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Add pgreadlink() on Windows to read junction points

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Add support for reading back information about the symbolic
links we've created with pgsymlink(), which are actually
Junction Points. Just like pgsymlink() can only create directory
symlinks, pgreadlink() can only read directory symlinks.
This commit is contained in:
Magnus Hagander 2011-01-09 15:06:55 +01:00
parent 1066dbfb85
commit db4d22d0ef
2 changed files with 121 additions and 0 deletions
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3
src/include/port.h
View File

@ -284,8 +284,11 @@ extern int pgunlink(const char *path);
*/
#if defined(WIN32) && !defined(__CYGWIN__)
extern int pgsymlink(const char *oldpath, const char *newpath);
extern int pgreadlink(const char *path, char *buf, size_t size);
extern bool pgwin32_is_junction(char *path);
#define symlink(oldpath, newpath) pgsymlink(oldpath, newpath)
#define readlink(path, buf, size) pgreadlink(path, buf, size)
#endif
extern bool rmtree(const char *path, bool rmtopdir);

118
src/port/dirmod.c
View File

@ -297,6 +297,124 @@ pgsymlink(const char *oldpath, const char *newpath)
return 0;
}
/*
* pgreadlink - uses Win32 junction points
*/
int
pgreadlink(const char *path, char *buf, size_t size)
{
DWORD attr;
HANDLE h;
char buffer[MAX_PATH * sizeof(WCHAR) + sizeof(REPARSE_JUNCTION_DATA_BUFFER)];
REPARSE_JUNCTION_DATA_BUFFER *reparseBuf = (REPARSE_JUNCTION_DATA_BUFFER *) buffer;
DWORD len;
int r;
attr = GetFileAttributes(path);
if (attr == INVALID_FILE_ATTRIBUTES)
{
_dosmaperr(GetLastError());
return -1;
}
if ((attr & FILE_ATTRIBUTE_REPARSE_POINT) == 0)
{
errno = EINVAL;
return -1;
}
h = CreateFile(path,
GENERIC_READ,
FILE_SHARE_READ | FILE_SHARE_WRITE,
NULL,
OPEN_EXISTING,
FILE_FLAG_OPEN_REPARSE_POINT | FILE_FLAG_BACKUP_SEMANTICS,
0);
if (h == INVALID_HANDLE_VALUE)
{
_dosmaperr(GetLastError());
return -1;
}
if (!DeviceIoControl(h,
FSCTL_GET_REPARSE_POINT,
NULL,
0,
(LPVOID) reparseBuf,
sizeof(buffer),
&len,
NULL))
{
LPSTR msg;
errno = 0;
FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM,
NULL, GetLastError(),
MAKELANGID(LANG_ENGLISH, SUBLANG_DEFAULT),
(LPSTR) &msg, 0, NULL);
#ifndef FRONTEND
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not get junction for \"%s\": %s",
path, msg)));
#else
fprintf(stderr, _("could not get junction for \"%s\": %s\n"),
path, msg);
#endif
LocalFree(msg);
CloseHandle(h);
errno = EINVAL;
return -1;
}
CloseHandle(h);
/* Got it, let's get some results from this */
if (reparseBuf->ReparseTag != IO_REPARSE_TAG_MOUNT_POINT)
{
errno = EINVAL;
return -1;
}
r = WideCharToMultiByte(CP_ACP, 0,
reparseBuf->PathBuffer, -1,
buf,
size,
NULL, NULL);
if (r <= 0)
{
errno = EINVAL;
return -1;
}
/*
* If the path starts with "\??\", which it will do in most (all?) cases,
* strip those out.
*/
if (r > 4 && strncmp(buf, "\\??\\", 4) == 0)
{
memmove(buf, buf + 4, strlen(buf + 4) + 1);
r -= 4;
}
return r;
}
/*
* Assumes the file exists, so will return false if it doesn't
* (since a nonexistant file is not a junction)
*/
bool
pgwin32_is_junction(char *path)
{
DWORD attr = GetFileAttributes(path);
if (attr == INVALID_FILE_ATTRIBUTES)
{
_dosmaperr(GetLastError());
return false;
}
return ((attr & FILE_ATTRIBUTE_REPARSE_POINT) == FILE_ATTRIBUTE_REPARSE_POINT);
}
#endif /* defined(WIN32) && !defined(__CYGWIN__) */