Proper log initialization

libuavcan/include/uavcan/protocol/dynamic_node_id_allocation_server.hpp

@@ -143,6 +143,8 @@ private:
     int readEntryFromStorage(Index index, protocol::dynamic_node_id::server::Entry& out_entry);
     int writeEntryToStorage(Index index, const protocol::dynamic_node_id::server::Entry& entry);
 
+    int initEmptyLogStorage();
+
 public:
     Log(IDynamicNodeIDStorageBackend& storage)
         : storage_(storage)

libuavcan/src/protocol/uc_dynamic_node_id_allocation_server.cpp

@@ -224,9 +224,37 @@ int Log::writeEntryToStorage(Index index, const protocol::dynamic_node_id::serve
     return (temp == entry) ? 0 : -ErrFailure;
 }
 
+int Log::initEmptyLogStorage()
+{
+    MarshallingStorageDecorator io(storage_);
+
+    // Initializing last index
+    last_index_ = 0;
+    uint32_t stored_index = 0;
+    int res = io.setAndGetBack(getLastIndexKey(), stored_index);
+    if (res < 0)
+    {
+        return res;
+    }
+    if (stored_index != 0)
+    {
+        return -ErrFailure;
+    }
+
+    // Writing the zero entry - it must always be default-initialized
+    entries_[0] = protocol::dynamic_node_id::server::Entry();
+    res = writeEntryToStorage(0, entries_[0]);
+    if (res < 0)
+    {
+        return res;
+    }
+
+    return 0;
+}
+
 int Log::init()
 {
-    const MarshallingStorageDecorator io(storage_);
+    MarshallingStorageDecorator io(storage_);
 
     // Reading max index
     {
@@ -235,10 +263,8 @@ int Log::init()
         {
             if (storage_.get(getLastIndexKey()).empty())
             {
-                // It appears like there's no log in the storage - initializing empty log then
-                last_index_ = 0;
-                UAVCAN_TRACE("dynamic_node_id_server_impl::Log", "Initializing empty log");
-                return 0;
+                UAVCAN_TRACE("dynamic_node_id_server_impl::Log", "Initializing empty storage");
+                return initEmptyLogStorage();
             }
             else
             {
@@ -253,7 +279,7 @@ int Log::init()
         last_index_ = Index(value);
     }
 
-    // Restoring log entries
+    // Restoring log entries - note that index 0 always exists
     for (Index index = 0; index <= last_index_; index++)
     {
         const int result = readEntryFromStorage(index, entries_[index]);

libuavcan/test/protocol/dynamic_node_id_allocation_server.cpp

@@ -9,10 +9,16 @@
 
 class StorageBackend : public uavcan::IDynamicNodeIDStorageBackend
 {
-public:
     typedef std::map<String, String> Container;
     Container container_;
 
+    bool fail_;
+
+public:
+    StorageBackend()
+        : fail_(false)
+    { }
+
     virtual String get(const String& key) const
     {
         const Container::const_iterator it = container_.find(key);
@@ -28,7 +34,13 @@ public:
         container_[key] = value;
     }
 
-    void printContainer() const
+    void failOnSetCalls(bool really) { fail_ = really; }
+
+    void reset() { container_.clear(); }
+
+    unsigned getNumKeys() const { return unsigned(container_.size()); }
+
+    void print() const
     {
         for (Container::const_iterator it = container_.begin(); it != container_.end(); ++it)
         {
@@ -122,12 +134,16 @@ TEST(DynamicNodeIDAllocationServer, MarshallingStorageDecorator)
 
 TEST(DynamicNodeIDAllocationServer, LogInitialization)
 {
+    const unsigned NumEntriesInStorageWithEmptyLog = 4;  // last index + 3 items per log entry
+
     // No log data in the storage - initializing empty log
     {
         StorageBackend storage;
         uavcan::dynamic_node_id_server_impl::Log log(storage);
 
+        ASSERT_EQ(0, storage.getNumKeys());
         ASSERT_LE(0, log.init());
+        ASSERT_EQ(NumEntriesInStorageWithEmptyLog, storage.getNumKeys());
         ASSERT_EQ(0, log.getLastIndex());
         ASSERT_EQ(0, log.getEntryAtIndex(0)->term);
         ASSERT_EQ(0, log.getEntryAtIndex(0)->node_id);
@@ -141,11 +157,13 @@ TEST(DynamicNodeIDAllocationServer, LogInitialization)
 
         storage.set("log_last_index", "0");
         ASSERT_LE(-uavcan::ErrFailure, log.init());     // Expected one entry, none found
+        ASSERT_EQ(1, storage.getNumKeys());
 
         storage.set("log0_term",      "0");
         storage.set("log0_unique_id", "00000000000000000000000000000000");
         storage.set("log0_node_id",   "0");
         ASSERT_LE(0, log.init());                       // OK now
+        ASSERT_EQ(NumEntriesInStorageWithEmptyLog, storage.getNumKeys());
         ASSERT_EQ(0, log.getLastIndex());
         ASSERT_EQ(0, log.getEntryAtIndex(0)->term);
     }
@@ -161,7 +179,8 @@ TEST(DynamicNodeIDAllocationServer, LogInitialization)
         ASSERT_LE(-uavcan::ErrFailure, log.init());     // Bad value
 
         storage.set("log_last_index", "0");
-        ASSERT_LE(-uavcan::ErrFailure, log.init());     // OK
+        ASSERT_LE(-uavcan::ErrFailure, log.init());     // No log items
+        ASSERT_EQ(1, storage.getNumKeys());
 
         storage.set("log0_term",      "0");
         storage.set("log0_unique_id", "00000000000000000000000000000000");
@@ -169,6 +188,7 @@ TEST(DynamicNodeIDAllocationServer, LogInitialization)
         ASSERT_LE(-uavcan::ErrFailure, log.init());     // Failed
         ASSERT_EQ(0, log.getLastIndex());
         ASSERT_EQ(0, log.getEntryAtIndex(0)->term);
+        ASSERT_EQ(4, storage.getNumKeys());
     }
     // Nonempty storage, many items
     {
@@ -184,6 +204,7 @@ TEST(DynamicNodeIDAllocationServer, LogInitialization)
         storage.set("log1_node_id",   "127");
 
         ASSERT_LE(0, log.init());                       // OK now
+        ASSERT_EQ(7, storage.getNumKeys());
         ASSERT_EQ(1, log.getLastIndex());
 
         ASSERT_EQ(0, log.getEntryAtIndex(0)->term);