Crate wnfs

The crate implements the Web Native File System (WNFS) version 2.

The Web Native File System is a file system written for the web. It is versioned, logged, programmable, has strong-yet-flexible security, and is fully controlled by the end user. Service providers can validate writes without reading the contents of the file system, and minimal metadata is leaked.

This implementation is based off of the typescript implementation but designed with immutability in mind.

Let’s see an example of working with a public filesystem. We will use the in-memory block store provided by the library.

use anyhow::Result;
use chrono::Utc;
use wnfs::{
    common::{MemoryBlockStore, Storable},
    public::PublicDirectory,
};

#[async_std::main]
async fn main() -> Result<()> {
    // Create a new public directory.
    let dir = &mut PublicDirectory::new_rc(Utc::now());

    // Create an in-memory block store.
    let store = &MemoryBlockStore::new();

    // Add a /pictures/cats subdirectory.
    dir.mkdir(&["pictures".into(), "cats".into()], Utc::now(), store)
        .await?;

    // Store the the file tree in the in-memory block store.
    dir.store(store).await?;

    // List all files in /pictures directory.
    let result = dir.ls(&["pictures".into()], store).await?;

    println!("Files in /pictures: {:#?}", result);

    Ok(())
}

Here we create a root directory dir and subsequently add a /pictures/cats subdirectory to it. As mentioned earlier, system-level operations like time are passed in from the API. In this case, we use the Utc::now() function from the [chrono][chrono-crate] crate to get the current time.

PublicDirectory gets wrapped in Rc here because it lets us pass it around without worrying about ownership and lifetimes. Making the Rc &mut futher allows us to relinquish ownership to the interior PublicDirectory and point to a new one when needed (essentially for every write). This immutable way of handling changes has cool benefits like tracking and rolling back changes. It also makes collaborative editing easier to implement and reason about. You can find more examples in the wnfs/examples/ folder.

That’s the public filesystem, the private filesystem, on the other hand, is a bit more involved. The Hash Array Mapped Trie (HAMT) is where we store the private filesystem tree and some other information related to it. HAMT allows for effective storage and retrieval of encrypted and obfuscated filesystem trees and PrivateForest is basically a HAMT that can contain multiple file trees with hash for keys and CIDs for values.

use anyhow::Result;
use chrono::Utc;
use rand_chacha::ChaCha12Rng;
use rand_core::SeedableRng;
use wnfs::{
    common::MemoryBlockStore,
    private::{
        PrivateDirectory,
        forest::{hamt::HamtForest, traits::PrivateForest},
    }
};

#[async_std::main]
async fn main() -> Result<()> {
    // Create an in-memory block store.
    let store = &MemoryBlockStore::default();

    // A random number generator.
    let rng = &mut ChaCha12Rng::from_entropy();

    // Create a private forest.
    let forest = &mut HamtForest::new_trusted_rc(rng);

    // Create a new private directory.
    let dir = &mut PrivateDirectory::new_rc(&forest.empty_name(), Utc::now(), rng);

    // Add a file to /pictures/cats directory.
    dir.mkdir(
        &["pictures".into(), "cats".into()],
        true,
        Utc::now(),
        forest,
        store,
        rng,
    )
    .await?;

    // Add a file to /pictures/dogs/billie.jpg file.
    dir.write(
        &["pictures".into(), "dogs".into(), "billie.jpg".into()],
        true,
        Utc::now(),
        b"Hello! This is billie".to_vec(),
        forest,
        store,
        rng,
    )
    .await?;

    // List all files in /pictures directory.
    let result = dir.ls(&["pictures".into()], true, forest, store).await?;

    println!("Files in /pictures: {:#?}", result);

    Ok(())
}

This example introduces a few new concepts. The first is the HamtForest which is a HAMT that can contain multiple file trees and implements the PrivateForest interface needed for persisting private file systems.

The second is the Name (returned from forest.empty_name()) and NameAccumulator that lets us identify nodes in the filesystem, and are suitable for offspring proving.

Finally, we have the random number generator, rng, that the library uses for generating new keys and other random values needed for the protocol.

Check the wnfs/examples/ folder for more examples.

Modules

common

Re-exports of wnfs-common lib.

error

WNFS Errors

hamt

Re-exports of wnfs-hamt lib.

nameaccumulator

Re-exports of wnfs-nameaccumulator lib.

private

Primitives for working with the private file system.

public

Primitives for working with the public file system.

rand_core

Re-exports of rand-core lib.

traits

Constants

WNFS_VERSION

The version of the WNFS data format that this library outputs

Functions

get_wnfs_version_req

The WNFS data format version requirement for this version of the library

is_readable_wnfs_version

Whether given WNFS data format version can be read by this library