DataTypeSignature

libuavcan/include/uavcan/internal/data_type.hpp

@@ -7,6 +7,7 @@
 #include <cassert>
 #include <stdint.h>
 #include <algorithm>
+#include <uavcan/internal/transport/crc.hpp>
 
 namespace uavcan
 {
@@ -60,6 +61,30 @@ public:
 };
 
 
+class DataTypeSignature
+{
+    uint64_t value_;
+
+    void mixin64(uint64_t x);
+
+    DataTypeSignature() : value_(0) { }
+
+public:
+    static DataTypeSignature zero() { return DataTypeSignature(); }
+
+    explicit DataTypeSignature(uint64_t value) : value_(value) { }
+
+    void extend(DataTypeSignature dts);
+
+    TransferCRC toTransferCRC() const;
+
+    uint64_t get() const { return value_; }
+
+    bool operator==(DataTypeSignature rhs) const { return value_ == rhs.value_; }
+    bool operator!=(DataTypeSignature rhs) const { return !operator==(rhs); }
+};
+
+
 struct DataTypeHash
 {
     enum { NumBytes = 16 };

libuavcan/src/data_type.cpp

@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 2014 Pavel Kirienko <pavel.kirienko@gmail.com>
+ */
+
+#include <cstdio>
+#include <cassert>
+#include <uavcan/internal/data_type.hpp>
+
+namespace uavcan
+{
+/*
+ * DataTypeSignature
+ */
+void DataTypeSignature::mixin64(uint64_t x)
+{
+    DataTypeSignatureCRC crc = DataTypeSignatureCRC::extend(value_);
+    for (int i = 0; i < 64; i += 8)   // LSB first
+        crc.add((x >> i) & 0xFF);
+    value_ = crc.get();
+}
+
+void DataTypeSignature::extend(DataTypeSignature dts)
+{
+    const uint64_t y = value_;
+    mixin64(dts.get());
+    mixin64(y);
+}
+
+TransferCRC DataTypeSignature::toTransferCRC() const
+{
+    TransferCRC tcrc;
+    for (int i = 0; i < 64; i += 8)    // LSB first
+        tcrc.add((value_ >> i) & 0xFF);
+    return tcrc;
+}
+
+}

libuavcan/test/data_type.cpp

@@ -35,3 +35,51 @@ TEST(DataTypeSignatureCRC, Extension)
 
     ASSERT_EQ(0x62EC59E3F1A4F00A, crc2.get());
 }
+
+
+TEST(DataTypeSignature, Correctness)
+{
+    using uavcan::DataTypeSignature;
+    using uavcan::DataTypeSignatureCRC;
+
+    DataTypeSignature signature = DataTypeSignature::zero();
+    ASSERT_EQ(0, signature.get());
+
+    /*
+     * First extension
+     */
+    signature.extend(DataTypeSignature(0x123456789abcdef0));
+
+    DataTypeSignatureCRC crc;
+    crc.add(0xF0);
+    crc.add(0xDE);
+    crc.add(0xBC);
+    crc.add(0x9A);
+    crc.add(0x78);
+    crc.add(0x56);
+    crc.add(0x34);
+    crc.add(0x12);
+    for (int i = 0; i < 8; i++)
+        crc.add(0);
+
+    ASSERT_EQ(crc.get(), signature.get());
+
+    const uint64_t old_signature = signature.get();
+
+    /*
+     * Second extension
+     */
+    signature.extend(DataTypeSignature(0xfedcba9876543210));
+    crc.add(0x10);
+    crc.add(0x32);
+    crc.add(0x54);
+    crc.add(0x76);
+    crc.add(0x98);
+    crc.add(0xba);
+    crc.add(0xdc);
+    crc.add(0xfe);
+    for (int i = 0; i < 64; i += 8)
+        crc.add((old_signature >> i) & 0xFF);
+
+    ASSERT_EQ(crc.get(), signature.get());
+}