@waku/rln/dist/root_tracker.js

RLN (Rate Limiting Nullifier) implementation for Waku

class RootPerBlock {
    root;
    blockNumber;
    constructor(root, blockNumber) {
        this.root = root;
        this.blockNumber = blockNumber;
    }
}
const maxBufferSize = 20;
export class MerkleRootTracker {
    acceptableRootWindowSize;
    validMerkleRoots = new Array();
    merkleRootBuffer = new Array();
    constructor(acceptableRootWindowSize, initialRoot) {
        this.acceptableRootWindowSize = acceptableRootWindowSize;
        this.pushRoot(0, initialRoot);
    }
    backFill(fromBlockNumber) {
        if (this.validMerkleRoots.length == 0)
            return;
        let numBlocks = 0;
        for (let i = this.validMerkleRoots.length - 1; i >= 0; i--) {
            if (this.validMerkleRoots[i].blockNumber >= fromBlockNumber) {
                numBlocks++;
            }
        }
        if (numBlocks == 0)
            return;
        const olderBlock = fromBlockNumber < this.validMerkleRoots[0].blockNumber;
        // Remove last roots
        let rootsToPop = numBlocks;
        if (this.validMerkleRoots.length < rootsToPop) {
            rootsToPop = this.validMerkleRoots.length;
        }
        this.validMerkleRoots = this.validMerkleRoots.slice(0, this.validMerkleRoots.length - rootsToPop);
        if (this.merkleRootBuffer.length == 0)
            return;
        if (olderBlock) {
            const idx = this.merkleRootBuffer.findIndex((x) => x.blockNumber == fromBlockNumber);
            if (idx > -1) {
                this.merkleRootBuffer = this.merkleRootBuffer.slice(0, idx);
            }
        }
        // Backfill the tree's acceptable roots
        let rootsToRestore = this.acceptableRootWindowSize - this.validMerkleRoots.length;
        if (this.merkleRootBuffer.length < rootsToRestore) {
            rootsToRestore = this.merkleRootBuffer.length;
        }
        for (let i = 0; i < rootsToRestore; i++) {
            const x = this.merkleRootBuffer.pop();
            if (x)
                this.validMerkleRoots.unshift(x);
        }
    }
    pushRoot(blockNumber, root) {
        this.validMerkleRoots.push(new RootPerBlock(root, blockNumber));
        // Maintain valid merkle root window
        if (this.validMerkleRoots.length > this.acceptableRootWindowSize) {
            const x = this.validMerkleRoots.shift();
            if (x)
                this.merkleRootBuffer.push(x);
        }
        // Maintain merkle root buffer
        if (this.merkleRootBuffer.length > maxBufferSize) {
            this.merkleRootBuffer.shift();
        }
    }
    roots() {
        return this.validMerkleRoots.map((x) => x.root);
    }
    buffer() {
        return this.merkleRootBuffer.map((x) => x.root);
    }
}
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