codec: Moving structure around

1 files changed, 64 insertions, 0 deletions

diff --git a/modules/codec/c++/stream_value.h b/modules/codec/c++/stream_value.h
new file mode 100644
index 0000000..09203cb
--- /dev/null
+++ b/modules/codec/c++/stream_value.h
@@ -0,0 +1,64 @@
+#pragma once
+
+#include "schema.h"
+
+#include <forstio/core/buffer.h>
+#include <forstio/core/error.h>
+
+#include <cstdint>
+#include <cstring>
+
+namespace saw {
+/**
+ * Helper class to encode/decode any primtive type into/from litte endian.
+ * The shift class does this by shifting bytes. This type of procedure is
+ * platform independent. So it does not matter if the memory layout is
+ * little endian or big endian
+ */
+template<typename T> class shift_stream_value {
+	static_assert(always_false<T>, "Shift Stream Value only supports Primitives");
+};
+
+template <typename T, size_t N> class shift_stream_value<schema::Primitive<T,N>> {
+public:
+	inline static error_or<void> decode(typename native_data_type<schema::Primitive<T,N>>::type &val, buffer &buff) {
+		if (buff.read_composite_length() < N) {
+			return make_error<err::buffer_exhausted>();
+		}
+
+		typename native_data_type<schema::Primitive<schema::UnsignedInteger,N>>::type raw = 0;
+
+		for (size_t i = 0; i < N; ++i) {
+			raw |= (static_cast<typename native_data_type<schema::Primitive<T,N>>::type>(buff.read(i)) << (i * 8));
+		}
+
+		memcpy(&val, &raw, N);
+		buff.read_advance(N);
+
+		return void_t{};
+	}
+
+	inline static error_or<void> encode(const typename native_data_type<schema::Primitive<T,N>>::type &val, buffer &buff) {
+		error err = buff.write_require_length(N);
+		if (err.failed()) {
+			return err;
+		}
+
+		typename native_data_type<schema::Primitive<schema::UnsignedInteger,N>>::type raw{};
+		memcpy(&raw, &val, N);
+
+		for (size_t i = 0; i < N; ++i) {
+			buff.write(i) = raw >> (i * 8);
+		}
+
+		buff.write_advance(N);
+
+		return void_t{};
+	}
+
+	inline static size_t size() { return N; }
+};
+
+template <typename T> using stream_value = shift_stream_value<T>;
+
+} // namespace saw