pkg/image: factor out from prog

Move image compression-related function to a separate package.
In preperation for subsequent changes that make decompression
more complex. Prog package is already large and complex.
Also makes running compression tests/benchmarks much faster.

3 files changed, 118 insertions, 2 deletions

diff --git a/pkg/image/compression.go b/pkg/image/compression.go
new file mode 100644
index 000000000..9878b460d
--- /dev/null
+++ b/pkg/image/compression.go
@@ -0,0 +1,71 @@
+// Copyright 2022 syzkaller project authors. All rights reserved.
+// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
+
+package image
+
+import (
+	"bytes"
+	"compress/zlib"
+	"encoding/base64"
+	"fmt"
+	"io"
+)
+
+func Compress(rawData []byte) []byte {
+	var buffer bytes.Buffer
+	zlibWriter := zlib.NewWriter(&buffer)
+
+	_, err := zlibWriter.Write(rawData)
+	if err != nil {
+		panic(fmt.Sprintf("could not compress with zlib: %v", err))
+	}
+
+	err = zlibWriter.Close()
+	if err != nil {
+		panic(fmt.Sprintf("could not finalize compression with zlib: %v", err))
+	}
+
+	return buffer.Bytes()
+}
+
+func Decompress(compressedData []byte) ([]byte, error) {
+	buf := new(bytes.Buffer)
+	err := DecompressWriter(buf, compressedData)
+	return buf.Bytes(), err
+}
+
+func DecompressWriter(w io.Writer, compressedData []byte) error {
+	zlibReader, err := zlib.NewReader(bytes.NewReader(compressedData))
+	if err != nil {
+		return fmt.Errorf("could not initialise zlib: %v", err)
+	}
+
+	if _, err := io.Copy(w, zlibReader); err != nil {
+		return fmt.Errorf("could not read data with zlib: %v", err)
+	}
+
+	return zlibReader.Close()
+}
+
+func DecodeB64(b64Data []byte) ([]byte, error) {
+	decoder := base64.NewDecoder(base64.StdEncoding, bytes.NewReader(b64Data))
+	rawData, err := io.ReadAll(decoder)
+	if err != nil {
+		return nil, fmt.Errorf("could not decode Base64: %v", err)
+	}
+	return rawData, nil
+}
+
+func EncodeB64(rawData []byte) []byte {
+	var buf bytes.Buffer
+	encoder := base64.NewEncoder(base64.StdEncoding, &buf)
+	_, err := encoder.Write(rawData)
+	if err != nil {
+		panic(fmt.Sprintf("could not encode Base64: %v", err))
+	}
+	err = encoder.Close()
+	if err != nil {
+		panic(fmt.Sprintf("could not finalize encoding to Base64: %v", err))
+	}
+	return buf.Bytes()
+}
diff --git a/pkg/image/compression_test.go b/pkg/image/compression_test.go
new file mode 100644
index 000000000..cf18ed340
--- /dev/null
+++ b/pkg/image/compression_test.go
@@ -0,0 +1,44 @@
+// Copyright 2022 syzkaller project authors. All rights reserved.
+// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
+
+package image
+
+import (
+	"bytes"
+	"fmt"
+	"math/rand"
+	"testing"
+
+	"github.com/google/syzkaller/pkg/testutil"
+)
+
+func TestCompress(t *testing.T) {
+	r := rand.New(testutil.RandSource(t))
+	err := testRoundTrip(r, Compress, Decompress)
+	if err != nil {
+		t.Fatalf("compress/decompress %v", err)
+	}
+}
+
+func TestEncode(t *testing.T) {
+	r := rand.New(testutil.RandSource(t))
+	err := testRoundTrip(r, EncodeB64, DecodeB64)
+	if err != nil {
+		t.Fatalf("encode/decode Base64 %v", err)
+	}
+}
+
+func testRoundTrip(r *rand.Rand, transform func([]byte) []byte, inverse func([]byte) ([]byte, error)) error {
+	for i := 0; i < testutil.IterCount(); i++ {
+		randBytes := testutil.RandMountImage(r)
+		resultBytes := transform(randBytes)
+		resultBytes, err := inverse(resultBytes)
+		if err != nil {
+			return err
+		}
+		if !bytes.Equal(randBytes, resultBytes) {
+			return fmt.Errorf("roundtrip changes data (original length %d)", len(randBytes))
+		}
+	}
+	return nil
+}
diff --git a/pkg/ipc/ipc_test.go b/pkg/ipc/ipc_test.go
index c1d3af69a..a3ab140f1 100644
--- a/pkg/ipc/ipc_test.go
+++ b/pkg/ipc/ipc_test.go
@@ -13,6 +13,7 @@ import (
 	"time"
 
 	"github.com/google/syzkaller/pkg/csource"
+	"github.com/google/syzkaller/pkg/image"
 	. "github.com/google/syzkaller/pkg/ipc"
 	"github.com/google/syzkaller/pkg/ipc/ipcconfig"
 	"github.com/google/syzkaller/pkg/osutil"
@@ -210,9 +211,9 @@ func TestZlib(t *testing.T) {
 	r := rand.New(testutil.RandSource(t))
 	for i := 0; i < 10; i++ {
 		data := testutil.RandMountImage(r)
-		compressed := prog.Compress(data)
+		compressed := image.Compress(data)
 		text := fmt.Sprintf(`syz_compare_zlib(&(0x7f0000000000)="$%s", AUTO, &(0x7f0000800000)="$%s", AUTO)`,
-			prog.EncodeB64(data), prog.EncodeB64(compressed))
+			image.EncodeB64(data), image.EncodeB64(compressed))
 		p, err := target.Deserialize([]byte(text), prog.Strict)
 		if err != nil {
 			t.Fatalf("failed to deserialize empty program: %v", err)