Dartus

Dartus is a Dart/Flutter SDK for Walrus decentralized blob storage. It provides three operational modes — from simple HTTP uploads to full client-side erasure coding with wallet-signed transactions.

SDK Overview

Dartus supports three modes, each building on the previous:

Mode	Class	Who Pays	Dependencies	Use Case
HTTP	`WalrusClient`	Publisher operator (SUI+WAL)	None (HTTP only)	Simple apps, server-side
Relay	`WalrusDirectClient` + upload relay	User's wallet	`sui` package	dApps with wallet signing
Direct	`WalrusDirectClient`	User's wallet	`sui` + Rust FFI	Full control, best performance

HTTP mode sends blobs to a publisher/aggregator over HTTP. The publisher operator covers storage costs. This is the simplest integration — no wallet required.

Relay mode encodes blobs via an upload relay server, then the user signs the Sui transaction with their wallet. The user pays storage costs directly.

Direct mode performs client-side erasure coding using Rust FFI (libwalrus_ffi), writes slivers directly to storage nodes, and builds/signs Sui transactions. This gives full control and the best performance but requires the native library.

Features

HTTP uploads: putBlob, putBlobFromFile, putBlobStreaming
HTTP downloads: getBlob, getBlobByObjectId, getBlobAsFile with automatic disk caching
Direct reads: readBlob, getSlivers, getBlobMetadata, getVerifiedBlobStatus from storage nodes
Direct writes: writeBlob, writeFiles, writeQuilt with client-side encoding
Step-by-step flows: WriteBlobFlow, WriteFilesFlow for dApp wallet integration (encode → register → upload → certify)
Quilt support: Pack multiple files into a single blob with encodeQuilt / QuiltReader
File abstractions: WalrusFile, WalrusBlob with .bytes(), .text(), .json(), .files()
Upload relay: UploadRelayClient with configurable tip strategies (const/linear)
On-chain ops: registerBlobTransaction, certifyBlobTransaction, deleteBlobTransaction
On-chain reads: getOwnedBlobs, getBlobObjectInfo, readBlobAttributes, writeBlobAttributes
Storage costs: storageCost(size, epochs) for cost estimation
Error hierarchy: 18+ typed errors with retry semantics (RetryableWalrusClientError)
Caching: Disk-based LRU cache with SHA-256 filenames, configurable size limits
Auth: JWT support via instance-level or per-call tokens
TLS: Configurable certificate validation
Logging: Six-level structured logging (none, error, warning, info, debug, verbose) with custom handler support
Network presets: WalrusNetwork.testnet / WalrusNetwork.mainnet with pre-configured package IDs
BLS12-381: Cryptographic operations via bls_dart

Installation

Add Dartus to your pubspec.yaml:

dependencies:
  dartus: ^0.2.0

For direct mode (wallet-signed transactions), also add the Sui SDK:

dependencies:
  dartus: ^0.2.0
  sui: ^0.3.7

Then install:

dart pub get  # or: flutter pub get

Native library setup (direct mode only)

Direct mode requires libwalrus_ffi for client-side erasure coding. Build it from the included Rust crate:

# Prerequisites: Rust toolchain (https://rustup.rs)
cd Dartus/native
./build.sh release

The library loads automatically from standard paths. To override the search:

export WALRUS_FFI_LIB=/path/to/libwalrus_ffi.dylib

Without the native library, the encoder falls back to a pure-Dart implementation. The fallback works for testing but produces incompatible blob IDs — the upload relay and storage nodes will reject uploads encoded with it.

Quick Start — HTTP Mode

import 'package:dartus/dartus.dart';
import 'dart:io';

void main() async {
  final client = WalrusClient(
    publisherBaseUrl: Uri.parse('https://publisher.walrus-testnet.walrus.space'),
    aggregatorBaseUrl: Uri.parse('https://aggregator.walrus-testnet.walrus.space'),
    useSecureConnection: true,
  );

  // Upload
  final imageBytes = await File('photo.png').readAsBytes();
  final response = await client.putBlob(data: imageBytes);
  final blobId = response['newlyCreated']?['blobObject']?['blobId']
      ?? response['alreadyCertified']?['blobId'];
  print('Uploaded: $blobId');

  // Download (cached automatically on subsequent calls)
  final data = await client.getBlob(blobId);
  print('Downloaded ${data.length} bytes');

  await client.close();
}

Quick Start — Direct Mode

import 'package:dartus/dartus.dart';
import 'package:sui/sui.dart';

void main() async {
  // Create a direct client from a network preset
  final client = WalrusDirectClient.fromNetwork(
    network: WalrusNetwork.testnet,
  );

  // Read a blob by its base64 blob ID
  final data = await client.readBlob(blobId: 'wAtcbEtCYyCX2gPcAv6z...');
  print('Read ${data.length} bytes');

