Eliminate SettingsHandler's SetBytes and Reset methods

Also make the `Decrypt` method private.

As far as I can tell, the only motivation for exposing the `SetBytes`
and `Reset` methods is to allow `CBoot::SetupWiiMemory` to use the same
`SettingsHandler` instance to read settings data and then write it back.
It seems cleaner to just use two separate instances, and require a given
`SettingsHandler` instance to be used for either writing data to a
buffer or reading data from a buffer, but not both.

A natural next step is to split the `SettingsHandler` class into two
classes, one for writing data and one for reading data. I've deferred
that change for a future PR.

Source/Core/Common/SettingsHandler.cpp

@@ -17,28 +17,21 @@
 
 namespace Common
 {
-SettingsHandler::SettingsHandler()
+SettingsHandler::SettingsHandler() : m_buffer{}, m_position{0}, m_key{INITIAL_SEED}, decoded{""}
 {
-  Reset();
 }
 
-SettingsHandler::SettingsHandler(const Buffer& buffer)
+SettingsHandler::SettingsHandler(const Buffer& buffer) : SettingsHandler()
 {
-  SetBytes(buffer);
+  m_buffer = buffer;
+  Decrypt();
 }
 
 const SettingsHandler::Buffer& SettingsHandler::GetBytes() const
 {
   return m_buffer;
 }
 
-void SettingsHandler::SetBytes(const Buffer& buffer)
-{
-  Reset();
-  m_buffer = buffer;
-  Decrypt();
-}
-
 std::string SettingsHandler::GetValue(std::string_view key) const
 {
   constexpr char delim[] = "\n";
@@ -84,14 +77,6 @@ void SettingsHandler::Decrypt()
   std::erase(decoded, '\x0d');
 }
 
-void SettingsHandler::Reset()
-{
-  decoded = "";
-  m_position = 0;
-  m_key = INITIAL_SEED;
-  m_buffer = {};
-}
-
 void SettingsHandler::AddSetting(std::string_view key, std::string_view value)
 {
   WriteLine(fmt::format("{}={}\r\n", key, value));

Source/Core/Common/SettingsHandler.h

@@ -30,14 +30,12 @@ class SettingsHandler
   void AddSetting(std::string_view key, std::string_view value);
 
   const Buffer& GetBytes() const;
-  void SetBytes(const Buffer& buffer);
   std::string GetValue(std::string_view key) const;
 
-  void Decrypt();
-  void Reset();
   static std::string GenerateSerialNumber();
 
 private:
+  void Decrypt();
   void WriteLine(std::string_view str);
   void WriteByte(u8 b);
 

Source/Core/Core/Boot/Boot_BS2Emu.cpp

@@ -363,7 +363,6 @@ bool CBoot::SetupWiiMemory(Core::System& system, IOS::HLE::IOSC::ConsoleType con
   auto entryPos = region_settings.find(SConfig::GetInstance().m_region);
   RegionSetting region_setting = entryPos->second;
 
-  Common::SettingsHandler gen;
   std::string serno;
   std::string model = "RVL-001(" + region_setting.area + ")";
   CreateSystemMenuTitleDirs();
@@ -377,9 +376,9 @@ bool CBoot::SetupWiiMemory(Core::System& system, IOS::HLE::IOSC::ConsoleType con
                                    IOS::HLE::FS::Mode::Read);
     if (file && file->Read(data.data(), data.size()))
     {
-      gen.SetBytes(data);
-      serno = gen.GetValue("SERNO");
-      model = gen.GetValue("MODEL");
+      Common::SettingsHandler settings_reader(data);
+      serno = settings_reader.GetValue("SERNO");
+      model = settings_reader.GetValue("MODEL");
 
       bool region_matches = false;
       if (Config::Get(Config::MAIN_OVERRIDE_REGION_SETTINGS))
@@ -388,24 +387,23 @@ bool CBoot::SetupWiiMemory(Core::System& system, IOS::HLE::IOSC::ConsoleType con
       }
       else
       {
-        const std::string code = gen.GetValue("CODE");
+        const std::string code = settings_reader.GetValue("CODE");
         if (code.size() >= 2 && CodeRegion(code[1]) == SConfig::GetInstance().m_region)
           region_matches = true;
       }
 
       if (region_matches)
       {
-        region_setting = RegionSetting{gen.GetValue("AREA"), gen.GetValue("VIDEO"),
-                                       gen.GetValue("GAME"), gen.GetValue("CODE")};
+        region_setting =
+            RegionSetting{settings_reader.GetValue("AREA"), settings_reader.GetValue("VIDEO"),
+                          settings_reader.GetValue("GAME"), settings_reader.GetValue("CODE")};
       }
       else
       {
         const size_t parenthesis_pos = model.find('(');
         if (parenthesis_pos != std::string::npos)
           model = model.substr(0, parenthesis_pos) + '(' + region_setting.area + ')';
       }
-
-      gen.Reset();
     }
   }
   fs->Delete(IOS::SYSMENU_UID, IOS::SYSMENU_GID, settings_file_path);
@@ -423,6 +421,7 @@ bool CBoot::SetupWiiMemory(Core::System& system, IOS::HLE::IOSC::ConsoleType con
     INFO_LOG_FMT(BOOT, "Using serial number: {}", serno);
   }
 
+  Common::SettingsHandler gen;
   gen.AddSetting("AREA", region_setting.area);
   gen.AddSetting("MODEL", model);
   gen.AddSetting("DVD", "0");

Source/Core/Core/IOS/DolphinDevice.cpp

@@ -138,8 +138,7 @@ IPCReply GetRealProductCode(Core::System& system, const IOCtlVRequest& request)
   if (!file.ReadBytes(data.data(), data.size()))
     return IPCReply(IPC_ENOENT);
 
-  Common::SettingsHandler gen;
-  gen.SetBytes(data);
+  Common::SettingsHandler gen(data);
   const std::string code = gen.GetValue("CODE");
 
   const size_t length = std::min<size_t>(request.io_vectors[0].size, code.length());

Source/UnitTests/Common/SettingsHandlerTest.cpp

@@ -75,35 +75,11 @@ TEST(SettingsHandlerTest, DecryptMultipleSettings)
   EXPECT_EQ(handler.GetValue("foo"), "bar");
 }
 
-TEST(SettingsHandlerTest, SetBytesOverwritesExistingBuffer)
-{
-  Common::SettingsHandler handler(BUFFER_A);
-  ASSERT_EQ(handler.GetValue("key"), "val");
-  ASSERT_EQ(handler.GetValue("foo"), "");
-
-  handler.SetBytes(BUFFER_B);
-  EXPECT_EQ(handler.GetValue("foo"), "bar");
-  EXPECT_EQ(handler.GetValue("key"), "");
-}
-
 TEST(SettingsHandlerTest, GetValueOnSameInstance)
 {
   Common::SettingsHandler handler;
   handler.AddSetting("key", "val");
   EXPECT_EQ(handler.GetValue("key"), "");
-
-  Common::SettingsHandler::Buffer buffer = handler.GetBytes();
-  handler.SetBytes(buffer);
-  EXPECT_EQ(handler.GetValue("key"), "val");
-}
-
-TEST(SettingsHandlerTest, GetValueAfterReset)
-{
-  Common::SettingsHandler handler(BUFFER_A);
-  ASSERT_EQ(handler.GetValue("key"), "val");
-
-  handler.Reset();
-  EXPECT_EQ(handler.GetValue("key"), "");
 }
 
 TEST(SettingsHandlerTest, EncryptAddsLFOnNullChar)