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Commitee21910

Browse files
macdiceadunstan
authored andcommitted
Provide lstat() for Windows.
Junction points will be reported with S_ISLNK(x.st_mode), simulatingPOSIX lstat(). stat() will follow pseudo-symlinks, like in POSIX (butonly one level before giving up, unlike in POSIX).This completes a TODO left by commitbed9075.Tested-by: Andrew Dunstan <andrew@dunslane.net> (earlier version)Discussion:https://postgr.es/m/CA%2BhUKGLfOOeyZpm5ByVcAt7x5Pn-%3DxGRNCvgiUPVVzjFLtnY0w%40mail.gmail.com(cherry picked from commitc5cb8f3)Author: Thomas Munro <tmunro@postgresql.org>Author: Alexandra Wang <alexandra.wang.oss@gmail.com>
1 parentfa56aa2 commitee21910

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2 files changed

+123
-5
lines changed

2 files changed

+123
-5
lines changed

‎src/include/port/win32_port.h‎

Lines changed: 17 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -270,10 +270,11 @@ struct stat/* This should match struct __stat64 */
270270

271271
externint_pgfstat64(intfileno,structstat*buf);
272272
externint_pgstat64(constchar*name,structstat*buf);
273+
externint_pglstat64(constchar*name,structstat*buf);
273274

274275
#definefstat(fileno,sb)_pgfstat64(fileno, sb)
275276
#definestat(path,sb)_pgstat64(path, sb)
276-
#definelstat(path,sb)_pgstat64(path, sb)
277+
#definelstat(path,sb)_pglstat64(path, sb)
277278

278279
/* These macros are not provided by older MinGW, nor by MSVC */
279280
#ifndefS_IRUSR
@@ -319,6 +320,21 @@ extern int_pgstat64(const char *name, struct stat *buf);
319320
#defineS_ISREG(m) (((m) & S_IFMT) == S_IFREG)
320321
#endif
321322

323+
/*
324+
* In order for lstat() to be able to report junction points as symlinks, we
325+
* need to hijack a bit in st_mode, since neither MSVC nor MinGW provides
326+
* S_ISLNK and there aren't any spare bits. We'll steal the one for character
327+
* devices, because we don't otherwise make use of those.
328+
*/
329+
#ifdefS_ISLNK
330+
#error "S_ISLNK is already defined"
331+
#endif
332+
#ifdefS_IFLNK
333+
#error "S_IFLNK is already defined"
334+
#endif
335+
#defineS_IFLNK S_IFCHR
336+
#defineS_ISLNK(m) (((m) & S_IFLNK) == S_IFLNK)
337+
322338
/*
323339
* Supplement to <fcntl.h>.
324340
* This is the same value as _O_NOINHERIT in the MS header file. This is

‎src/port/win32stat.c‎

Lines changed: 106 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -15,7 +15,11 @@
1515

1616
#ifdefWIN32
1717

18+
#defineUMDF_USING_NTSTATUS
19+
1820
#include"c.h"
21+
#include"port/win32ntdll.h"
22+
1923
#include<windows.h>
2024

2125
/*
@@ -107,12 +111,10 @@ fileinfo_to_stat(HANDLE hFile, struct stat *buf)
107111
}
108112

109113
/*
110-
* Windows implementation of stat().
111-
*
112-
* This currently also implements lstat(), though perhaps that should change.
114+
* Windows implementation of lstat().
113115
*/
114116
int
115-
_pgstat64(constchar*name,structstat*buf)
117+
_pglstat64(constchar*name,structstat*buf)
116118
{
117119
/*
118120
* Our open wrapper will report STATUS_DELETE_PENDING as ENOENT. We
@@ -129,10 +131,110 @@ _pgstat64(const char *name, struct stat *buf)
129131

130132
ret=fileinfo_to_stat(hFile,buf);
131133

134+
/*
135+
* Junction points appear as directories to fileinfo_to_stat(), so we'll
136+
* need to do a bit more work to distinguish them.
137+
*/
138+
if (ret==0&&S_ISDIR(buf->st_mode))
139+
{
140+
charnext[MAXPGPATH];
141+
ssize_tsize;
142+
143+
/*
144+
* POSIX says we need to put the length of the target path into
145+
* st_size. Use readlink() to get it, or learn that this is not a
146+
* junction point.
147+
*/
148+
size=readlink(name,next,sizeof(next));
149+
if (size<0)
150+
{
151+
if (errno==EACCES&&
152+
pg_RtlGetLastNtStatus()==STATUS_DELETE_PENDING)
153+
{
154+
/* Unlinked underneath us. */
155+
errno=ENOENT;
156+
ret=-1;
157+
}
158+
elseif (errno==EINVAL)
159+
{
160+
/* It's not a junction point, nothing to do. */
161+
}
162+
else
163+
{
164+
/* Some other failure. */
165+
ret=-1;
166+
}
167+
}
168+
else
169+
{
170+
/* It's a junction point, so report it as a symlink. */
171+
buf->st_mode &= ~S_IFDIR;
172+
buf->st_mode |=S_IFLNK;
173+
buf->st_size=size;
174+
}
175+
}
176+
132177
CloseHandle(hFile);
133178
returnret;
134179
}
135180

181+
/*
182+
* Windows implementation of stat().
183+
*/
184+
int
185+
_pgstat64(constchar*name,structstat*buf)
186+
{
187+
intret;
188+
189+
ret=_pglstat64(name,buf);
190+
191+
/* Do we need to follow a symlink (junction point)? */
192+
if (ret==0&&S_ISLNK(buf->st_mode))
193+
{
194+
charnext[MAXPGPATH];
195+
ssize_tsize;
196+
197+
/*
198+
* _pglstat64() already called readlink() once to be able to fill in
199+
* st_size, and now we need to do it again to get the path to follow.
200+
* That could be optimized, but stat() on symlinks is probably rare
201+
* and this way is simple.
202+
*/
203+
size=readlink(name,next,sizeof(next));
204+
if (size<0)
205+
{
206+
if (errno==EACCES&&
207+
pg_RtlGetLastNtStatus()==STATUS_DELETE_PENDING)
208+
{
209+
/* Unlinked underneath us. */
210+
errno=ENOENT;
211+
}
212+
return-1;
213+
}
214+
if (size >=sizeof(next))
215+
{
216+
errno=ENAMETOOLONG;
217+
return-1;
218+
}
219+
next[size]=0;
220+
221+
ret=_pglstat64(next,buf);
222+
if (ret==0&&S_ISLNK(buf->st_mode))
223+
{
224+
/*
225+
* We're only prepared to go one hop, because we only expect to
226+
* deal with the simple cases that we create. The error for too
227+
* many symlinks is supposed to be ELOOP, but Windows hasn't got
228+
* it.
229+
*/
230+
errno=EIO;
231+
return-1;
232+
}
233+
}
234+
235+
returnret;
236+
}
237+
136238
/*
137239
* Windows implementation of fstat().
138240
*/

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