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:sha256:6938b69798ff6f8f105b928836da27634d9dddbe46b56f12cdc4fdae97d55259","contract":["flate.NewWriter compresses data stream and flate.NewReader decompresses to restore exact original payload","flate.NewWriter compresses with specified compression levels including BestSpeed and BestCompression","flate.NewWriter and flate.NewReader correctly roundtrip empty input payload","flate.NewReader returns error when reading invalid or corrupted flate stream","flate.NewWriter and flate.NewReader support stream reuse via Reset","flate.NewWriterDict and flate.NewReaderDict support preset dictionaries for compression and decompression"],"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/flate"
)

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

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

	reader := flate.NewReader(&buf)
	defer reader.Close()

	decompressed, err := io.ReadAll(reader)
	if err != nil {
		log.Fatalf("failed to read decompressed flate 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/flate"
)

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

		zr := flate.NewReader(&buf)
		decompressed, err := io.ReadAll(zr)
		if err != nil {
			fmt.Fprintf(os.Stderr, "flate.NewReader ReadAll failed: %v\n", err)
			os.Exit(1)
		}
		if err := zr.Close(); err != nil {
			fmt.Fprintf(os.Stderr, "flate.NewReader Close 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. flate.NewWriter compresses with specified compression levels including BestSpeed and BestCompression
	{
		sampleData := bytes.Repeat([]byte("High repetition pattern for testing klauspost flate compression levels. "), 40)
		for _, level := range []int{flate.BestSpeed, flate.BestCompression, flate.HuffmanOnly} {
			var b bytes.Buffer
			zw, err := flate.NewWriter(&b, level)
			if err != nil {
				fmt.Fprintf(os.Stderr, "flate.NewWriter(%d) failed: %v\n", level, err)
				os.Exit(1)
			}
			if _, err := zw.Write(sampleData); err != nil {
				fmt.Fprintf(os.Stderr, "flate write with level %d failed: %v\n", level, err)
				os.Exit(1)
			}
			if err := zw.Close(); err != nil {
				fmt.Fprintf(os.Stderr, "flate close with level %d failed: %v\n", level, err)
				os.Exit(1)
			}

			zr := flate.NewReader(&b)
			decomp, err := io.ReadAll(zr)
			if err != nil {
				fmt.Fprintf(os.Stderr, "flate read for level %d failed: %v\n", level, err)
				os.Exit(1)
			}
			if err := zr.Close(); err != nil {
				fmt.Fprintf(os.Stderr, "flate reader close for level %d failed: %v\n", level, err)
				os.Exit(1)
			}
			if !bytes.Equal(sampleData, decomp) {
				fmt.Fprintf(os.Stderr, "level %d roundtrip mismatch\n", level)
				os.Exit(1)
			}
		}
	}

	// 3. flate.NewWriter and flate.NewReader correctly roundtrip empty input payload
	{
		var emptyBuf bytes.Buffer
		zwEmpty, err := flate.NewWriter(&emptyBuf, flate.DefaultCompression)
		if err != nil {
			fmt.Fprintf(os.Stderr, "flate empty writer creation failed: %v\n", err)
			os.Exit(1)
		}
		if err := zwEmpty.Close(); err != nil {
			fmt.Fprintf(os.Stderr, "flate empty write close failed: %v\n", err)
			os.Exit(1)
		}
		zrEmpty := flate.NewReader(&emptyBuf)
		emptyDecomp, err := io.ReadAll(zrEmpty)
		if err != nil {
			fmt.Fprintf(os.Stderr, "flate empty read failed: %v\n", err)
			os.Exit(1)
		}
		if err := zrEmpty.Close(); err != nil {
			fmt.Fprintf(os.Stderr, "flate empty reader close 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. flate.NewReader returns error when reading invalid or corrupted flate stream
	{
		corrupted := []byte{0x78, 0x9c, 0xff, 0xff, 0x00, 0x00}
		zrBad := flate.NewReader(bytes.NewReader(corrupted))
		_, readErr := io.ReadAll(zrBad)
		_ = zrBad.Close()
		if readErr == nil {
			fmt.Fprintf(os.Stderr, "expected error reading corrupted flate stream, got nil\n")
			os.Exit(1)
		}
	}

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

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

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

		if resetter, ok := zrReuse.(flate.Resetter); ok {
			if err := resetter.Reset(&buf2, nil); err != nil {
				fmt.Fprintf(os.Stderr, "resetter.Reset failed: %v\n", err)
				os.Exit(1)
			}
			res2, err := io.ReadAll(zrReuse)
			if err != nil || !bytes.Equal(res2, p2) {
				fmt.Fprintf(os.Stderr, "p2 mismatch: %v\n", err)
				os.Exit(1)
			}
		} else {
			fmt.Fprintf(os.Stderr, "reader does not implement flate.Resetter\n")
			os.Exit(1)
		}
		_ = zrReuse.Close()
	}

	// 6. flate.NewWriterDict and flate.NewReaderDict support preset dictionaries for compression and decompression
	{
		dict := []byte("frequently occurring common dictionary words and phrases")
		payload := []byte("frequently occurring common dictionary words and phrases used in the payload text")
		var buf bytes.Buffer
		zwDict, err := flate.NewWriterDict(&buf, flate.DefaultCompression, dict)
		if err != nil {
			fmt.Fprintf(os.Stderr, "flate.NewWriterDict failed: %v\n", err)
			os.Exit(1)
		}
		if _, err := zwDict.Write(payload); err != nil {
			fmt.Fprintf(os.Stderr, "zwDict write failed: %v\n", err)
			os.Exit(1)
		}
		if err := zwDict.Close(); err != nil {
			fmt.Fprintf(os.Stderr, "zwDict close failed: %v\n", err)
			os.Exit(1)
		}

		zrDict := flate.NewReaderDict(&buf, dict)
		decompDict, err := io.ReadAll(zrDict)
		if err != nil {
			fmt.Fprintf(os.Stderr, "zrDict read failed: %v\n", err)
			os.Exit(1)
		}
		if err := zrDict.Close(); err != nil {
			fmt.Fprintf(os.Stderr, "zrDict close failed: %v\n", err)
			os.Exit(1)
		}
		if !bytes.Equal(payload, decompDict) {
			fmt.Fprintf(os.Stderr, "dict roundtrip mismatch: got %q, want %q\n", string(decompDict), string(payload))
			os.Exit(1)
		}
	}

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