github.com/klauspost/compress v1.20.0

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/klauspost/compress@v1.20.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/klauspost/compress@v1.20.0

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:sha256:85dc910c42fc5778dceda8f0a7cf91f0d1e024d17c26441e58e2ce1da6bce52e","contract":["s2.NewWriter compresses data stream and s2.NewReader decompresses to restore exact original payload","s2.NewWriter with WriterBetterCompression compresses data stream","s2.NewWriter and s2.NewReader correctly roundtrip empty input payload","s2.NewReader returns error when reading invalid or corrupted s2 stream","s2.NewWriter and s2.NewReader support stream reuse via Reset","s2.Encode compresses byte slice and s2.Decode decompresses to restore exact original payload"],"goal":"verify pkg:golang/github.com/klauspost/compress@v1.20.0","kind":"HOW","packages":["pkg:golang/github.com/klauspost/compress@v1.20.0"],"schemaVersion":1},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/github.com/klauspost/compress@v1.20.0"],"schemaVersion":1,"subject":"pkg:golang/github.com/klauspost/compress@v1.20.0","verifierAdapter":"golang@1"}

module example.com/sample

go 1.26.6

require github.com/klauspost/compress v1.20.0

github.com/klauspost/compress v1.20.0 h1:a3C1ke2ohxFymNlb2HWAHjDeKCI90scRskErZkR0ezA=
github.com/klauspost/compress v1.20.0/go.mod h1:LUdAzn7YLVvxLpc7y3V1m40wESHTgc1422pwwBSKYuI=

package main

import (
	"bytes"
	"fmt"
	"io"
	"log"

	"github.com/klauspost/compress/s2"
)

func main() {
	original := []byte("Hello, CodeSampleX with klauspost/compress s2!")

	var buf bytes.Buffer
	writer := s2.NewWriter(&buf)
	if _, err := writer.Write(original); err != nil {
		log.Fatalf("failed to write compressed data: %v", err)
	}
	if err := writer.Close(); err != nil {
		log.Fatalf("failed to close s2 writer: %v", err)
	}

	reader := s2.NewReader(&buf)
	decompressed, err := io.ReadAll(reader)
	if err != nil {
		log.Fatalf("failed to read decompressed data: %v", err)
	}

	fmt.Printf("Original:     %s\n", string(original))
	fmt.Printf("Decompressed: %s\n", string(decompressed))
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:golang/github.com/klauspost/compress@v1.20.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/klauspost/compress@v1.20.0"
  ]
}

package main

import (
	"bytes"
	"fmt"
	"io"
	"os"

	"github.com/klauspost/compress/s2"
)

func main() {
	// 1. s2.NewWriter compresses data stream and s2.NewReader decompresses to restore exact original payload
	{
		original := []byte("CodeSampleX verification payload for github.com/klauspost/compress/s2 streaming compression.")
		var buf bytes.Buffer
		sw := s2.NewWriter(&buf)
		if _, err := sw.Write(original); err != nil {
			fmt.Fprintf(os.Stderr, "s2.NewWriter Write failed: %v\n", err)
			os.Exit(1)
		}
		if err := sw.Close(); err != nil {
			fmt.Fprintf(os.Stderr, "s2.NewWriter Close failed: %v\n", err)
			os.Exit(1)
		}

		sr := s2.NewReader(&buf)
		decompressed, err := io.ReadAll(sr)
		if err != nil {
			fmt.Fprintf(os.Stderr, "s2.NewReader ReadAll failed: %v\n", err)
			os.Exit(1)
		}

		if !bytes.Equal(original, decompressed) {
			fmt.Fprintf(os.Stderr, "decompressed mismatch: got %q, want %q\n", string(decompressed), string(original))
			os.Exit(1)
		}
	}

	// 2. s2.NewWriter with WriterBetterCompression compresses data stream
	{
		sampleData := bytes.Repeat([]byte("High repetition pattern for testing klauspost s2 compression options. "), 40)
		var b bytes.Buffer
		sw := s2.NewWriter(&b, s2.WriterBetterCompression(), s2.WriterBlockSize(64*1024))
		if _, err := sw.Write(sampleData); err != nil {
			fmt.Fprintf(os.Stderr, "s2 write with options failed: %v\n", err)
			os.Exit(1)
		}
		if err := sw.Close(); err != nil {
			fmt.Fprintf(os.Stderr, "s2 close failed: %v\n", err)
			os.Exit(1)
		}

		sr := s2.NewReader(&b)
		decomp, err := io.ReadAll(sr)
		if err != nil {
			fmt.Fprintf(os.Stderr, "s2 read failed: %v\n", err)
			os.Exit(1)
		}

		if !bytes.Equal(sampleData, decomp) {
			fmt.Fprintf(os.Stderr, "options roundtrip mismatch\n")
			os.Exit(1)
		}
	}

