bianhaifeng789-hue/skills-experimental/djb2-hash-pattern

djb2 Hash Pattern Skill

djb2 Hash Pattern - djb2Hash function + signed 32-bit int + hash << 5 - hash + charCode | 0 + fast non-cryptographic + deterministic cross-runtime + Bun.hash fallback + hashContent + hashPair seed-chain + wyhash vs SHA-256。

功能概述

从Claude Code的utils/hash.ts提取的djb2 hash模式，用于OpenClaw的快速哈希计算。

核心机制

djb2Hash Function

export function djb2Hash(str: string): number {
  let hash = 0
  for (let i = 0; i < str.length; i++) {
    hash = ((hash << 5) - hash + str.charCodeAt(i)) | 0
  }
  return hash
}
// djb2 string hash
# Signed 32-bit int
# Fast non-cryptographic

signed 32-bit int

| 0  // Convert to signed 32-bit integer
// JavaScript bitwise OR coerces to 32-bit signed int
# Prevents overflow
# Deterministic across runtimes

hash << 5 - hash + charCode

hash = ((hash << 5) - hash + str.charCodeAt(i)) | 0
// hash * 33 + charCode (equivalent to << 5 - hash)
# djb2 algorithm
# Daniel J. Bernstein hash

fast Non-Cryptographic

// djb2 string hash — fast non-cryptographic hash returning a signed 32-bit int.
// ~100x faster than SHA-256
// Not crypto-safe (collision-prone)
# Speed over security

deterministic Cross-Runtime

// Deterministic across runtimes (unlike Bun.hash which uses wyhash)
// Use as a fallback when Bun.hash isn't available
// Or when you need on-disk-stable output (e.g. cache directory names)
// Same hash across Bun, Node, browsers
# On-disk-stable

Bun.hash Fallback

export function hashContent(content: string): string {
  if (typeof Bun !== 'undefined') {
    return Bun.hash(content).toString()  // ~100x faster
  }
  const crypto = require('crypto')
  return crypto.createHash('sha256').update(content).digest('hex')  // Fallback
}
// Bun.hash ~100x faster than SHA-256
# Node fallback to SHA-256

hashContent Function

// Hash arbitrary content for change detection
// Bun.hash is ~100x faster than sha256
// Collision-resistant enough for diff detection (not crypto-safe)
// For diff/change detection
# Not crypto-safe

hashPair Seed-Chain

export function hashPair(a: string, b: string): string {
  if (typeof Bun !== 'undefined') {
    return Bun.hash(b, Bun.hash(a)).toString()  // Seed-chain
  }
  const crypto = require('crypto')
  return crypto
    .createHash('sha256')
    .update(a)
    .update('\0')  // Separator for Node
    .update(b)
    .digest('hex')
}
// Bun: seed-chain wyhash
# Node: incremental SHA-256 with separator

wyhash vs SHA-256

// Bun.hash uses wyhash (fast)
// Node uses SHA-256 (slow but standard)
// wyhash: ~100x faster than SHA-256
// SHA-256: crypto-safe (but slower)
# Bun: wyhash fast
# Node: SHA-256 safe

Separator-free Seed-Chain

// Bun path seed-chains wyhash (hash(a) feeds as seed to hash(b))
// Naturally disambiguates ("ts","code") vs ("tsc","ode")
// No separator needed under Bun
// Seed-chain disambiguates
# No separator

Node Separator

// Node path uses incremental SHA-256 update
// .update('\0') separator needed
// Separator prevents collisions
# '\0' separator for Node

实现建议

OpenClaw适配

1. djb2Hash: djb2Hash function
2. signed32bit: Signed 32-bit int pattern
3. deterministicHash: Deterministic cross-runtime
4. bunHashFallback: Bun.hash fallback pattern
5. hashPairSeedChain: hashPair seed-chain pattern

状态文件示例

{
  "djb2Hash": 1234567890,
  "hashContent": "abc123",
  "runtime": "bun"
}

关键模式

djb2 Algorithm

hash << 5 - hash + charCode | 0 → hash * 33 + char → signed 32-bit → fast non-crypto
# djb2算法
# hash * 33 + charCode
# | 0转signed 32-bit

Cross-Runtime Determinism

djb2Hash: same result in Bun/Node/Browser | Bun.hash: wyhash runtime-specific
# djb2跨runtime确定性
# Bun.hash使用wyhash（runtime-specific）

Bun.hash ~100x Faster

Bun.hash(content) → wyhash → ~100x faster than SHA-256 → change detection
# Bun.hash快100倍
# wyhash算法
# change detection用途

Seed-Chain Disambiguation

Bun.hash(b, Bun.hash(a)) → seed-chain → ("ts","code") ≠ ("tsc","ode") → no separator
# Bun seed-chain disambiguates
# 无需separator
# wyhash特性

Node Separator vs Bun None

Node: update('\0') separator | Bun: seed-chain no separator → different handling
# Node需要separator
# Bun不需要
# 不同处理方式

借用价值

• ⭐⭐⭐⭐⭐ djb2Hash fast non-crypto pattern
• ⭐⭐⭐⭐⭐ Signed 32-bit int coercion
• ⭐⭐⭐⭐⭐ Cross-runtime determinism
• ⭐⭐⭐⭐⭐ Bun.hash ~100x faster fallback
• ⭐⭐⭐⭐⭐ hashPair seed-chain pattern

来源

• Claude Code: utils/hash.ts (46 lines)
• 分析报告: P52-4