<img src="./site/logo.svg" />

# hashery
Browser / Nodejs Compatible Object Hashing

[![tests](https://github.com/jaredwray/hashery/actions/workflows/tests.yml/badge.svg)](https://github.com/jaredwray/hashery/actions/workflows/tests.yml)
[![codecov](https://codecov.io/gh/jaredwray/hashery/graph/badge.svg?token=JTuDzWoTRn)](https://codecov.io/gh/jaredwray/hashery)
[![GitHub license](https://img.shields.io/github/license/jaredwray/hashery)](https://github.com/jaredwray/hashery/blob/master/LICENSE)
[![npm](https://img.shields.io/npm/dm/hashery)](https://npmjs.com/package/hashery)
[![jsDelivr](https://data.jsdelivr.com/v1/package/npm/hashery/badge)](https://www.jsdelivr.com/package/npm/hashery)
[![npm](https://img.shields.io/npm/v/hashery)](https://npmjs.com/package/hashery)

# Features
- **Simple and Easy Object Hashing** - Object hashing based on multiple algorithms.
- **Browser and Node.js Compatible** - Built using `WebCrypto` API for both environments
- **Multiple Hash Algorithms** - Supports SHA-256, SHA-384, SHA-512 (WebCrypto), plus DJB2, FNV1, Murmer, and CRC32
- **Synchronous & Asynchronous** - Both sync and async methods for flexible integration
- **Custom Serialization** - Easily replace JSON `parse` and `stringify` with custom functions
- **Deterministic Hashing** - Generate consistent hashes for the same input
- **Hash to Number** - Convert hashes to deterministic numbers within a specified range. Great for slot management
- **Provider System** - Extensible hash provider architecture for custom algorithms
- **Fuzzy Provider Matching** - Case-insensitive and dash-tolerant algorithm name matching
- **Hooks Support** - Extends Hookified for event-based functionality
- **Maintained on a Regular Basis** - Active maintenance and updates

# Table of Contents

- [Features](#features)
- [Installation](#installation)
- [Usage](#usage)
  - [Basic Hashing](#basic-hashing)
  - [Synchronous Hashing](#synchronous-hashing)
  - [Using Different Hash Algorithms](#using-different-hash-algorithms)
  - [Setting a Default Algorithm](#setting-a-default-algorithm)
  - [Truncating Hash Output](#truncating-hash-output)
  - [Hash to Number (Great for Slot Management)](#hash-to-number-great-for-slot-management)
  - [Hash to Number Synchronous](#hash-to-number-synchronous)
  - [Browser Usage](#browser-usage)
- [Hooks](#hooks)
- [Caching](#caching)
- [Web Crypto](#web-crypto)
- [DJB2 Hashing](#djb2-hashing)
- [FNV1 Hashing](#fnv1-hashing)
- [CRC Hashing](#crc-hashing)
- [API - Properties](#api---properties)
  - [parse](#parse)
  - [stringify](#stringify)
  - [providers](#providers)
  - [names](#names)
  - [defaultAlgorithm](#defaultalgorithm)
  - [defaultAlgorithmSync](#defaultalgorithmsync)
- [API - Functions](#api---functions)
  - [toHash(data, options?)](#toHashdata-options)
  - [toHashSync(data, options?)](#toHashsyncdata-options)
  - [toNumber(data, options?)](#tonumberdata-options)
  - [toNumberSync(data, options?)](#tonumbersyncdata-options)
  - [loadProviders(providers?, options?)](#loadprovidersproviders-options)
- [Benchmarks](#benchmarks)
- [Code of Conduct and Contributing](#code-of-conduct-and-contributing)
- [License and Copyright](#license-and-copyright)

# Installation

```bash
npm install hashery
```

# Usage

## Basic Hashing

```typescript
import { Hashery } from 'hashery';

const hashery = new Hashery();

// Hash an object (defaults to SHA-256)
const hash = await hashery.toHash({ name: 'John', age: 30 });
console.log(hash); // SHA-256 hash string

// Hash a string
const stringHash = await hashery.toHash('hello world');

// Hash any value (numbers, arrays, etc.)
const numberHash = await hashery.toHash(42);
const arrayHash = await hashery.toHash([1, 2, 3, 4, 5]);
```

## Synchronous Hashing

For performance-critical applications or when you need to avoid async/await, use the synchronous hashing methods. These work with non-cryptographic hash algorithms (djb2, fnv1, murmer, crc32) and are significantly faster than WebCrypto methods.

```typescript
import { Hashery } from 'hashery';

const hashery = new Hashery();

// Synchronous hash (defaults to djb2)
const hash = hashery.toHashSync({ name: 'John', age: 30 });
console.log(hash); // djb2 hash string (8 hex characters)

// Sync with specific algorithm
const fnv1Hash = hashery.toHashSync({ data: 'example' }, { algorithm: 'fnv1' });
const murmerHash = hashery.toHashSync({ data: 'example' }, { algorithm: 'murmer' });
const crcHash = hashery.toHashSync({ data: 'example' }, { algorithm: 'crc32' });

// Note: WebCrypto algorithms (SHA-256, SHA-384, SHA-512) are NOT supported in sync mode
// This will throw an error:
// hashery.toHashSync({ data: 'example' }, { algorithm: 'SHA-256' }); // ❌ Error!
```

