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.

1 files changed, 50 insertions, 0 deletions

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
+}