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Closes: #118 Basic traversal functionality for deterministic DAG walking with no repeat block visits and support for block skipping. User supplies a block loader, which can be used to watch the block ordering of the walk.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,38 @@ | ||
| import { base58btc } from 'multiformats/bases/base58' | ||
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| /** | ||
| * @typedef {import('./cid.js').CID} CID | ||
| */ | ||
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| /** | ||
| * @template T | ||
| * @typedef {import('./block.js').Block<T>} Block | ||
| */ | ||
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| /** | ||
| * @template T | ||
| * @param {Object} options | ||
| * @param {CID} options.cid | ||
| * @param {(cid: CID) => Promise<Block<T>|null>} options.load | ||
| * @param {Set<string>?} options.seen | ||
| */ | ||
| const walk = async ({ cid, load, seen }) => { | ||
| seen = seen || new Set() | ||
| const b58Cid = cid.toString(base58btc) | ||
| if (seen.has(b58Cid)) { | ||
| return | ||
| } | ||
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| const block = await load(cid) | ||
| seen.add(b58Cid) | ||
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| if (block === null) { // the loader signals with `null` that we should skip this block | ||
| return | ||
| } | ||
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| for (const [, cid] of block.links()) { | ||
| await walk({ cid, load, seen }) | ||
| } | ||
| } | ||
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| export { walk } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,162 @@ | ||
| /* globals describe, it */ | ||
| import * as codec from 'multiformats/codecs/json' | ||
| import * as dagPB from '@ipld/dag-pb' | ||
| import { sha256 as hasher } from 'multiformats/hashes/sha2' | ||
| import * as main from 'multiformats/block' | ||
| import { walk } from 'multiformats/traversal' | ||
| import { deepStrictEqual as same } from 'assert' | ||
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| const test = it | ||
| const { createLink, createNode } = dagPB | ||
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| describe('traversal', () => { | ||
| describe('walk', async () => { | ||
| // Forming the following DAG for testing | ||
| // A | ||
| // / \ | ||
| // B C | ||
| // / \ / \ | ||
| // D D D E | ||
| const linksE = [] | ||
| const valueE = createNode(Uint8Array.from('string E qacdswa'), linksE) | ||
| const blockE = await main.encode({ value: valueE, codec, hasher }) | ||
| const cidE = blockE.cid | ||
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| const linksD = [] | ||
| const valueD = createNode(Uint8Array.from('string D zasa'), linksD) | ||
| const blockD = await main.encode({ value: valueD, codec, hasher }) | ||
| const cidD = blockD.cid | ||
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| const linksC = [createLink('link1', 100, cidD), createLink('link2', 100, cidE)] | ||
| const valueC = createNode(Uint8Array.from('string C zxc'), linksC) | ||
| const blockC = await main.encode({ value: valueC, codec, hasher }) | ||
| const cidC = blockC.cid | ||
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| const linksB = [createLink('link1', 100, cidD), createLink('link2', 100, cidD)] | ||
| const valueB = createNode(Uint8Array.from('string B lpokjiasd'), linksB) | ||
| const blockB = await main.encode({ value: valueB, codec, hasher }) | ||
| const cidB = blockB.cid | ||
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| const linksA = [createLink('link1', 100, cidB), createLink('link2', 100, cidC)] | ||
| const valueA = createNode(Uint8Array.from('string A qwertcfdgshaa'), linksA) | ||
| const blockA = await main.encode({ value: valueA, codec, hasher }) | ||
| const cidA = blockA.cid | ||
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| const load = async (cid) => { | ||
| if (cid.equals(cidE)) { | ||
| return blockE | ||
| } | ||
| if (cid.equals(cidD)) { | ||
| return blockD | ||
| } | ||
| if (cid.equals(cidC)) { | ||
| return blockC | ||
| } | ||
| if (cid.equals(cidB)) { | ||
| return blockB | ||
| } | ||
| if (cid.equals(cidA)) { | ||
| return blockA | ||
| } | ||
| return null | ||
| } | ||
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| const loadWrapper = (load, arr = []) => (cid) => { | ||
| arr.push(cid.toString()) | ||
| return load(cid) | ||
| } | ||
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| test('block with no links', async () => { | ||
| // Test Case 1 | ||
| // Input DAG | ||
| // D | ||
| // | ||
| // Expect load to be called with D | ||
| const expectedCallArray = [cidD.toString()] | ||
| const callArray = [] | ||
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| await walk({ cid: cidD, load: loadWrapper(load, callArray) }) | ||
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| expectedCallArray.forEach((value, index) => { | ||
| same(value, callArray[index]) | ||
| }) | ||
| }) | ||
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| test('block with links', async () => { | ||
| // Test Case 2 | ||
| // Input | ||
| // C | ||
| // / \ | ||
| // D E | ||
| // | ||
| // Expect load to be called with C, then D, then E | ||
| const expectedCallArray = [cidC.toString(), cidD.toString(), cidE.toString()] | ||
| const callArray = [] | ||
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| await walk({ cid: cidC, load: loadWrapper(load, callArray) }) | ||
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| expectedCallArray.forEach((value, index) => { | ||
| same(value, callArray[index]) | ||
| }) | ||
| }) | ||
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| test('block with matching links', async () => { | ||
| // Test Case 3 | ||
| // Input | ||
| // B | ||
| // / \ | ||
| // D D | ||
| // | ||
| // Expect load to be called with B, then D | ||
| const expectedCallArray = [cidB.toString(), cidD.toString()] | ||
| const callArray = [] | ||
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| await walk({ cid: cidB, load: loadWrapper(load, callArray) }) | ||
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| expectedCallArray.forEach((value, index) => { | ||
| same(value, callArray[index]) | ||
| }) | ||
| }) | ||
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| test('depth first with duplicated block', async () => { | ||
| // Test Case 4 | ||
| // Input | ||
| // A | ||
| // / \ | ||
| // B C | ||
| // / \ / \ | ||
| // D D D E | ||
| // | ||
| // Expect load to be called with A, then B, then D, then C, then E | ||
| const expectedCallArray = [ | ||
| cidA.toString(), | ||
| cidB.toString(), | ||
| cidD.toString(), | ||
| cidC.toString(), | ||
| cidE.toString() | ||
| ] | ||
| const callArray = [] | ||
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| await walk({ cid: cidA, load: loadWrapper(load, callArray) }) | ||
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| expectedCallArray.forEach((value, index) => { | ||
| same(value, callArray[index]) | ||
| }) | ||
| }) | ||
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| test('null return', async () => { | ||
| const links = [] | ||
| const value = createNode(Uint8Array.from('test'), links) | ||
| const block = await main.encode({ value: value, codec, hasher }) | ||
| const cid = block.cid | ||
| const expectedCallArray = [cid.toString()] | ||
| const callArray = [] | ||
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| await walk({ cid, load: loadWrapper(load, callArray) }) | ||
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| expectedCallArray.forEach((value, index) => { | ||
| same(value, callArray[index]) | ||
| }) | ||
| }) | ||
| }) | ||
| }) |