  // Or get a high-level WalrusBlob handle
  final blob = await client.getBlob(blobId: 'wAtcbEtCYyCX2gPcAv6z...');
  final file = await blob.asFile();
  print('File: ${await file.text()}');

  client.close();
}

Writing Blobs (Direct Mode)

Simple write

final signer = SuiAccount.fromMnemonics(mnemonics, SignatureScheme.Ed25519);

final result = await client.writeBlob(
  blob: utf8.encode('Hello Walrus!'),
  epochs: 3,
  signer: signer,
  deletable: true,
);

print('Blob ID: ${result.blobId}');
print('Object ID: ${result.blobObjectId}');

Step-by-step flow (for dApp wallets)

When the signer is a browser wallet, use the flow API to separate encoding from signing:

// 1. Encode (no wallet needed)
final flow = await client.writeBlobFlow(
  blob: utf8.encode('Hello Walrus!'),
);
await flow.encode();

// 2. Register (returns a Transaction for wallet signing)
final registerTx = flow.register(WriteBlobFlowRegisterOptions(
  epochs: 3,
  signer: walletAddress,
  deletable: true,
));
// Sign & execute registerTx with the user's wallet...

// 3. Upload slivers to storage nodes
await flow.upload(WriteBlobFlowUploadOptions(
  registerResult: registerResult,
));

// 4. Certify (returns a Transaction for wallet signing)
final certifyTx = flow.certify();
// Sign & execute certifyTx...

Writing Files & Quilts

Pack multiple files into a single quilt blob:

final files = [
  WalrusFile.from(utf8.encode('Hello'), identifier: 'hello.txt'),
  WalrusFile.from(utf8.encode('World'), identifier: 'world.txt'),
];

final results = await client.writeFiles(
  files: files,
  epochs: 3,
  signer: signer,
  deletable: true,
);

for (final r in results) {
  print('${r.identifier}: blobId=${r.blobId}');
}

Read a quilt:

final blob = await client.getBlob(blobId: quiltBlobId);
final files = await blob.files();
for (final file in files) {
  final name = await file.getIdentifier();
  final text = await file.text();
  print('$name: $text');
}

Upload Relay

Use an upload relay when you want the server to handle erasure coding but the user to pay:

final client = WalrusDirectClient.fromNetwork(
  network: WalrusNetwork.testnet,
  // Upload relay is auto-configured for testnet.
  // To override or add a max tip:
  uploadRelay: UploadRelayConfig(
    host: 'https://upload-relay.testnet.walrus.space',
    maxTip: BigInt.from(1000), // max tip in MIST
  ),
);

Error Handling

Dartus provides a typed error hierarchy matching the TS SDK:

try {
  final data = await client.readBlob(blobId: blobId);
} on BlobNotCertifiedError {
  print('Blob was registered but never certified by storage nodes');
} on NotEnoughSliversReceivedError {
  // Retryable — reset cached state and retry
  client.reset();
  final data = await client.readBlob(blobId: blobId);
} on BehindCurrentEpochError {
  client.reset(); // Refresh epoch state, then retry
} on StorageNodeConnectionError catch (e) {
  print('Storage node unreachable: $e');
} on WalrusClientError catch (e) {
  print('Client error: $e');
}

Retryable errors extend RetryableWalrusClientError. After catching one, call client.reset() to refresh cached committee/epoch state, then retry.

Error Classes

Error	Retryable	Description
`WalrusClientError`	—	Base error class
`RetryableWalrusClientError`	Yes	Base retryable error
`NoBlobMetadataReceivedError`	Yes	No metadata from any node
`NotEnoughSliversReceivedError`	Yes	Insufficient slivers for decoding
`NotEnoughBlobConfirmationsError`	Yes	Insufficient write confirmations
`BehindCurrentEpochError`	Yes	Client behind current epoch
`BlobNotCertifiedError`	Yes	Blob not yet certified
`NoBlobStatusReceivedError`	No	No storage node returned status
`InconsistentBlobError`	No	Blob encoded incorrectly
`InsufficientWalBalanceError`	No	Not enough WAL tokens
`BlobBlockedError`	No	Blob blocked by quorum
`StorageNodeApiError`	—	Base storage-node HTTP error
`BadRequestError`	No	400 — malformed request
`NotFoundError`	No	404 — blob/sliver not found
`AuthenticationError`	No	401/403 — auth failure
`RateLimitError`	Yes	429 — rate limited
`InternalServerError`	Yes	500 — storage-node error

API Reference

`WalrusClient` (HTTP Mode)

WalrusClient({
  required Uri publisherBaseUrl,
  required Uri aggregatorBaseUrl,
  Duration timeout = const Duration(seconds: 30),
  Directory? cacheDirectory,
  int cacheMaxSize = 100,
  bool useSecureConnection = false,
  String? jwtToken,
  WalrusLogLevel logLevel = WalrusLogLevel.none, // silent by default
  WalrusLogHandler? onLog,                       // custom log routing
})

