General: Make use of std::nullopt where applicable

Allows some implementations to avoid completely zeroing out the internal
buffer of the optional, and instead only set the validity byte within
the structure.

This also makes it consistent how we return empty optionals.

10 files changed, 31 insertions, 27 deletions

diff --git a/src/core/arm/dynarmic/arm_dynarmic_cp15.cpp b/src/core/arm/dynarmic/arm_dynarmic_cp15.cpp
index 54556e0f9..caefc09f4 100644
--- a/src/core/arm/dynarmic/arm_dynarmic_cp15.cpp
+++ b/src/core/arm/dynarmic/arm_dynarmic_cp15.cpp
@@ -34,7 +34,7 @@ std::optional<Callback> DynarmicCP15::CompileInternalOperation(bool two, unsigne
                                                                CoprocReg CRm, unsigned opc2) {
     LOG_CRITICAL(Core_ARM, "CP15: cdp{} p15, {}, {}, {}, {}, {}", two ? "2" : "", opc1, CRd, CRn,
                  CRm, opc2);
-    return {};
+    return std::nullopt;
 }
 
 CallbackOrAccessOneWord DynarmicCP15::CompileSendOneWord(bool two, unsigned opc1, CoprocReg CRn,
@@ -115,7 +115,7 @@ std::optional<Callback> DynarmicCP15::CompileLoadWords(bool two, bool long_trans
         LOG_CRITICAL(Core_ARM, "CP15: mrrc{}{} p15, {}, [...]", two ? "2" : "",
                      long_transfer ? "l" : "", CRd);
     }
-    return {};
+    return std::nullopt;
 }
 
 std::optional<Callback> DynarmicCP15::CompileStoreWords(bool two, bool long_transfer, CoprocReg CRd,
@@ -127,7 +127,7 @@ std::optional<Callback> DynarmicCP15::CompileStoreWords(bool two, bool long_tran
         LOG_CRITICAL(Core_ARM, "CP15: mrrc{}{} p15, {}, [...]", two ? "2" : "",
                      long_transfer ? "l" : "", CRd);
     }
-    return {};
+    return std::nullopt;
 }
 
 } // namespace Core
diff --git a/src/core/file_sys/content_archive.cpp b/src/core/file_sys/content_archive.cpp
index 426fb6bb5..76af47ff9 100644
--- a/src/core/file_sys/content_archive.cpp
+++ b/src/core/file_sys/content_archive.cpp
@@ -323,7 +323,7 @@ bool NCA::ReadRomFSSection(const NCASectionHeader& section, const NCASectionTabl
         subsection_buckets.back().entries.push_back({section.bktr.relocation.offset, {0}, ctr_low});
         subsection_buckets.back().entries.push_back({size, {0}, 0});
 
-        std::optional<Core::Crypto::Key128> key = {};
+        std::optional<Core::Crypto::Key128> key;
         if (encrypted) {
             if (has_rights_id) {
                 status = Loader::ResultStatus::Success;
@@ -442,18 +442,18 @@ std::optional<Core::Crypto::Key128> NCA::GetTitlekey() {
     memcpy(rights_id.data(), header.rights_id.data(), 16);
     if (rights_id == u128{}) {
         status = Loader::ResultStatus::ErrorInvalidRightsID;
-        return {};
+        return std::nullopt;
     }
 
     auto titlekey = keys.GetKey(Core::Crypto::S128KeyType::Titlekey, rights_id[1], rights_id[0]);
     if (titlekey == Core::Crypto::Key128{}) {
         status = Loader::ResultStatus::ErrorMissingTitlekey;
-        return {};
+        return std::nullopt;
     }
 
     if (!keys.HasKey(Core::Crypto::S128KeyType::Titlekek, master_key_id)) {
         status = Loader::ResultStatus::ErrorMissingTitlekek;
-        return {};
+        return std::nullopt;
     }
 
