Add for windows and Android

Signed-off-by: lizzie <lizzie@eden-emu.dev>

src/common/fs/file.cpp

@@ -13,12 +13,17 @@
 #include "common/fs/fs_android.h"
 #endif
 #include "common/logging/log.h"
+#include "common/literals.h"
 
 #ifdef _WIN32
 #include <io.h>
 #include <share.h>
+#include <windows.h>
 #else
 #include <unistd.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <fcntl.h>
 #endif
 
 #ifdef _MSC_VER
@@ -36,13 +41,13 @@ namespace {
 #ifdef _WIN32
 
 /**
- * Converts the file access mode and file type enums to a file access mode wide string.
- *
- * @param mode File access mode
- * @param type File type
- *
- * @returns A pointer to a wide string representing the file access mode.
- */
+* Converts the file access mode and file type enums to a file access mode wide string.
+*
+* @param mode File access mode
+* @param type File type
+*
+* @returns A pointer to a wide string representing the file access mode.
+*/
 [[nodiscard]] constexpr const wchar_t* AccessModeToWStr(FileAccessMode mode, FileType type) {
     switch (type) {
     case FileType::BinaryFile:
@@ -79,12 +84,12 @@ namespace {
 }
 
 /**
- * Converts the file-share access flag enum to a Windows defined file-share access flag.
- *
- * @param flag File-share access flag
- *
- * @returns Windows defined file-share access flag.
- */
+* Converts the file-share access flag enum to a Windows defined file-share access flag.
+*
+* @param flag File-share access flag
+*
+* @returns Windows defined file-share access flag.
+*/
 [[nodiscard]] constexpr int ToWindowsFileShareFlag(FileShareFlag flag) {
     switch (flag) {
     case FileShareFlag::ShareNone:
@@ -102,13 +107,13 @@ namespace {
 #else
 
 /**
- * Converts the file access mode and file type enums to a file access mode string.
- *
- * @param mode File access mode
- * @param type File type
- *
- * @returns A pointer to a string representing the file access mode.
- */
+* Converts the file access mode and file type enums to a file access mode string.
+*
+* @param mode File access mode
+* @param type File type
+*
+* @returns A pointer to a string representing the file access mode.
+*/
 [[nodiscard]] constexpr const char* AccessModeToStr(FileAccessMode mode, FileType type) {
     switch (type) {
     case FileType::BinaryFile:
@@ -147,12 +152,12 @@ namespace {
 #endif
 
 /**
- * Converts the seek origin enum to a seek origin integer.
- *
- * @param origin Seek origin
- *
- * @returns Seek origin integer.
- */
+* Converts the seek origin enum to a seek origin integer.
+*
+* @param origin Seek origin
+*
+* @returns Seek origin integer.
+*/
 [[nodiscard]] constexpr int ToSeekOrigin(SeekOrigin origin) {
     switch (origin) {
     case SeekOrigin::SetOrigin:
@@ -178,7 +183,7 @@ std::string ReadStringFromFile(const std::filesystem::path& path, FileType type)
 }
 
 size_t WriteStringToFile(const std::filesystem::path& path, FileType type,
-                         std::string_view string) {
+                        std::string_view string) {
     if (Exists(path) && !IsFile(path)) {
         return 0;
     }
@@ -189,7 +194,7 @@ size_t WriteStringToFile(const std::filesystem::path& path, FileType type,
 }
 
 size_t AppendStringToFile(const std::filesystem::path& path, FileType type,
-                          std::string_view string) {
+                        std::string_view string) {
     if (Exists(path) && !IsFile(path)) {
         return 0;
     }
@@ -244,15 +249,103 @@ FileType IOFile::GetType() const {
     return file_type;
 }
 
