github.com/cespare/xxhash/v2 v2.1.1: Sum64, Sum64String, New

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify pkg:golang/github.com/cespare/xxhash/v2@v2.1.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/cespare/xxhash/v2@v2.1.1
Constraints:
  - executionContext: node
Required runtime conditions:
  - ecosystem: npm
  - language: javascript
  - moduleSystem: cjs
  - packageManager: npm@10.9.8
  - runtime: node@22.23.2

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:cdcf7b48c52b2dbed4edc1591c14ea5c777bddd9acadaf26e51107a71ec04665","contract":["xxhash.Sum64 returns consistent 64-bit hash for byte slice","xxhash.Sum64String produces identical hash to Sum64 on matching string","xxhash.Sum64 and Sum64String handle empty input identically","xxhash.New streaming Digest matches one-shot Sum64 calculation","xxhash.Digest Reset clears state for subsequent hashing"],"goal":"verify pkg:golang/github.com/cespare/xxhash/v2@v2.1.1","kind":"HOW","packages":["pkg:golang/github.com/cespare/xxhash/v2@v2.1.1"],"schemaVersion":1,"symbols":["github.com/cespare/xxhash/v2.Sum64","github.com/cespare/xxhash/v2.Sum64String","github.com/cespare/xxhash/v2.New"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","ecosystem":"golang","os":"linux","osVersionBucket":"24","packageManager":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/github.com/cespare/xxhash/v2@v2.1.1"],"schemaVersion":1,"subject":"pkg:golang/github.com/cespare/xxhash/v2@v2.1.1","symbols":["github.com/cespare/xxhash/v2.Sum64","github.com/cespare/xxhash/v2.Sum64String","github.com/cespare/xxhash/v2.New"],"verifierAdapter":"golang@1"}

module sample

go 1.26

require github.com/cespare/xxhash/v2 v2.1.1

github.com/cespare/xxhash/v2 v2.1.1 h1:6MnRN8NT7+YBpUIWxHtefFZOKTAPgGjpQSxqLNn0+qY=
github.com/cespare/xxhash/v2 v2.1.1/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=

package main

import (
	"fmt"
	"hash"

	"github.com/cespare/xxhash/v2"
)

// HashBytes computes the 64-bit xxHash checksum of a byte slice.
func HashBytes(b []byte) uint64 {
	return xxhash.Sum64(b)
}

// HashString computes the 64-bit xxHash checksum of a string.
func HashString(s string) uint64 {
	return xxhash.Sum64String(s)
}

// NewHasher returns a new hash.Hash64 instance for streaming hashing.
func NewHasher() hash.Hash64 {
	return xxhash.New()
}

func main() {
	data := "hello world"
	h1 := HashBytes([]byte(data))
	h2 := HashString(data)

	hasher := NewHasher()
	hasher.Write([]byte(data))
	h3 := hasher.Sum64()

	fmt.Printf("Sum64:       %d\n", h1)
	fmt.Printf("Sum64String: %d\n", h2)
	fmt.Printf("Streaming:   %d\n", h3)
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:golang/github.com/cespare/xxhash/v2@v2.1.1",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/cespare/xxhash/v2@v2.1.1"
  ],
  "symbols": [
    "github.com/cespare/xxhash/v2.Sum64",
    "github.com/cespare/xxhash/v2.Sum64String",
    "github.com/cespare/xxhash/v2.New"
  ]
}

package main

import (
	"fmt"
	"os"

	"github.com/cespare/xxhash/v2"
)

func assertTrue(name string, condition bool) {
	if !condition {
		fmt.Fprintf(os.Stderr, "Assertion failed for %s: expected true, got false\n", name)
		os.Exit(1)
	}
}

func assertEqualUint64(name string, actual, expected uint64) {
	if actual != expected {
		fmt.Fprintf(os.Stderr, "Assertion failed for %s: got %d, expected %d\n", name, actual, expected)
		os.Exit(1)
	}
}

func main() {
	// Contract: xxhash.Sum64 returns consistent 64-bit hash for byte slice
	bytesInput := []byte("CodeSampleX xxhash test payload")
	hash1 := xxhash.Sum64(bytesInput)
	hash2 := xxhash.Sum64(bytesInput)
	assertEqualUint64("xxhash.Sum64 returns consistent hash", hash1, hash2)
	assertTrue("xxhash.Sum64 returns non-zero hash", hash1 != 0)

	// Contract: xxhash.Sum64String produces identical hash to Sum64 on matching string
	stringInput := "CodeSampleX xxhash test payload"
	stringHash := xxhash.Sum64String(stringInput)
	assertEqualUint64("xxhash.Sum64String matches Sum64", stringHash, hash1)

	// Contract: xxhash.Sum64 and Sum64String handle empty input identically
	emptyBytesHash := xxhash.Sum64([]byte{})
	emptyStringHash := xxhash.Sum64String("")
	assertEqualUint64("empty input produces matching hash", emptyBytesHash, emptyStringHash)

	// Contract: xxhash.New streaming Digest matches one-shot Sum64 calculation
	digest := xxhash.New()
	n, err := digest.Write([]byte("CodeSampleX "))
	assertTrue("digest.Write returns nil error", err == nil)
	assertTrue("digest.Write writes correct byte count", n == len("CodeSampleX "))

	n, err = digest.WriteString("xxhash test payload")
	assertTrue("digest.WriteString returns nil error", err == nil)
	assertTrue("digest.WriteString writes correct byte count", n == len("xxhash test payload"))

	streamingHash := digest.Sum64()
	assertEqualUint64("streaming Sum64 matches one-shot Sum64", streamingHash, hash1)

	// Contract: xxhash.Digest Reset clears state for subsequent hashing
	digest.Reset()
	digest.Write([]byte("different payload"))
	resetHash := digest.Sum64()
	expectedDifferentHash := xxhash.Sum64String("different payload")
	assertEqualUint64("reset digest computes correct hash for new data", resetHash, expectedDifferentHash)
	assertTrue("different data produces different hash", resetHash != hash1)

	fmt.Println("All contract assertions passed successfully.")
}