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Generator #3
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,78 @@ | ||
| import { ethers as eth } from 'ethers' | ||
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| const { arrayify, concat, hexlify, isHexString, keccak256, padZeros } = eth.utils | ||
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| const combinedHash = (first: string, second: string): string => { | ||
| if (!second) { return first } | ||
| if (!first) { return second } | ||
| return keccak256(concat([first, second].sort())) | ||
| } | ||
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| export class MerkleTree { | ||
| public elements: string[] | ||
| public root: string | ||
| public layers: string[][] | ||
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| public constructor(_elements: string[]) { | ||
| if (!_elements.every((e: string): boolean => isHexString(e) && arrayify(e).length === 32)) { | ||
| throw new Error('Each element must be a 32 byte hex string') | ||
| } | ||
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| // deduplicate elements | ||
| this.elements = _elements.filter((element: string, i: number): boolean => | ||
| _elements.findIndex((e: string): boolean => element === e) === i, | ||
| ).sort() | ||
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| // Can't have an odd number of leaves | ||
| if (this.elements.length % 2 !== 0) { | ||
| this.elements.push(eth.constants.HashZero) | ||
| } | ||
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| // Build merkle tree layers | ||
| this.layers = [] | ||
| // Set root to HashZero if given zero elements | ||
| if (this.elements.length === 0) { | ||
| this.layers.push([eth.constants.HashZero]) | ||
| } else { | ||
| this.layers.push(this.elements) | ||
| while (this.topLayer.length > 1) { | ||
| this.layers.push(this.topLayer.reduce( | ||
| (layer: string[], element: string, index: number, arr: string[]): string[] => | ||
| index % 2 ? layer : layer.concat([combinedHash(element, arr[index + 1])]), | ||
| [], | ||
| )) | ||
| } | ||
| } | ||
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| this.root = this.topLayer[0] | ||
| } | ||
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| public get topLayer(): string[] { | ||
| return this.layers[this.layers.length -1] | ||
| } | ||
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| public proof(element: string): string { | ||
| let index = this.elements.findIndex((e: string): boolean => e === element) | ||
| if (index === -1) { throw new Error('element not found in merkle tree') } | ||
| const proofArray = this.layers.reduce((proof: string[], layer: string[]): string[] => { | ||
| const pairIndex: number = index % 2 ? index - 1 : index + 1 | ||
| if (pairIndex < layer.length) { | ||
| proof.push(layer[pairIndex]) | ||
| } | ||
| index = Math.floor(index / 2) | ||
| return proof | ||
| }, [element]) | ||
| return hexlify(concat(proofArray)) | ||
| } | ||
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| public verify(proof: string): boolean { | ||
| const proofArray: RegExpMatchArray = proof.substring(2).match(/.{64}/g) || [] | ||
| if (!proofArray || proofArray.length * 64 !== proof.length -2) { | ||
| console.warn(`Invalid proof: expected a hex string describing n 32 byte chunks`) | ||
| return false | ||
| } | ||
| const proofs: string[] = proofArray.map((p: string): string => `0x${p.replace('0x', '')}`) | ||
| return this.root === (proofs.slice(1).reduce(combinedHash, proofs[0])) | ||
| } | ||
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| } | ||
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I'm not entirely sure I see why this needs to be a class as opposed to just pure functions.