postgres/src/port/win32stat.c

/*-------------------------------------------------------------------------
 *
 * win32stat.c
 *	  Replacements for <sys/stat.h> functions using GetFileInformationByHandle
 *
 * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  src/port/win32stat.c
 *
 *-------------------------------------------------------------------------
 */

#ifdef WIN32

#include "c.h"
#include <windows.h>

/*
 * In order to support MinGW and MSVC2013 we use NtQueryInformationFile as an
 * alternative for GetFileInformationByHandleEx. It is loaded from the ntdll
 * library.
 */
#if _WIN32_WINNT < 0x0600
#include <winternl.h>

#if !defined(__MINGW32__) && !defined(__MINGW64__)
/* MinGW includes this in <winternl.h>, but it is missing in MSVC */
typedef struct _FILE_STANDARD_INFORMATION
{
	LARGE_INTEGER AllocationSize;
	LARGE_INTEGER EndOfFile;
	ULONG		NumberOfLinks;
	BOOLEAN		DeletePending;
	BOOLEAN		Directory;
} FILE_STANDARD_INFORMATION;
#define FileStandardInformation 5
#endif							/* !defined(__MINGW32__) &&
								 * !defined(__MINGW64__) */

typedef NTSTATUS (NTAPI * PFN_NTQUERYINFORMATIONFILE)
			(IN HANDLE FileHandle,
			 OUT PIO_STATUS_BLOCK IoStatusBlock,
			 OUT PVOID FileInformation,
			 IN ULONG Length,
			 IN FILE_INFORMATION_CLASS FileInformationClass);

static PFN_NTQUERYINFORMATIONFILE _NtQueryInformationFile = NULL;

static HMODULE ntdll = NULL;

/*
 * Load DLL file just once regardless of how many functions we load/call in it.
 */
static void
LoadNtdll(void)
{
	if (ntdll != NULL)
		return;
	ntdll = LoadLibraryEx("ntdll.dll", NULL, 0);
}

#endif							/* _WIN32_WINNT < 0x0600 */


/*
 * Convert a FILETIME struct into a 64 bit time_t.
 */
static __time64_t
filetime_to_time(const FILETIME *ft)
{
	ULARGE_INTEGER unified_ft = {0};
	static const uint64 EpochShift = UINT64CONST(116444736000000000);

	unified_ft.LowPart = ft->dwLowDateTime;
	unified_ft.HighPart = ft->dwHighDateTime;

	if (unified_ft.QuadPart < EpochShift)
		return -1;

	unified_ft.QuadPart -= EpochShift;
	unified_ft.QuadPart /= 10 * 1000 * 1000;

	return unified_ft.QuadPart;
}

/*
 * Convert WIN32 file attributes to a Unix-style mode.
 *
 * Only owner permissions are set.
 */
static unsigned short
fileattr_to_unixmode(int attr)
{
	unsigned short uxmode = 0;

	uxmode |= (unsigned short) ((attr & FILE_ATTRIBUTE_DIRECTORY) ?
								(_S_IFDIR) : (_S_IFREG));

	uxmode |= (unsigned short) ((attr & FILE_ATTRIBUTE_READONLY) ?
								(_S_IREAD) : (_S_IREAD | _S_IWRITE));

	/* there is no need to simulate _S_IEXEC using CMD's PATHEXT extensions */
	uxmode |= _S_IEXEC;

	return uxmode;
}

/*
 * Convert WIN32 file information (from a HANDLE) to a struct stat.
 */
static int
fileinfo_to_stat(HANDLE hFile, struct stat *buf)
{
	BY_HANDLE_FILE_INFORMATION fiData;

	memset(buf, 0, sizeof(*buf));

	/*
	 * GetFileInformationByHandle minimum supported version: Windows XP and
	 * Windows Server 2003, so it exists everywhere we care about.
	 */
	if (!GetFileInformationByHandle(hFile, &fiData))
	{
		_dosmaperr(GetLastError());
		return -1;
	}

	if (fiData.ftLastWriteTime.dwLowDateTime ||
		fiData.ftLastWriteTime.dwHighDateTime)
		buf->st_mtime = filetime_to_time(&fiData.ftLastWriteTime);

	if (fiData.ftLastAccessTime.dwLowDateTime ||
		fiData.ftLastAccessTime.dwHighDateTime)
		buf->st_atime = filetime_to_time(&fiData.ftLastAccessTime);
	else
		buf->st_atime = buf->st_mtime;

	if (fiData.ftCreationTime.dwLowDateTime ||
		fiData.ftCreationTime.dwHighDateTime)
		buf->st_ctime = filetime_to_time(&fiData.ftCreationTime);
	else
		buf->st_ctime = buf->st_mtime;

	buf->st_mode = fileattr_to_unixmode(fiData.dwFileAttributes);
	buf->st_nlink = fiData.nNumberOfLinks;

	buf->st_size = ((((uint64) fiData.nFileSizeHigh) << 32) |
					fiData.nFileSizeLow);

	return 0;
}

/*
 * Windows implementation of stat().
 *
 * This currently also implements lstat(), though perhaps that should change.
 */
int
_pgstat64(const char *name, struct stat *buf)
{
	/*
	 * We must use a handle so lstat() returns the information of the target
	 * file.  To have a reliable test for ERROR_DELETE_PENDING, we use
	 * NtQueryInformationFile from Windows 2000 or
	 * GetFileInformationByHandleEx from Server 2008 / Vista.
	 */
	SECURITY_ATTRIBUTES sa;
	HANDLE		hFile;
	int			ret;
#if _WIN32_WINNT < 0x0600
	IO_STATUS_BLOCK ioStatus;
	FILE_STANDARD_INFORMATION standardInfo;
#else
	FILE_STANDARD_INFO standardInfo;
#endif

	if (name == NULL || buf == NULL)
	{
		errno = EINVAL;
		return -1;
	}

	/* fast not-exists check */
	if (GetFileAttributes(name) == INVALID_FILE_ATTRIBUTES)
	{
		_dosmaperr(GetLastError());
		return -1;
	}

