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/*-------------------------------------------------------------------------
*
* 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>
/*
* 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, this uses a
* method similar to open() with a loop using stat() and some waits when
* facing ERROR_ACCESS_DENIED.
*/
SECURITY_ATTRIBUTES sa;
HANDLE hFile;
int ret;
int loops = 0;
if (name == NULL || buf == NULL)
{
errno = EINVAL;
return -1;
}
/* fast not-exists check */
if (GetFileAttributes(name) == INVALID_FILE_ATTRIBUTES)
{
DWORD err = GetLastError();
if (err != ERROR_ACCESS_DENIED)
{
_dosmaperr(err);
return -1;
}
}
/* get a file handle as lightweight as we can */
sa.nLength = sizeof(SECURITY_ATTRIBUTES);
sa.bInheritHandle = TRUE;
sa.lpSecurityDescriptor = NULL;
while ((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)) == INVALID_HANDLE_VALUE)
{
DWORD err = GetLastError();
/*
* ERROR_ACCESS_DENIED is returned if the file is deleted but not yet
* gone (Windows NT status code is STATUS_DELETE_PENDING). In that
* case we want to wait a bit and try again, giving up after 1 second
* (since this condition should never persist very long). However,
* there are other commonly-hit cases that return ERROR_ACCESS_DENIED,
* so care is needed. In particular that happens if we try to open a
* directory, or of course if there's an actual file-permissions
* problem. To distinguish these cases, try a stat(). In the
* delete-pending case, it will either also get STATUS_DELETE_PENDING,
* or it will see the file as gone and fail with ENOENT. In other
* cases it will usually succeed. The only somewhat-likely case where
* this coding will uselessly wait is if there's a permissions problem
* with a containing directory, which we hope will never happen in any
* performance-critical code paths.
*/
if (err == ERROR_ACCESS_DENIED)
{
if (loops < 10)
{
struct microsoft_native_stat st;
if (microsoft_native_stat(name, &st) != 0)
{
pg_usleep(100000);
loops++;
continue;
}
}
}
_dosmaperr(err);
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);
if (hFile == INVALID_HANDLE_VALUE || buf == NULL)
{
errno = EINVAL;
return -1;
}
/*
* Since we already have a file handle there is no need to check for
* ERROR_DELETE_PENDING.
*/
return fileinfo_to_stat(hFile, buf);
}
#endif /* WIN32 */
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