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FileSystem: Make CopyFilePath() atomic

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Stenzek
2026-06-30 21:57:54 +10:00
parent c80552f1ce
commit ab30d1da54
1 changed files with 52 additions and 17 deletions
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69
src/common/file_system.cpp
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@@ -1830,20 +1830,39 @@ bool FileSystem::RecursiveDeleteDirectory(const char* path, Error* error)
bool FileSystem::CopyFilePath(const char* source, const char* destination, bool replace, Error* error) bool FileSystem::CopyFilePath(const char* source, const char* destination, bool replace, Error* error)
{ {
#ifndef _WIN32 #ifdef _WIN32
// TODO: There's technically a race here between checking and opening the file.. const std::wstring source_wpath = GetWin32Path(source);
// But fopen doesn't specify any way to say "don't create if it exists"... const std::wstring destination_wpath = GetWin32Path(destination);
if (!replace && FileExists(destination)) std::string temp_path;
auto temp_fp = OpenTemporaryManagedCFile(destination, &temp_path, error);
if (!temp_fp)
return false;
temp_fp.reset();
const std::wstring temp_wpath = GetWin32Path(temp_path);
if (!CopyFileW(source_wpath.c_str(), temp_wpath.c_str(), FALSE))
{ {
Error::SetStringView(error, "File already exists."); Error::SetWin32(error, "CopyFileW() failed: ", GetLastError());
DeleteFileW(temp_wpath.c_str());
return false; return false;
} }
const DWORD move_flags = replace ? MOVEFILE_REPLACE_EXISTING : 0;
if (!MoveFileExW(temp_wpath.c_str(), destination_wpath.c_str(), move_flags))
{
Error::SetWin32(error, "MoveFileExW() failed: ", GetLastError());
DeleteFileW(temp_wpath.c_str());
return false;
}
return true;
#else
auto in_fp = OpenManagedCFile(source, "rb", error); auto in_fp = OpenManagedCFile(source, "rb", error);
if (!in_fp) if (!in_fp)
return false; return false;
auto out_fp = OpenManagedCFile(destination, "wb", error); std::string temp_path;
auto out_fp = OpenTemporaryManagedCFile(destination, &temp_path, error);
if (!out_fp) if (!out_fp)
return false; return false;
@@ -1856,26 +1875,42 @@ bool FileSystem::CopyFilePath(const char* source, const char* destination, bool
{ {
Error::SetErrno(error, "fread() or fwrite() failed: ", errno); Error::SetErrno(error, "fread() or fwrite() failed: ", errno);
out_fp.reset(); out_fp.reset();
DeleteFile(destination); DeleteFile(temp_path.c_str());
return false; return false;
} }
} }
if (std::fflush(out_fp.get()) != 0) if (std::fclose(out_fp.release()) != 0)
{ {
Error::SetErrno(error, "fflush() failed: ", errno); Error::SetErrno(error, "fclose() failed: ", errno);
out_fp.reset(); DeleteFile(temp_path.c_str());
DeleteFile(destination);
return false; return false;
} }
return true; if (replace)
#else {
if (CopyFileW(GetWin32Path(source).c_str(), GetWin32Path(destination).c_str(), !replace)) if (!RenamePath(temp_path.c_str(), destination, error))
return true; {
DeleteFile(temp_path.c_str());
return false;
}
}
else
{
// link() atomically publishes the completed temporary file without replacing an existing file.
// Removing the temporary name afterwards leaves the destination referring to the copied file.
if (link(temp_path.c_str(), destination) != 0)
{
Error::SetErrno(error, "link() failed: ", errno);
DeleteFile(temp_path.c_str());
return false;
}
Error::SetWin32(error, "CopyFileW() failed(): ", GetLastError()); if (unlink(temp_path.c_str()) != 0)
return false; WARNING_LOG("Failed to remove temporary copy '{}': {}", temp_path, std::strerror(errno));
}
return true;
#endif #endif
} }