+#ifdef __unix__
+int PlatformMapReadOnly(IOFile& io, const char* path) {
+    io.mmap_fd = open(path., O_RDONLY);
+    if (io.mmap_fd > 0) {
+        struct stat st;
+        fstat(io.mmap_fd, &st);
+        io.mmap_size = st.st_size;
+
+        int map_flags = MAP_PRIVATE;
+#ifdef MAP_PREFAULT_READ
+        // Prefaults reads so the final resulting pagetable from this big stupid mmap()
+        // isn't comically lazily loaded, we just coalesce everything in-place for our
+        // lovely mmap flags; if we didn't prefault the reads the page table will be
+        // constructed in-place (i.e on a read-by-read basis) causing lovely soft-faults
+        // which would nuke any performance gains.
+        //
+        // This of course incurs a cost in the initial mmap(2) call, but that is fine.
+        map_flags |= MAP_PREFAULT_READ;
+#endif
+#ifdef MAP_NOSYNC
+        // This causes physical media to not be synched to our file/memory
+        // This means that if the read-only file is written to, we won't see changes
+        // or we may see changes which are just funnily scattered, in any case
+        // this presumes the files won't be changed during execution
+        //
+        // Do not ever use this on write files (if we ever support that); this will create
+        // a fun amount of fragmentation on the disk.
+        map_flags |= MAP_NOSYNC;
+#endif
+#ifdef MAP_ALIGNED_SUPER
+        // File must be big enough that it's worth to super align. We can't just super-align every
+        // file otherwise we will run out of alignments for actually important files :)
+        // System doesn't guarantee a super alignment, but if it's available it will delete
+        // about 3 layers(?) of the TLB tree for each read/write.
+        // Again the cost of faults may make this negligible gains, but hey, we gotta work
+        // what we gotta work with.
+        using namespace Common::Literals;
+        u64 big_file_threshold = 512_MiB;
+        map_flags |= u64(st.st_size) >= big_file_threshold ? MAP_ALIGNED_SUPER : 0;
+#endif
+        io.mmap_base = (u8*)mmap(nullptr, io.mmap_size, PROT_READ, map_flags, io.mmap_fd, 0);
+        if (io.mmap_base == MAP_FAILED) {
+            close(io.mmap_fd);
+            io.mmap_fd = -1;
+        } else {
+            posix_madvise(mmap_base, io.mmap_size, POSIX_MADV_WILLNEED);
+        }
+    }
+    return io.mmap_fd;
+}
+void PlatformUnmap(IOFile& io) {
+    if (io.mmap_fd != -1) {
+        munmap(io.mmap_base, io.mmap_size);
+        close(io.mmap_fd);
+        io.mmap_fd = -1;
+    }
+}
+#else
+int PlatformMapReadOnly(IOFile& io, const char* path) {
+    io.file_handle = CreateFileA(path, GENERIC_READ, FILE_SHARE_READ, nullptr, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL | FILE_FLAG_SEQUENTIAL_SCAN, nullptr);
+    if (HANDLE(io.file_handle) != INVALID_HANDLE_VALUE) {
+        io.mapping_handle = CreateFileMappingW(file_handle, nullptr, PAGE_READONLY, 0, 0, nullptr);
+        if (io.mapping_handle) {
+            io.mmap_base = (char const*)MapViewOfFile(HANDLE(io.mapping_handle), FILE_MAP_READ, 0, 0, 0);
+            if (io.mmap_base) {
+                _LARGE_INTEGER pvalue;
+                GetFileSizeEx(file_handle, &pvalue);
+                io.mmap_size = uint32_t(pvalue.QuadPart);
+            } else {
+                CloseHandle(io.mapping_handle);
+                CloseHandle(io.file_handle);
+                return -1;
+            }
+        } else {
+            CloseHandle(io.file_handle);
+            return -1;
+        }
+    }
+    return 0;
+}
+void PlatformUnmap(IOFile& io) {
+    if(io.mapping_handle) {
+        if(io.mmap_base)
+            UnmapViewOfFile(HANDLE(io.mmap_base));
+        CloseHandle(HANDLE(io.mapping_handle));
+    }
+    if(io.file_handle != INVALID_HANDLE_VALUE)
+        CloseHandle(HANDLE(io.file_handle));
+}
+#endif
+
 void IOFile::Open(const fs::path& path, FileAccessMode mode, FileType type, FileShareFlag flag) {
     Close();
-
     file_path = path;
     file_access_mode = mode;
     file_type = type;
-
     errno = 0;
-
 #ifdef _WIN32
     if (flag != FileShareFlag::ShareNone) {
         file = _wfsopen(path.c_str(), AccessModeToWStr(mode, type), ToWindowsFileShareFlag(flag));
@@ -262,51 +355,58 @@ void IOFile::Open(const fs::path& path, FileAccessMode mode, FileType type, File
 #elif ANDROID
     if (Android::IsContentUri(path)) {
         ASSERT_MSG(mode == FileAccessMode::Read, "Content URI file access is for read-only!");
-        const auto fd = Android::OpenContentUri(path, Android::OpenMode::Read);
-        if (fd != -1) {
-            file = fdopen(fd, "r");
-            const auto error_num = errno;
-            if (error_num != 0 && file == nullptr) {
-                LOG_ERROR(Common_Filesystem, "Error opening file: {}, error: {}", path.c_str(),
-                          strerror(error_num));
+        if (PlatformMapReadOnly(*this, path.c_str()) == -1) {
+            LOG_ERROR(Common_Filesystem, "Error mmap'ing file: {}", path.c_str());
+            int const fd = Android::OpenContentUri(path, Android::OpenMode::Read);
+            if (fd != -1) {
+                file = fdopen(fd, "r");
+                if (errno != 0 && file == nullptr)
+                    LOG_ERROR(Common_Filesystem, "Error opening file: {}, error: {}", path.c_str(), strerror(errno));
+            } else {
+                LOG_ERROR(Common_Filesystem, "Error opening file: {}", path.c_str());
             }
-        } else {
-            LOG_ERROR(Common_Filesystem, "Error opening file: {}", path.c_str());
         }
     } else {
         file = std::fopen(path.c_str(), AccessModeToStr(mode, type));
     }
+#elif defined(__HAIKU__) || defined(__managarm__) || defined(__OPENORBIS__) || defined(__APPLE__)
+    file = std::fopen(path.c_str(), AccessModeToStr(mode, type));
+#elif defined(__unix__)
+    if (type == FileType::BinaryFile && mode == FileAccessMode::Read) {
+        if (PlatformMapReadOnly(*this, path.c_str()) == -1) {
+            LOG_ERROR(Common_Filesystem, "Error mmap'ing file: {}", path.c_str());
+        }
+    }
+    if (mmap_fd == -1) {
+        file = std::fopen(path.c_str(), AccessModeToStr(mode, type)); // mmap(2) failed or simply we can't use it
+    }
 #else
+    // Some other fancy OS (ahem fucking Darwin/Mac OSX)
     file = std::fopen(path.c_str(), AccessModeToStr(mode, type));
 #endif
-
     if (!IsOpen()) {
         const auto ec = std::error_code{errno, std::generic_category()};
         LOG_ERROR(Common_Filesystem, "Failed to open the file at path={}, ec_message={}",
-                  PathToUTF8String(file_path), ec.message());
+            PathToUTF8String(file_path), ec.message());
     }
 }
 
