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Support dirfd relative iops on Windows

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We always favor calling functions like openat(), fstatat(), etc. because
Linux, XNU, FreeBSD, and OpenBSD all elected to support them, while some
systems like Android love them so much, that they stopped supporting the
old interfaces.

This change ensures that when dirfd is actually a dirfd and not AT_FDCWD
we'll do the right thing on Windows NT. We use an API that's been around
since Vista to accomplish that.

This change also adds exponential backoff to chdir() on Windows since it
seems almost as flaky on Windows 7 as the rmdir() function.
This commit is contained in:
Justine Tunney 2021-01-30 01:49:43 -08:00
parent b8d26e2418
commit 417797d218
42 changed files with 361 additions and 241 deletions
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44
libc/calls/mkntpathat.c Normal file
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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2021 Justine Alexandra Roberts Tunney │
│ │
│ Permission to use, copy, modify, and/or distribute this software for │
│ any purpose with or without fee is hereby granted, provided that the │
│ above copyright notice and this permission notice appear in all copies. │
│ │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/calls/internal.h"
#include "libc/macros.h"
#include "libc/nt/files.h"
#include "libc/str/str.h"
#include "libc/sysv/consts/at.h"
#include "libc/sysv/errfuns.h"
int __mkntpathat(int dirfd, const char *path, int flags,
char16_t file[PATH_MAX]) {
char16_t dir[PATH_MAX];
uint32_t dirlen, filelen;
if ((filelen = __mkntpath2(path, file, flags)) == -1) return -1;
if (file[0] != u'\\' && dirfd != AT_FDCWD) { /* ProTip: \\?\C:\foo */
if (!__isfdkind(dirfd, kFdFile)) return ebadf();
dirlen = GetFinalPathNameByHandle(g_fds.p[dirfd].handle, dir, ARRAYLEN(dir),
kNtFileNameNormalized | kNtVolumeNameDos);
if (!dirlen) return __winerr();
if (dirlen + 1 + filelen + 1 > ARRAYLEN(dir)) return enametoolong();
dir[dirlen] = u'\\';
memcpy(dir + dirlen + 1, file, (filelen + 1) * sizeof(char16_t));
memcpy(file, dir, (dirlen + 1 + filelen + 1) * sizeof(char16_t));
return dirlen + 1 + filelen;
} else {
return filelen;
}
}