next.js/packages/next/src/shared/lib/hash.ts

// http://www.cse.yorku.ca/~oz/hash.html
// More specifically, 32-bit hash via djbxor
// (ref: https://gist.github.com/eplawless/52813b1d8ad9af510d85?permalink_comment_id=3367765#gistcomment-3367765)
// This is due to number type differences between rust for turbopack to js number types,
// where rust does not have easy way to repreesnt js's 53-bit float number type for the matching
// overflow behavior. This is more `correct` in terms of having canonical hash across different runtime / implementation
// as can gaurantee determinstic output from 32bit hash.
export function djb2Hash(str: string) {
  let hash = 5381
  for (let i = 0; i < str.length; i++) {
    const char = str.charCodeAt(i)
    hash = ((hash << 5) + hash + char) & 0xffffffff
  }
  return hash >>> 0
}

export function hexHash(str: string) {
  return djb2Hash(str).toString(36).slice(0, 5)
}