github.com/dgryski/go-farm v0.0.0-20190423205320-6a90982ecee2: Fingerprint32

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 github.com/dgryski/go-farm.Fingerprint32 in pkg:golang/github.com/dgryski/go-farm@v0.0.0-20190423205320-6a90982ecee2
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/dgryski/go-farm@v0.0.0-20190423205320-6a90982ecee2
Demonstrate these symbols/APIs:
  - github.com/dgryski/go-farm.Fingerprint32
Required runtime conditions:
  - ecosystem: golang
  - language: go
  - packageManager: go@1.26.6
  - runtime: go@1.26.6

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:sha256:531eab55ceaad707605616d38be26c21e19834146d53edf7ebb5e129374cff49","contract":["farm.Fingerprint32 computes a deterministic 32-bit fingerprint","farm.Fingerprint32 returns distinct fingerprints for distinct inputs","farm.Fingerprint32 handles empty byte slice without error"],"goal":"verify github.com/dgryski/go-farm.Fingerprint32 in pkg:golang/github.com/dgryski/go-farm@v0.0.0-20190423205320-6a90982ecee2","kind":"HOW","packages":["pkg:golang/github.com/dgryski/go-farm@v0.0.0-20190423205320-6a90982ecee2"],"schemaVersion":1,"symbols":["github.com/dgryski/go-farm.Fingerprint32"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","language":"go","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","packageManagerVersion":"1.26.6","runtime":"go","runtimeVersion":"1.26.6","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/github.com/dgryski/go-farm@v0.0.0-20190423205320-6a90982ecee2"],"schemaVersion":1,"subject":"pkg:golang/github.com/dgryski/go-farm@v0.0.0-20190423205320-6a90982ecee2","symbols":["github.com/dgryski/go-farm.Fingerprint32"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.22

require github.com/dgryski/go-farm v0.0.0-20190423205320-6a90982ecee2

github.com/dgryski/go-farm v0.0.0-20190423205320-6a90982ecee2 h1:tdlZCpZ/P9DhczCTSixgIKmwPv6+wP5DGjqLYw5SUiA=
github.com/dgryski/go-farm v0.0.0-20190423205320-6a90982ecee2/go.mod h1:SqUrOPUnsFjfmXRMNPybcSiG0BgUW2AuFH8PAnS2iTw=

package main

import (
	"fmt"

	farm "github.com/dgryski/go-farm"
)

func main() {
	data := []byte("Hello, FarmHash!")
	fp32 := farm.Fingerprint32(data)
	fmt.Printf("Fingerprint32: 0x%08x\n", fp32)
}

{
  "schemaVersion": 1,
  "goal": "verify github.com/dgryski/go-farm.Fingerprint32 in pkg:golang/github.com/dgryski/go-farm@v0.0.0-20190423205320-6a90982ecee2",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/dgryski/go-farm@v0.0.0-20190423205320-6a90982ecee2"
  ],
  "symbols": [
    "github.com/dgryski/go-farm.Fingerprint32"
  ],
  "runtimeConditions": {
    "ecosystem": "golang",
    "language": "go",
    "packageManager": "go@1.26.6",
    "runtime": "go@1.26.6"
  }
}

package main

import (
	"fmt"
	"os"

	farm "github.com/dgryski/go-farm"
)

func main() {
	input1 := []byte("The quick brown fox jumps over the lazy dog.")
	input2 := []byte("The quick brown fox jumps over the lazy cog.")

	// Test 1: farm.Fingerprint32 computes a deterministic 32-bit fingerprint
	fp1 := farm.Fingerprint32(input1)
	fp2 := farm.Fingerprint32(input1)
	if fp1 != fp2 {
		fmt.Fprintf(os.Stderr, "Fingerprint32 is non-deterministic: %d != %d\n", fp1, fp2)
		os.Exit(1)
	}

	// Test 2: farm.Fingerprint32 returns distinct fingerprints for distinct inputs
	fpDistinct := farm.Fingerprint32(input2)
	if fp1 == fpDistinct {
		fmt.Fprintf(os.Stderr, "Fingerprint32 collision on distinct inputs: %d\n", fp1)
		os.Exit(1)
	}

	// Test 3: farm.Fingerprint32 handles empty byte slice without error
	emptyFP := farm.Fingerprint32([]byte{})
	emptyFP2 := farm.Fingerprint32(nil)
	if emptyFP != emptyFP2 {
		fmt.Fprintf(os.Stderr, "Fingerprint32 empty vs nil mismatch: %d != %d\n", emptyFP, emptyFP2)
		os.Exit(1)
	}

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