go 40 lines · 5 steps

Gzip round-trip compression in Go

A pair of functions that compress bytes into a gzip stream and read them back out again.

Explained by highlit
Intermediate compression io error-handling buffers
1package archive
2 
3import (
4 "bytes"
5 "compress/gzip"
6 "fmt"
7 "io"
8)
9 
10func Compress(data []byte, name string) ([]byte, error) {
11 var buf bytes.Buffer
12 zw, err := gzip.NewWriterLevel(&buf, gzip.BestCompression)
13 if err != nil {
14 return nil, fmt.Errorf("init gzip writer: %w", err)
15 }
16 zw.Name = name
17 
18 if _, err := zw.Write(data); err != nil {
19 zw.Close()
20 return nil, fmt.Errorf("write payload: %w", err)
21 }
22 if err := zw.Close(); err != nil {
23 return nil, fmt.Errorf("flush gzip stream: %w", err)
24 }
25 return buf.Bytes(), nil
26}
27 
28func Decompress(gzipped []byte) ([]byte, error) {
29 zr, err := gzip.NewReader(bytes.NewReader(gzipped))
30 if err != nil {
31 return nil, fmt.Errorf("open gzip stream: %w", err)
32 }
33 defer zr.Close()
34 
35 out, err := io.ReadAll(zr)
36 if err != nil {
37 return nil, fmt.Errorf("read %q: %w", zr.Name, err)
38 }
39 return out, nil
40}
01 / 01
STEP 01

Walkthrough

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Three takeaways
  1. 1Wrapping a bytes.Buffer with a gzip writer lets you build a compressed blob entirely in memory.
  2. 2The gzip Close call flushes trailing data, so its error must be checked rather than deferred and ignored.
  3. 3Wrapping errors with %w preserves the underlying cause while adding context about which stage failed.

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