protoio: Add a generic protobuf store

This patch adds a generic protobuf store, where one can put and retreive
protobufs, indexed by a string.

This will be used in subsequent patches.

internal/protoio/protoio_test.go

@@ -65,3 +65,41 @@ func TestText(t *testing.T) {
 		os.RemoveAll(dir)
 	}
 }
+
+func TestStore(t *testing.T) {
+	dir := mustTempDir(t)
+	st, err := NewStore(dir + "/store")
+	if err != nil {
+		t.Fatalf("failed to create store: %v", err)
+	}
+
+	if ids, err := st.ListIDs(); len(ids) != 0 || err != nil {
+		t.Errorf("expected no ids, got %v - %v", ids, err)
+	}
+
+	pb := &testpb.M{"hola"}
+
+	if err := st.Put("f", pb); err != nil {
+		t.Error(err)
+	}
+
+	pb2 := &testpb.M{}
+	if ok, err := st.Get("f", pb2); err != nil || !ok {
+		t.Errorf("Get(f): %v - %v", ok, err)
+	}
+	if pb.Content != pb2.Content {
+		t.Errorf("content mismatch, got %q, expected %q", pb2.Content, pb.Content)
+	}
+
+	if ok, err := st.Get("notexists", pb2); err != nil || ok {
+		t.Errorf("Get(notexists): %v - %v", ok, err)
+	}
+
+	if ids, err := st.ListIDs(); len(ids) != 1 || ids[0] != "f" || err != nil {
+		t.Errorf("expected [f], got %v - %v", ids, err)
+	}
+
+	if !t.Failed() {
+		os.RemoveAll(dir)
+	}
+}