** |
275 | * returns the state of an empty tree |
276 | */ |
277 | static get emptyTreeState () { |
278 | return [null, null, null] |
279 | } |
280 | |
281 | /** |
282 | * returns an Uint1Array constructir which is used to repersent keys |
283 | * @returns {object} |
284 | */ |
285 | static get ArrayConstructor () { |
286 | return Uint1Array |
287 | } |
288 | |
289 | /** |
290 | * returns a merkle link for some given data |
291 | * @param {Buffer} data - the data which you would like to hash |
292 | * @returns {Buffer} |
293 | */ |
294 | static getMerkleLink (data) { |
295 | return DataStore.getMerkleLink(data) |
296 | } |
297 | } |
298 | |
299 | function createNode (ex, branch, value) { |
300 | const node = { |
301 | '/': [] |
302 | } |
303 | |
304 | treeNode.setValue(node, value) |
305 | treeNode.setExtension(node, ex) |
306 | treeNode.setBranch(node, branch) |
307 | |
308 | return node |
309 | } |
310 | |
311 | function findMatchBits (key, node) { |
312 | let extensionIndex = 0 |
313 | const extension = treeNode.getExtension(node) |
314 | const extensionLen = extension.length |
315 | |
316 | // checks the extension against the key |
317 | while (extensionIndex < extensionLen && extension[extensionIndex] === key[extensionIndex]) { |
318 | extensionIndex++ |
319 | } |
320 | |
321 | return { |
322 | extensionIndex, |
323 | extensionLen, |
324 | extension |
325 | } |
326 | } |
327 |
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