cids

What is cids?

The 'cids' npm package is used for handling Content Identifiers (CIDs) in the context of IPFS (InterPlanetary File System). CIDs are a fundamental part of IPFS, allowing for unique identification of content based on its cryptographic hash. This package provides utilities for creating, parsing, and working with CIDs.

What are cids's main functionalities?

Creating a CID

This feature allows you to create a new CID instance. The constructor takes the version, codec, and multihash as parameters. The example demonstrates creating a CID of version 1 with the 'dag-pb' codec.

const CID = require('cids');
const cid = new CID(1, 'dag-pb', Buffer.from('1220...'));
console.log(cid.toString());

Parsing a CID

This feature allows you to parse an existing CID string. The example shows how to parse a CID and access its version property.

const CID = require('cids');
const cid = new CID('Qm...');
console.log(cid.version);

Converting CID to different formats

This feature allows you to convert a CID to different versions. The example demonstrates converting a CID to version 1 and then converting it to a string.

const CID = require('cids');
const cid = new CID('Qm...');
console.log(cid.toV1().toString());

Other packages similar to cids

multihashes

The 'multihashes' package provides utilities for working with multihashes, which are a key component of CIDs. While 'cids' focuses on the entire CID structure, 'multihashes' is more specialized in handling the multihash part of CIDs.

multibase

The 'multibase' package is used for encoding and decoding data in various base encodings. CIDs often use multibase for encoding their string representations. This package is more focused on the encoding aspect, whereas 'cids' handles the entire CID structure.

ipld

The 'ipld' package provides tools for working with InterPlanetary Linked Data (IPLD), which is the data model used by IPFS. While 'cids' is specifically for handling CIDs, 'ipld' provides a broader set of tools for working with the data structures that CIDs point to.

README

js-cid

CID implementation in JavaScript.

Lead Maintainer

Volker Mische

Table of Contents

• Install
• Usage
• API
• Contribute
• License

Install

In Node.js through npm

$ npm install --save cids

Browser: Browserify, Webpack, other bundlers

The code published to npm that gets loaded on require is in fact an ES5 transpiled version with the right shims added. This means that you can require it and use with your favourite bundler without having to adjust asset management process.

const CID = require('cids')

In the Browser through <script> tag

Loading this module through a script tag will make the Cids obj available in the global namespace.

<script src="https://unpkg.com/cids/dist/index.min.js"></script>
<!-- OR -->
<script src="https://unpkg.com/cids/dist/index.js"></script>

Gotchas

You will need to use Node.js Buffer API compatible, if you are running inside the browser, you can access it by multihash.Buffer or you can install Feross's Buffer.

Usage

You can create an instance from a CID string or CID Buffer

const CID = require('cids')

const cid = new CID('bafybeig6xv5nwphfmvcnektpnojts33jqcuam7bmye2pb54adnrtccjlsu')

cid.version       // 1
cid.codec         // 'dag-pb'
cid.multibaseName // 'base32'
cid.toString()
// 'bafybeig6xv5nwphfmvcnektpnojts33jqcuam7bmye2pb54adnrtccjlsu'

or by specifying the cid version, multicodec name and multihash:

const CID = require('cids')
const multihashing = require('multihashing-async')

const hash = await multihashing(Buffer.from('OMG!'), 'sha2-256')
const cid = new CID(1, 'dag-pb', hash)
console.log(cid.toString())
// bafybeig6xv5nwphfmvcnektpnojts33jqcuam7bmye2pb54adnrtccjlsu

The string form of v1 CIDs defaults to base32 encoding (v0 CIDs are always base58btc encoded). When creating a new instance you can optionally specify the default multibase to use when calling toBaseEncodedString() or toString()

const cid = new CID(1, 'raw', hash, 'base64')
console.log(cid.toString())
// mAXASIN69ets85WVE0ipva5M5b2mAqAZ8LME08PeAG2MxCSuV

If you construct an instance from a valid CID string, the base you provided will be preserved as the default.

// e.g. a base64url encoded CID
const cid = new CID('uAXASIHJSUj5lkfuP5VPWf_VahvhARLRqPkF24QxY-lKaSqvV')
cid.toString()
// uAXASIHJSUj5lkfuP5VPWf_VahvhARLRqPkF24QxY-lKaSqvV

API

CID.isCID(cid)

Returns true if object is a valid CID instance, false if not valid.

It's important to use this method rather than instanceof checks in order to handle CID objects from different versions of this module.

CID.validateCID(cid)

Validates the different components (version, codec, multihash, multibaseName) of the CID instance. Throws an Error if not valid.

new CID(version, codec, multihash, [multibaseName])

version must be either 0 or 1.

codec must be a string of a valid registered codec.

multihash must be a Buffer instance of a valid multihash.

multibaseName optional string. Must be a valid multibase name. Default is base58btc for v0 CIDs or base32 for v1 CIDs.

new CID(baseEncodedString)

Additionally, you can instantiate an instance from a base encoded string.

new CID(Buffer)

Additionally, you can instantiate an instance from a buffer.

cid.codec

Property containing the codec string.

cid.version

Property containing the CID version integer.

cid.multihash

Property containing the multihash buffer.

cid.multibaseName

Property containing the default base to use when calling .toString

cid.buffer

Property containing the full CID encoded as a Buffer.

cid.prefix

Proprety containing a buffer of the CID version, codec, and the prefix section of the multihash.

cid.toV0()

Returns the CID encoded in version 0. Only works for dag-pb codecs.

Throws if codec is not dag-pb.

cid.toV1()

Returns the CID encoded in version 1.

cid.toBaseEncodedString(base=this.multibaseName)

Returns a base encoded string of the CID. Defaults to the base encoding in this.multibaseName.

The value of this.multibaseName depends on how the instance was constructed:

1. If the CID was constructed from an object that already had a multibase (a string or an existing CID) then it retains that base.
2. If the CID was constructed from an object that did not have a multibase (a buffer, or by passing only version + codec + multihash to the constructor), then multibaseName will be base58btc for a v0 CID or base32 for a v1 CID.

cid.toString(base=this.multibaseName)

Shorthand for cid.toBaseEncodedString described above.

cid.equals(cid)

Compare cid instance. Returns true if CID's are identical, false if otherwise.

Contribute

Contributions welcome. Please check out the issues.

Check out our contributing document for more information on how we work, and about contributing in general. Please be aware that all interactions related to multiformats are subject to the IPFS Code of Conduct.

Small note: If editing the Readme, please conform to the standard-readme specification.

License

MIT