multiformat-multicodec
v1.0.0
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An interface for (de)encoding a wide range of multicodecs simultaneously
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multiformat-multicodec
An interface for encoding/decoding across multiple multiformat BlockEncoders, BlockDecoders, BlockCodecs, and Hashers.
This interface lets library authors expose a dynamic dependency injection system to their users, so as to not be locked into any particular suite of codecs/hashers -- much like the IPFS modular interfaces. The library also provides a default trivial implementation of the interfaces.
If you need to decode blocks which may come encoded using many different codecs, or need your library users to give you the codecs and hashers they want you to use, this is probably what you're looking for.
Interfaces
The library exports three interfaces which encapsulate the notion of (de)encoding for given codec and hasher codes:
Multidecoder
is an interface that can decode using multiple decoders/hashers:
interface Multidecoder {
addDecoder(decoder: BlockDecoder): void;
addHasher(hasher: Hasher): void;
decode(opts: {
codec: number;
hasher: number;
bytes: ByteView<T>;
}): Promise<Block<T>>;
}
Multiencoder
is its dual, and can encode using multiple encoders/hashers (you pick which one):
interface Multiencoder {
addEncoder(encoder: BlockEncoder): void;
addHasher(hasher: Hasher): void;
encode(opts: { codec: number; hasher: number; value: T }): Promise<Block<T>>;
}
If you need both interfaces simultaneously, the Multicodec
interface simply extends the two:
interface Multicodec extends Multidecoder, Multiencoder {}
Implementation
The library also exports a default implementation of Multicodec
, called
BlockMulticodec
. By default, it already has sha256
hasher support. It has an
extra method addCodec()
which isn't in the Multicodec
interface.
import { BlockMulticodec, Multidecoder } from "multiformat-multicodec";
import { CID } from "multiformats";
import * as json from "@ipld/dag-json";
import * as cbor from "@ipld/dag-cbor";
import * as pb from "@ipld/dag-pb";
const multidecoder = new BlockMulticodec<any>({
codecs: [json, cbor, pb],
});
const cid = CID.parse("QmQy6xmJhrcC5QLboAcGFcAE1tC8CrwDVkrHdEYJkLscrQ");
await multidecoder.decode({
codec: cid.code,
hasher: cid.multihash.code,
block.get(cid),
});