Start of a client app

tlv.cc

@@ -1,8 +1,39 @@
+#include <cassert>
+
 #include "tlv.h"
 
+struct header {
+	uint16_t type;
+	uint16_t value_length;
+};
+
 TLVNode::TLVNode(const uint16_t type)
 	: type_(type) {}
 
 TLVNode::TLVNode(const uint16_t type, const std::string value)
 	: type_(type),
 	  value_(value) {}
+
+void TLVNode::Encode(std::string *output) {
+	assert(value_.length() <= UINT16_MAX);
+	struct header header = {
+		.type = type_,
+		.value_length = (uint16_t)value_.length(),
+	};
+	size_t header_start = output->length();
+	output->append((char*)&header, sizeof(header));
+
+	if (IsContainer()) {
+		for (auto child : children_) {
+			child.Encode(output);
+		}
+		size_t total_child_length = output->length() - header_start - sizeof(header);
+		assert(total_child_length <= UINT16_MAX);
+		header.value_length = (uint16_t)total_child_length;
+		output->replace(header_start, sizeof(header), (char*)&header, sizeof(header));
+	}
+}
+
+bool TLVNode::IsContainer() {
+	return type_ & 0x8000;
+}