 void IOFile::Close() {
-    if (!IsOpen()) {
-        return;
+    PlatformUnmap(*this);
+    if (file) {
+        errno = 0;
+        const auto close_result = std::fclose(file) == 0;
+        if (!close_result) {
+            const auto ec = std::error_code{errno, std::generic_category()};
+            LOG_ERROR(Common_Filesystem, "Failed to close the file at path={}, ec_message={}",
+                PathToUTF8String(file_path), ec.message());
+        }
+        file = nullptr;
     }
-
-    errno = 0;
-
-    const auto close_result = std::fclose(file) == 0;
-
-    if (!close_result) {
-        const auto ec = std::error_code{errno, std::generic_category()};
-        LOG_ERROR(Common_Filesystem, "Failed to close the file at path={}, ec_message={}",
-                  PathToUTF8String(file_path), ec.message());
-    }
-
-    file = nullptr;
 }
 
 bool IOFile::IsOpen() const {
-    return file != nullptr;
+    return file != nullptr || IsMappedFile();
 }
 
 std::string IOFile::ReadString(size_t length) const {
@@ -323,137 +423,132 @@ size_t IOFile::WriteString(std::span<const char> string) const {
 }
 
 bool IOFile::Flush() const {
-    if (!IsOpen()) {
-        return false;
+    ASSERT(!IsMappedFile());
+    if (file) {
+        errno = 0;
+        auto const flush_result = std::fflush(file) == 0;
+        if (!flush_result) {
+            const auto ec = std::error_code{errno, std::generic_category()};
+            LOG_ERROR(Common_Filesystem, "Failed to flush the file at path={}, ec_message={}",
+                PathToUTF8String(file_path), ec.message());
+        }
+        return flush_result;
     }
-
-    errno = 0;
-
-#ifdef _WIN32
-    const auto flush_result = std::fflush(file) == 0;
-#else
-    const auto flush_result = std::fflush(file) == 0;
-#endif
-
-    if (!flush_result) {
-        const auto ec = std::error_code{errno, std::generic_category()};
-        LOG_ERROR(Common_Filesystem, "Failed to flush the file at path={}, ec_message={}",
-                  PathToUTF8String(file_path), ec.message());
-    }
-
-    return flush_result;
+    return false;
 }
 
 bool IOFile::Commit() const {
-    if (!IsOpen()) {
-        return false;
-    }
-
-    errno = 0;
-
+    ASSERT(!IsMappedFile());
+    if (file) {
+        errno = 0;
 #ifdef _WIN32
-    const auto commit_result = std::fflush(file) == 0 && _commit(fileno(file)) == 0;
+        const auto commit_result = std::fflush(file) == 0 && _commit(fileno(file)) == 0;
 #else
-    const auto commit_result = std::fflush(file) == 0 && fsync(fileno(file)) == 0;
+        const auto commit_result = std::fflush(file) == 0 && fsync(fileno(file)) == 0;
 #endif
-
-    if (!commit_result) {
-        const auto ec = std::error_code{errno, std::generic_category()};
-        LOG_ERROR(Common_Filesystem, "Failed to commit the file at path={}, ec_message={}",
-                  PathToUTF8String(file_path), ec.message());
+        if (!commit_result) {
+            const auto ec = std::error_code{errno, std::generic_category()};
+            LOG_ERROR(Common_Filesystem, "Failed to commit the file at path={}, ec_message={}",
+                PathToUTF8String(file_path), ec.message());
+        }
+        return commit_result;
     }
-
-    return commit_result;
+    return false;
 }
 
 bool IOFile::SetSize(u64 size) const {
-    if (!IsOpen()) {
-        return false;
-    }
-
-    errno = 0;
-
+    ASSERT(!IsMappedFile());
+    if (file) {
+        errno = 0;
 #ifdef _WIN32
-    const auto set_size_result = _chsize_s(fileno(file), static_cast<s64>(size)) == 0;
+        const auto set_size_result = _chsize_s(fileno(file), s64(size)) == 0;
 #else
-    const auto set_size_result = ftruncate(fileno(file), static_cast<s64>(size)) == 0;
+        const auto set_size_result = ftruncate(fileno(file), s64(size)) == 0;
 #endif
-
-    if (!set_size_result) {
-        const auto ec = std::error_code{errno, std::generic_category()};
-        LOG_ERROR(Common_Filesystem, "Failed to resize the file at path={}, size={}, ec_message={}",
-                  PathToUTF8String(file_path), size, ec.message());
+        if (!set_size_result) {
+            const auto ec = std::error_code{errno, std::generic_category()};
+            LOG_ERROR(Common_Filesystem, "Failed to resize the file at path={}, size={}, ec_message={}",
+                PathToUTF8String(file_path), size, ec.message());
+        }
+        return set_size_result;
     }
-
-    return set_size_result;
+    return false;
 }
 
