solana-pubkey-compare

High-performance Solana public key comparison using optimized BPF assembly.

Overview

This crate provides ultra-fast public key comparison for Solana blockchain programs, achieving significant performance improvements through hand-optimized BPF assembly. Perfect for performance-critical Solana programs where compute unit efficiency matters.

Performance

• Assembly implementation: 19 compute units on Solana BPF
• Standard comparison: 28 compute units on Solana BPF
• Improvement: ~32% reduction in compute units

Features

• ✅ Zero dependencies and #[no_std] compatible
• ✅ Hand-optimized BPF assembly for Solana runtime
• ✅ Automatic fallback to standard comparison for native testing
• ✅ Generic interface supporting any 32-byte key types
• ✅ Compile-time safety with Rust's type system
• ✅ Early exit optimization for maximum efficiency

Installation

Add this to your Cargo.toml:

[dependencies]
solana-pubkey-compare = "0.1.0"

Usage

Basic Example

use solana_pubkey_compare::fast_eq;
use solana_program::pubkey::Pubkey;

// Compare Solana Pubkeys
let key1 = Pubkey::new_unique();  
let key2 = Pubkey::new_unique();

if fast_eq(&key1, &key2) {
    // Keys are equal - this is very fast!
}

// Works with any 32-byte types
let bytes1: [u8; 32] = [0; 32];
let bytes2: [u8; 32] = [1; 32]; 
assert!(!fast_eq(&bytes1, &bytes2));

In Solana Programs

use solana_program::{
    account_info::AccountInfo,
    entrypoint::ProgramResult,
    pubkey::Pubkey,
};
use solana_pubkey_compare::fast_eq;

pub fn process_instruction(
    program_id: &Pubkey,
    accounts: &[AccountInfo],
    _instruction_data: &[u8],
) -> ProgramResult {
    let expected_authority = Pubkey::from([/* your authority key */]);
    
    // Fast authority check - saves compute units!
    if !fast_eq(&accounts[0].key, &expected_authority) {
        return Err(/* unauthorized error */);
    }
    
    // Continue processing...
    Ok(())
}

Performance-Critical Loops

use solana_pubkey_compare::fast_eq;

fn find_account_index(accounts: &[AccountInfo], target: &Pubkey) -> Option<usize> {
    accounts.iter().position(|account| {
        // Each comparison saves ~9 compute units
        fast_eq(&account.key, target)
    })
}

How It Works

Assembly Implementation

The core of this crate is a hand-optimized BPF assembly function that:

1. Loads 64-bit chunks: Uses ldxdw to load 8 bytes at a time
2. Early exit: Uses conditional jumps (jne) to exit immediately on first mismatch
3. Minimal instructions: Only 11-19 instructions depending on where difference is found
4. Register-optimized: Uses minimal register pressure for maximum efficiency

Instruction Sequence

// Compare bytes 0-7
ldxdw r3, [r1+0]      // Load first 8 bytes of key1
ldxdw r4, [r2+0]      // Load first 8 bytes of key2  
jne r3, r4, not_equal // Exit early if different

// Repeat for bytes 8-15, 16-23, 24-31...
// Return 1 if all equal, 0 if any different

Fallback Implementation

On non-Solana platforms, the function falls back to the standard PartialEq implementation for compatibility with testing and development workflows.

Benchmarks

Performance measurements on Solana BPF runtime:

CU = Compute Units

Type Requirements

The generic type T must implement:

• AsRef<[u8]> - For accessing the underlying byte data
• PartialEq - For the native fallback implementation

This includes:

• solana_program::pubkey::Pubkey
• [u8; 32]
• Vec<u8> (if exactly 32 bytes)
• Any custom types that dereference to 32-byte arrays

Safety

This function is completely safe to call. While it uses unsafe internally to interface with the assembly function, all safety invariants are maintained:

• References are valid for the duration of the call
• Data alignment is handled by the BPF runtime
• No memory is mutated - this is a pure comparison
• All bounds are compile-time verified

Development

Building

# Build for native (testing)
cargo build

# Build for Solana BPF  
cargo build-sbf

Testing

# Run tests (uses fallback implementation)
cargo test

# Test on Solana BPF runtime
cargo test-sbf

Contributing

Contributions are welcome! Please ensure:

• All tests pass on both native and BPF targets
• Assembly changes are documented and benchmarked
• New features maintain the #[no_std] compatibility

License

MIT License - see LICENSE file for details.

Credits

Created by Switchboard for high-performance Solana applications.