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.
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());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.
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.
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.
CID implementation in JavaScript.
$ npm install --save cids
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')
<script> tagLoading 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>
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.
You can create an instance from a CID string or CID Buffer
const CID = require('cids')
const cid = new CID('zdj7WkRPAX9o9nb9zPbXzwG7JEs78uyhwbUs8JSUayB98DWWY')
cid.version // 1
cid.codec // 'dag-pb'
cid.multibaseName // 'base58btc'
cid.toString()
// 'zdj7WkRPAX9o9nb9zPbXzwG7JEs78uyhwbUs8JSUayB98DWWY'
or by specifying the cid version, multicodec name and multihash:
const CID = require('cids')
const multihashing = require('multihashing-async')
multihashing(Buffer.from('OMG!'), 'sha2-256', (err, hash) => {
const cid = new CID(1, 'dag-pb', hash)
console.log(cid.toString())
// zdj7WkRPAX9o9nb9zPbXzwG7JEs78uyhwbUs8JSUayB98DWWY
})
The string form of CIDs currently defaults to base58btc flavour. (This is soon to change to base32. 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, 'base32')
console.log(cid.toString())
// bafybeig6xv5nwphfmvcnektpnojts33jqcuam7bmye2pb54adnrtccjlsu
If you construct an instance from a valid CID string, the base you provided will be preserved as the default.
const cid = new CID('bafkreigh2akiscaildcqabsyg3dfr6chu3fgpregiymsck7e7aqa4s52zy')
cid.toString()
// bafkreigh2akiscaildcqabsyg3dfr6chu3fgpregiymsck7e7aqa4s52zy
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.
Validates the different components (version, codec, multihash, multibaseName) of the CID instance. Returns true if valid, false if not valid.
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.
Additionally, you can instantiate an instance from a base encoded string.
Additionally, you can instantiate an instance from a buffer.
Property containing the codec string.
Property containing the CID version integer.
Property containing the multihash buffer.
Property containing the default base to use when calling .toString
Property containing the full CID encoded as a Buffer.
Proprety containing a buffer of the CID version, codec, and the prefix section of the multihash.
Returns the CID encoded in version 0. Only works for dag-pb codecs.
Throws if codec is not dag-pb.
Returns the CID encoded in version 1.
Returns a base encodec string of the CID. Defaults to the base encoding in this.multibaseName
Shorthand for cid.toBaseEncodedString described above.
Compare cid instance. Returns true if CID's are identical, false if otherwise.
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.
MIT
0.6.0 (2019-04-08)
The default will change to base32 in https://github.com/multiformats/js-cid/pull/73/files
The idea behind this change is that we shouldnt lose information when the user passes us a base encoded string, but keep it and use it as the default base so toString returns the same string they provided.
I'd like this as a fix for ipld explorer, which currently forces all CIDs into base58btc, seee: https://github.com/ipfs-shipyard/ipfs-webui/issues/999
License: MIT Signed-off-by: Oli Evans oli@tableflip.io
<a name="0.5.8"></a>
FAQs
CID Implementation in JavaScript
The npm package cids receives a total of 274,465 weekly downloads. As such, cids popularity was classified as popular.
We found that cids demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 5 open source maintainers collaborating on the project.
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