bcat: Add backend class to generify the functions of BCAT

Provides the most abstract simplified functions of BCAT as functions. Also includes a NullBackend class which is just a no-op.

src/core/hle/service/bcat/backend/backend.cpp

+// Copyright 2019 yuzu emulator team
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include "common/hex_util.h"
+#include "common/logging/log.h"
+#include "core/hle/service/bcat/backend/backend.h"
+
+namespace Service::BCAT {
+
+Backend::Backend(DirectoryGetter getter) : dir_getter(std::move(getter)) {}
+
+Backend::~Backend() = default;
+
+NullBackend::NullBackend(const DirectoryGetter& getter) : Backend(std::move(getter)) {}
+
+NullBackend::~NullBackend() = default;
+
+bool NullBackend::Synchronize(TitleIDVersion title, CompletionCallback callback) {
+    LOG_DEBUG(Service_BCAT, "called, title_id={:016X}, build_id={:016X}", title.title_id,
+              title.build_id);
+
+    callback(true);
+    return true;
+}
+
+bool NullBackend::SynchronizeDirectory(TitleIDVersion title, std::string name,
+                                       CompletionCallback callback) {
+    LOG_DEBUG(Service_BCAT, "called, title_id={:016X}, build_id={:016X}, name={}", title.title_id,
+              title.build_id, name);
+
+    callback(true);
+    return true;
+}
+
+bool NullBackend::Clear(u64 title_id) {
+    LOG_DEBUG(Service_BCAT, "called, title_id={:016X}");
+
+    return true;
+}
+
+void NullBackend::SetPassphrase(u64 title_id, const Passphrase& passphrase) {
+    LOG_DEBUG(Service_BCAT, "called, title_id={:016X}, passphrase = {}", title_id,
+              Common::HexArrayToString(passphrase));
+}
+
+} // namespace Service::BCAT

src/core/hle/service/bcat/backend/backend.h

+// Copyright 2019 yuzu emulator team
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <functional>
+#include "common/common_types.h"
+#include "core/file_sys/vfs_types.h"
+
+namespace Service::BCAT {
+
+using CompletionCallback = std::function<void(bool)>;
+using DirectoryGetter = std::function<FileSys::VirtualDir(u64)>;
+using Passphrase = std::array<u8, 0x20>;
+
+struct TitleIDVersion {
+    u64 title_id;
+    u64 build_id;
+};
+
+class Backend {
+public:
+    explicit Backend(DirectoryGetter getter);
+    virtual ~Backend();
+
+    virtual bool Synchronize(TitleIDVersion title, CompletionCallback callback) = 0;
+    virtual bool SynchronizeDirectory(TitleIDVersion title, std::string name,
+                                      CompletionCallback callback) = 0;
+
+    virtual bool Clear(u64 title_id) = 0;
+
+    virtual void SetPassphrase(u64 title_id, const Passphrase& passphrase) = 0;
+
+protected:
+    DirectoryGetter dir_getter;
+};
+
+class NullBackend : public Backend {
+public:
+    explicit NullBackend(const DirectoryGetter& getter);
+    ~NullBackend() override;
+
+    bool Synchronize(TitleIDVersion title, CompletionCallback callback) override;
+    bool SynchronizeDirectory(TitleIDVersion title, std::string name,
+                              CompletionCallback callback) override;
+
+    bool Clear(u64 title_id) override;
+
+    void SetPassphrase(u64 title_id, const Passphrase& passphrase) override;
+};
+
+} // namespace Service::BCAT