RLP WASM Implementation

WebAssembly-accelerated RLP encoding compiled from Zig

Try it Live

Run RLP examples in the interactive playground

RLP WASM Implementation

High-performance WebAssembly RLP encoder compiled from Zig for performance-critical operations.

Overview

The WASM implementation provides accelerated RLP encoding methods compiled from Zig. Currently supports encoding operations with significant performance improvements over JavaScript.

Features:

• Fast encoding - Compiled Zig code for maximum performance
• Memory efficient - Zero-copy operations where possible
• Type safe - TypeScript bindings with full type safety
• Drop-in replacement - Compatible with JavaScript API

Currently Available:

• encodeBytes - Encode byte arrays
• encodeUint - Encode 256-bit unsigned integers
• toHex / fromHex - Hex conversion utilities

Setup

WASM module loads automatically when available:

import * as RlpWasm from 'tevm/Rlp.wasm'

// WASM methods available immediately
const encoded = RlpWasm.encodeBytes(new Uint8Array([1, 2, 3]))

encodeBytes

Encode byte arrays using WASM.

Performance

WASM encodeBytes significantly faster than JavaScript:

import { Rlp } from 'tevm'
import * as RlpWasm from 'tevm/Rlp.wasm'

// Benchmark encoding 10,000 byte arrays
const items = Array({ length: 10000 }, () =>
  new Uint8Array(100).fill(0x42)
)

// JavaScript implementation
console.time('JS encode')
for (const item of items) {
  Rlp.encodeBytes(item)
}
console.timeEnd('JS encode')
// JS encode: ~50ms

// WASM implementation
console.time('WASM encode')
for (const item of items) {
  RlpWasm.encodeBytes(item)
}
console.timeEnd('WASM encode')
// WASM encode: ~10ms (5x faster)

encodeUint

Encode 256-bit unsigned integers.

encodeUintFromBigInt

Encode bigint directly to RLP.

Hex Utilities

Convert between RLP bytes and hex strings.

Architecture

//! RLP encoding implementation in Zig
//! Compiled to WebAssembly for browser/Node.js use

const std = @import("std");
const Hex = @import("../Hex/Hex.zig");

/// Maximum recursion depth
pub const MAX_RLP_DEPTH: u32 = 32;

/// Encode byte array to RLP
pub fn encodeBytes(allocator: Allocator, bytes: []const u8) ![]u8 {
    // Efficient implementation with minimal allocations
}

/// Encode u256 value to RLP
pub fn encodeUint(allocator: Allocator, value: [32]u8) ![]u8 {
    // Optimized integer encoding
}

Source: Rlp.zig:1-1489

Benefits

Performance:

• Compiled to optimized WASM bytecode
• No JIT warmup time
• Predictable performance characteristics

Memory:

• Manual memory management for efficiency
• Zero-copy operations where possible
• Minimal allocations

Safety:

• Zig’s compile-time safety checks
• No undefined behavior
• Bounds checking in debug mode

When to Use WASM

Use WASM implementation for:

High-throughput encoding:

import * as RlpWasm from 'tevm/Rlp.wasm'

// Encoding many transactions
async function encodeBatch(transactions: Transaction[]) {
  return Promise.all(
    transactions.map(async (tx) => {
      const fields = await prepareFields(tx)
      return fields.map(field => RlpWasm.encodeBytes(field))
    })
  )
}

Large data structures:

import * as RlpWasm from 'tevm/Rlp.wasm'

// Encoding block with many transactions
function encodeBlock(block: Block) {
  return {
    header: block.header.map(field => RlpWasm.encodeBytes(field)),
    transactions: block.transactions.map(tx =>
      tx.fields.map(field => RlpWasm.encodeBytes(field))
    ),
    uncles: block.uncles.map(uncle =>
      uncle.map(field => RlpWasm.encodeBytes(field))
    )
  }
}

Performance-critical paths:

import * as RlpWasm from 'tevm/Rlp.wasm'

// Real-time transaction signing
async function signTransaction(tx: Transaction) {
  // Use WASM for encoding (faster)
  const encoded = encodeTransactionFields(tx).map(field =>
    RlpWasm.encodeBytes(field)
  )

  // Sign encoded data
  const signature = await sign(encoded)

  return { encoded, signature }
}

Fallback to JavaScript

WASM loader handles fallback automatically:

import * as RlpWasm from 'tevm/Rlp.wasm'

// Uses WASM if available, falls back to JS
const encoded = RlpWasm.encodeBytes(data)

// Check WASM availability
if (typeof WebAssembly !== 'undefined') {
  console.log('WASM available')
} else {
  console.log('Using JavaScript fallback')
}

Limitations

Current WASM implementation has limitations:

No decoding yet:

// Available: encoding
import * as RlpWasm from 'tevm/Rlp.wasm'
const encoded = RlpWasm.encodeBytes(data)

// Not available: decoding (use JS)
import { Rlp } from 'tevm'
const decoded = Rlp.decode(encoded)

No list encoding:

// Not available: encodeList (use JS)
import { Rlp } from 'tevm'
const encoded = Rlp.encodeList([bytes1, bytes2])

32-byte constraint for uint:

// Must be exactly 32 bytes
const value = Bytes32()
RlpWasm.encodeUint(value)  // OK

const wrong = Bytes16()
RlpWasm.encodeUint(wrong)  // Error

Future Enhancements

Planned WASM features:

• decode - WASM decoding implementation
• encodeList - WASM list encoding
• stream encoding - Streaming encode support
• parallel encoding - Multi-threaded encoding for large data

Override Patterns

Replace JavaScript methods with WASM:

import { Rlp } from 'tevm'
import * as RlpWasm from 'tevm/Rlp.wasm'

// Override encodeBytes with WASM version
const originalEncodeBytes = Rlp.encodeBytes
Rlp.encodeBytes = RlpWasm.encodeBytes

// Now Rlp.encodeBytes uses WASM
const encoded = Rlp.encodeBytes(new Uint8Array([1, 2, 3]))

// Restore original
Rlp.encodeBytes = originalEncodeBytes

Or create hybrid encoder:

import { Rlp } from 'tevm'
import * as RlpWasm from 'tevm/Rlp.wasm'

function encodeBytes(data: Uint8Array): Uint8Array {
  // Use WASM for large data
  if (data.length > 1000) {
    return RlpWasm.encodeBytes(data)
  }

  // Use JS for small data (less overhead)
  return Rlp.encodeBytes(data)
}

Related

• Encoding - JavaScript encoding
• Algorithm - RLP specification
• Performance - Optimization tips