260 lines
13 KiB
Markdown
260 lines
13 KiB
Markdown
# multiformats <!-- omit in toc -->
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[](http://multiformats.io)
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[](https://codecov.io/gh/multiformats/js-multiformats)
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[](https://github.com/multiformats/js-multiformats/actions/workflows/js-test-and-release.yml?query=branch%3Amaster)
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> Interface for multihash, multicodec, multibase and CID
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## Table of contents <!-- omit in toc -->
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- [Install](#install)
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- [Browser `<script>` tag](#browser-script-tag)
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- [Interfaces](#interfaces)
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- [Creating Blocks](#creating-blocks)
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- [Multibase Encoders / Decoders / Codecs](#multibase-encoders--decoders--codecs)
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- [Multicodec Encoders / Decoders / Codecs](#multicodec-encoders--decoders--codecs)
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- [Multihash Hashers](#multihash-hashers)
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- [Traversal](#traversal)
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- [Legacy interface](#legacy-interface)
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- [Implementations](#implementations)
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- [Multibase codecs](#multibase-codecs)
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- [Multihash hashers](#multihash-hashers-1)
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- [IPLD codecs (multicodec)](#ipld-codecs-multicodec)
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- [API Docs](#api-docs)
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- [License](#license)
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- [Contribution](#contribution)
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## Install
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```console
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$ npm i multiformats
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```
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### Browser `<script>` tag
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Loading this module through a script tag will make it's exports available as `Multiformats` in the global namespace.
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```html
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<script src="https://unpkg.com/multiformats/dist/index.min.js"></script>
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```
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## Interfaces
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This library defines common interfaces and low level building blocks for various interrelated multiformat technologies (multicodec, multihash, multibase, and CID). They can be used to implement custom base encoders / decoders / codecs, codec encoders /decoders and multihash hashers that comply to the interface that layers above assume.
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This library provides implementations for most basics and many others can be found in linked repositories.
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```js
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import { CID } from 'multiformats/cid'
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import * as json from 'multiformats/codecs/json'
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import { sha256 } from 'multiformats/hashes/sha2'
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const bytes = json.encode({ hello: 'world' })
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const hash = await sha256.digest(bytes)
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const cid = CID.create(1, json.code, hash)
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//> CID(bagaaierasords4njcts6vs7qvdjfcvgnume4hqohf65zsfguprqphs3icwea)
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```
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### Creating Blocks
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```js
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import * as Block from 'multiformats/block'
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import * as codec from '@ipld/dag-cbor'
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import { sha256 as hasher } from 'multiformats/hashes/sha2'
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const value = { hello: 'world' }
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// encode a block
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let block = await Block.encode({ value, codec, hasher })
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block.value // { hello: 'world' }
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block.bytes // Uint8Array
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block.cid // CID() w/ sha2-256 hash address and dag-cbor codec
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// you can also decode blocks from their binary state
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block = await Block.decode({ bytes: block.bytes, codec, hasher })
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// if you have the cid you can also verify the hash on decode
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block = await Block.create({ bytes: block.bytes, cid: block.cid, codec, hasher })
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```
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### Multibase Encoders / Decoders / Codecs
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CIDs can be serialized to string representation using multibase encoders that implement [`MultibaseEncoder`](https://github.com/multiformats/js-multiformats/blob/master/src/bases/interface.ts) interface. This library provides quite a few implementations that can be imported:
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```js
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import { base64 } from "multiformats/bases/base64"
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cid.toString(base64.encoder)
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//> 'mAYAEEiCTojlxqRTl6svwqNJRVM2jCcPBxy+7mRTUfGDzy2gViA'
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```
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Parsing CID string serialized CIDs requires multibase decoder that implements [`MultibaseDecoder`](https://github.com/multiformats/js-multiformats/blob/master/src/bases/interface.ts) interface. This library provides a decoder for every encoder it provides:
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```js
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CID.parse('mAYAEEiCTojlxqRTl6svwqNJRVM2jCcPBxy+7mRTUfGDzy2gViA', base64.decoder)
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//> CID(bagaaierasords4njcts6vs7qvdjfcvgnume4hqohf65zsfguprqphs3icwea)
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```
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Dual of multibase encoder & decoder is defined as multibase codec and it exposes
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them as `encoder` and `decoder` properties. For added convenience codecs also
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implement `MultibaseEncoder` and `MultibaseDecoder` interfaces so they could be
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used as either or both:
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```js
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cid.toString(base64)
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CID.parse(cid.toString(base64), base64)