 u64 IOFile::GetSize() const {
-    if (!IsOpen()) {
-        return 0;
-    }
-
-    // Flush any unwritten buffered data into the file prior to retrieving the file size.
-    std::fflush(file);
-
+    if (IsMappedFile())
+        return mmap_size;
+    if (file) {
+        // Flush any unwritten buffered data into the file prior to retrieving the file mmap_size.
+        std::fflush(file);
 #if ANDROID
-    u64 file_size = 0;
-    if (Android::IsContentUri(file_path)) {
-        file_size = Android::GetSize(file_path);
-    } else {
+        u64 file_size = 0;
+        if (Android::IsContentUri(file_path)) {
+            file_size = Android::GetSize(file_path);
+        } else {
+            std::error_code ec;
+
+            file_size = fs::file_size(file_path, ec);
+
+            if (ec) {
+                LOG_ERROR(Common_Filesystem, "Failed to retrieve the file mmap_size of path={}, ec_message={}",
+                    PathToUTF8String(file_path), ec.message());
+                return 0;
+            }
+        }
+#else
         std::error_code ec;
-
-        file_size = fs::file_size(file_path, ec);
-
+        auto const file_size = fs::file_size(file_path, ec);
         if (ec) {
-            LOG_ERROR(Common_Filesystem,
-                      "Failed to retrieve the file size of path={}, ec_message={}",
-                      PathToUTF8String(file_path), ec.message());
+            LOG_ERROR(Common_Filesystem, "Failed to retrieve the file mmap_size of path={}, ec_message={}",
+                PathToUTF8String(file_path), ec.message());
             return 0;
         }
-    }
-#else
-    std::error_code ec;
-
-    const auto file_size = fs::file_size(file_path, ec);
-
-    if (ec) {
-        LOG_ERROR(Common_Filesystem, "Failed to retrieve the file size of path={}, ec_message={}",
-                  PathToUTF8String(file_path), ec.message());
-        return 0;
-    }
 #endif
-
-    return file_size;
+        return file_size;
+    }
+    return 0;
 }
 
 bool IOFile::Seek(s64 offset, SeekOrigin origin) const {
-    if (!IsOpen()) {
-        return false;
+    if (IsMappedFile()) {
+        // fuck you to whoever made this method const
+        switch (origin) {
+        case SeekOrigin::SetOrigin:
+            mmap_offset = off_t(offset);
+            break;
+        case SeekOrigin::CurrentPosition:
+            mmap_offset += off_t(offset);
+            break;
+        case SeekOrigin::End:
+            mmap_offset = off_t(mmap_size) + off_t(offset);
+            break;
+        }
+        return true;
     }
-
-    errno = 0;
-
-    const auto seek_result = fseeko(file, offset, ToSeekOrigin(origin)) == 0;
-
-    if (!seek_result) {
-        const auto ec = std::error_code{errno, std::generic_category()};
-        LOG_ERROR(Common_Filesystem,
-                  "Failed to seek the file at path={}, offset={}, origin={}, ec_message={}",
-                  PathToUTF8String(file_path), offset, origin, ec.message());
+    if (file) {
+        errno = 0;
+        const auto seek_result = fseeko(file, offset, ToSeekOrigin(origin)) == 0;
+        if (!seek_result) {
+            const auto ec = std::error_code{errno, std::generic_category()};
+            LOG_ERROR(Common_Filesystem, "Failed to seek the file at path={}, offset={}, origin={}, ec_message={}",
+                PathToUTF8String(file_path), offset, origin, ec.message());
+        }
+        return seek_result;
     }
-
-    return seek_result;
+    return false;
 }
 
 s64 IOFile::Tell() const {
-    if (!IsOpen()) {
-        return 0;
+    if (IsMappedFile()) {
+        errno = 0;
+        return s64(mmap_offset);
     }
-
-    errno = 0;
-
-    return ftello(file);
+    if (file) {
+        errno = 0;
+        return ftello(file);
+    }
+    return 0;
 }
 
 } // namespace Common::FS

src/common/fs/file.h

@@ -1,9 +1,13 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 // SPDX-FileCopyrightText: Copyright 2021 yuzu Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #pragma once
 
 #include <cstdio>
+#include <cstring>
 #include <filesystem>
 #include <span>
 #include <type_traits>
@@ -21,12 +25,12 @@ enum class SeekOrigin {
 };
 
 /**
- * Opens a file stream at path with the specified open mode.
- *
- * @param file_stream Reference to file stream
- * @param path Filesystem path
- * @param open_mode File stream open mode
- */
+* Opens a file stream at path with the specified open mode.
+*
+* @param file_stream Reference to file stream
+* @param path Filesystem path
+* @param open_mode File stream open mode
+*/
 template <typename FileStream>
 void OpenFileStream(FileStream& file_stream, const std::filesystem::path& path,
                     std::ios_base::openmode open_mode) {
@@ -45,14 +49,14 @@ void OpenFileStream(FileStream& file_stream, const Path& path, std::ios_base::op
 #endif
 