Method	Description
`putBlob({data, epochs?, deletable?, ...})`	Upload bytes
`putBlobFromFile({file, ...})`	Upload from file
`putBlobStreaming({file, ...})`	Stream large uploads
`getBlob(blobId)`	Download with caching
`getBlobByObjectId(objectId)`	Download by Sui object ID
`getBlobAsFile({blobId, destination})`	Save to file
`getBlobMetadata(blobId)`	Get response headers
`setJwtToken(token)` / `clearJwtToken()`	JWT auth
`setLogLevel(level)`	Adjust logging verbosity
`close()`	Release HTTP client and cache resources

`WalrusDirectClient` (Direct Mode)

WalrusDirectClient.fromNetwork(
  network: WalrusNetwork.testnet, // or .mainnet
  uploadRelayConfig: ...,        // optional relay config
)

Method	Description
`readBlob({blobId})`	Read & decode from storage nodes
`getBlob({blobId})`	Get a `WalrusBlob` handle
`getFiles({ids})`	Read files by blob/quilt ID
`writeBlob({blob, epochs, signer, ...})`	Full write flow
`writeFiles({files, epochs, signer, ...})`	Write files as quilt
`writeBlobFlow({blob})`	Step-by-step write
`writeFilesFlow({files})`	Step-by-step quilt write
`getBlobMetadata({blobId})`	Metadata from storage nodes
`getSlivers({blobId})`	Raw slivers from storage nodes
`getVerifiedBlobStatus({blobId})`	Quorum-verified blob status
`getBlobObjectInfo({objectId})`	On-chain blob info
`resolveBlobId(id)`	Resolve `0x...` → base64 blob ID
`getOwnedBlobs({owner})`	List wallet's blob objects
`storageCost(size, epochs)`	Calculate storage cost
`registerBlobTransaction(...)`	Build register transaction
`certifyBlobTransaction(...)`	Build certify transaction
`deleteBlobTransaction(...)`	Build delete transaction
`readBlobAttributes(...)`	Read on-chain attributes
`writeBlobAttributes(...)`	Write on-chain attributes
`reset()`	Refresh cached epoch/committee state
`close()`	Release all resources

`WalrusFile` & `WalrusBlob`

// Create a file for upload
final file = WalrusFile.from(
  utf8.encode('Hello, World!'),
  identifier: 'hello.txt',
  tags: {'type': 'text'},
);

// Read from a blob handle
final blob = await client.getBlob(blobId: id);
final data = await blob.bytes();       // raw bytes
final text = await blob.text();         // UTF-8 string
final json = await blob.json();         // decoded JSON
final asFile = await blob.asFile();     // WalrusFile handle

// Read quilt files
final files = await blob.files();       // list of WalrusFile
for (final f in files) {
  print('${await f.getIdentifier()}: ${await f.text()}');
}

Utility Functions

Function	Description
`blobIdFromInt(BigInt)`	Numeric blob ID → URL-safe base64
`blobIdToInt(String)`	URL-safe base64 → BigInt
`encodeQuilt(blobs)`	Encode multiple blobs into quilt format
`computeBlobId(rootHash, unencodedLength, encodingType)`	Compute blob ID from encoding metadata

Logging

Logging is silent by default. Enable it by setting a log level:

// At construction
final client = WalrusClient(
  publisherBaseUrl: publisherUrl,
  aggregatorBaseUrl: aggregatorUrl,
  logLevel: WalrusLogLevel.info, // show info messages and above
);

// Or for direct mode
final directClient = WalrusDirectClient.fromNetwork(
  network: WalrusNetwork.testnet,
  logLevel: WalrusLogLevel.debug,
);

Log Levels

Level	Output
`none`	Silent (default)
`error`	Errors only
`warning`	Warnings + errors
`info`	Key events: uploads, downloads, cache hits/misses
`debug`	Internal decisions, transaction building, retry logic
`verbose`	Every HTTP request/response, sliver operations

Custom Log Handler

Route SDK logs to your own logging system:

final client = WalrusClient(
  publisherBaseUrl: publisherUrl,
  aggregatorBaseUrl: aggregatorUrl,
  logLevel: WalrusLogLevel.info,
  onLog: (record) {
    // record.level, record.message, record.time, record.error
    myLogger.log(record.level.name, record.message);
  },
);

// Or change at runtime
client.logger.level = WalrusLogLevel.verbose;
client.logger.onRecord = (record) => print(record);

TLS Configuration

// Testnet (some community endpoints use self-signed certs)
final client = WalrusClient(
  publisherBaseUrl: Uri.parse('https://publisher.walrus-testnet.walrus.space'),
  aggregatorBaseUrl: Uri.parse('https://aggregator.walrus-testnet.walrus.space'),
  useSecureConnection: false, // accepts any certificate
);

// Production — use your own publisher/aggregator or an authenticated service
final client = WalrusClient(
  publisherBaseUrl: Uri.parse('https://your-publisher.example.com'),
  aggregatorBaseUrl: Uri.parse('https://your-aggregator.example.com'),
  useSecureConnection: true, // enforce TLS validation
);

Warning: useSecureConnection: false disables certificate validation entirely. Only use for testnet or local development.

