Merge pull request #9 from AkihiroSuda/dev

go-qcow2reader-example: add zstd

Author: AkihiroSuda

.github/dependabot.yml

@@ -0,0 +1,16 @@
+version: 2
+updates:
+- package-ecosystem: gomod
+  directory: "/"
+  schedule:
+    interval: daily
+  open-pull-requests-limit: 10
+  reviewers:
+  - AkihiroSuda
+- package-ecosystem: github-actions
+  directory: "/"
+  schedule:
+    interval: daily
+  open-pull-requests-limit: 10
+  reviewers:
+  - AkihiroSuda

.github/workflows/test.yml

@@ -1,6 +1,8 @@
 name: test
 on:
   push:
+    branches:
+      - master
   pull_request:
 jobs:
   integration:
@@ -21,7 +23,7 @@ jobs:
       - name: Unit tests
         run: go test -v ./...
       - name: Install go-qcow2reader-example
-        run: go install ./cmd/go-qcow2reader-example
+        run: cd ./cmd/go-qcow2reader-example && go install
       - name: Install qemu-img as a test dependency
         run: |
           sudo apt-get update
@@ -43,9 +45,13 @@ jobs:
           # Create a child image, with a custom size
           qemu-img create -f qcow2 -b debian-11-genericcloud-amd64-20230501-1367.qcow2 -F qcow2 debian-11-genericcloud-amd64-20230501-1367.child_4G.qcow2 4G
           # TODO: write something to the child image (with qemu-nbd?)
+          # Convert to zstd
+          qemu-img convert -f qcow2 -O qcow2 -o compression_type=zstd debian-11-genericcloud-amd64-20230501-1367.qcow2 debian-11-genericcloud-amd64-20230501-1367.zstd.qcow2
       - name: Prepare test-images
         run: cp -a test-images-ro test-images
       - name: "Test debian-11-genericcloud-amd64-20230501-1367.qcow2"
         run: hack/compare-with-qemu-img.sh test-images/debian-11-genericcloud-amd64-20230501-1367.qcow2
       - name: "Test debian-11-genericcloud-amd64-20230501-1367.child_4G.qcow2 (child image, with a custom size)"
         run: hack/compare-with-qemu-img.sh test-images/debian-11-genericcloud-amd64-20230501-1367.child_4G.qcow2
+      - name: "Test debian-11-genericcloud-amd64-20230501-1367.zstd.qcow2"
+        run: hack/compare-with-qemu-img.sh test-images/debian-11-genericcloud-amd64-20230501-1367.zstd.qcow2

cmd/go-qcow2reader-example/go.mod

@@ -0,0 +1,10 @@
+module github.com/lima-vm/go-qcow2reader/cmd/go-qcow2reader-example
+
+go 1.20
+
+require (
+	github.com/klauspost/compress v1.16.5
+	github.com/lima-vm/go-qcow2reader v0.0.0-00010101000000-000000000000
+)
+
+replace github.com/lima-vm/go-qcow2reader => ../../

cmd/go-qcow2reader-example/go.sum

@@ -0,0 +1,2 @@
+github.com/klauspost/compress v1.16.5 h1:IFV2oUNUzZaz+XyusxpLzpzS8Pt5rh0Z16For/djlyI=
+github.com/klauspost/compress v1.16.5/go.mod h1:ntbaceVETuRiXiv4DpjP66DpAtAGkEQskQzEyD//IeE=

cmd/go-qcow2reader-example/main.go

@@ -8,8 +8,10 @@ import (
 	"io"
 	"os"
 
+	"github.com/klauspost/compress/zstd"
 	"github.com/lima-vm/go-qcow2reader"
 	"github.com/lima-vm/go-qcow2reader/image"
+	"github.com/lima-vm/go-qcow2reader/image/qcow2"
 	"github.com/lima-vm/go-qcow2reader/log"
 )
 
@@ -21,8 +23,29 @@ func debugPrint(s string) {
 	fmt.Fprintln(os.Stderr, "DEBUG: "+s)
 }
 
+type zstdDecompressor struct {
+	*zstd.Decoder
+}
+
+func (x *zstdDecompressor) Close() error {
+	x.Decoder.Close()
+	return nil
+}
+
+func newZstdDecompressor(r io.Reader) (io.ReadCloser, error) {
+	dec, err := zstd.NewReader(r)
+	if err != nil {
+		return nil, err
+	}
+	return &zstdDecompressor{dec}, nil
+}
+
 func main() {
 	log.SetWarnFunc(warn)
+
+	// zlib (deflate) decompressor is registered by default, but zstd is not.
+	qcow2.SetDecompressor(qcow2.CompressionTypeZstd, newZstdDecompressor)
+
 	if err := xmain(); err != nil {
 		fmt.Fprintln(os.Stderr, "ERROR: "+err.Error())
 		os.Exit(1)

image/qcow2/qcow2.go

@@ -184,10 +184,13 @@ func (x CompressionType) MarshalText() ([]byte, error) {
 	return []byte(x.String()), nil
 }
 
-type Decompressor func(r io.Reader) io.ReadCloser
+type Decompressor func(r io.Reader) (io.ReadCloser, error)
 
 var decompressors = map[CompressionType]Decompressor{
-	CompressionTypeZlib: flate.NewReader, // no zlib header
+	// no zlib header
+	CompressionTypeZlib: func(r io.Reader) (io.ReadCloser, error) {
+		return flate.NewReader(r), nil
+	},
 }
 
 // SetDecompressor sets a custom decompressor.
@@ -749,7 +752,10 @@ func (img *Qcow2) readAtAlignedCompressed(p []byte, off int64, desc compressedCl
 	additionalSectors := desc.additionalSectors(int(img.Header.ClusterBits))
 	compressedSize := img.clusterSize + 512*additionalSectors
 	compressedSR := io.NewSectionReader(img.ra, int64(hostClusterOffset), int64(compressedSize))
-	zr := img.decompressor(compressedSR)
+	zr, err := img.decompressor(compressedSR)
+	if err != nil {
+		return 0, fmt.Errorf("could not open the decompressor: %w", err)
+	}
 	defer zr.Close()
 	if discard := off % int64(img.clusterSize); discard != 0 {
 		if _, err := io.CopyN(io.Discard, zr, discard); err != nil {