## Using Different Hash Algorithms

```typescript
import { Hashery } from 'hashery';

const hashery = new Hashery();

// Use SHA-384
const hash384 = await hashery.toHash({ data: 'example' }, { algorithm: 'SHA-384' });

// Use SHA-512
const hash512 = await hashery.toHash({ data: 'example' }, { algorithm: 'SHA-512' });

// Use non-crypto hash algorithms
const fastHash = await hashery.toHash({ data: 'example' }, { algorithm: 'djb2' });
```

## Setting a Default Algorithm

You can set a default algorithm for all hash operations via constructor or property:

```typescript
import { Hashery } from 'hashery';

// Set default algorithm via constructor
const hashery = new Hashery({ defaultAlgorithm: 'SHA-512' });

// Now all hashes use SHA-512 by default
const hash1 = await hashery.toHash({ data: 'example' }); // Uses SHA-512
console.log(hash1.length); // 128 (SHA-512 produces 128 hex characters)

// You can still override it per call
const hash2 = await hashery.toHash({ data: 'example' }, { algorithm: 'SHA-256' });
console.log(hash2.length); // 64 (SHA-256 produces 64 hex characters)

// Change default algorithm at runtime
hashery.defaultAlgorithm = 'djb2';
const hash3 = await hashery.toHash({ data: 'example' }); // Uses djb2
```

## Truncating Hash Output

You can limit the length of the hash output using the `maxLength` option:

```typescript
import { Hashery } from 'hashery';

const hashery = new Hashery();

// Get a shorter hash (16 characters instead of 64)
const shortHash = await hashery.toHash(
  { data: 'example' },
  { algorithm: 'SHA-256', maxLength: 16 }
);
console.log(shortHash); // "3f79bb7b435b0518" (16 chars)

// Full hash for comparison
const fullHash = await hashery.toHash({ data: 'example' });
console.log(fullHash); // "3f79bb7b435b05181e4ccf0d4e8..." (64 chars)
```

## Hash to Number (Great for Slot Management)

```typescript
import { Hashery } from 'hashery';

const hashery = new Hashery();

// Convert hash to a number within a range
const slot = await hashery.toNumber({ userId: 123 }, { min: 0, max: 100 });
console.log(slot); // Deterministic number between 0-100

// Use for consistent slot assignment
const userSlot = await hashery.toNumber({ userId: 'user@example.com' }, { min: 0, max: 9 });
// Same user will always get the same slot number
```

## Hash to Number Synchronous

Generate deterministic numbers synchronously for high-performance scenarios. Perfect for A/B testing, sharding, and load balancing without async overhead.

```typescript
import { Hashery } from 'hashery';

const hashery = new Hashery();

// Synchronous number generation (defaults to djb2)
const slot = hashery.toNumberSync({ userId: 123 }, { min: 0, max: 100 });
console.log(slot); // Deterministic number between 0-100

// A/B testing without async/await
const variant = hashery.toNumberSync({ userId: 'user123' }, { min: 0, max: 1 });
console.log(variant === 0 ? 'Group A' : 'Group B');

// Load balancing across servers
const serverIndex = hashery.toNumberSync(
  { requestId: 'req_abc123' },
  { min: 0, max: 9, algorithm: 'fnv1' } // 10 servers
);

// Sharding assignment
const shardId = hashery.toNumberSync(
  { customerId: 'cust_xyz' },
  { min: 0, max: 15, algorithm: 'murmer' } // 16 shards
);

// Set default sync algorithm for all sync operations
const hashery2 = new Hashery({ defaultAlgorithmSync: 'fnv1' });
const num = hashery2.toNumberSync({ data: 'test' }); // Uses fnv1 by default
```

## Browser Usage

Hashery works seamlessly in the browser using the Web Crypto API. You can include it via CDN or bundle it with your application.

### Using via CDN (jsDelivr)

```html
<!DOCTYPE html>
<html>
<head>
  <title>Hashery Browser Example</title>
</head>
<body>
  <script type="module">
    import { Hashery } from 'https://cdn.jsdelivr.net/npm/hashery@latest/dist/browser/index.js';

    const hashery = new Hashery();

    // Hash data in the browser
    const hash = await hashery.toHash({ page: 'home', userId: 123 });
    console.log('Hash:', hash);

    // Generate slot numbers for A/B testing
    const variant = await hashery.toNumber({ userId: 'user123' }, { min: 0, max: 1 });
    console.log('A/B Test Variant:', variant === 0 ? 'A' : 'B');
  </script>
</body>
</html>
```

# Hooks

Hashery extends [Hookified](https://github.com/jaredwray/hookified) to provide event-based functionality through hooks. Hooks allow you to intercept and modify behavior during the hashing process.

