cid

Description:

cid

cid #
A dart implementation of
cid ("content id") = human-friendly
(readable/typeable) unique ID for distributed/decentralised systems.
Why 🤷 #
In a database that is distributed,
creating IDs that reference records
with virtually no risk of collision is a must.
We need a standardized way of creating
IDs for both the server and the client-side
of our app,
in an offline-first approach.
As we are using Flutter for developing
our application, we needed a way to create
these IDs using the Dart language.
What? 🔐 #
If you are a newbie when it comes to
cids and how they are applicable
to distributed scenarios,
we highly encourage you
to check the dwyl/cid
repo.
Although it was made for Elixir,
you can find more about real-life situations
of how these are used,
especially with IPFS.
And yes, it will answer the
obvious question of
Why are you not using UUIDs? 😉
How? 💡 #
Using this package is as easy as pie.
You just need an input string that will
be hashed and used to create a corresponding cid.
This cid will be, as the name implies,
the content identifier -
something that will identify that string.
Let's see it in action.
Installing #
Add the following to your
pubspec.yaml file, under dependencies.
dependencies:
cid: ^1.0.0
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and run the following command
to fetch the dependencies.
flutter pub get
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Usage #
Creating a CID #
Now just call the createCid() function!
You may decide what
multibase
you want to use.
This library tries to support the official/default bases.
If you see one that's missing,
do open
an issue.
import 'package:cid/cid.dart';

String input = 'hello world';
CIDInfo output = CID.createCid(input, Multibase.base58btc);

print(output.cid)
// "zb2rhj7crUKTQYRGCRATFaQ6YFLTde2YzdqbbhAASkL9uRDXn"
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and you're done! 🎉
You just created your own fancy cid!

Note
Every cid generated with this
package will use the raw codec
and will be hashed using the sha2-258
algorithm.
You may choose which base you want to encode it as, though.

Decoding a CID #
If you're given a CID and you wish to decode it,
you can use the decodeCid() function.
CIDInfo cidInfo = decodeCid("some_cid");
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This function will return an instance of CIDInfo,
holding relevant information of the provided CID.
Converting CIDv0 to CIDv1 #
If you've decoded a CIDv0 string,
you can convert it to a CIDv1 object by calling toV1().
This function can receive a multibase parameter if you wish to encode
it in a different base (e.g. toV1(Multibase.base58btc)).
By default, it is encoded to base32.
// Decode a v0 cid.
CIDInfo cidInfo = decodeCid("QmcRD4wkPPi6dig81r5sLj9Zm1gDCL4zgpEj9CfuRrGbzF");

// Convert it to v1
cidInfo.toV1();
print(cidInfo.cid)
// "bafybeigrf2dwtpjkiovnigysyto3d55opf6qkdikx6d65onrqnfzwgdkfa"

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Considerations #
If you're interested in learning more about a given CID's components...
zb2rhj7crUKTQYRGCRATFaQ6YFLTde2YzdqbbhAASkL9uRDXn
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...you can use the
IPFS cid inspector
to see the information that is
hashed into the string.
Open https://cid.ipfs.tech/#zb2rhj7crUKTQYRGCRATFaQ6YFLTde2YzdqbbhAASkL9uRDXn
and see it for yourself!

As you can see,
the cid contains leading identifiers
that clarify which representation is used,
along with the content-hash.
It includes:

multibase
prefix which specifies the encoding of the cid.
cid version
multicodec
which indicates the format of the target content.


For more information about the
format of cids,
check this link ->
https://docs.ipfs.tech/concepts/content-addressing/#cid-versions

I need help! ❓ #
If you have some feedback
or have any question,
do not hesitate and
open an issue!
We are here to help and are
happy for your contribution!
License #
MIT