Common: Add a DirectIOFile class that allows for copies which are entirely thread safe.

2026-06-19 01:16:48 -07:00 · 2025-11-09 03:08:14 -06:00
parent db997e9963
commit 405baed805
5 changed files with 791 additions and 0 deletions
@@ -0,0 +1,372 @@
+// Copyright 2025 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "Common/DirectIOFile.h"
+
+#include <utility>
+
+#if defined(_WIN32)
+#include <windows.h>
+
+#include <cstring>
+
+#include "Common/Buffer.h"
+#include "Common/CommonFuncs.h"
+#include "Common/MathUtil.h"
+#include "Common/StringUtil.h"
+#else
+#include <string>
+
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#ifdef ANDROID
+#include "jni/AndroidCommon/AndroidCommon.h"
+
+#include "Common/Lazy.h"
+#endif
+
+#include "Common/FileUtil.h"
+#endif
+
+#include "Common/Assert.h"
+
+namespace File
+{
+DirectIOFile::DirectIOFile() = default;
+
+DirectIOFile::~DirectIOFile()
+{
+  Close();
+}
+
+DirectIOFile::DirectIOFile(const DirectIOFile& other)
+{
+  *this = other.Duplicate();
+}
+
+DirectIOFile& DirectIOFile::operator=(const DirectIOFile& other)
+{
+  return *this = other.Duplicate();
+}
+
+DirectIOFile::DirectIOFile(DirectIOFile&& other)
+{
+  Swap(other);
+}
+
+DirectIOFile& DirectIOFile::operator=(DirectIOFile&& other)
+{
+  Close();
+  Swap(other);
+  return *this;
+}
+
+DirectIOFile::DirectIOFile(const std::string& path, AccessMode access_mode, OpenMode open_mode)
+{
+  Open(path, access_mode, open_mode);
+}
+
+bool DirectIOFile::Open(const std::string& path, AccessMode access_mode, OpenMode open_mode)
+{
+  ASSERT(!IsOpen());
+
+  if (open_mode == OpenMode::Default)
+    open_mode = (access_mode == AccessMode::Write) ? OpenMode::Truncate : OpenMode::Existing;
+
+  // This is not a sensible combination. Fail here to not rely on OS-specific behaviors.
+  if (access_mode == AccessMode::Read && open_mode == OpenMode::Truncate)
+    return false;
+
+#if defined(_WIN32)
+  DWORD desired_access = GENERIC_READ | GENERIC_WRITE;
+  if (access_mode == AccessMode::Read)
+    desired_access = GENERIC_READ;
+  else if (access_mode == AccessMode::Write)
+    desired_access = GENERIC_WRITE;
+
+  // Allow deleting and renaming through our handle.
+  desired_access |= DELETE;
+
+  // All sharing is allowed to more closely match default behavior on other OSes.
+  constexpr DWORD share_mode = FILE_SHARE_DELETE | FILE_SHARE_READ | FILE_SHARE_WRITE;
+
+  DWORD creation_disposition = OPEN_ALWAYS;
+  if (open_mode == OpenMode::Truncate)
+    creation_disposition = CREATE_ALWAYS;
+  else if (open_mode == OpenMode::Create)
+    creation_disposition = CREATE_NEW;
+  else if (open_mode == OpenMode::Existing)
+    creation_disposition = OPEN_EXISTING;
+
+  m_handle = CreateFile(UTF8ToTStr(path).c_str(), desired_access, share_mode, nullptr,
+                        creation_disposition, FILE_ATTRIBUTE_NORMAL, nullptr);
+  if (!IsOpen())
+    WARN_LOG_FMT(COMMON, "CreateFile: {}", Common::GetLastErrorString());
+
+#else
+#if defined(ANDROID)
+  if (IsPathAndroidContent(path))
+  {
+    // Android documentation says that "w" may or may not truncate.
+    // In case it does, we'll use "rw" when we don't want truncation.
+    // This wrongly enables read access when we don't need it.
+    if (access_mode == AccessMode::Write && open_mode != OpenMode::Truncate)
+      access_mode = AccessMode::ReadAndWrite;
+
+    std::string open_mode_str = "rw";
+    if (access_mode == AccessMode::Read)
+      open_mode_str = "r";
+    else if (access_mode == AccessMode::Write)
+      open_mode_str = "w";
+
+    // FYI: File::Exists can be slow on Android.