## Available Hooks

### Asynchronous Method Hooks

#### `before:toHash`

Fired before hashing occurs. This hook receives a context object containing:
- `data` - The data to be hashed (can be modified)
- `algorithm` - The hash algorithm to use (can be modified)
- `maxLength` - Optional maximum length for the hash output

#### `after:toHash`

Fired after hashing completes. This hook receives a result object containing:
- `hash` - The generated hash (can be modified)
- `data` - The data that was hashed
- `algorithm` - The algorithm that was used

### Synchronous Method Hooks

#### `before:toHashSync`

Fired before synchronous hashing occurs. This hook receives a context object containing:
- `data` - The data to be hashed (can be modified)
- `algorithm` - The hash algorithm to use (can be modified)
- `maxLength` - Optional maximum length for the hash output

**Note:** This hook fires asynchronously (non-blocking) to maintain the synchronous nature of `toHashSync()`. Hook execution happens in the background and won't delay the method's return.

#### `after:toHashSync`

Fired after synchronous hashing completes. This hook receives a result object containing:
- `hash` - The generated hash (can be modified)
- `data` - The data that was hashed
- `algorithm` - The algorithm that was used

**Note:** This hook fires asynchronously (non-blocking) to maintain the synchronous nature of `toHashSync()`. Hook execution happens in the background.

## Basic Hook Usage

```typescript
import { Hashery } from 'hashery';

const hashery = new Hashery();

// Listen to before:toHash hook
hashery.onHook('before:toHash', async (context) => {
  console.log('About to hash:', context.data);
  console.log('Using algorithm:', context.algorithm);
});

// Listen to after:toHash hook
hashery.onHook('after:toHash', async (result) => {
  console.log('Hash generated:', result.hash);
  console.log('Original data:', result.data);
});

await hashery.toHash({ name: 'John', age: 30 });
```

## Modifying Data with Hooks

You can modify the data before it's hashed:

```typescript
const hashery = new Hashery();

// Add a timestamp to all hashed data
hashery.onHook('before:toHash', async (context) => {
  context.data = {
    original: context.data,
    timestamp: new Date().toISOString()
  };
});

const hash = await hashery.toHash({ userId: 123 });
// Data will be hashed with timestamp included
```

## Modifying Algorithms with Hooks

You can force a specific algorithm regardless of what's requested:

```typescript
const hashery = new Hashery();

// Force all hashes to use SHA-512
hashery.onHook('before:toHash', async (context) => {
  context.algorithm = 'SHA-512';
});

// Even though we request SHA-256, it will use SHA-512
const hash = await hashery.toHash({ data: 'example' }, { algorithm: 'SHA-256' });
console.log(hash.length); // 128 (SHA-512 hash length)
```

## Modifying Hash Results

You can transform the hash after it's generated:

```typescript
const hashery = new Hashery();

// Convert all hashes to uppercase
hashery.onHook('after:toHash', async (result) => {
  result.hash = result.hash.toUpperCase();
});

const hash = await hashery.toHash({ data: 'example' });
console.log(hash); // Hash will be in uppercase
```

## Implementing Caching with Hooks

Use hooks to implement a caching layer:

```typescript
const hashery = new Hashery();
const cache = new Map<string, string>();

// Store hashes in cache after generation
hashery.onHook('after:toHash', async (result) => {
  const cacheKey = `${result.algorithm}:${JSON.stringify(result.data)}`;
  cache.set(cacheKey, result.hash);
});

// Later you can check the cache before hashing
// (Note: You would need to implement cache lookup logic in your application)
```

## Logging and Debugging

Hooks are perfect for logging and debugging:

```typescript
const hashery = new Hashery();

hashery.onHook('before:toHash', async (context) => {
  console.log(`[DEBUG] Hashing data with ${context.algorithm}:`, context.data);
});

hashery.onHook('after:toHash', async (result) => {
  console.log(`[DEBUG] Hash generated: ${result.hash.substring(0, 8)}...`);
});

await hashery.toHash({ userId: 'user123' });
```

## Multiple Hooks

You can register multiple hooks, and they will execute in the order they were registered:

```typescript
const hashery = new Hashery();

hashery.onHook('before:toHash', async (context) => {
  console.log('First hook');
  context.data = { step: 1, original: context.data };
});

hashery.onHook('before:toHash', async (context) => {
  console.log('Second hook');
  context.data = { step: 2, previous: context.data };
});

await hashery.toHash({ name: 'test' });
// Output: "First hook" then "Second hook"
// Data will be wrapped twice
```

## Synchronous Method Hooks

Synchronous methods (`toHashSync`, `toNumberSync`) support hooks, but they fire asynchronously in the background to maintain the synchronous nature of the methods.

```typescript
const hashery = new Hashery();

// Listen to synchronous hash hooks
hashery.onHook('before:toHashSync', async (context) => {
  console.log('About to hash synchronously:', context.data);
  console.log('Using algorithm:', context.algorithm);
});

hashery.onHook('after:toHashSync', async (result) => {
  console.log('Sync hash generated:', result.hash);
});

// Call synchronous method - hooks fire in background
const hash = hashery.toHashSync({ name: 'John', age: 30 });
console.log('Method returned:', hash);
// Method returns immediately, hooks execute asynchronously
```

**Important Notes:**
- Synchronous method hooks fire asynchronously (non-blocking)
- The method returns immediately without waiting for hooks to complete
- Hook modifications to context/result may not affect the returned value
- For guaranteed hook execution, use async methods (`toHash`, `toNumber`)

### Why Are Sync Hooks Asynchronous?

Synchronous methods are designed for maximum performance. Making hooks blocking would defeat this purpose. The async hook execution allows:
- Logging and monitoring without performance impact
- Side effects (like caching) without blocking
- Maintaining the synchronous contract of the method

If you need hooks that modify data or behavior, use the async methods (`toHash`, `toNumber`).

