github.com/klauspost/compress v1.18.0: zstd.NewReader

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/klauspost/compress/zstd.NewReader in pkg:golang/github.com/klauspost/compress@v1.18.0
Kind: HOW

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

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

func TestZstdNewReaderValidStream(t *testing.T) {
	original := []byte("CodeSampleX verification payload for github.com/klauspost/compress/zstd.NewReader")

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

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

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

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

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

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

	if len(decompressed) != 0 {
		t.Fatalf("Decompressed data should be empty, got %d bytes", len(decompressed))
	}
}

func TestZstdNewReaderCorruptedStream(t *testing.T) {
	corruptedData := []byte("invalid non-zstd header bytes payload")

	reader, err := zstd.NewReader(bytes.NewReader(corruptedData))
	if err != nil {
		// NewReader returned error immediately on invalid header
		return
	}
	defer reader.Close()

	_, readErr := io.ReadAll(reader)
	if readErr == nil {
		t.Fatalf("expected error reading corrupted zstd stream, but got nil")
	}
}

func TestZstdNewReaderWithOptionsAndReset(t *testing.T) {
	payload1 := []byte("First zstd stream chunk")
	payload2 := []byte("Second zstd stream chunk after decoder reset")

	compressed1, err := CompressBytes(payload1)
	if err != nil {
		t.Fatalf("CompressBytes payload1 failed: %v", err)
	}
	compressed2, err := CompressBytes(payload2)
	if err != nil {
		t.Fatalf("CompressBytes payload2 failed: %v", err)
	}

	// Initialize with decoder option
	reader, err := zstd.NewReader(bytes.NewReader(compressed1), zstd.WithDecoderConcurrency(1))
	if err != nil {
		t.Fatalf("zstd.NewReader with options failed: %v", err)
	}
	defer reader.Close()

	out1, err := io.ReadAll(reader)
	if err != nil {
		t.Fatalf("ReadAll payload1 failed: %v", err)
	}
	if !bytes.Equal(payload1, out1) {
		t.Fatalf("payload1 mismatch: got %q, want %q", string(out1), string(payload1))
	}

	// Reset decoder with payload2
	if err := reader.Reset(bytes.NewReader(compressed2)); err != nil {
		t.Fatalf("reader.Reset failed: %v", err)
	}

	out2, err := io.ReadAll(reader)
	if err != nil {
		t.Fatalf("ReadAll payload2 failed: %v", err)
	}
	if !bytes.Equal(payload2, out2) {
		t.Fatalf("payload2 mismatch: got %q, want %q", string(out2), string(payload2))
	}
}

{"case":{"caseId":"case:sha256:692ab0216a813f03897ffd4479ef357c878cee8ce1826ba52bb00d714efd2941","constraints":{"executionContext":"node"},"contract":["zstd.NewReader decompresses valid zstd stream and restores exact original payload","zstd.NewReader decompresses empty stream payload correctly","zstd.NewReader returns error when reading invalid or corrupted stream","zstd.NewReader supports concurrent decoder options and stream resetting"],"goal":"verify github.com/klauspost/compress/zstd.NewReader in pkg:golang/github.com/klauspost/compress@v1.18.0","kind":"HOW","packages":["pkg:golang/github.com/klauspost/compress@v1.18.0"],"schemaVersion":1,"symbols":["github.com/klauspost/compress/zstd.NewReader"]},"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":["github.com/klauspost/compress/zstd.NewReader"],"verifierAdapter":"golang@1"}

module example.com/zstd-reader-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=

package sample

import (
	"bytes"
	"fmt"
	"io"

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

// CompressBytes encodes source data into zstd compressed stream format.
func CompressBytes(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
}

// DecompressReader creates a zstd.NewReader stream decoder to read and decompress data.
func DecompressReader(r io.Reader, opts ...zstd.DOption) ([]byte, error) {
	reader, err := zstd.NewReader(r, opts...)
	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 all: %w", err)
	}

	return decompressed, nil
}

// DecompressBytes decodes zstd compressed bytes using zstd.NewReader on a byte stream.
func DecompressBytes(compressed []byte, opts ...zstd.DOption) ([]byte, error) {
	return DecompressReader(bytes.NewReader(compressed), opts...)
}

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