prog: add (de)compression wrappers

Add the file `compression.go`, with entry points for
compressing/decompressing using `zlib`, and encoding/decoding Base64.

Also add roundtrip compress/decompress and encode/decode tests.

2 files changed, 117 insertions, 0 deletions

diff --git a/prog/compression.go b/prog/compression.go
new file mode 100644
index 000000000..07c3bd02c
--- /dev/null
+++ b/prog/compression.go
@@ -0,0 +1,67 @@
+// 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 prog
+
+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) {
+	zlibReader, err := zlib.NewReader(bytes.NewReader(compressedData))
+	if err != nil {
+		return nil, fmt.Errorf("could not initialise zlib: %v", err)
+	}
+
+	data, err := io.ReadAll(zlibReader)
+	if err != nil {
+		return nil, fmt.Errorf("could not read data with zlib: %v", err)
+	}
+
+	err = zlibReader.Close()
+	return data, err
+}
+
+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/prog/compression_test.go b/prog/compression_test.go
new file mode 100644
index 000000000..b46f70999
--- /dev/null
+++ b/prog/compression_test.go
@@ -0,0 +1,50 @@
+// 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 prog
+
+import (
+	"bytes"
+	"fmt"
+	"math/rand"
+	"testing"
+)
+
+func TestCompress(t *testing.T) {
+	r := rand.New(randSource(t))
+	err := testRoundTrip(r, Compress, Decompress)
+	if err != nil {
+		t.Fatalf("compress/decompress %v", err)
+	}
+}
+
+func TestEncode(t *testing.T) {
+	r := rand.New(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 < iterCount(); i++ {
+		randBytes := randomBytes(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
+}
+
+func randomBytes(r *rand.Rand) []byte {
+	const maxLen = 1 << 20 // 1 MB.
+	len := r.Intn(maxLen)
+	slice := make([]byte, len)
+	r.Read(slice)
+	return slice
+}