2 files changed, 153 insertions, 0 deletions
diff --git a/storage/filter/filter.go b/storage/filter/filter.go
new file mode 100644
index 0000000..52ecbfd
--- /dev/null
+++ b/storage/filter/filter.go
@@ -0,0 +1,77 @@
+package filter
+
+import (
+	"bytes"
+	"code.laria.me/petrific/objects"
+	"code.laria.me/petrific/storage"
+	"errors"
+	"os/exec"
+)
+
+type Filter interface {
+	Transform([]byte) ([]byte, error)
+}
+
+type PipeFilter []string
+
+var emptyCommand = errors.New("Need at least one argument for pipeFilter")
+
+func (pf PipeFilter) Transform(b []byte) ([]byte, error) {
+	if len(pf) == 0 {
+		return []byte{}, emptyCommand
+	}
+
+	cmd := exec.Command(pf[0], pf[1:]...)
+
+	buf := new(bytes.Buffer)
+	cmd.Stdout = buf
+	cmd.Stdin = bytes.NewReader(b)
+
+	if err := cmd.Run(); err != nil {
+		return []byte{}, err
+	}
+
+	return buf.Bytes(), nil
+}
+
+type FilterStorage struct {
+	Base           storage.Storage
+	Decode, Encode Filter
+}
+
+func (filt FilterStorage) Get(id objects.ObjectId) ([]byte, error) {
+	data, err := filt.Base.Get(id)
+	if err != nil {
+		return data, err
+	}
+
+	if filt.Decode == nil {
+		return data, nil
+	}
+
+	return filt.Decode.Transform(data)
+}
+
+func (filt FilterStorage) Has(id objects.ObjectId) (bool, error) {
+	return filt.Base.Has(id)
+}
+
+func (filt FilterStorage) Set(id objects.ObjectId, typ objects.ObjectType, raw []byte) error {
+	if filt.Encode != nil {
+		var err error
+		raw, err = filt.Encode.Transform(raw)
+		if err != nil {
+			return err
+		}
+	}
+
+	return filt.Base.Set(id, typ, raw)
+}
+
+func (filt FilterStorage) List(typ objects.ObjectType) ([]objects.ObjectId, error) {
+	return filt.Base.List(typ)
+}
+
+func (filt FilterStorage) Close() error {
+	return filt.Base.Close()
+}
diff --git a/storage/filter/filter_test.go b/storage/filter/filter_test.go
new file mode 100644
index 0000000..78d4e7f
--- /dev/null
+++ b/storage/filter/filter_test.go
@@ -0,0 +1,76 @@
+package filter
+
+import (
+	"bytes"
+	"code.laria.me/petrific/backup"
+	"code.laria.me/petrific/storage/memory"
+	"testing"
+)
+
+type XorFilter byte
+
+func (xf XorFilter) Transform(b []byte) ([]byte, error) {
+	for i := range b {
+		b[i] ^= byte(xf)
+	}
+	return b, nil
+}
+
+func genTestData(size int) []byte {
+	data := make([]byte, size)
+	for i := range data {
+		data[i] = byte(i & 0xff)
+	}
+	return data
+}
+
+func TestXorReverse(t *testing.T) {
+	orig := genTestData(1 << 20)
+
+	filter := XorFilter(42)
+
+	filtered := make([]byte, len(orig))
+	copy(filtered, orig)
+
+	filtered, _ = filter.Transform(filtered)
+	filtered, _ = filter.Transform(filtered)
+
+	if !bytes.Equal(filtered, orig) {
+		t.Errorf("orig != filtered:\n{%x}\n{%x}", orig, filtered)
+	}
+}
+
+func testFilter(t *testing.T, encode, decode Filter) {
+	base := memory.NewMemoryStorage()
+	storage := FilterStorage{
+		Base:   base,
+		Encode: encode,
+		Decode: decode,
+	}
+
+	size := backup.BlobChunkSize*2 + 10
+	data := genTestData(size)
+
+	id, err := backup.WriteFile(storage, bytes.NewReader(data))
+	if err != nil {
+		t.Fatalf("Unexpeced error from WriteFile: %s", err)
+	}
+
+	buf := new(bytes.Buffer)
+	if err := backup.RestoreFile(storage, id, buf); err != nil {
+		t.Fatalf("Unexpeced error from RestoreFile: %s", err)
+	}
+
+	if !bytes.Equal(data, buf.Bytes()) {
+		t.Errorf("data != buf.Bytes()")
+	}
+
+}
+
+func TestFilterStorage(t *testing.T) {
+	testFilter(t, XorFilter(42), XorFilter(42))
+}
+
+func TestPipeFilter(t *testing.T) {
+	testFilter(t, PipeFilter([]string{"cat"}), PipeFilter([]string{"cat"}))
+}