ipfs-unixfs-importer/dist/src/layout/trickle.js

JavaScript implementation of the UnixFs importer used by IPFS

import batch from 'it-batch';
const DEFAULT_LAYER_REPEAT = 4;
const DEFAULT_MAX_CHILDREN_PER_NODE = 174;
/**
 * @see https://github.com/ipfs/specs/pull/57#issuecomment-265205384
 */
export function trickle(options) {
    const layerRepeat = options?.layerRepeat ?? DEFAULT_LAYER_REPEAT;
    const maxChildrenPerNode = options?.maxChildrenPerNode ?? DEFAULT_MAX_CHILDREN_PER_NODE;
    return async function trickleLayout(source, reduce) {
        const root = new Root(layerRepeat);
        let iteration = 0;
        let maxDepth = 1;
        let subTree = root;
        for await (const layer of batch(source, maxChildrenPerNode)) {
            if (subTree.isFull()) {
                if (subTree !== root) {
                    root.addChild(await subTree.reduce(reduce));
                }
                if (iteration > 0 && iteration % layerRepeat === 0) {
                    maxDepth++;
                }
                subTree = new SubTree(maxDepth, layerRepeat, iteration);
                iteration++;
            }
            subTree.append(layer);
        }
        if (subTree != null && subTree !== root) {
            root.addChild(await subTree.reduce(reduce));
        }
        return await root.reduce(reduce);
    };
}
class SubTree {
    constructor(maxDepth, layerRepeat, iteration = 0) {
        this.maxDepth = maxDepth;
        this.layerRepeat = layerRepeat;
        this.currentDepth = 1;
        this.iteration = iteration;
        this.root = this.node = this.parent = {
            children: [],
            depth: this.currentDepth,
            maxDepth,
            maxChildren: (this.maxDepth - this.currentDepth) * this.layerRepeat
        };
    }
    isFull() {
        if (this.root.data == null) {
            return false;
        }
        if (this.currentDepth < this.maxDepth && this.node.maxChildren > 0) {
            // can descend
            this._addNextNodeToParent(this.node);
            return false;
        }
        // try to find new node from node.parent
        const distantRelative = this._findParent(this.node, this.currentDepth);
        if (distantRelative != null) {
            this._addNextNodeToParent(distantRelative);
            return false;
        }
        return true;
    }
    _addNextNodeToParent(parent) {
        this.parent = parent;
        // find site for new node
        const nextNode = {
            children: [],
            depth: parent.depth + 1,
            parent,
            maxDepth: this.maxDepth,
            maxChildren: Math.floor(parent.children.length / this.layerRepeat) * this.layerRepeat
        };
        // @ts-expect-error
        parent.children.push(nextNode);
        this.currentDepth = nextNode.depth;
        this.node = nextNode;
    }
    append(layer) {
        this.node.data = layer;
    }
    async reduce(reduce) {
        return await this._reduce(this.root, reduce);
    }
    async _reduce(node, reduce) {
        let children = [];
        if (node.children.length > 0) {
            children = await Promise.all(node.children
                // @ts-expect-error
                .filter(child => child.data)
                // @ts-expect-error
                .map(async (child) => await this._reduce(child, reduce)));
        }
        return await reduce((node.data ?? []).concat(children));
    }
    _findParent(node, depth) {
        const parent = node.parent;
        if (parent == null || parent.depth === 0) {
            return;
        }
        if (parent.children.length === parent.maxChildren || parent.maxChildren === 0) {
            // this layer is full, may be able to traverse to a different branch
            return this._findParent(parent, depth);
        }
        return parent;
    }
}
class Root extends SubTree {
    constructor(layerRepeat) {
        super(0, layerRepeat);
        this.root.depth = 0;
        this.currentDepth = 1;
    }
    addChild(child) {
        this.root.children.push(child);
    }
    async reduce(reduce) {
        return await reduce((this.root.data ?? []).concat(this.root.children));
    }
}
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