     Core::Crypto::AESCipher<Core::Crypto::Key128> cipher(
@@ -477,7 +477,7 @@ VirtualFile NCA::Decrypt(const NCASectionHeader& s_header, VirtualFile in, u64 s
     case NCASectionCryptoType::BKTR:
         LOG_TRACE(Crypto, "called with mode=CTR, starting_offset={:016X}", starting_offset);
         {
-            std::optional<Core::Crypto::Key128> key = {};
+            std::optional<Core::Crypto::Key128> key;
             if (has_rights_id) {
                 status = Loader::ResultStatus::Success;
                 key = GetTitlekey();
diff --git a/src/core/file_sys/vfs.cpp b/src/core/file_sys/vfs.cpp
index a4c3f67c4..b2f026b6d 100644
--- a/src/core/file_sys/vfs.cpp
+++ b/src/core/file_sys/vfs.cpp
@@ -169,11 +169,12 @@ VfsDirectory::~VfsDirectory() = default;
 
 std::optional<u8> VfsFile::ReadByte(std::size_t offset) const {
     u8 out{};
-    std::size_t size = Read(&out, 1, offset);
-    if (size == 1)
+    const std::size_t size = Read(&out, sizeof(u8), offset);
+    if (size == 1) {
         return out;
+    }
 
-    return {};
+    return std::nullopt;
 }
 
 std::vector<u8> VfsFile::ReadBytes(std::size_t size, std::size_t offset) const {
diff --git a/src/core/file_sys/vfs_offset.cpp b/src/core/file_sys/vfs_offset.cpp
index c96f88488..7714d3de5 100644
--- a/src/core/file_sys/vfs_offset.cpp
+++ b/src/core/file_sys/vfs_offset.cpp
@@ -58,10 +58,11 @@ std::size_t OffsetVfsFile::Write(const u8* data, std::size_t length, std::size_t
 }
 
 std::optional<u8> OffsetVfsFile::ReadByte(std::size_t r_offset) const {
-    if (r_offset < size)
-        return file->ReadByte(offset + r_offset);
+    if (r_offset >= size) {
+        return std::nullopt;
+    }
 
-    return {};
+    return file->ReadByte(offset + r_offset);
 }
 
 std::vector<u8> OffsetVfsFile::ReadBytes(std::size_t r_size, std::size_t r_offset) const {
diff --git a/src/core/file_sys/vfs_static.h b/src/core/file_sys/vfs_static.h
index 9f5a90b1b..8b27c30fa 100644
--- a/src/core/file_sys/vfs_static.h
+++ b/src/core/file_sys/vfs_static.h
@@ -54,9 +54,11 @@ public:
     }
 
     std::optional<u8> ReadByte(std::size_t offset) const override {
-        if (offset < size)
-            return value;
-        return {};
+        if (offset >= size) {
+            return std::nullopt;
+        }
+
+        return value;
     }
 
     std::vector<u8> ReadBytes(std::size_t length, std::size_t offset) const override {
diff --git a/src/core/hle/service/nvdrv/devices/nvhost_as_gpu.cpp b/src/core/hle/service/nvdrv/devices/nvhost_as_gpu.cpp
index d4ba88147..39bd2a45b 100644
--- a/src/core/hle/service/nvdrv/devices/nvhost_as_gpu.cpp
+++ b/src/core/hle/service/nvdrv/devices/nvhost_as_gpu.cpp
@@ -265,7 +265,7 @@ std::optional<nvhost_as_gpu::BufferMap> nvhost_as_gpu::FindBufferMap(GPUVAddr gp
         }
     }
 
-    return {};
+    return std::nullopt;
 }
 
 void nvhost_as_gpu::AddBufferMap(GPUVAddr gpu_addr, std::size_t size, VAddr cpu_addr,
@@ -286,7 +286,7 @@ std::optional<std::size_t> nvhost_as_gpu::RemoveBufferMap(GPUVAddr gpu_addr) {
         return size;
     }
 
