first commit

src/sp/common/VarInt.cpp

@@ -0,0 +1,52 @@
+#include <sp/common/VarInt.h>
+
+#include <stdexcept>
+#include <sp/common/DataBuffer.h>
+
+namespace sp {
+
+static constexpr int SEGMENT_BITS = 0x7F;
+static constexpr int CONTINUE_BIT = 0x80;
+
+std::size_t VarInt::GetSerializedLength() const {
+	DataBuffer buffer;
+	buffer << *this;
+	return buffer.GetSize();
+}
+
+DataBuffer& operator<<(DataBuffer& out, const VarInt& var) {
+	std::uint64_t value = var.m_Value;
+	while (true) {
+		if ((value & ~static_cast<std::uint64_t>(SEGMENT_BITS)) == 0) {
+			out << static_cast<std::uint8_t>(value);
+			return out;
+		}
+
+		out << static_cast<std::uint8_t>((value & SEGMENT_BITS) | CONTINUE_BIT);
+
+		value >>= 7;
+	}
+}
+
+DataBuffer& operator>>(DataBuffer& in, VarInt& var) {
+	var.m_Value = 0;
+	unsigned int position = 0;
+	std::uint8_t currentByte;
+
+	while (true) {
+		in.ReadSome(&currentByte, 1);
+		var.m_Value |= static_cast<std::uint64_t>(currentByte & SEGMENT_BITS) << position;
+
+		if ((currentByte & CONTINUE_BIT) == 0)
+			break;
+
+		position += 7;
+
+		if (position >= 8 * sizeof(var.m_Value))
+			throw std::runtime_error("VarInt is too big");
+	}
+
+	return in;
+}
+
+}  // namespace sp