	// 3. s2.NewWriter and s2.NewReader correctly roundtrip empty input payload
	{
		var emptyBuf bytes.Buffer
		swEmpty := s2.NewWriter(&emptyBuf)
		if err := swEmpty.Close(); err != nil {
			fmt.Fprintf(os.Stderr, "s2 empty write close failed: %v\n", err)
			os.Exit(1)
		}

		srEmpty := s2.NewReader(&emptyBuf)
		emptyDecomp, err := io.ReadAll(srEmpty)
		if err != nil {
			fmt.Fprintf(os.Stderr, "s2 empty read failed: %v\n", err)
			os.Exit(1)
		}

		if len(emptyDecomp) != 0 {
			fmt.Fprintf(os.Stderr, "expected empty decompressed payload, got %d bytes\n", len(emptyDecomp))
			os.Exit(1)
		}
	}

	// 4. s2.NewReader returns error when reading invalid or corrupted s2 stream
	{
		corrupted := []byte{0x12, 0x34, 0x56, 0x78, 0x9a, 0xbc}
		srBad := s2.NewReader(bytes.NewReader(corrupted))
		_, readErr := io.ReadAll(srBad)
		if readErr == nil {
			fmt.Fprintf(os.Stderr, "expected error reading corrupted s2 stream, got nil\n")
			os.Exit(1)
		}
	}

	// 5. s2.NewWriter and s2.NewReader support stream reuse via Reset
	{
		var buf1 bytes.Buffer
		swReuse := s2.NewWriter(&buf1)
		p1 := []byte("first stream payload for reusable s2 writer")
		if _, err := swReuse.Write(p1); err != nil {
			fmt.Fprintf(os.Stderr, "p1 write failed: %v\n", err)
			os.Exit(1)
		}
		if err := swReuse.Close(); err != nil {
			fmt.Fprintf(os.Stderr, "p1 close failed: %v\n", err)
			os.Exit(1)
		}

		var buf2 bytes.Buffer
		swReuse.Reset(&buf2)
		p2 := []byte("second stream payload after s2 writer reset")
		if _, err := swReuse.Write(p2); err != nil {
			fmt.Fprintf(os.Stderr, "p2 write failed: %v\n", err)
			os.Exit(1)
		}
		if err := swReuse.Close(); err != nil {
			fmt.Fprintf(os.Stderr, "p2 close failed: %v\n", err)
			os.Exit(1)
		}

		srReuse := s2.NewReader(&buf1)
		res1, err := io.ReadAll(srReuse)
		if err != nil || !bytes.Equal(res1, p1) {
			fmt.Fprintf(os.Stderr, "p1 mismatch: %v\n", err)
			os.Exit(1)
		}

		srReuse.Reset(&buf2)
		res2, err := io.ReadAll(srReuse)
		if err != nil || !bytes.Equal(res2, p2) {
			fmt.Fprintf(os.Stderr, "p2 mismatch: %v\n", err)
			os.Exit(1)
		}
	}

	// 6. s2.Encode compresses byte slice and s2.Decode decompresses to restore exact original payload
	{
		payload := []byte("Block-level s2 encoding and decoding contract test payload.")
		encoded := s2.Encode(nil, payload)
		if len(encoded) == 0 {
			fmt.Fprintf(os.Stderr, "s2.Encode returned empty slice\n")
			os.Exit(1)
		}
		decoded, err := s2.Decode(nil, encoded)
		if err != nil {
			fmt.Fprintf(os.Stderr, "s2.Decode failed: %v\n", err)
			os.Exit(1)
		}
		if !bytes.Equal(payload, decoded) {
			fmt.Fprintf(os.Stderr, "s2 block decode mismatch: got %q, want %q\n", string(decoded), string(payload))
			os.Exit(1)
		}
	}

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