ax-rnd

Axrnd is a fast, small random number generator (rnd) library and CLI tool written in Rust.

Features:

• Fast: Outperforms fastrand in both single-call and bulk operations
• Small: Single u64 state (32 bytes with alignment)
• Pure Rust: No external dependencies
• CLI Tool: Installable via cargo install ax-rnd

Performance

Benchmark Results (Release Mode)

Single-call (next_u64):

Bulk fill (fill_bytes/1MB):

Algorithm: Custom variant based on Golden Ratio constant with XOR-first-then-multiply pattern.

Installation

As a Library

Add to your Cargo.toml:

[dependencies]
ax-rnd = "0.1.0"

As a CLI Tool

cargo install ax-rnd

Library API

Basic Usage

use ax_rnd::{rnd, Axrnd};

// Create rnd with seed
let mut rnd = Axrnd::new(12345);

// Or use convenience function
let mut rnd = rnd(12345);

// Generate random values
let x = rnd.next_u64();
let y = rnd.next_u32();
let b = rnd.next_bool();
let f = rnd.next_f64();

Alphanumeric Strings

use ax_rnd::rnd;

let mut rnd = rnd(42);

// Base62 (A-Z, a-z, 0-9) - 62 characters
let alpha = rnd.alpha(32); // "aB3xY9..."

// Base64url (A-Z, a-z, 0-9, -, _) - 64 characters, URL-safe
let token = rnd.token(32); // "UxelSo4vKQ3CgvhV..."

Bounded Random Numbers

use ax_rnd::rnd;

let mut rnd = rnd(42);

// Random number in [0, upper)
let x = rnd.bounded_u64(100);
let y = rnd.bounded_u32(50);

Bulk Operations

use ax_rnd::rnd;

let mut rnd = rnd(42);

// Fill byte buffer
let mut buf = [0u8; 1024];
rnd.fill_bytes(&mut buf);

// Fill u64 buffer
let mut u64_buf = [0u64; 16];
rnd.fill_u64(&mut u64_buf);

// Fill u32 buffer
let mut u32_buf = [0u32; 32];
rnd.fill_u32(&mut u32_buf);

State Management

use ax_rnd::Axrnd;

let mut rnd = Axrnd::new(12345);

// Get current state
let state = rnd.state(); // [u64; 1]

// Restore from state
let mut restored = Axrnd::from_raw(state[0]);

// Split for independent streams
let mut other = rnd.split();

// Reseed
rnd.reseed(54321);

Top-level Functions

use ax_rnd;

// One-off random values (creates new rnd each time)
let x = ax_rnd::random_u64(42);
let y = ax_rnd::random_u32(42);
let b = ax_rnd::random_bool(42);
let f = ax_rnd::random_f64(42);

// One-off bounded
let z = ax_rnd::bounded_u64(42, 100);

// One-off strings
let alpha = ax_rnd::alpha(42, 32);
let token = ax_rnd::token(42, 32);

CLI Usage

Commands

ax-rnd <command> [args]

Examples

# Generate 64 random bytes (binary output)
ax-rnd bytes 64 > random.bin

# Generate 32 bytes as hex string
ax-rnd bytes 32 --hex
# 836233f222448066354d9340859e3743

# Generate 16-char alphanumeric string
ax-rnd alpha 16
# SEV3G6JYHei5YFhe

# Generate 32-char URL-safe token
ax-rnd token 32
# UxelSo4vKQ3CgvhV

# Generate 5 random u64 numbers
ax-rnd u64 5
# 9370916739074745922
# 8432900285853589045
# ...

# Generate 3 UUIDs
ax-rnd uuid 3
# f59ba06a-85b2-4423-b795-999e1bd2e038
# adea1bad-c71d-49d3-8ab2-2bef2010a96a
# ...

# Shuffle lines from stdin
echo -e "a\nb\nc\nd" | ax-rnd shuffle
# b
# d
# a
# c

# Shuffle lines from file
ax-rnd shuffle file.txt

# Use specific seed for reproducibility
ax-rnd bytes 32 12345

Options

• count/len - Number of bytes/chars/numbers (default: 32)
• --hex - Output bytes as hex string
• seed - rnd seed (default: current timestamp)
  • Use time for current timestamp
  • Use numeric value for fixed seed

Testing

Unit Tests

cargo test

Test Coverage:

• Deterministic sequences
• Different seeds produce different streams
• Fill operations
• Bounded range correctness
• Float range correctness
• State roundtrip
• Split functionality
• Alphanumeric character sets
• Base64url character sets
• Statistical quality tests (avalanche, bit distribution, stream correlation)

Results: 28 tests passing

Statistical Quality Tests

The library includes statistical quality tests in tests/statistical.rs:

• Bit histogram uniformity
• Avalanche effect
• Stream correlation
• Low byte uniformity
• PractRand stream quality (8MB sample)

Results: All statistical tests passing

Benchmarking

cargo run --example manual_bench --release

Algorithm

Core Algorithm: Custom variant based on Golden Ratio constant (0x9E3779B97F4A7C15)

Pattern:

state += GR;              // Golden ratio increment
xored = state ^ GR;       // XOR first
math = state * xored;     // Multiply (128-bit)
return (math as u64) ^ ((math >> 64) as u64);  // Fold

License

MIT