 /**
- * Reads an entire file at path and returns a string of the contents read from the file.
- * If the filesystem object at path is not a regular file, this function returns an empty string.
- *
- * @param path Filesystem path
- * @param type File type
- *
- * @returns A string of the contents read from the file.
- */
+* Reads an entire file at path and returns a string of the contents read from the file.
+* If the filesystem object at path is not a regular file, this function returns an empty string.
+*
+* @param path Filesystem path
+* @param type File type
+*
+* @returns A string of the contents read from the file.
+*/
 [[nodiscard]] std::string ReadStringFromFile(const std::filesystem::path& path, FileType type);
 
 #ifdef _WIN32
@@ -67,18 +71,18 @@ template <typename Path>
 #endif
 
 /**
- * Writes a string to a file at path and returns the number of characters successfully written.
- * If a file already exists at path, its contents will be erased.
- * If a file does not exist at path, it creates and opens a new empty file for writing.
- * If the filesystem object at path exists and is not a regular file, this function returns 0.
- *
- * @param path Filesystem path
- * @param type File type
- *
- * @returns Number of characters successfully written.
- */
+* Writes a string to a file at path and returns the number of characters successfully written.
+* If a file already exists at path, its contents will be erased.
+* If a file does not exist at path, it creates and opens a new empty file for writing.
+* If the filesystem object at path exists and is not a regular file, this function returns 0.
+*
+* @param path Filesystem path
+* @param type File type
+*
+* @returns Number of characters successfully written.
+*/
 [[nodiscard]] size_t WriteStringToFile(const std::filesystem::path& path, FileType type,
-                                       std::string_view string);
+                                    std::string_view string);
 
 #ifdef _WIN32
 template <typename Path>
@@ -92,15 +96,15 @@ template <typename Path>
 #endif
 
 /**
- * Appends a string to a file at path and returns the number of characters successfully written.
- * If a file does not exist at path, it creates and opens a new empty file for appending.
- * If the filesystem object at path exists and is not a regular file, this function returns 0.
- *
- * @param path Filesystem path
- * @param type File type
- *
- * @returns Number of characters successfully written.
- */
+* Appends a string to a file at path and returns the number of characters successfully written.
+* If a file does not exist at path, it creates and opens a new empty file for appending.
+* If the filesystem object at path exists and is not a regular file, this function returns 0.
+*
+* @param path Filesystem path
+* @param type File type
+*
+* @returns Number of characters successfully written.
+*/
 [[nodiscard]] size_t AppendStringToFile(const std::filesystem::path& path, FileType type,
                                         std::string_view string);
 
@@ -128,14 +132,14 @@ public:
                     FileShareFlag flag = FileShareFlag::ShareReadOnly);
 
     /**
-     * An IOFile is a lightweight wrapper on C Library file operations.
-     * Automatically closes an open file on the destruction of an IOFile object.
-     *
-     * @param path Filesystem path
-     * @param mode File access mode
-     * @param type File type, default is BinaryFile. Use TextFile to open the file as a text file
-     * @param flag (Windows only) File-share access flag, default is ShareReadOnly
-     */
+    * An IOFile is a lightweight wrapper on C Library file operations.
+    * Automatically closes an open file on the destruction of an IOFile object.
+    *
+    * @param path Filesystem path
+    * @param mode File access mode
+    * @param type File type, default is BinaryFile. Use TextFile to open the file as a text file
+    * @param flag (Windows only) File-share access flag, default is ShareReadOnly
+    */
     explicit IOFile(const std::filesystem::path& path, FileAccessMode mode,
                     FileType type = FileType::BinaryFile,
                     FileShareFlag flag = FileShareFlag::ShareReadOnly);
@@ -149,84 +153,70 @@ public:
     IOFile& operator=(IOFile&& other) noexcept;
 
     /**
-     * Gets the path of the file.
-     *
-     * @returns The path of the file.
-     */
+    * Gets the path of the file.
+    *
+    * @returns The path of the file.
+    */
     [[nodiscard]] std::filesystem::path GetPath() const;
 
     /**
-     * Gets the access mode of the file.
-     *
-     * @returns The access mode of the file.
-     */
+    * Gets the access mode of the file.
+    *
+    * @returns The access mode of the file.
+    */
     [[nodiscard]] FileAccessMode GetAccessMode() const;
 
     /**
-     * Gets the type of the file.
-     *
-     * @returns The type of the file.
-     */
+    * Gets the type of the file.
+    *
+    * @returns The type of the file.
+    */
     [[nodiscard]] FileType GetType() const;
 
     /**
-     * Opens a file at path with the specified file access mode.
-     * This function behaves differently depending on the FileAccessMode.
-     * These behaviors are documented in each enum value of FileAccessMode.
-     *
-     * @param path Filesystem path
-     * @param mode File access mode
-     * @param type File type, default is BinaryFile. Use TextFile to open the file as a text file
-     * @param flag (Windows only) File-share access flag, default is ShareReadOnly
-     */
+    * Opens a file at path with the specified file access mode.
+    * This function behaves differently depending on the FileAccessMode.
+    * These behaviors are documented in each enum value of FileAccessMode.
+    *
+    * @param path Filesystem path
+    * @param mode File access mode
+    * @param type File type, default is BinaryFile. Use TextFile to open the file as a text file
+    * @param flag (Windows only) File-share access flag, default is ShareReadOnly
+    */
     void Open(const std::filesystem::path& path, FileAccessMode mode,
-              FileType type = FileType::BinaryFile,
-              FileShareFlag flag = FileShareFlag::ShareReadOnly);
-
-// #ifdef _WIN32
-//     template <typename Path>
-//     void Open(const Path& path, FileAccessMode mode, FileType type = FileType::BinaryFile,
-//               FileShareFlag flag = FileShareFlag::ShareReadOnly) {
-//         using ValueType = typename Path::value_type;
-//         if constexpr (IsChar<ValueType>) {
-//             Open(ToU8String(path), mode, type, flag);
-//         } else {
-//             Open(std::filesystem::path{path}, mode, type, flag);
-//         }
-//     }
-// #endif
+            FileType type = FileType::BinaryFile,
+            FileShareFlag flag = FileShareFlag::ShareReadOnly);
 