## Removing Hooks

You can remove hooks when they're no longer needed:

```typescript
const hashery = new Hashery();

const myHook = async (context: any) => {
  console.log('Hook called');
};

// Add the hook
hashery.onHook('before:toHash', myHook);

// Remove the hook
hashery.offHook('before:toHash', myHook);

// Same works for sync hooks
hashery.onHook('before:toHashSync', myHook);
hashery.offHook('before:toHashSync', myHook);
```

## Error Handling in Hooks

Control how errors in hooks are handled using the `throwOnEmitError` option:

```typescript
// Throw errors that occur in hooks
const hashery1 = new Hashery({ throwOnEmitError: true });

hashery1.onHook('before:toHash', async (context) => {
  throw new Error('Hook error');
});

// This will throw the error
await hashery1.toHash({ data: 'example' }); // Throws Error: Hook error

// Silently handle errors in hooks
const hashery2 = new Hashery({ throwOnEmitError: false });

hashery2.onHook('before:toHash', async (context) => {
  throw new Error('Hook error');
});

// This will not throw, hashing continues
const hash = await hashery2.toHash({ data: 'example' }); // Returns hash successfully
```

# Caching

Hashery includes a built-in FIFO (First In, First Out) cache that stores computed hash values. When the same data is hashed with the same algorithm, the cached result is returned instead of recomputing.

- **Enabled by Default** - Caching works out of the box
- **FIFO Eviction** - Oldest entries removed when `maxSize` is reached (default: 4000)
- **Shared Cache** - Both sync and async methods share the same cache

## Configuration

```typescript
import { Hashery } from 'hashery';

// Default: cache enabled with maxSize of 4000
const hashery = new Hashery();

// Custom configuration
const hashery2 = new Hashery({
  cache: {
    enabled: true,   // default: true
    maxSize: 10000   // default: 4000
  }
});

// Disable cache
const hashery3 = new Hashery({ cache: { enabled: false } });

// Toggle at runtime
hashery.cache.enabled = false;
hashery.cache.enabled = true;
```

## Cache Properties and Methods

```typescript
const hashery = new Hashery();

hashery.cache.enabled;  // boolean - is caching enabled
hashery.cache.maxSize;  // number - maximum entries (default: 4000)
hashery.cache.size;     // number - current cached entries
hashery.cache.store;    // Map<string, string> - underlying store
hashery.cache.clear();  // Clear all cached entries
```

## Memory Considerations

The default `maxSize` of 4000 provides a good balance (~1-2 MB memory). JavaScript Maps can hold up to 2^24 (~16.7 million) entries, but practical limits depend on available memory. For most use cases, 4000-10000 entries is sufficient.

# Web Crypto

Hashery is built on top of the Web Crypto API, which provides cryptographic operations in both browser and Node.js environments. This ensures consistent, secure hashing across all platforms.

## Browser Support

The Web Crypto API is supported in all modern browsers:
- Chrome 37+
- Firefox 34+
- Safari 11+
- Edge 12+

## Node.js Support

Node.js 15+ includes the Web Crypto API via the `crypto.webcrypto` global. Hashery automatically detects and uses the appropriate crypto implementation for your environment.

## Available Algorithms

### Web Crypto Algorithms (Async Only)
These algorithms use the Web Crypto API and are only available asynchronously:
- **SHA-256** - Secure Hash Algorithm 256-bit (default for async methods)
- **SHA-384** - Secure Hash Algorithm 384-bit
- **SHA-512** - Secure Hash Algorithm 512-bit

These are cryptographically secure and suitable for security-sensitive applications.

### Non-Crypto Algorithms (Async & Sync)
These algorithms support both synchronous and asynchronous operation:
- **djb2** - Fast hash function by Daniel J. Bernstein (default for sync methods)
- **fnv1** - Fowler-Noll-Vo hash function
- **murmer** - MurmurHash algorithm
- **crc32** - Cyclic Redundancy Check 32-bit

**Async methods** (`toHash`, `toNumber`):
- Default to `SHA-256`
- Can use any algorithm (WebCrypto or non-crypto)
- Return Promises

**Sync methods** (`toHashSync`, `toNumberSync`):
- Default to `djb2`
- Only work with non-crypto algorithms (djb2, fnv1, murmer, crc32)
- Return values immediately
- Throw an error if you try to use WebCrypto algorithms

## Example: Using Web Crypto

```typescript
import { Hashery } from 'hashery';

const hashery = new Hashery();

// Web Crypto algorithms
const sha256 = await hashery.toHash({ data: 'example' }); // Default SHA-256
const sha384 = await hashery.toHash({ data: 'example' }, { algorithm: 'SHA-384' });
const sha512 = await hashery.toHash({ data: 'example' }, { algorithm: 'SHA-512' });

// Non-crypto algorithms (faster, but not cryptographically secure)
const djb2Hash = await hashery.toHash({ data: 'example' }, { algorithm: 'djb2' });
const fnv1Hash = await hashery.toHash({ data: 'example' }, { algorithm: 'fnv1' });
```

# DJB2 Hashing

DJB2 is a non-cryptographic hash function created by Daniel J. Bernstein. It's known for its simplicity and speed, making it ideal for hash tables, checksums, and other non-security applications.