+    Common::Lazy<bool> file_exists{[&] { return Exists(path); }};
+
+    // A few features are emulated in a non-atomic manner.
+    if (open_mode == OpenMode::Existing)
+    {
+      if (access_mode != AccessMode::Read && !*file_exists)
+        return false;
+    }
+    else
+    {
+      if (open_mode == OpenMode::Truncate)
+        open_mode_str += 't';
+      else if (open_mode == OpenMode::Create && *file_exists)
+        return false;
+
+      // Modes other than `Existing` may create a file, but "r" won't do that automatically.
+      if (access_mode == AccessMode::Read && !*file_exists)
+        CreateEmptyFile(path);
+    }
+
+    m_fd = OpenAndroidContent(path, open_mode_str);
+
+    return IsOpen();
+  }
+#endif
+  int flags = O_RDWR;
+  if (access_mode == AccessMode::Read)
+    flags = O_RDONLY;
+  else if (access_mode == AccessMode::Write)
+    flags = O_WRONLY;
+
+  if (open_mode == OpenMode::Truncate)
+    flags |= O_CREAT | O_TRUNC;
+  else if (open_mode == OpenMode::Create)
+    flags |= O_CREAT | O_EXCL;
+  else if (open_mode != OpenMode::Existing)
+    flags |= O_CREAT;
+
+  m_fd = open(path.c_str(), flags, 0666);
+
+#endif
+
+  return IsOpen();
+}
+
+bool DirectIOFile::Close()
+{
+  if (!IsOpen())
+    return false;
+
+  m_current_offset = 0;
+
+#if defined(_WIN32)
+  return CloseHandle(std::exchange(m_handle, INVALID_HANDLE_VALUE)) != 0;
+#else
+  return close(std::exchange(m_fd, -1)) == 0;
+#endif
+}
+
+bool DirectIOFile::IsOpen() const
+{
+#if defined(_WIN32)
+  return m_handle != INVALID_HANDLE_VALUE;
+#else
+  return m_fd != -1;
+#endif
+}
+
+#if defined(_WIN32)
+template <auto* TransferFunc>
+static bool OverlappedTransfer(HANDLE handle, u64 offset, auto* data_ptr, u64 size)
+{
+  // ReadFile/WriteFile take a 32bit size so we must loop to handle our 64bit size.
+  while (true)
+  {
+    OVERLAPPED overlapped{};
+    overlapped.Offset = DWORD(offset);
+    overlapped.OffsetHigh = DWORD(offset >> 32);
+
+    DWORD bytes_transferred{};
+    if (TransferFunc(handle, data_ptr, MathUtil::SaturatingCast<DWORD>(size), &bytes_transferred,
+                     &overlapped) == 0)
+    {
+      ERROR_LOG_FMT(COMMON, "OverlappedTransfer: {}", Common::GetLastErrorString());
+      return false;
+    }
+
+    size -= bytes_transferred;
+
+    if (size == 0)
+      return true;
+
+    offset += bytes_transferred;
+    data_ptr += bytes_transferred;
+  }
+}
+#endif
+
+bool DirectIOFile::OffsetRead(u64 offset, u8* out_ptr, u64 size)
+{
+#if defined(_WIN32)
+  return OverlappedTransfer<ReadFile>(m_handle, offset, out_ptr, size);
+#else
+  return pread(m_fd, out_ptr, size, off_t(offset)) == ssize_t(size);
+#endif
+}
+
+bool DirectIOFile::OffsetWrite(u64 offset, const u8* in_ptr, u64 size)
+{
+#if defined(_WIN32)
+  return OverlappedTransfer<WriteFile>(m_handle, offset, in_ptr, size);
+#else
+  return pwrite(m_fd, in_ptr, size, off_t(offset)) == ssize_t(size);
+#endif
+}
+
+u64 DirectIOFile::GetSize() const
+{
+#if defined(_WIN32)
+  LARGE_INTEGER result{};
+  if (GetFileSizeEx(m_handle, &result) != 0)
+    return result.QuadPart;
+#else
+  struct stat st{};
+  if (fstat(m_fd, &st) == 0)
+    return st.st_size;
+#endif
+
+  return 0;
+}
+
+bool DirectIOFile::Seek(s64 offset, SeekOrigin origin)
+{
+  if (!IsOpen())
+    return false;
+
+  u64 reference_pos = 0;
+  switch (origin)
+  {
+  case SeekOrigin::Current:
+    reference_pos = m_current_offset;
+    break;
+  case SeekOrigin::End:
+    reference_pos = GetSize();
+    break;
+  default:
+    break;
+  }
+
+  // Don't let our current offset underflow.
