First step in changing the CAN frame format - introduced various transfer lengths per transfer type

libuavcan/dsdl_compiler/libuavcan_dsdl_compiler/data_type_template.tmpl

@@ -94,7 +94,7 @@ struct UAVCAN_EXPORT ${t.cpp_type_name}
     % endfor
     {
         enum { MaxByteLen = ::uavcan::BitLenToByteLen<MaxBitLen>::Result };
-        ::uavcan::StaticAssert<int(MaxByteLen) <= int(::uavcan::MaxTransferPayloadLen)>::check();
+        ::uavcan::StaticAssert<int(MaxByteLen) <= int(::uavcan::MaxPossibleTransferPayloadLen)>::check();
 
         ::uavcan::StaticAssert<_tmpl == 0>::check();  // Usage check
 

libuavcan/include/uavcan/node/generic_subscriber.hpp

@@ -124,7 +124,7 @@ template <typename DataStruct_,
 class UAVCAN_EXPORT TransferListenerInstantiationHelper
 {
     enum { DataTypeMaxByteLen = BitLenToByteLen<DataStruct_::MaxBitLen>::Result };
-    enum { NeedsBuffer = int(DataTypeMaxByteLen) > int(MaxSingleFrameTransferPayloadLen) };
+    enum { NeedsBuffer = int(DataTypeMaxByteLen) > int(GuaranteedPayloadLenPerFrame) };
     enum { BufferSize = NeedsBuffer ? DataTypeMaxByteLen : 0 };
 #if UAVCAN_TINY
     enum { NumStaticBufs = 0 };

libuavcan/include/uavcan/node/marshal_buffer.hpp

@@ -46,7 +46,7 @@ public:
  * This implementation provides the buffer large enough to
  * serialize any UAVCAN data structure.
  */
-template <unsigned MaxSize_ = MaxTransferPayloadLen>
+template <unsigned MaxSize_ = MaxPossibleTransferPayloadLen>
 class UAVCAN_EXPORT MarshalBufferProvider : public IMarshalBufferProvider
 {
     class Buffer : public IMarshalBuffer

libuavcan/include/uavcan/node/node.hpp

@@ -60,7 +60,7 @@ template <std::size_t MemPoolSize_,
           unsigned OutgoingTransferMaxPayloadLen = 264
 #else
           unsigned OutgoingTransferRegistryStaticEntries = 10,
-          unsigned OutgoingTransferMaxPayloadLen = MaxTransferPayloadLen
+          unsigned OutgoingTransferMaxPayloadLen = MaxPossibleTransferPayloadLen
 #endif
           >
 class UAVCAN_EXPORT Node : public INode

libuavcan/include/uavcan/transport/transfer.hpp

@@ -11,10 +11,16 @@
 
 namespace uavcan
 {
+/**
+ * Refer to the UAVCAN specification for more info about transfers.
+ */
+static const unsigned MaxMessageBroadcastTransferPayloadLen = 126; ///< 16 frames, 8 bytes per frame, 2 byte CRC
+static const unsigned MaxMessageUnicastTransferPayloadLen   = 110; ///< 16 frames, 7 bytes per frame, 2 byte CRC
+static const unsigned MaxServiceTransferPayloadLen          = 439; ///< 63 frames, 7 bytes per frame, 2 byte CRC
 
-static const unsigned MaxTransferPayloadLen = 439; ///< According to the specification.
+static const unsigned GuaranteedPayloadLenPerFrame = 7;            ///< Guaranteed for all transfers, all CAN standards
 
-static const unsigned MaxSingleFrameTransferPayloadLen = 7;
+static const unsigned MaxPossibleTransferPayloadLen = MaxServiceTransferPayloadLen;
 
 enum TransferType
 {
@@ -26,6 +32,27 @@ enum TransferType
 };
 
 
+static inline unsigned getMaxPayloadLenForTransferType(const TransferType type)
+{
+    static const unsigned lens[NumTransferTypes] =
+    {
+        MaxServiceTransferPayloadLen,
+        MaxServiceTransferPayloadLen,
+        MaxMessageBroadcastTransferPayloadLen,
+        MaxMessageUnicastTransferPayloadLen
+    };
+    if (static_cast<int>(type) < NumTransferTypes)
+    {
+        return lens[static_cast<int>(type)];
+    }
+    else
+    {
+        UAVCAN_ASSERT(0);
+        return 0;
+    }
+}
+
+
 class UAVCAN_EXPORT TransferID
 {
     uint8_t value_;

libuavcan/src/transport/uc_transfer_sender.cpp

@@ -19,7 +19,7 @@ int TransferSender::send(const uint8_t* payload, unsigned payload_len, Monotonic
                          MonotonicTime blocking_deadline, TransferType transfer_type, NodeID dst_node_id,
                          TransferID tid)
 {
-    if (payload_len > MaxTransferPayloadLen)
+    if (payload_len > getMaxPayloadLenForTransferType(transfer_type))
     {
         UAVCAN_ASSERT(0);
         return -ErrInvalidParam;

libuavcan/test/transport/transfer_listener.cpp

@@ -225,21 +225,24 @@ TEST(TransferListener, MaximumTransferLength)
 
     uavcan::PoolManager<1> poolmgr;
     uavcan::TransferPerfCounter perf;
-    TestListener<uavcan::MaxTransferPayloadLen * 2, 2, 2> subscriber(perf, type, poolmgr);
+    TestListener<uavcan::MaxPossibleTransferPayloadLen * 2, 3, 3> subscriber(perf, type, poolmgr);
-
-    static const std::string DATA_OK(uavcan::MaxTransferPayloadLen, 'z');
 
     TransferListenerEmulator emulator(subscriber, type);
     const Transfer transfers[] =
     {
-        emulator.makeTransfer(uavcan::TransferTypeMessageUnicast,   1, DATA_OK),
+        emulator.makeTransfer(uavcan::TransferTypeServiceRequest,   1,
-        emulator.makeTransfer(uavcan::TransferTypeMessageBroadcast, 1, DATA_OK)
+                              std::string(uavcan::MaxServiceTransferPayloadLen, 'z')),            // Longer
+        emulator.makeTransfer(uavcan::TransferTypeMessageUnicast,   2,
+                              std::string(uavcan::MaxMessageUnicastTransferPayloadLen, 'z')),     // Shorter
+        emulator.makeTransfer(uavcan::TransferTypeMessageBroadcast, 3,
+                              std::string(uavcan::MaxMessageBroadcastTransferPayloadLen, 'z'))    // Same as above
     };
 
     emulator.send(transfers);
 
-    ASSERT_TRUE(subscriber.matchAndPop(transfers[1]));    // Broadcast is shorter, so will complete first
+    ASSERT_TRUE(subscriber.matchAndPop(transfers[1]));
-    ASSERT_TRUE(subscriber.matchAndPop(transfers[0]));
+    ASSERT_TRUE(subscriber.matchAndPop(transfers[2]));
+    ASSERT_TRUE(subscriber.matchAndPop(transfers[0]));    // Service takes more frames
 
     ASSERT_TRUE(subscriber.isEmpty());
 }