Loading newsgroup list from database implemented

include/usenetsearch/Database.h

@@ -18,6 +18,7 @@
 #include <cstdint>
 #include <filesystem>
 #include <fstream>
+#include <memory>
 #include <vector>
 
 #include "usenetsearch/UsenetClient.h"
@@ -26,10 +27,18 @@ namespace usenetsearch {
 
 static constexpr const std::uint64_t DatabaseVersion{1};
 
+struct DatabaseException: public UsenetSearchException
+{
+    DatabaseException(int errorCode, const std::string& message):
+        UsenetSearchException(errorCode, message){}
+
+    virtual ~DatabaseException() = default;
+};
+
 class Database{
 
     std::filesystem::path m_databasePath;
-    std::uint64_t m_databaseVersion{0};
+    std::uint64_t m_databaseVersion{DatabaseVersion};
     std::ifstream m_newsGroupFileInput;
     std::ofstream m_newsGroupFileOutput;
 
@@ -38,6 +47,7 @@ class Database{
 public:
 
     ~Database();
+    std::unique_ptr<std::vector<NntpListEntry>> LoadNewsgroupList();
     void Open(std::filesystem::path dbPath);
     void UpdateNewsgroupList(const std::vector<NntpListEntry>& list);
 

src/Database.cpp

@@ -36,6 +36,38 @@ Database::~Database()
         m_newsGroupFileOutput.close();
     }
 }
+std::unique_ptr<std::vector<NntpListEntry>> Database::LoadNewsgroupList()
+{
+    OpenNewsGroupFile();
+
+    std::uint64_t dbVersion{0};
+    m_newsGroupFileInput.read(
+        reinterpret_cast<char*>(&dbVersion),
+        sizeof(dbVersion)
+    );
+    if (dbVersion != m_databaseVersion)
+    {
+        throw DatabaseException(EINVAL,
+            "The loaded database version (" + std::to_string(dbVersion) 
+            + ") does not match the current database version ("
+            + std::to_string(m_databaseVersion) + ")");
+    }
+
+    size_t newsGroupCount{0};
+    m_newsGroupFileInput.read(
+        reinterpret_cast<char*>(&newsGroupCount),
+        sizeof(newsGroupCount)
+    );
+
+    auto result = std::make_unique<std::vector<NntpListEntry>>();
+    for (size_t numLoaded = 0; numLoaded != newsGroupCount; ++numLoaded)
+    {
+        NntpListEntry entry;
+        m_newsGroupFileInput >> entry;
+        result->emplace_back(entry);
+    }
+    return result;
+}
 
 void Database::Open(std::filesystem::path dbPath)
 {
@@ -68,15 +100,18 @@ void Database::OpenNewsGroupFile()
 void Database::UpdateNewsgroupList(const std::vector<NntpListEntry>& list)
 {
     OpenNewsGroupFile();
+
     m_newsGroupFileOutput.write(
         reinterpret_cast<const char*>(&m_databaseVersion),
         sizeof(m_databaseVersion)
     );
-    const size_t newsGroupCount = list.size();
+
+    const std::uint64_t newsGroupCount = list.size();
     m_newsGroupFileOutput.write(
         reinterpret_cast<const char*>(&newsGroupCount),
         sizeof(newsGroupCount)
     );
+
     for (const auto& entry: list)
     {
         m_newsGroupFileOutput << entry;

src/StringUtils.cpp

@@ -35,7 +35,7 @@ std::ifstream& operator>>(std::ifstream& in, std::string& str)
 {
     std::uint64_t size{0};
     in.read(reinterpret_cast<char*>(&size), sizeof(size));
-    char buf[size];
+    char buf[size + 1];
     in.read(buf, size);
     buf[size] = 0;
     str = buf;
@@ -57,7 +57,7 @@ std::ifstream& operator>>(std::ifstream& in, std::wstring& str)
 {
     std::uint64_t size{0};
     in.read(reinterpret_cast<char*>(&size), sizeof(size));
-    wchar_t buf[size];
+    wchar_t buf[size + 1];
     in.read(reinterpret_cast<char*>(buf), size * sizeof(wchar_t));
     buf[size] = 0;
     str = buf;

src/main.cpp

@@ -75,6 +75,7 @@ int main(int argc, char* argv[])
     std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>> conv;
     try 
     {
+        
         client.Connect(
             config.NNTPServerHost(),
             config.NNTPServerPort(),
@@ -88,8 +89,13 @@ int main(int argc, char* argv[])
         // Just testing the list command for now.
         const auto list = client.List();
         db.UpdateNewsgroupList(list);
-        std::cout << "Number of newsgroups in newsgroup list: "
+        std::cout << "Number of newsgroups in newsgroup list (saved): "
                   << list.size() << std::endl;
+
+        const auto listLoaded = db.LoadNewsgroupList();
+        std::cout << "Number of newsgroups in newsgroup list (loaded): "
+                  << listLoaded->size() << std::endl;
+                  
     }
     catch (const usenetsearch::UsenetSearchException& e)
     {