Storage Costs

Mode	Who Pays	How
HTTP (`WalrusClient`)	Publisher operator	Operator's wallet covers SUI gas + WAL
Direct (`WalrusDirectClient`)	User's wallet	User signs transactions, pays SUI gas + WAL
Aggregator reads	Free	No tokens needed

Use client.storageCost(size, epochs) to estimate WAL cost before writing:

final cost = await client.storageCost(1024 * 1024, 3); // 1 MB for 3 epochs
print('Storage: ${cost.storageCost} WAL');
print('Write:   ${cost.writeCost} WAL');
print('Total:   ${cost.totalCost} WAL');

Testnet — Public publishers subsidize costs. Free for developers.
Mainnet — Run your own publisher, use an authenticated service, or use direct mode with a funded wallet.

Testing

Dartus has 473+ tests covering all three operational modes.

cd Dartus

# Run ALL tests (recommended — includes Phase 2/3 tests)
flutter test

# Run Phase 1 tests only (no Flutter SDK required)
dart test

# Specific suite
flutter test test/blob_cache_test.dart

# Verbose output
flutter test --reporter expanded

# Static analysis (strict mode)
dart analyze --fatal-infos

# Format check
dart format --set-exit-if-changed .

Note: 5 test files (read_committee_test, object_data_loader_test, epoch_state_test, wal_exchange_test, blob_attributes_test) require flutter test because they import package:sui which transitively depends on dart:ui. Running dart test will show these as failures — this is expected. Use flutter test for the complete suite.

Example Apps

In-package example

A Flutter demo app lives in example/:

cd Dartus/example
flutter pub get
flutter run -d macos  # or: flutter run -d ios / android

Demonstrates HTTP-mode upload and download with WalrusClient.

Showcase app (full demo)

A comprehensive Flutter app showcasing all SDK features is available in the Dartus-Demo repository:

HTTP uploads & downloads
Direct-mode reads & writes
Wallet creation & faucet
Blob inspection & metadata
Quilt reading
Transaction builder
Encoding & BLS operations
System state viewer

Requirements

Requirement	Version
Dart SDK	>= 3.9.2
Flutter SDK	>= 3.35.0 (for Flutter projects)
`sui` package	^0.3.7 (direct mode only)
Rust toolchain	Latest stable (native library only)

HTTP mode has no additional requirements beyond Dart.
Direct mode requires the sui package and optionally the Rust-built libwalrus_ffi for client-side encoding.

For iOS apps using testnet HTTP endpoints, add ATS exceptions to Info.plist.

API Documentation

Full generated API docs are available on pub.dev:

pub.dev/documentation/dartus/latest

Generate locally:

dart doc
# Then open doc/api/index.html

License

MIT — see LICENSE.

Dartus

SDK Overview

Features

Installation

Native library setup (direct mode only)

Quick Start — HTTP Mode

Quick Start — Direct Mode

Writing Blobs (Direct Mode)

Simple write

Step-by-step flow (for dApp wallets)

Writing Files & Quilts

Upload Relay

Error Handling

Error Classes

API Reference

`WalrusClient` (HTTP Mode)

`WalrusDirectClient` (Direct Mode)

`WalrusFile` & `WalrusBlob`

Utility Functions

Logging

Log Levels

Custom Log Handler

TLS Configuration

Storage Costs

Testing

Example Apps

In-package example

Showcase app (full demo)

Requirements

API Documentation

License

Links

Libraries

dartus package

Dartus

SDK Overview

Features

Installation

Native library setup (direct mode only)

Quick Start — HTTP Mode

Quick Start — Direct Mode

Writing Blobs (Direct Mode)

Simple write

Step-by-step flow (for dApp wallets)

Writing Files & Quilts

Upload Relay

Error Handling

Error Classes

API Reference

WalrusClient (HTTP Mode)

WalrusDirectClient (Direct Mode)

WalrusFile & WalrusBlob

Utility Functions

Logging

Log Levels

Custom Log Handler

TLS Configuration

Storage Costs

Testing

Example Apps

In-package example

Showcase app (full demo)

Requirements

API Documentation

License

Links

Libraries

dartus package

`WalrusClient` (HTTP Mode)

`WalrusDirectClient` (Direct Mode)

`WalrusFile` & `WalrusBlob`