     /// Closes the file if it is opened.
     void Close();
 
     /**
-     * Checks whether the file is open.
-     * Use this to check whether the calls to Open() or Close() succeeded.
-     *
-     * @returns True if the file is open, false otherwise.
-     */
+    * Checks whether the file is open.
+    * Use this to check whether the calls to Open() or Close() succeeded.
+    *
+    * @returns True if the file is open, false otherwise.
+    */
     [[nodiscard]] bool IsOpen() const;
 
     /**
-     * Helper function which deduces the value type of a contiguous STL container used in ReadSpan.
-     * If T is not a contiguous container as defined by the concept IsContiguousContainer, this
-     * calls ReadObject and T must be a trivially copyable object.
-     *
-     * See ReadSpan for more details if T is a contiguous container.
-     * See ReadObject for more details if T is a trivially copyable object.
-     *
-     * @tparam T Contiguous container or trivially copyable object
-     *
-     * @param data Container of T::value_type data or reference to object
-     *
-     * @returns Count of T::value_type data or objects successfully read.
-     */
+    * Helper function which deduces the value type of a contiguous STL container used in ReadSpan.
+    * If T is not a contiguous container as defined by the concept IsContiguousContainer, this
+    * calls ReadObject and T must be a trivially copyable object.
+    *
+    * See ReadSpan for more details if T is a contiguous container.
+    * See ReadObject for more details if T is a trivially copyable object.
+    *
+    * @tparam T Contiguous container or trivially copyable object
+    *
+    * @param data Container of T::value_type data or reference to object
+    *
+    * @returns Count of T::value_type data or objects successfully read.
+    */
     template <typename T>
     [[nodiscard]] size_t Read(T& data) const {
         if constexpr (IsContiguousContainer<T>) {
             using ContiguousType = typename T::value_type;
-            static_assert(std::is_trivially_copyable_v<ContiguousType>,
-                          "Data type must be trivially copyable.");
+            static_assert(std::is_trivially_copyable_v<ContiguousType>, "Data type must be trivially copyable.");
             return ReadSpan<ContiguousType>(data);
         } else {
             return ReadObject(data) ? 1 : 0;
@@ -234,25 +224,24 @@ public:
     }
 
     /**
-     * Helper function which deduces the value type of a contiguous STL container used in WriteSpan.
-     * If T is not a contiguous STL container as defined by the concept IsContiguousContainer, this
-     * calls WriteObject and T must be a trivially copyable object.
-     *
-     * See WriteSpan for more details if T is a contiguous container.
-     * See WriteObject for more details if T is a trivially copyable object.
-     *
-     * @tparam T Contiguous container or trivially copyable object
-     *
-     * @param data Container of T::value_type data or const reference to object
-     *
-     * @returns Count of T::value_type data or objects successfully written.
-     */
+    * Helper function which deduces the value type of a contiguous STL container used in WriteSpan.
+    * If T is not a contiguous STL container as defined by the concept IsContiguousContainer, this
+    * calls WriteObject and T must be a trivially copyable object.
+    *
+    * See WriteSpan for more details if T is a contiguous container.
+    * See WriteObject for more details if T is a trivially copyable object.
+    *
+    * @tparam T Contiguous container or trivially copyable object
+    *
+    * @param data Container of T::value_type data or const reference to object
+    *
+    * @returns Count of T::value_type data or objects successfully written.
+    */
     template <typename T>
     [[nodiscard]] size_t Write(const T& data) const {
         if constexpr (IsContiguousContainer<T>) {
             using ContiguousType = typename T::value_type;
-            static_assert(std::is_trivially_copyable_v<ContiguousType>,
-                          "Data type must be trivially copyable.");
+            static_assert(std::is_trivially_copyable_v<ContiguousType>, "Data type must be trivially copyable.");
             return WriteSpan<ContiguousType>(data);
         } else {
             static_assert(std::is_trivially_copyable_v<T>, "Data type must be trivially copyable.");
@@ -261,199 +250,209 @@ public:
     }
 
