vfs_static: Add StaticVfsFile

Always returns the template argument byte for all reads. Doesn't support writes.

src/core/CMakeLists.txt

@@ -63,6 +63,7 @@ add_library(core STATIC
     file_sys/vfs_offset.h
     file_sys/vfs_real.cpp
     file_sys/vfs_real.h
+    file_sys/vfs_static.h
     file_sys/vfs_vector.cpp
     file_sys/vfs_vector.h
     file_sys/xts_archive.cpp

src/core/file_sys/vfs_static.h

@@ -0,0 +1,77 @@
+// Copyright 2018 yuzu emulator team
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <memory>
+#include <string_view>
+
+#include "core/file_sys/vfs.h"
+
+namespace FileSys {
+
+template <u8 value>
+class StaticVfsFile : public VfsFile {
+public:
+    explicit StaticVfsFile(size_t size = 0, std::string name = "", VirtualDir parent = nullptr)
+        : size(size), name(name), parent(parent) {}
+
+    std::string GetName() const override {
+        return name;
+    }
+
+    size_t GetSize() const override {
+        return size;
+    }
+
+    bool Resize(size_t new_size) override {
+        size = new_size;
+        return true;
+    }
+
+    std::shared_ptr<VfsDirectory> GetContainingDirectory() const override {
+        return parent;
+    }
+
+    bool IsWritable() const override {
+        return false;
+    }
+
+    bool IsReadable() const override {
+        return true;
+    }
+
+    size_t Read(u8* data, size_t length, size_t offset) const override {
+        const auto read = std::min(length, size - offset);
+        std::fill(data, data + read, value);
+        return read;
+    }
+
+    size_t Write(const u8* data, size_t length, size_t offset) override {
+        return 0;
+    }
+
+    boost::optional<u8> ReadByte(size_t offset) const override {
+        if (offset < size)
+            return value;
+        return boost::none;
+    }
+
+    std::vector<u8> ReadBytes(size_t length, size_t offset) const override {
+        const auto read = std::min(length, size - offset);
+        return std::vector<u8>(read, value);
+    }
+
+    bool Rename(std::string_view new_name) override {
+        name = new_name;
+        return true;
+    }
+
+private:
+    size_t size;
+    std::string name;
+    VirtualDir parent;
+};
+
+} // namespace FileSys