github.com/klauspost/compress v1.18.0: compress and decompress data using zstd encoder and decoder

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: compress and decompress data using zstd encoder and decoder
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/klauspost/compress@v1.18.0
Demonstrate these symbols/APIs:
  - zstd.NewReader
  - zstd.NewWriter
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.

package sample

import (
	"bytes"
	"fmt"
	"io"

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

// Compress compresses the input data using zstd writer.
func Compress(src []byte) ([]byte, error) {
	var buf bytes.Buffer
	writer, err := zstd.NewWriter(&buf)
	if err != nil {
		return nil, fmt.Errorf("zstd new writer: %w", err)
	}

	if _, err := writer.Write(src); err != nil {
		_ = writer.Close()
		return nil, fmt.Errorf("zstd write: %w", err)
	}

	if err := writer.Close(); err != nil {
		return nil, fmt.Errorf("zstd close: %w", err)
	}

	return buf.Bytes(), nil
}

// Decompress decompresses the zstd-compressed data using zstd reader.
func Decompress(src []byte) ([]byte, error) {
	reader, err := zstd.NewReader(bytes.NewReader(src))
	if err != nil {
		return nil, fmt.Errorf("zstd new reader: %w", err)
	}
	defer reader.Close()

	decompressed, err := io.ReadAll(reader)
	if err != nil {
		return nil, fmt.Errorf("zstd read: %w", err)
	}

	return decompressed, nil
}

package sample

import (
	"bytes"
	"testing"
)

func TestZstdCompressDecompress(t *testing.T) {
	original := []byte("Hello, CodeSampleX zstd compression and decompression contract test!")

	compressed, err := Compress(original)
	if err != nil {
		t.Fatalf("Compress failed: %v", err)
	}

	if len(compressed) == 0 {
		t.Fatalf("Compressed data is empty")
	}

	decompressed, err := Decompress(compressed)
	if err != nil {
		t.Fatalf("Decompress failed: %v", err)
	}

	if !bytes.Equal(original, decompressed) {
		t.Fatalf("Decompressed data mismatch: got %q, want %q", string(decompressed), string(original))
	}
}

func TestZstdEmptyData(t *testing.T) {
	original := []byte("")

	compressed, err := Compress(original)
	if err != nil {
		t.Fatalf("Compress empty failed: %v", err)
	}

	decompressed, err := Decompress(compressed)
	if err != nil {
		t.Fatalf("Decompress empty failed: %v", err)
	}

	if !bytes.Equal(original, decompressed) {
		t.Fatalf("Decompressed data mismatch on empty input: got %q, want %q", string(decompressed), string(original))
	}
}

{"case":{"caseId":"case:sha256:47a17c42741f84ed2c3d160700077fb907bae0b2dd682e3abc78c1636f89d7f8","contract":["zstd.NewWriter compresses data stream and flushes successfully","zstd.NewReader decompresses data stream and restores exact original payload","compress and decompress roundtrips empty input payload without error"],"goal":"compress and decompress data using zstd encoder and decoder","kind":"HOW","packages":["pkg:golang/github.com/klauspost/compress@v1.18.0"],"schemaVersion":1,"symbols":["zstd.NewReader","zstd.NewWriter"]},"contractCommand":["go","test","-v","./..."],"environment":{"arch":"amd64","compiler":"go","compilerVersion":"1.26.6","ecosystem":"golang","language":"go","os":"linux","packageManager":"go","packageManagerVersion":"1.26.6","runtime":"go","runtimeVersion":"1.26.6","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/github.com/klauspost/compress@v1.18.0"],"schemaVersion":1,"subject":"pkg:golang/github.com/klauspost/compress@v1.18.0","symbols":["zstd.NewReader","zstd.NewWriter"],"verifierAdapter":"golang@1"}

module example.com/zstd-sample

go 1.26

require github.com/klauspost/compress v1.18.0

github.com/klauspost/compress v1.18.0 h1:c/Cqfb0r+Yi+JtIEq73FWXVkRonBlf0CRNYc8Zttxdo=
github.com/klauspost/compress v1.18.0/go.mod h1:2Pp+KzxcywXVXMr50+X0Q/Lsb43OQHYWRCY2AiWywWQ=

{
  "schemaVersion": 1,
  "goal": "compress and decompress data using zstd encoder and decoder",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/klauspost/compress@v1.18.0"
  ],
  "symbols": [
    "zstd.NewReader",
    "zstd.NewWriter"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}