     /**
-     * Reads a span of T data from a file sequentially.
-     * This function reads from the current position of the file pointer and
-     * advances it by the (count of T * sizeof(T)) bytes successfully read.
-     *
-     * Failures occur when:
-     * - The file is not open
-     * - The opened file lacks read permissions
-     * - Attempting to read beyond the end-of-file
-     *
-     * @tparam T Data type
-     *
-     * @param data Span of T data
-     *
-     * @returns Count of T data successfully read.
-     */
+    * Reads a span of T data from a file sequentially.
+    * This function reads from the current position of the file pointer and
+    * advances it by the (count of T * sizeof(T)) bytes successfully read.
+    *
+    * Failures occur when:
+    * - The file is not open
+    * - The opened file lacks read permissions
+    * - Attempting to read beyond the end-of-file
+    *
+    * @tparam T Data type
+    *
+    * @param data Span of T data
+    *
+    * @returns Count of T data successfully read.
+    */
     template <typename T>
     [[nodiscard]] size_t ReadSpan(std::span<T> data) const {
         static_assert(std::is_trivially_copyable_v<T>, "Data type must be trivially copyable.");
-
-        if (!IsOpen()) {
-            return 0;
+        if (IsMappedFile()) {
+            std::memcpy(data.data(), mmap_base + mmap_offset, sizeof(T) * data.size());
+            return data.size();
         }
-
-        return std::fread(data.data(), sizeof(T), data.size(), file);
+        return IsOpen() ? std::fread(data.data(), sizeof(T), data.size(), file) : 0;
     }
 
     /**
-     * Writes a span of T data to a file sequentially.
-     * This function writes from the current position of the file pointer and
-     * advances it by the (count of T * sizeof(T)) bytes successfully written.
-     *
-     * Failures occur when:
-     * - The file is not open
-     * - The opened file lacks write permissions
-     *
-     * @tparam T Data type
-     *
-     * @param data Span of T data
-     *
-     * @returns Count of T data successfully written.
-     */
+    * Writes a span of T data to a file sequentially.
+    * This function writes from the current position of the file pointer and
+    * advances it by the (count of T * sizeof(T)) bytes successfully written.
+    *
+    * Failures occur when:
+    * - The file is not open
+    * - The opened file lacks write permissions
+    *
+    * @tparam T Data type
+    *
+    * @param data Span of T data
+    *
+    * @returns Count of T data successfully written.
+    */
     template <typename T>
     [[nodiscard]] size_t WriteSpan(std::span<const T> data) const {
         static_assert(std::is_trivially_copyable_v<T>, "Data type must be trivially copyable.");
-
-        if (!IsOpen()) {
-            return 0;
+        if (IsMappedFile()) {
+            std::memcpy(mmap_base + mmap_offset, data.data(), sizeof(T) * data.size());
+            return data.size();
         }
-
-        return std::fwrite(data.data(), sizeof(T), data.size(), file);
+        return IsOpen() ? std::fwrite(data.data(), sizeof(T), data.size(), file) : 0;
     }
 
     /**
-     * Reads a T object from a file sequentially.
-     * This function reads from the current position of the file pointer and
-     * advances it by the sizeof(T) bytes successfully read.
-     *
-     * Failures occur when:
-     * - The file is not open
-     * - The opened file lacks read permissions
-     * - Attempting to read beyond the end-of-file
-     *
-     * @tparam T Data type
-     *
-     * @param object Reference to object
-     *
-     * @returns True if the object is successfully read from the file, false otherwise.
-     */
+    * Reads a T object from a file sequentially.
+    * This function reads from the current position of the file pointer and
+    * advances it by the sizeof(T) bytes successfully read.
+    *
+    * Failures occur when:
+    * - The file is not open
+    * - The opened file lacks read permissions
+    * - Attempting to read beyond the end-of-file
+    *
+    * @tparam T Data type
+    *
+    * @param object Reference to object
+    *
+    * @returns True if the object is successfully read from the file, false otherwise.
+    */
     template <typename T>
     [[nodiscard]] bool ReadObject(T& object) const {
         static_assert(std::is_trivially_copyable_v<T>, "Data type must be trivially copyable.");
         static_assert(!std::is_pointer_v<T>, "T must not be a pointer to an object.");
-
-        if (!IsOpen()) {
-            return false;
+        if (IsMappedFile()) {
+            std::memcpy(&object, mmap_base + mmap_offset, sizeof(T));
+            return sizeof(T);
         }
-
-        return std::fread(&object, sizeof(T), 1, file) == 1;
+        return IsOpen() ? std::fread(&object, sizeof(T), 1, file) == 1 : false;
     }
 
     /**
-     * Writes a T object to a file sequentially.
-     * This function writes from the current position of the file pointer and
-     * advances it by the sizeof(T) bytes successfully written.
-     *
-     * Failures occur when:
-     * - The file is not open
-     * - The opened file lacks write permissions
-     *
-     * @tparam T Data type
-     *
-     * @param object Const reference to object
-     *
-     * @returns True if the object is successfully written to the file, false otherwise.
-     */
+    * Writes a T object to a file sequentially.
+    * This function writes from the current position of the file pointer and
+    * advances it by the sizeof(T) bytes successfully written.
+    *
+    * Failures occur when:
+    * - The file is not open
+    * - The opened file lacks write permissions
+    *
+    * @tparam T Data type
+    *
+    * @param object Const reference to object
+    *
+    * @returns True if the object is successfully written to the file, false otherwise.
+    */
     template <typename T>
     [[nodiscard]] bool WriteObject(const T& object) const {
         static_assert(std::is_trivially_copyable_v<T>, "Data type must be trivially copyable.");
         static_assert(!std::is_pointer_v<T>, "T must not be a pointer to an object.");
-
-        if (!IsOpen()) {
-            return false;
+        if (IsMappedFile()) {
+            std::memcpy(mmap_base + mmap_offset, &object, sizeof(T));
+            return sizeof(T);
         }
-
-        return std::fwrite(&object, sizeof(T), 1, file) == 1;
+        return IsOpen() ? std::fwrite(&object, sizeof(T), 1, file) == 1 : false;
     }
 