## Why Use DJB2?

- **Fast Performance** - Significantly faster than cryptographic hash functions
- **Good Distribution** - Provides good hash distribution for most data
- **Simple Algorithm** - Easy to understand and implement
- **Low Collision Rate** - Works well for hash tables and data structures
- **Deterministic** - Same input always produces the same output

## When to Use DJB2

**Good for:**
- Hash tables and data structures
- Non-security checksums
- Fast data lookups
- Cache keys
- General-purpose hashing where security isn't a concern

**Not suitable for:**
- Password hashing
- Cryptographic signatures
- Security-sensitive applications
- Data integrity verification where tampering is a concern

## DJB2 vs Cryptographic Hashes

| Feature | DJB2 | SHA-256 |
|---------|------|---------|
| Speed | Very Fast | Slower |
| Security | Not Secure | Cryptographically Secure |
| Hash Length | 32-bit | 256-bit |
| Collision Resistance | Good | Excellent |
| Use Case | General Purpose | Security |

## Example: Using DJB2

```typescript
import { Hashery } from 'hashery';

const hashery = new Hashery();

// Hash with DJB2 (fast, non-cryptographic)
const djb2Hash = await hashery.toHash({ userId: 123, action: 'login' }, { algorithm: 'djb2' });

// Use for cache keys
const cacheKey = await hashery.toHash({
  endpoint: '/api/users',
  params: { page: 1, limit: 10 }
}, { algorithm: 'djb2' });

// Generate slot numbers with DJB2
const slot = await hashery.toNumber({ userId: 'user123' }, { min: 0, max: 99, algorithm: 'djb2' });
```

## Algorithm Details

DJB2 uses a simple formula:
```
hash = 5381
for each character c:
    hash = ((hash << 5) + hash) + c
```

This translates to: `hash * 33 + c`, where 5381 is the magic initial value chosen by Daniel J. Bernstein for its distribution properties.

# FNV1 Hashing

FNV1 (Fowler-Noll-Vo) is a non-cryptographic hash function designed for fast hash table and checksum use. Created by Glenn Fowler, Landon Curt Noll, and Kiem-Phong Vo, it's known for its excellent distribution properties and simplicity.

## Why Use FNV1?

- **Excellent Distribution** - Superior hash distribution reduces collisions
- **Fast Performance** - Very fast computation with minimal operations
- **Simple Implementation** - Easy to understand and implement
- **Public Domain** - No licensing restrictions
- **Well-Tested** - Extensively used and tested in production systems
- **Deterministic** - Same input always produces the same output

## When to Use FNV1

**Good for:**
- Hash tables and associative arrays
- Checksums and fingerprints
- Data deduplication
- Bloom filters
- Fast lookups and indexing
- Non-cryptographic applications

**Not suitable for:**
- Password hashing
- Cryptographic signatures
- Security-critical applications
- Digital signatures
- Data integrity in adversarial environments

## FNV1 vs Other Hash Functions

| Feature | FNV1 | DJB2 | SHA-256 |
|---------|------|------|---------|
| Speed | Very Fast | Very Fast | Slower |
| Distribution | Excellent | Good | Excellent |
| Security | Not Secure | Not Secure | Cryptographically Secure |
| Collision Resistance | Good | Good | Excellent |
| Use Case | Hash Tables | General Purpose | Security |

## Example: Using FNV1

```typescript
import { Hashery } from 'hashery';

const hashery = new Hashery();

// Hash with FNV1 (fast, excellent distribution)
const fnv1Hash = await hashery.toHash({ productId: 'ABC123', variant: 'red' }, { algorithm: 'fnv1' });

// Use for hash table keys
const tableKey = await hashery.toHash({
  userId: 'user@example.com',
  resource: 'profile'
}, { algorithm: 'fnv1' });

// Generate distributed slot numbers with FNV1
const slot = await hashery.toNumber({ sessionId: 'sess_xyz789' }, { min: 0, max: 999, algorithm: 'fnv1' });

// Use for data deduplication
const fingerprint = await hashery.toHash({
  content: 'document content here',
  metadata: { author: 'John', date: '2024-01-01' }
}, { algorithm: 'fnv1' });
```

## Algorithm Details

FNV1 uses the following formula:
```
hash = FNV_offset_basis
for each byte b:
    hash = hash * FNV_prime
    hash = hash XOR b
```

Where:
- **FNV_offset_basis**: Initial hash value (different for 32-bit, 64-bit, etc.)
- **FNV_prime**: A carefully chosen prime number for good distribution
- **XOR**: Bitwise exclusive OR operation

The algorithm multiplies by a prime and XORs with each input byte, creating excellent avalanche properties where small input changes result in very different hash values.

# CRC Hashing

CRC (Cyclic Redundancy Check) is a non-cryptographic hash function designed primarily for detecting accidental changes to data. CRC32 is a 32-bit variant widely used in network protocols, file formats, and data integrity verification.

