Files: 679937360074d0e31e59880b76fbfa01da58efd3 / index.js
8679 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 | key = this.formatKey(key) |
35 | await this.done() |
36 | const {root} = await this._get(key, decode) |
37 | return new RadixTree({dag: this.dag, root: root, appendKeyToRoot: true}) |
38 | } |
39 | |
40 | /** |
41 | * gets a value given a key |
42 | * @param {*} key |
43 | * @return {Promise} |
44 | */ |
45 | async get (key, decode) { |
46 | key = this.formatKey(key) |
47 | await this.done() |
48 | const result = await this._get(key) |
49 | return result.value |
50 | } |
51 | |
52 | async _get (key) { |
53 | let index = 0 |
54 | let root = this.root |
55 | let parent |
56 | |
57 | while (1) { |
58 | // load the root |
59 | const exNode = await this.graph.get(root, treeNode.EXTENSION, true) |
60 | if (exNode) { |
61 | let subKey = key.subarray(index) |
62 | |
63 | const {extensionIndex, extensionLen, extension} = findMatchBits(subKey, root) |
64 | index += extensionIndex |
65 | // check if we compelete travered the extension |
66 | if (extensionIndex !== extensionLen) { |
67 | return { |
68 | index, |
69 | root, |
70 | extension, |
71 | extensionIndex |
72 | } |
73 | } |
74 | } |
75 | |
76 | let keySegment = key[index] |
77 | if (keySegment !== undefined) { |
78 | const branch = treeNode.getBranch(root) |
79 | await this.graph.get(branch, keySegment, true) |
80 | // preseves the '/' |
81 | const nextRoot = branch[keySegment] |
82 | if (!nextRoot) { |
83 | return { |
84 | root: root, |
85 | index: index |
86 | } |
87 | } else { |
88 | parent = root |
89 | root = nextRoot |
90 | } |
91 | } else { |
92 | break |
93 | } |
94 | |
95 | index++ |
96 | } |
97 | |
98 | const value = treeNode.getValue(root) |
99 | |
100 | return { |
101 | value, |
102 | root, |
103 | parent, |
104 | index |
105 | } |
106 | } |
107 | |
108 | /** |
109 | * stores a value at a given key |
110 | * @param {*} key |
111 | * @return {Promise} |
112 | */ |
113 | set (key, value) { |
114 | key = this.formatKey(key) |
115 | return this._mutationLock(this._set.bind(this, key, value)) |
116 | } |
117 | |
118 | async _set (key, value) { |
119 | if (treeNode.isEmpty(this.root)) { |
120 | this.root['/'] = createNode(key, [null, null], value)['/'] |
121 | } else { |
122 | let {root, extensionIndex, extension, index, value: rValue} = await this._get(key) |
123 | |
124 | if (rValue) { |
125 | treeNode.setValue(root, value) |
126 | } else { |
127 | if (extensionIndex !== undefined) { |
128 | // split the extension node in two |
129 | const extensionKey = extension[extensionIndex] |
130 | const remExtension = extension.subarray(extensionIndex + 1) |
131 | extension = extension.subarray(0, extensionIndex) |
132 | |
133 | treeNode.setExtension(root, remExtension) |
134 | const branch = [null, null] |
135 | branch[extensionKey] = { |
136 | '/': root['/'] |
137 | } |
138 | root['/'] = createNode(extension, branch)['/'] |
139 | } |
140 | |
141 | // if there are remaning key segments create an extension node |
142 | if (index < key.length) { |
143 | const keySegment = key[index] |
144 | const extension = key.subarray(index + 1, key.length) |
145 | const newNode = createNode(extension, [null, null], value) |
146 | const rootBranch = treeNode.getBranch(root) |
147 | rootBranch[keySegment] = newNode |
148 | treeNode.setBranch(root, rootBranch) |
149 | } else { |
150 | treeNode.setValue(root, value) |
151 | } |
152 | } |
153 | } |
154 | } |
155 | |
156 | /** |
157 | * deletes a value at a given key |
158 | * @param {*} key |
159 | * @return {Promise} |
160 | */ |
161 | delete (key) { |
162 | key = this.formatKey(key) |
163 | return this._mutationLock(this._delete.bind(this, key)) |
164 | } |
165 | |
166 | async _delete (key) { |
167 | const results = await this._get(key) |
168 | if (results.value !== undefined) { |
169 | const root = results.root |
170 | const parent = results.parent |
171 | |
172 | treeNode.deleteValue(root) |
173 | |
174 | const branch = treeNode.getBranch(root) |
175 | if (branch.some(el => el !== null)) { |
176 | joinNodes(root) |
177 | } else { |
178 | if (!parent) { |
179 | root['/'] = RadixTree.emptyTreeState |