-    return {};
+    return std::nullopt;
 }
 
 } // namespace Service::Nvidia::Devices
diff --git a/src/core/hle/service/nvdrv/nvdrv.h b/src/core/hle/service/nvdrv/nvdrv.h
index d7a1bef91..7706a5590 100644
--- a/src/core/hle/service/nvdrv/nvdrv.h
+++ b/src/core/hle/service/nvdrv/nvdrv.h
@@ -54,7 +54,7 @@ struct EventInterface {
             }
             mask = mask >> 1;
         }
-        return {};
+        return std::nullopt;
     }
     void SetEventStatus(const u32 event_id, EventState new_status) {
         EventState old_status = status[event_id];
diff --git a/src/core/hle/service/nvflinger/nvflinger.cpp b/src/core/hle/service/nvflinger/nvflinger.cpp
index f644a460d..c64673dba 100644
--- a/src/core/hle/service/nvflinger/nvflinger.cpp
+++ b/src/core/hle/service/nvflinger/nvflinger.cpp
@@ -114,7 +114,7 @@ std::optional<u64> NVFlinger::OpenDisplay(std::string_view name) {
                      [&](const VI::Display& display) { return display.GetName() == name; });
 
     if (itr == displays.end()) {
-        return {};
+        return std::nullopt;
     }
 
     return itr->GetID();
@@ -124,7 +124,7 @@ std::optional<u64> NVFlinger::CreateLayer(u64 display_id) {
     auto* const display = FindDisplay(display_id);
 
     if (display == nullptr) {
-        return {};
+        return std::nullopt;
     }
 
     const u64 layer_id = next_layer_id++;
@@ -144,7 +144,7 @@ std::optional<u32> NVFlinger::FindBufferQueueId(u64 display_id, u64 layer_id) co
     const auto* const layer = FindLayer(display_id, layer_id);
 
     if (layer == nullptr) {
-        return {};
+        return std::nullopt;
     }
 
     return layer->GetBufferQueue().GetId();
diff --git a/src/core/hle/service/sockets/bsd.cpp b/src/core/hle/service/sockets/bsd.cpp
index 7b9dd42d8..a74be9370 100644
--- a/src/core/hle/service/sockets/bsd.cpp
+++ b/src/core/hle/service/sockets/bsd.cpp
@@ -497,7 +497,7 @@ std::pair<s32, Errno> BSD::PollImpl(std::vector<u8>& write_buffer, std::vector<u
             return {0, Errno::SUCCESS};
         }
 
-        std::optional<FileDescriptor>& descriptor = file_descriptors[pollfd.fd];
+        const std::optional<FileDescriptor>& descriptor = file_descriptors[pollfd.fd];
         if (!descriptor) {
             LOG_ERROR(Service, "File descriptor handle={} is not allocated", pollfd.fd);
             pollfd.revents = POLL_NVAL;
diff --git a/src/core/loader/nso.cpp b/src/core/loader/nso.cpp
index 60373cc5f..1e70f6e11 100644
--- a/src/core/loader/nso.cpp
+++ b/src/core/loader/nso.cpp
@@ -76,16 +76,16 @@ std::optional<VAddr> AppLoader_NSO::LoadModule(Kernel::Process& process, Core::S
                                                bool should_pass_arguments, bool load_into_process,
                                                std::optional<FileSys::PatchManager> pm) {
     if (file.GetSize() < sizeof(NSOHeader)) {
-        return {};
+        return std::nullopt;
     }
 
     NSOHeader nso_header{};
     if (sizeof(NSOHeader) != file.ReadObject(&nso_header)) {
-        return {};
+        return std::nullopt;
     }
 
     if (nso_header.magic != Common::MakeMagic('N', 'S', 'O', '0')) {
-        return {};
+        return std::nullopt;
     }
 
     // Build program image