## Why Use CRC?

- **Error Detection** - Excellent at detecting accidental data corruption
- **Industry Standard** - Widely used in ZIP, PNG, Ethernet, and many other standards
- **Fast Performance** - Very efficient computation using lookup tables
- **Hardware Support** - Often implemented in hardware for maximum speed
- **Well-Understood** - Decades of use and mathematical analysis
- **Deterministic** - Same input always produces the same output

## When to Use CRC

**Good for:**
- Data integrity verification
- Error detection in network protocols
- File format checksums (ZIP, PNG, etc.)
- Storage integrity checks
- Detecting accidental corruption
- Quick data validation

**Not suitable for:**
- Cryptographic applications
- Password hashing
- Digital signatures
- Security-sensitive checksums
- Protection against intentional tampering
- Hash tables (not designed for this use case)

## CRC vs Other Hash Functions

| Feature | CRC32 | DJB2 | FNV1 | SHA-256 |
|---------|-------|------|------|---------|
| Primary Use | Error Detection | Hash Tables | Hash Tables | Security |
| Speed | Very Fast | Very Fast | Very Fast | Slower |
| Security | Not Secure | Not Secure | Not Secure | Cryptographically Secure |
| Hash Length | 32-bit | 32-bit | 32-bit/64-bit | 256-bit |
| Error Detection | Excellent | Poor | Poor | Excellent |
| Use Case | Data Integrity | General Purpose | Hash Tables | Security |

## Example: Using CRC

```typescript
import { Hashery } from 'hashery';

const hashery = new Hashery();

// Hash with CRC32 for data integrity
const crcHash = await hashery.toHash({ fileData: 'content here' }, { algorithm: 'crc32' });

// Verify file integrity
const fileChecksum = await hashery.toHash({
  filename: 'document.pdf',
  size: 1024000,
  modified: '2024-01-01'
}, { algorithm: 'crc32' });

// Network packet validation
const packetChecksum = await hashery.toHash({
  header: { type: 'data', seq: 123 },
  payload: 'packet payload data'
}, { algorithm: 'crc32' });

// Quick data validation
const dataIntegrity = await hashery.toHash({
  recordId: 'rec_123',
  data: { field1: 'value1', field2: 'value2' }
}, { algorithm: 'crc32' });
```

## Algorithm Details

CRC32 uses polynomial division in a finite field (GF(2)):

```
CRC32 polynomial: 0x04C11DB7 (IEEE 802.3 standard)

for each byte b:
    crc = (crc >> 8) XOR table[(crc XOR b) & 0xFF]
```

Key characteristics:
- **Polynomial**: Uses a standardized polynomial for consistent results
- **Lookup Table**: Pre-computed table for fast calculation
- **Bit Shifting**: Efficient XOR and shift operations
- **Finite Field**: Mathematical properties ensure good error detection

## Important Notes

⚠️ **Security Warning**: CRC is NOT cryptographically secure. It's designed to detect accidental errors, not intentional tampering. For security applications, use SHA-256 or other cryptographic hash functions.

✅ **Best Practice**: Use CRC32 for checksums and error detection in non-adversarial environments. Use cryptographic hashes (SHA-256, SHA-512) when security matters.

# API - Properties

## `parse`

Gets or sets the parse function used to deserialize stored values.

**Type:** `ParseFn`

**Default:** `JSON.parse`

```typescript
const hashery = new Hashery();
hashery.parse = customParseFunction;
```

## `stringify`

Gets or sets the stringify function used to serialize values for storage.

**Type:** `StringifyFn`

**Default:** `JSON.stringify`

```typescript
const hashery = new Hashery();
hashery.stringify = customStringifyFunction;
```

## `providers`

Gets or sets the HashProviders instance used to manage hash providers.

**Type:** `HashProviders`

```typescript
const hashery = new Hashery();
console.log(hashery.providers);
```

## `names`

Gets the names of all registered hash algorithm providers.

**Type:** `Array<string>`

**Returns:** An array of provider names (e.g., ['SHA-256', 'SHA-384', 'SHA-512', 'djb2', 'fnv1', 'murmer', 'crc32'])

```typescript
const hashery = new Hashery();
console.log(hashery.names); // ['SHA-256', 'SHA-384', 'SHA-512', 'djb2', 'fnv1', 'murmer', 'crc32']
```

## `defaultAlgorithm`

Gets or sets the default hash algorithm to use when none is specified for async methods.

**Type:** `string`

**Default:** `'SHA-256'`

```typescript
const hashery = new Hashery();

// Get default algorithm
console.log(hashery.defaultAlgorithm); // 'SHA-256'

// Set default algorithm
hashery.defaultAlgorithm = 'SHA-512';

// Now all async hashes use SHA-512 by default
const hash = await hashery.toHash({ data: 'example' });
console.log(hash.length); // 128 (SHA-512 produces 128 hex characters)
```

## `defaultAlgorithmSync`

Gets or sets the default hash algorithm to use when none is specified for synchronous methods.