     /**
-     * Specialized function to read a string of a given length from a file sequentially.
-     * This function writes from the current position of the file pointer and
-     * advances it by the number of characters successfully read.
-     * The size of the returned string may not match length if not all bytes are successfully read.
-     *
-     * @param length Length of the string
-     *
-     * @returns A string read from the file.
-     */
+    * Specialized function to read a string of a given length from a file sequentially.
+    * This function writes from the current position of the file pointer and
+    * advances it by the number of characters successfully read.
+    * The size of the returned string may not match length if not all bytes are successfully read.
+    *
+    * @param length Length of the string
+    *
+    * @returns A string read from the file.
+    */
     [[nodiscard]] std::string ReadString(size_t length) const;
 
     /**
-     * Specialized function to write a string to a file sequentially.
-     * This function writes from the current position of the file pointer and
-     * advances it by the number of characters successfully written.
-     *
-     * @param string Span of const char backed std::string or std::string_view
-     *
-     * @returns Number of characters successfully written.
-     */
+    * Specialized function to write a string to a file sequentially.
+    * This function writes from the current position of the file pointer and
+    * advances it by the number of characters successfully written.
+    *
+    * @param string Span of const char backed std::string or std::string_view
+    *
+    * @returns Number of characters successfully written.
+    */
     [[nodiscard]] size_t WriteString(std::span<const char> string) const;
 
     /**
-     * Attempts to flush any unwritten buffered data into the file.
-     *
-     * @returns True if the flush was successful, false otherwise.
-     */
+    * Attempts to flush any unwritten buffered data into the file.
+    *
+    * @returns True if the flush was successful, false otherwise.
+    */
     bool Flush() const;
 
     /**
-     * Attempts to commit the file into the disk.
-     * Note that this is an expensive operation as this forces the operating system to write
-     * the contents of the file associated with the file descriptor into the disk.
-     *
-     * @returns True if the commit was successful, false otherwise.
-     */
+    * Attempts to commit the file into the disk.
+    * Note that this is an expensive operation as this forces the operating system to write
+    * the contents of the file associated with the file descriptor into the disk.
+    *
+    * @returns True if the commit was successful, false otherwise.
+    */
     bool Commit() const;
 
     /**
-     * Resizes the file to a given size.
-     * If the file is resized to a smaller size, the remainder of the file is discarded.
-     * If the file is resized to a larger size, the new area appears as if zero-filled.
-     *
-     * Failures occur when:
-     * - The file is not open
-     *
-     * @param size File size in bytes
-     *
-     * @returns True if the file resize succeeded, false otherwise.
-     */
+    * Resizes the file to a given size.
+    * If the file is resized to a smaller size, the remainder of the file is discarded.
+    * If the file is resized to a larger size, the new area appears as if zero-filled.
+    *
+    * Failures occur when:
+    * - The file is not open
+    *
+    * @param size File size in bytes
+    *
+    * @returns True if the file resize succeeded, false otherwise.
+    */
     [[nodiscard]] bool SetSize(u64 size) const;
 
     /**
-     * Gets the size of the file.
-     *
-     * Failures occur when:
-     * - The file is not open
-     *
-     * @returns The file size in bytes of the file. Returns 0 on failure.
-     */
+    * Gets the size of the file.
+    *
+    * Failures occur when:
+    * - The file is not open
+    *
+    * @returns The file size in bytes of the file. Returns 0 on failure.
+    */
     [[nodiscard]] u64 GetSize() const;
 
     /**
-     * Moves the current position of the file pointer with the specified offset and seek origin.
-     *
-     * @param offset Offset from seek origin
-     * @param origin Seek origin
-     *
-     * @returns True if the file pointer has moved to the specified offset, false otherwise.
-     */
+    * Moves the current position of the file pointer with the specified offset and seek origin.
+    *
+    * @param offset Offset from seek origin
+    * @param origin Seek origin
+    *
+    * @returns True if the file pointer has moved to the specified offset, false otherwise.
+    */
     [[nodiscard]] bool Seek(s64 offset, SeekOrigin origin = SeekOrigin::SetOrigin) const;
 
     /**
-     * Gets the current position of the file pointer.
-     *
-     * @returns The current position of the file pointer.
-     */
+    * Gets the current position of the file pointer.
+    *
+    * @returns The current position of the file pointer.
+    */
     [[nodiscard]] s64 Tell() const;
 
 private:
     std::filesystem::path file_path;
     FileAccessMode file_access_mode{};
     FileType file_type{};
-
     std::FILE* file = nullptr;
+
+    // Any decent system should have mmap() for files
+    // Systems with artifical mmap() limitations should simply change the logic within file.cpp
+    // and reduce the threshold for which the mmap() is set to
+#ifdef _WIN32
+    void *mapping_handle = nullptr;
+    void *file_handle = nullptr;
+    bool IsMappedFile() { return file_handle != nullptr; }
+#else // POSIX
+    int mmap_fd = -1;
+    bool IsMappedFile() { return mmap_fd != -1; }
+#endif
+    u8* mmap_base = nullptr;
+    size_t mmap_size = 0;
+    mutable off_t mmap_offset = 0; // fuck you
 };
 
 } // namespace Common::FS