	/* get a file handle as lightweight as we can */
	sa.nLength = sizeof(SECURITY_ATTRIBUTES);
	sa.bInheritHandle = TRUE;
	sa.lpSecurityDescriptor = NULL;
	hFile = CreateFile(name,
					   GENERIC_READ,
					   (FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE),
					   &sa,
					   OPEN_EXISTING,
					   (FILE_FLAG_NO_BUFFERING | FILE_FLAG_BACKUP_SEMANTICS |
						FILE_FLAG_OVERLAPPED),
					   NULL);
	if (hFile == INVALID_HANDLE_VALUE)
	{
		DWORD		err = GetLastError();

		CloseHandle(hFile);
		_dosmaperr(err);
		return -1;
	}

	memset(&standardInfo, 0, sizeof(standardInfo));

#if _WIN32_WINNT < 0x0600
	if (_NtQueryInformationFile == NULL)
	{
		/* First time through: load ntdll.dll and find NtQueryInformationFile */
		LoadNtdll();
		if (ntdll == NULL)
		{
			DWORD		err = GetLastError();

			CloseHandle(hFile);
			_dosmaperr(err);
			return -1;
		}

		_NtQueryInformationFile = (PFN_NTQUERYINFORMATIONFILE) (pg_funcptr_t)
			GetProcAddress(ntdll, "NtQueryInformationFile");
		if (_NtQueryInformationFile == NULL)
		{
			DWORD		err = GetLastError();

			CloseHandle(hFile);
			_dosmaperr(err);
			return -1;
		}
	}

	if (!NT_SUCCESS(_NtQueryInformationFile(hFile, &ioStatus, &standardInfo,
											sizeof(standardInfo),
											FileStandardInformation)))
	{
		DWORD		err = GetLastError();

		CloseHandle(hFile);
		_dosmaperr(err);
		return -1;
	}
#else
	if (!GetFileInformationByHandleEx(hFile, FileStandardInfo, &standardInfo,
									  sizeof(standardInfo)))
	{
		DWORD		err = GetLastError();

		CloseHandle(hFile);
		_dosmaperr(err);
		return -1;
	}
#endif							/* _WIN32_WINNT < 0x0600 */

	if (standardInfo.DeletePending)
	{
		/*
		 * File has been deleted, but is not gone from the filesystem yet.
		 * This can happen when some process with FILE_SHARE_DELETE has it
		 * open, and it will be fully removed once that handle is closed.
		 * Meanwhile, we can't open it, so indicate that the file just doesn't
		 * exist.
		 */
		CloseHandle(hFile);
		errno = ENOENT;
		return -1;
	}

	/* At last we can invoke fileinfo_to_stat */
	ret = fileinfo_to_stat(hFile, buf);

	CloseHandle(hFile);
	return ret;
}

/*
 * Windows implementation of fstat().
 */
int
_pgfstat64(int fileno, struct stat *buf)
{
	HANDLE		hFile = (HANDLE) _get_osfhandle(fileno);
	DWORD		fileType = FILE_TYPE_UNKNOWN;
	DWORD		lastError;
	unsigned short st_mode;

	/*
	 * When stdin, stdout, and stderr aren't associated with a stream the
	 * special value -2 is returned:
	 * https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/get-osfhandle
	 */
	if (hFile == INVALID_HANDLE_VALUE || hFile == (HANDLE) -2 || buf == NULL)
	{
		errno = EINVAL;
		return -1;
	}

	fileType = GetFileType(hFile);
	lastError = GetLastError();

	/*
	 * Invoke GetLastError in order to distinguish between a "valid" return of
	 * FILE_TYPE_UNKNOWN and its return due to a calling error.  In case of
	 * success, GetLastError returns NO_ERROR.
	 */
	if (fileType == FILE_TYPE_UNKNOWN && lastError != NO_ERROR)
	{
		_dosmaperr(lastError);
		return -1;
	}

	switch (fileType)
	{
			/* The specified file is a disk file */
		case FILE_TYPE_DISK:
			return fileinfo_to_stat(hFile, buf);

			/*
			 * The specified file is a socket, a named pipe, or an anonymous
			 * pipe.
			 */
		case FILE_TYPE_PIPE:
			st_mode = _S_IFIFO;
			break;
			/* The specified file is a character file */
		case FILE_TYPE_CHAR:
			st_mode = _S_IFCHR;
			break;
			/* Unused flag and unknown file type */
		case FILE_TYPE_REMOTE:
		case FILE_TYPE_UNKNOWN:
		default:
			errno = EINVAL;
			return -1;
	}

	memset(buf, 0, sizeof(*buf));
	buf->st_mode = st_mode;
	buf->st_dev = fileno;
	buf->st_rdev = fileno;
	buf->st_nlink = 1;
	return 0;
}

#endif							/* WIN32 */