**Type:** `string`

**Default:** `'djb2'`

```typescript
const hashery = new Hashery();

// Get default sync algorithm
console.log(hashery.defaultAlgorithmSync); // 'djb2'

// Set default sync algorithm
hashery.defaultAlgorithmSync = 'fnv1';

// Now all sync hashes use fnv1 by default
const hash = hashery.toHashSync({ data: 'example' });

// You can also set it in the constructor
const hashery2 = new Hashery({ defaultAlgorithmSync: 'murmer' });
const hash2 = hashery2.toHashSync({ data: 'test' }); // Uses murmer
```

# API - Functions

## `toHash(data, options?)`

Generates a cryptographic hash of the provided data using the specified algorithm (async). The data is first stringified using the configured stringify function, then hashed.

**Parameters:**
- `data` (unknown) - The data to hash (will be stringified before hashing)
- `options` (object, optional) - Configuration options
  - `algorithm` (string, optional) - The hash algorithm to use (defaults to 'SHA-256')
  - `maxLength` (number, optional) - Maximum length for the hash output (truncates from the start)

**Returns:** `Promise<string>` - A Promise that resolves to the hexadecimal string representation of the hash

**Example:**

```typescript
const hashery = new Hashery();

// Using default SHA-256
const hash = await hashery.toHash({ name: 'John', age: 30 });

// Using a different algorithm
const hash512 = await hashery.toHash({ name: 'John' }, { algorithm: 'SHA-512' });
const fastHash = await hashery.toHash({ name: 'John' }, { algorithm: 'djb2' });

// Truncating hash output
const shortHash = await hashery.toHash(
  { name: 'John' },
  { algorithm: 'SHA-256', maxLength: 16 }
);
```

## `toHashSync(data, options?)`

Generates a hash of the provided data synchronously using a non-cryptographic hash algorithm. The data is first stringified using the configured stringify function, then hashed.

**Important:** This method only works with synchronous hash providers (djb2, fnv1, murmer, crc32). WebCrypto algorithms (SHA-256, SHA-384, SHA-512) are not supported and will throw an error.

**Parameters:**
- `data` (unknown) - The data to hash (will be stringified before hashing)
- `options` (object, optional) - Configuration options
  - `algorithm` (string, optional) - The hash algorithm to use (defaults to 'djb2')
  - `maxLength` (number, optional) - Maximum length for the hash output (truncates from the start)

**Returns:** `string` - The hexadecimal string representation of the hash

**Throws:** `Error` if the specified algorithm does not support synchronous hashing

**Example:**

```typescript
const hashery = new Hashery();

// Using default djb2
const hash = hashery.toHashSync({ name: 'John', age: 30 });

// Using a different algorithm
const hashFnv1 = hashery.toHashSync({ name: 'John' }, { algorithm: 'fnv1' });
const hashMurmer = hashery.toHashSync({ name: 'John' }, { algorithm: 'murmer' });
const hashCrc = hashery.toHashSync({ name: 'John' }, { algorithm: 'crc32' });

// Truncating hash output
const shortHash = hashery.toHashSync(
  { name: 'John' },
  { algorithm: 'djb2', maxLength: 4 }
);

// This will throw an error (WebCrypto not supported in sync mode)
// const invalid = hashery.toHashSync({ name: 'John' }, { algorithm: 'SHA-256' }); // ❌
```

## `toNumber(data, options?)`

Generates a deterministic number within a specified range based on the hash of the provided data (async). This method uses the toHash function to create a consistent hash, then maps it to a number between min and max (inclusive).

**Parameters:**
- `data` (unknown) - The data to hash (will be stringified before hashing)
- `options` (object, optional) - Configuration options
  - `min` (number, optional) - The minimum value of the range (inclusive, defaults to 0)
  - `max` (number, optional) - The maximum value of the range (inclusive, defaults to 100)
  - `algorithm` (string, optional) - The hash algorithm to use (defaults to 'SHA-256')
  - `hashLength` (number, optional) - Number of characters from hash to use for conversion (defaults to 16)

**Returns:** `Promise<number>` - A Promise that resolves to a number between min and max (inclusive)

**Throws:** Error if min is greater than max

**Example:**

```typescript
const hashery = new Hashery();

// Generate a number between 0 and 100 (default range)
const num = await hashery.toNumber({ user: 'john' });

// Generate a number with custom range
const num2 = await hashery.toNumber({ user: 'john' }, { min: 0, max: 100 });

// Using a different algorithm
const num512 = await hashery.toNumber({ user: 'john' }, { min: 0, max: 255, algorithm: 'SHA-512' });
```

## `toNumberSync(data, options?)`

Generates a deterministic number within a specified range based on the hash of the provided data synchronously. This method uses the toHashSync function to create a consistent hash, then maps it to a number between min and max (inclusive).

**Important:** This method only works with synchronous hash providers (djb2, fnv1, murmer, crc32).

**Parameters:**
- `data` (unknown) - The data to hash (will be stringified before hashing)
- `options` (object, optional) - Configuration options
  - `min` (number, optional) - The minimum value of the range (inclusive, defaults to 0)
  - `max` (number, optional) - The maximum value of the range (inclusive, defaults to 100)
  - `algorithm` (string, optional) - The hash algorithm to use (defaults to 'djb2')
  - `hashLength` (number, optional) - Number of characters from hash to use for conversion (defaults to 16)

