[Yunq] POC for moving yunq parsing to a library.

lib/yunq/message_view.h

@@ -0,0 +1,40 @@
+#pragma once
+
+#include <glacier/buffer/byte_buffer.h>
+#include <glacier/status/error_or.h>
+
+namespace yunq {
+
+const uint64_t kHeaderSize = 24;  // 4x uint32, 1x uint64
+
+struct ExtensionPointer {
+  uint32_t offset;
+  uint32_t length;
+};
+
+class MessageView {
+ public:
+  MessageView(const glcr::ByteBuffer& buffer, uint64_t offset)
+      : buffer_(buffer), offset_(offset) {}
+
+  // TODO: Implement glcr::StatusOr
+  template <typename T>
+  glcr::ErrorOr<T> ReadField(uint64_t field_index);
+
+ private:
+  const glcr::ByteBuffer& buffer_;
+  uint64_t offset_;
+
+  uint64_t field_offset(uint64_t field_index) {
+    return offset_ + kHeaderSize + (8 * field_index);
+  }
+};
+
+template <>
+glcr::ErrorOr<uint64_t> MessageView::ReadField<uint64_t>(uint64_t field_index);
+
+template <>
+glcr::ErrorOr<glcr::String> MessageView::ReadField<glcr::String>(
+    uint64_t field_index);
+
+}  // namespace yunq