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```
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**Note:** CID implementation comes bundled with `base32` and `base58btc`
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multibase codecs so that CIDs can be base serialized to (version specific)
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default base encoding and parsed without having to supply base encoders/decoders:
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```js
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const v1 = CID.parse('bagaaierasords4njcts6vs7qvdjfcvgnume4hqohf65zsfguprqphs3icwea')
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v1.toString()
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//> 'bagaaierasords4njcts6vs7qvdjfcvgnume4hqohf65zsfguprqphs3icwea'
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const v0 = CID.parse('QmdfTbBqBPQ7VNxZEYEj14VmRuZBkqFbiwReogJgS1zR1n')
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v0.toString()
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//> 'QmdfTbBqBPQ7VNxZEYEj14VmRuZBkqFbiwReogJgS1zR1n'
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v0.toV1().toString()
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//> 'bafybeihdwdcefgh4dqkjv67uzcmw7ojee6xedzdetojuzjevtenxquvyku'
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```
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### Multicodec Encoders / Decoders / Codecs
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This library defines [`BlockEncoder`, `BlockDecoder` and `BlockCodec` interfaces](https://github.com/multiformats/js-multiformats/blob/master/src/codecs/interface.ts).
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Codec implementations should conform to the `BlockCodec` interface which implements both `BlockEncoder` and `BlockDecoder`.
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Here is an example implementation of JSON `BlockCodec`.
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```js
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/**
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* @template T
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* @type {BlockCodec<0x0200, T>}
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*/
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export const { name, code, encode, decode } = {
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name: 'json',
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code: 0x0200,
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encode: json => new TextEncoder().encode(JSON.stringify(json)),
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decode: bytes => JSON.parse(new TextDecoder().decode(bytes))
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}
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```
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### Multihash Hashers
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This library defines [`MultihashHasher` and `MultihashDigest` interfaces](https://github.com/multiformats/js-multiformats/blob/master/src/hashes/interface.ts) and convinient function for implementing them:
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```js
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import * as hasher from 'multiformats/hashes/hasher'
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const sha256 = hasher.from({
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// As per multiformats table
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// https://github.com/multiformats/multicodec/blob/master/table.csv#L9
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name: 'sha2-256',
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code: 0x12,
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encode: (input) => new Uint8Array(crypto.createHash('sha256').update(input).digest())
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})
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const hash = await sha256.digest(json.encode({ hello: 'world' }))
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CID.create(1, json.code, hash)
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//> CID(bagaaierasords4njcts6vs7qvdjfcvgnume4hqohf65zsfguprqphs3icwea)
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```
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### Traversal
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This library contains higher-order functions for traversing graphs of data easily.
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`walk()` walks through the links in each block of a DAG calling a user-supplied loader function for each one, in depth-first order with no duplicate block visits. The loader should return a `Block` object and can be used to inspect and collect block ordering for a full DAG walk. The loader should `throw` on error, and return `null` if a block should be skipped by `walk()`.
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```js
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import { walk } from 'multiformats/traversal'
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import * as Block from 'multiformats/block'
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import * as codec from 'multiformats/codecs/json'
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import { sha256 as hasher } from 'multiformats/hashes/sha2'
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// build a DAG (a single block for this simple example)
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const value = { hello: 'world' }
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const block = await Block.encode({ value, codec, hasher })
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const { cid } = block
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console.log(cid)
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//> CID(bagaaierasords4njcts6vs7qvdjfcvgnume4hqohf65zsfguprqphs3icwea)
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// create a loader function that also collects CIDs of blocks in
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// their traversal order
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const load = (cid, blocks) => async (cid) => {
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// fetch a block using its cid
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// e.g.: const block = await fetchBlockByCID(cid)
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blocks.push(cid)
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return block
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}
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// collect blocks in this DAG starting from the root `cid`
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const blocks = []
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await walk({ cid, load: load(cid, blocks) })
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console.log(blocks)
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//> [CID(bagaaierasords4njcts6vs7qvdjfcvgnume4hqohf65zsfguprqphs3icwea)]
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```
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## Legacy interface
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[`blockcodec-to-ipld-format`](https://github.com/ipld/js-blockcodec-to-ipld-format) converts a multiformats [`BlockCodec`](https://github.com/multiformats/js-multiformats/blob/master/src/codecs/interface.ts#L21) into an
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[`interface-ipld-format`](https://github.com/ipld/interface-ipld-format) for use with the [`ipld`](https://github.com/ipld/ipld) package. This can help bridge IPLD codecs implemented using the structure and interfaces defined here to existing code that assumes, or requires `interface-ipld-format`. This bridge also includes the relevant TypeScript definitions.