**Returns:** `number` - A number between min and max (inclusive)

**Throws:**
- Error if min is greater than max
- Error if the specified algorithm does not support synchronous hashing

**Example:**

```typescript
const hashery = new Hashery();

// Generate a number between 0 and 100 (default range)
const num = hashery.toNumberSync({ user: 'john' });

// Generate a number with custom range
const slot = hashery.toNumberSync({ user: 'john' }, { min: 0, max: 9 });

// Using a different algorithm
const numFnv1 = hashery.toNumberSync({ user: 'john' }, { min: 0, max: 255, algorithm: 'fnv1' });

// A/B testing
const variant = hashery.toNumberSync({ userId: 'user123' }, { min: 0, max: 1 });
console.log(variant === 0 ? 'Group A' : 'Group B');

// Load balancing
const serverId = hashery.toNumberSync(
  { requestId: 'req_abc' },
  { min: 0, max: 9, algorithm: 'murmer' } // 10 servers
);

// This will throw an error (WebCrypto not supported in sync mode)
// const invalid = hashery.toNumberSync({ user: 'john' }, { algorithm: 'SHA-256' }); // ❌
```

## `loadProviders(providers?, options?)`

Loads hash providers into the Hashery instance. This allows you to add custom hash providers or replace the default ones.

**Parameters:**
- `providers` (Array<HashProvider>, optional) - Array of hash providers to add
- `options` (HasheryLoadProviderOptions, optional) - Options object
  - `includeBase` (boolean) - Whether to include base providers (default: true)

**Returns:** `void`

**Example:**

```typescript
const hashery = new Hashery();

// Add a custom provider
const customProvider = {
  name: 'custom',
  toHash: async (data: BufferSource) => 'custom-hash'
};

hashery.loadProviders([customProvider]);

// Load without base providers
hashery.loadProviders([customProvider], { includeBase: false });
```

# Benchmarks

Overall view of the current algorithm's and their performance using simple hashing with random data. `Sync` is when we use `toHashSync` and `Async` is the `toHash` function which requires `await`.

**NOTE: Many of these are not secure and should be used only for object hashing. Read about each one in the documentation and pick what works best for your use case.**

## Hashing
|      name       |  summary  |  ops/sec  |  time/op  |  margin  |  samples  |
|-----------------|:---------:|----------:|----------:|:--------:|----------:|
|  DJB2 Sync      |    🥇     |     708K  |      1µs  |  ±1.54%  |     669K  |
|  FNV1 Sync      |  -0.21%   |     707K  |      2µs  |  ±1.30%  |     665K  |
|  MURMER Sync    |   -1.2%   |     700K  |      2µs  |  ±0.60%  |     653K  |
|  CRC32 Sync     |   -1.2%   |     700K  |      2µs  |  ±1.55%  |     652K  |
|  CRC32 Async    |   -11%    |     630K  |      2µs  |  ±0.50%  |     598K  |
|  DJB2 Async     |   -11%    |     629K  |      2µs  |  ±0.55%  |     597K  |
|  FNV1 Async     |   -12%    |     623K  |      2µs  |  ±0.82%  |     581K  |
|  SHA-512 Async  |   -14%    |     612K  |      2µs  |  ±0.47%  |     548K  |
|  SHA-384 Async  |   -14%    |     611K  |      2µs  |  ±0.51%  |     549K  |
|  MURMER Async   |   -14%    |     608K  |      2µs  |  ±0.61%  |     569K  |
|  SHA-256 Async  |   -16%    |     593K  |      2µs  |  ±0.52%  |     522K  |

## Hashing without Caching
|      name       |  summary  |  ops/sec  |  time/op  |  margin  |  samples  |
|-----------------|:---------:|----------:|----------:|:--------:|----------:|
|  DJB2 Sync      |    🥇     |     542K  |      2µs  |  ±0.28%  |     514K  |
|  MURMER Sync    |   -1.5%   |     533K  |      2µs  |  ±0.71%  |     499K  |
|  FNV1 Sync      |   -12%    |     478K  |      2µs  |  ±0.33%  |     456K  |
|  DJB2 Async     |   -12%    |     477K  |      2µs  |  ±0.38%  |     451K  |
|  MURMER Async   |   -13%    |     471K  |      2µs  |  ±0.40%  |     447K  |
|  FNV1 Async     |   -22%    |     425K  |      2µs  |  ±1.32%  |     403K  |
|  CRC32 Sync     |   -37%    |     342K  |      3µs  |  ±0.84%  |     329K  |
|  CRC32 Async    |   -38%    |     338K  |      3µs  |  ±0.34%  |     326K  |
|  SHA-256 Async  |   -88%    |      67K  |     16µs  |  ±0.69%  |      63K  |
|  SHA-384 Async  |   -89%    |      62K  |     17µs  |  ±0.45%  |      59K  |
|  SHA-512 Async  |   -89%    |      59K  |     18µs  |  ±0.63%  |      55K  |

Caching is enabled by default and is a simple FIFO with default max keys at `4000`. The performance gain is greater than 20%+ on average. Some of the biggest gains are on `SHA` hashing which 10x when caching is enabled.

# Code of Conduct and Contributing
Please use our [Code of Conduct](CODE_OF_CONDUCT.md) and [Contributing](CONTRIBUTING.md) guidelines for development and testing. We appreciate your contributions!

# License and Copyright

[MIT](LICENSE) & © [Jared Wray](https://jaredwray.com)