180 | } else { |
181 | let branch = treeNode.getBranch(parent) |
182 | branch = branch.map(node => node === root ? null : node) |
183 | treeNode.setBranch(parent, branch) |
184 | await this.graph.tree(parent, 2) |
185 | |
186 | joinNodes(parent) |
187 | } |
188 | } |
189 | } |
190 | |
191 | function joinNodes (root) { |
192 | if (treeNode.getValue(root) === undefined) { |
193 | let index |
194 | const branch = treeNode.getBranch(root) |
195 | const nodes = branch.filter((node, i) => { |
196 | if (node) { |
197 | index = i |
198 | return true |
199 | } |
200 | }) |
201 | |
202 | if (nodes.length === 1) { |
203 | const child = nodes[0] |
204 | const pExtension = treeNode.getExtension(root) |
205 | const childExtension = treeNode.getExtension(child) |
206 | const newExtension = new RadixTree.ArrayConstructor(pExtension.length + childExtension.length + 1) |
207 | |
208 | newExtension.set(pExtension) |
209 | newExtension[pExtension.length] = index |
210 | newExtension.set(childExtension, pExtension.length + 1) |
211 | |
212 | treeNode.setExtension(child, newExtension) |
213 | root['/'] = child['/'] |
214 | } |
215 | } |
216 | } |
217 | } |
218 | |
219 | /** |
220 | * returns a promise that resolve when the tree is done with all of its writes |
221 | * @returns {Promise} |
222 | */ |
223 | async done () { |
224 | let setting |
225 | while (this._setting !== setting) { |
226 | setting = this._setting |
227 | await setting |
228 | } |
229 | } |
230 | |
231 | _mutationLock (func) { |
232 | const setting = this._setting |
233 | this._setting = new Promise((resolve, reject) => { |
234 | return setting.then(() => { |
235 | return func().then(resolve).catch(reject) |
236 | }) |
237 | }) |
238 | return this._setting |
239 | } |
240 | |
241 | /** |
242 | * creates a merkle root for the current tree and stores the data perstantly |
243 | * @returns {Promise} |
244 | */ |
245 | async flush () { |
246 | await this.done() |
247 | return this.graph.flush(this.root) |
248 | } |
249 | |
250 | formatKey (key) { |
251 | key = RadixTree.formatKey(key) |
252 | if (this.appendKeyToRoot) { |
253 | key = treeNode.getExtension(this.root).toJSON().concat(key.toJSON()) |
254 | key = new RadixTree.ArrayConstructor(key) |
255 | } |
256 | return key |
257 | } |
258 | |
259 | static formatKey (key) { |
260 | if (typeof key === 'string') { |
261 | key = encoder.encode(key) |
262 | } |
263 | |
264 | if (key.constructor !== RadixTree.ArrayConstructor) { |
265 | if (Buffer.isBuffer(key)) { |
266 | return new RadixTree.ArrayConstructor(new Uint8Array(key).buffer) |
267 | } else { |
268 | return new RadixTree.ArrayConstructor(key.buffer) |
269 | } |
270 | } else { |
271 | return key |
272 | } |
273 | } |
274 | |
275 | /** |
276 | * returns the state of an empty tree |
277 | */ |
278 | static get emptyTreeState () { |
279 | return [null, null, null] |
280 | } |
281 | |
282 | /** |
283 | * returns an Uint1Array constructir which is used to repersent keys |
284 | * @returns {object} |
285 | */ |
286 | static get ArrayConstructor () { |
287 | return Uint1Array |
288 | } |
289 | |
290 | /** |
291 | * returns a merkle link for some given data |
292 | * @param {Buffer} data - the data which you would like to hash |
293 | * @returns {Buffer} |
294 | */ |
295 | static getMerkleLink (data) { |
296 | return DataStore.getMerkleLink(data) |
297 | } |
298 | } |
299 | |
300 | function createNode (ex, branch, value) { |
301 | const node = { |
302 | '/': [] |
303 | } |
304 | |
305 | treeNode.setValue(node, value) |
306 | treeNode.setExtension(node, ex) |
307 | treeNode.setBranch(node, branch) |
308 | |
309 | return node |
310 | } |
311 | |
312 | function findMatchBits (key, node) { |
313 | let extensionIndex = 0 |
314 | const extension = treeNode.getExtension(node) |
315 | const extensionLen = extension.length |
316 | |
317 | // checks the extension against the key |
318 | while (extensionIndex < extensionLen && extension[extensionIndex] === key[extensionIndex]) { |
319 | extensionIndex++ |
320 | } |
321 | |
322 | return { |
323 | extensionIndex, |
324 | extensionLen, |
325 | extension |
326 | } |
327 | } |
328 |
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