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## Implementations
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By default, no base encodings (other than base32 & base58btc), hash functions,
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or codec implementations are exposed by `multiformats`, you need to
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import the ones you need yourself.
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### Multibase codecs
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| bases | import | repo |
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| ------------------------------------------------------------- | --------------------------- | ------------------------------------------------------------------------------------------------- |
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| `base16` | `multiformats/bases/base16` | [multiformats/js-multiformats](https://github.com/multiformats/js-multiformats/tree/master/bases) |
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| `base32`, `base32pad`, `base32hex`, `base32hexpad`, `base32z` | `multiformats/bases/base32` | [multiformats/js-multiformats](https://github.com/multiformats/js-multiformats/tree/master/bases) |
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| `base64`, `base64pad`, `base64url`, `base64urlpad` | `multiformats/bases/base64` | [multiformats/js-multiformats](https://github.com/multiformats/js-multiformats/tree/master/bases) |
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| `base58btc`, `base58flick4` | `multiformats/bases/base58` | [multiformats/js-multiformats](https://github.com/multiformats/js-multiformats/tree/master/bases) |
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Other (less useful) bases implemented in [multiformats/js-multiformats](https://github.com/multiformats/js-multiformats/tree/master/bases) include: `base2`, `base8`, `base10`, `base36` and `base256emoji`.
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### Multihash hashers
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| hashes | import | repo |
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| ------------------------------------------------------------------------------------------------------------------------------- | ------------------------------ | ------------------------------------------------------------------------------------------------------------------ |
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| `sha2-256`, `sha2-512` | `multiformats/hashes/sha2` | [multiformats/js-multiformats](https://github.com/multiformats/js-multiformats/tree/master/src/hashes) |
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| `sha3-224`, `sha3-256`, `sha3-384`,`sha3-512`, `shake-128`, `shake-256`, `keccak-224`, `keccak-256`, `keccak-384`, `keccak-512` | `@multiformats/sha3` | [multiformats/js-sha3](https://github.com/multiformats/js-sha3) |
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| `identity` | `multiformats/hashes/identity` | [multiformats/js-multiformats](https://github.com/multiformats/js-multiformats/tree/master/src/hashes/identity.js) |
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| `murmur3-128`, `murmur3-32` | `@multiformats/murmur3` | [multiformats/js-murmur3](https://github.com/multiformats/js-murmur3) |
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| `blake2b-*`, `blake2s-*` | `@multiformats/blake2` | [multiformats/js-blake2](https://github.com/multiformats/js-blake2) |
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### IPLD codecs (multicodec)
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| codec | import | repo |
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| ---------- | -------------------------- | ------------------------------------------------------------------------------------------------------ |
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| `raw` | `multiformats/codecs/raw` | [multiformats/js-multiformats](https://github.com/multiformats/js-multiformats/tree/master/src/codecs) |
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| `json` | `multiformats/codecs/json` | [multiformats/js-multiformats](https://github.com/multiformats/js-multiformats/tree/master/src/codecs) |
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| `dag-cbor` | `@ipld/dag-cbor` | [ipld/js-dag-cbor](https://github.com/ipld/js-dag-cbor) |
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| `dag-json` | `@ipld/dag-json` | [ipld/js-dag-json](https://github.com/ipld/js-dag-json) |
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| `dag-pb` | `@ipld/dag-pb` | [ipld/js-dag-pb](https://github.com/ipld/js-dag-pb) |
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| `dag-jose` | `dag-jose` | [ceramicnetwork/js-dag-jose](https://github.com/ceramicnetwork/js-dag-jose) |
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## API Docs
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- <https://multiformats.github.io/js-multiformats>
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## License
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Licensed under either of
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- Apache 2.0, ([LICENSE-APACHE](LICENSE-APACHE) / <http://www.apache.org/licenses/LICENSE-2.0>)
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- MIT ([LICENSE-MIT](LICENSE-MIT) / <http://opensource.org/licenses/MIT>)
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## Contribution
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Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.
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