ipfs-uniform-resolve

Resolve CIDs into data using a well-defined method, that works across both UnixFS and "regular" node types.

import Resolve from "ipfs-uniform-resolve";

const resolver = Resolve(blockApi, nameApi);
const cid = await resolver.resolveIpns(ipnsCid);
const { value, block, cid: finalCid } = await resolver.resolve(cid, "/dir/file.json/key/0");

console.log(value);

Resolution Algorithm

Starting from a CID pointing at a block, and given a path, resolve(cid, path) will dereference the CID to the block, and then follow each path segment in the path, dereferencing CIDs along the way if necessary.

If resolve() hits a DAG-PB (UnixFS) node, path segments will be treated as UnixFS path segments, i.e. /foo will actually be node.Links[foo].

If resolve() hits a regular (non DAG-PB) block, path segments will correspond directly to object entries, i.e. /a/b/0 will be node.a.b[0].

CIDs in regular (non DAG-PB) block are detected if:

• The node is a string, and CID.parse() succeeds
• The node is an object, and CID.asCID() succeeds

CID in this case being the definition in the multiformats package.

CIDs will be automatically dereferenced, if needed.

API

The library default exports a factory function that returns the library instance:

Resolver(block, name, multidecoder)

• block and name are object that implement the Block and Name API of the IPFS Core interface, respectively
• multidecoder is an optional parameter to which you can either pass { decoders, hashers }, or a Multidecoder implementation.

The resulting object contains two functions:

async resolveIpns(cid: CID | string, timeout?: number): Promise<CID>

Resolves a CID as if it were an IPNS link until it resolves into a regular block CID. The function will throw if given an invalid CID, or if resolution otherwise fails.

const cid = await resolver.resolveIpns("ipfs.io");

async resolve(cid: CID, path: string = "/", options?)

Resolve an IPLD value starting from a CID, following a path. The algorithm with which it does this is defined here.

options is an object which affects the particular behaviour of the resolution:

• options.followPb - Whether or not to follow path across DAG-PB nodes. Defaults to true
• options.followIpld - Whether or not to follow path across non-DAG-PB (regular) nodes. Defaults to true

Will throw TypeError if the passed CID has a codec of libp2p-key (0x72). Currently, this is treated as only being used for IPNS. Please submit a bug report if you have a different use case.

Will throw DeadEndError if resolution can't move forward because of a missing object entry. The error contains cid, at, and remaining properties which point to which block/path the error happened.

const { value, cid, block } =  await resolver.resolve(cid, path, { followIpld: false });