lp: encode sequence number as fixed-width integer
refs #4403
Change-Id: I37daeaf3d60dbaf81a8f38ec5deb72eea6dd89c2
diff --git a/src/lp/field-decl.hpp b/src/lp/field-decl.hpp
index fa584af..26336ff 100644
--- a/src/lp/field-decl.hpp
+++ b/src/lp/field-decl.hpp
@@ -24,6 +24,7 @@
#include "empty-value.hpp"
#include "field.hpp"
+#include "sequence.hpp"
#include "tlv.hpp"
#include "../encoding/block-helpers.hpp"
@@ -33,6 +34,10 @@
namespace ndn {
namespace lp {
+/** \brief Indicate a uint64_t field shall be decoded and encoded as a non-negative integer.
+ */
+struct NonNegativeIntegerTag;
+
template<typename TlvType, typename T>
struct DecodeHelper
{
@@ -54,7 +59,7 @@
{
if (wire.value_size() != 0) {
BOOST_THROW_EXCEPTION(ndn::tlv::Error("NDNLP field of TLV-TYPE " + to_string(wire.type()) +
- " must be empty"));
+ " must be empty"));
}
return EmptyValue{};
@@ -62,11 +67,25 @@
};
template<typename TlvType>
+struct DecodeHelper<TlvType, NonNegativeIntegerTag>
+{
+ static uint64_t
+ decode(const Block& wire)
+ {
+ return readNonNegativeInteger(wire);
+ }
+};
+
+template<typename TlvType>
struct DecodeHelper<TlvType, uint64_t>
{
static uint64_t
decode(const Block& wire)
{
+ // NDNLPv2 spec defines sequence number fields to be encoded as a fixed-width unsigned integer,
+ // but previous versions of ndn-cxx encode it as a NonNegativeInteger, so we decode it as such
+ // for backwards compatibility. In a future version, the decoder will be changed to accept
+ // 8-byte big endian only, to allow faster decoding.
return readNonNegativeInteger(wire);
}
};
@@ -79,7 +98,7 @@
{
if (wire.value_size() == 0) {
BOOST_THROW_EXCEPTION(ndn::tlv::Error("NDNLP field of TLV-TYPE " + to_string(wire.type()) +
- " cannot be empty"));
+ " cannot be empty"));
}
return std::make_pair(wire.value_begin(), wire.value_end());
@@ -111,12 +130,24 @@
};
template<typename encoding::Tag TAG, typename TlvType>
+struct EncodeHelper<TAG, TlvType, NonNegativeIntegerTag>
+{
+ static size_t
+ encode(EncodingImpl<TAG>& encoder, uint64_t value)
+ {
+ return prependNonNegativeIntegerBlock(encoder, TlvType::value, value);
+ }
+};
+
+template<typename encoding::Tag TAG, typename TlvType>
struct EncodeHelper<TAG, TlvType, uint64_t>
{
static size_t
- encode(EncodingImpl<TAG>& encoder, const uint64_t value)
+ encode(EncodingImpl<TAG>& encoder, uint64_t value)
{
- return prependNonNegativeIntegerBlock(encoder, TlvType::value, value);
+ uint64_t be = htobe64(value);
+ const uint8_t* buf = reinterpret_cast<const uint8_t*>(&be);
+ return encoder.prependByteArrayBlock(TlvType::value, buf, sizeof(be));
}
};
@@ -134,7 +165,16 @@
}
};
-template<typename LOCATION, typename VALUE, uint64_t TYPE, bool REPEATABLE = false>
+/** \brief Declare a field.
+ * \tparam LOCATION a tag that indicates where the field is in an LpPacket.
+ * \tparam VALUE type of field value.
+ * \tparam TYPE TLV-TYPE number of the field.
+ * \tparam REPEATABLE whether the field is repeatable.
+ * \tparam DECODER_TAG selects a specialization of DecodeHelper.
+ * \tparam ENCODER_TAG selects a specialization of EncodeHelper.
+ */
+template<typename LOCATION, typename VALUE, uint64_t TYPE, bool REPEATABLE = false,
+ typename DECODER_TAG = VALUE, typename ENCODER_TAG = VALUE>
class FieldDecl
{
public:
@@ -143,29 +183,30 @@
typedef std::integral_constant<uint64_t, TYPE> TlvType;
typedef std::integral_constant<bool, REPEATABLE> IsRepeatable;
- /** \brief decodes a field
- * \param wire a Block with top-level type \p TYPE
- * \return value of the field
+ /** \brief Decode a field.
+ * \param wire an element with top-level TLV-TYPE \c TlvType::value.
+ * \return value of the field.
+ * \throw ndn::tlv::Error decode failure.
*/
static ValueType
decode(const Block& wire)
{
if (wire.type() != TlvType::value) {
- BOOST_THROW_EXCEPTION(ndn::tlv::Error("Unexpected TLV type " + to_string(wire.type())));
+ BOOST_THROW_EXCEPTION(ndn::tlv::Error("Unexpected TLV-TYPE " + to_string(wire.type())));
}
- return DecodeHelper<TlvType, ValueType>::decode(wire);
+ return DecodeHelper<TlvType, DECODER_TAG>::decode(wire);
}
- /** \brief encodes a field and prepends to \p encoder its Block with top-level type \p TYPE
- * \param encoder Instance of the buffer encoder or buffer estimator
- * \param value value of the field
+ /** \brief Encode a field and prepend to \p encoder.
+ * \param encoder a buffer encoder or estimator.
+ * \param value value of the field.
*/
- template<typename encoding::Tag TAG, typename T>
+ template<typename encoding::Tag TAG>
static size_t
- encode(EncodingImpl<TAG>& encoder, const T& value)
+ encode(EncodingImpl<TAG>& encoder, const ValueType& value)
{
- return EncodeHelper<TAG, TlvType, T>::encode(encoder, value);
+ return EncodeHelper<TAG, TlvType, ENCODER_TAG>::encode(encoder, value);
}
};