+  if (offset < 0 && u64(-offset) > reference_pos)
+    return false;
+
+  m_current_offset = reference_pos + offset;
+  return true;
+}
+
+bool DirectIOFile::Flush()
+{
+#if defined(_WIN32)
+  return FlushFileBuffers(m_handle) != 0;
+#else
+  return fsync(m_fd) == 0;
+#endif
+}
+
+void DirectIOFile::Swap(DirectIOFile& other)
+{
+#if defined(_WIN32)
+  std::swap(m_handle, other.m_handle);
+#else
+  std::swap(m_fd, other.m_fd);
+#endif
+  std::swap(m_current_offset, other.m_current_offset);
+}
+
+DirectIOFile DirectIOFile::Duplicate() const
+{
+  DirectIOFile result;
+
+  if (!IsOpen())
+    return result;
+
+#if defined(_WIN32)
+  const auto current_process = GetCurrentProcess();
+  if (DuplicateHandle(current_process, m_handle, current_process, &result.m_handle, 0, FALSE,
+                      DUPLICATE_SAME_ACCESS) == 0)
+  {
+    ERROR_LOG_FMT(COMMON, "DuplicateHandle: {}", Common::GetLastErrorString());
+  }
+#else
+  result.m_fd = dup(m_fd);
+#endif
+
+  ASSERT(result.IsOpen());
+
+  result.m_current_offset = m_current_offset;
+
+  return result;
+}
+
+bool Resize(DirectIOFile& file, u64 size)
+{
+#if defined(_WIN32)
+  // This operation is not "atomic", but it's the only thing we're using the file pointer for.
+  // Concurrent `Resize` would need some external synchronization to prevent race regardless.
+  const LARGE_INTEGER distance{.QuadPart = LONGLONG(size)};
+  return (SetFilePointerEx(file.GetHandle(), distance, nullptr, FILE_BEGIN) != 0) &&
+         (SetEndOfFile(file.GetHandle()) != 0);
+#else
+  return ftruncate(file.GetHandle(), off_t(size)) == 0;
+#endif
+}
+
+bool Rename(DirectIOFile& file, const std::string& source_path [[maybe_unused]],
+            const std::string& destination_path)
+{
+#if defined(_WIN32)
+  const auto dest_name = UTF8ToWString(destination_path);
+  const auto dest_name_byte_size = DWORD(dest_name.size() * sizeof(WCHAR));
+  FILE_RENAME_INFO info{
+      .ReplaceIfExists = TRUE,
+      .FileNameLength = dest_name_byte_size,  // The size in bytes, not including null termination.
+  };
+  constexpr auto filename_struct_offset = offsetof(FILE_RENAME_INFO, FileName);
+  Common::UniqueBuffer<u8> buffer(filename_struct_offset + dest_name_byte_size + sizeof(WCHAR));
+  std::memcpy(buffer.data(), &info, filename_struct_offset);
+  std::memcpy(buffer.data() + filename_struct_offset, dest_name.c_str(),
+              dest_name_byte_size + sizeof(WCHAR));
+  return SetFileInformationByHandle(file.GetHandle(), FileRenameInfo, buffer.data(),
+                                    DWORD(buffer.size())) != 0;
+#else
+  return file.IsOpen() && Rename(source_path, destination_path);
+#endif
+}
+
+bool Delete(DirectIOFile& file, const std::string& filename)
+{
+#if defined(_WIN32)
+  FILE_DISPOSITION_INFO info{.DeleteFile = TRUE};
+  return SetFileInformationByHandle(file.GetHandle(), FileDispositionInfo, &info, sizeof(info)) !=
+         0;
+#else
+  return file.IsOpen() && Delete(filename, IfAbsentBehavior::NoConsoleWarning);
+#endif
+}
+
+}  // namespace File