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cosmopolitan/libc/calls/fcntl.c
Jōshin e16a7d8f3b
flip et / noet in modelines 
`et` means `expandtab`.

```sh
rg 'vi: .* :vi' -l -0 | \
  xargs -0 sed -i '' 's/vi: \(.*\) et\(.*\)  :vi/vi: \1 xoet\2:vi/'
rg 'vi: .*  :vi' -l -0 | \
  xargs -0 sed -i '' 's/vi: \(.*\)noet\(.*\):vi/vi: \1et\2  :vi/'
rg 'vi: .*  :vi' -l -0 | \
  xargs -0 sed -i '' 's/vi: \(.*\)xoet\(.*\):vi/vi: \1noet\2:vi/'
```
2023-12-07 22:17:11 -05:00

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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2020 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/calls.h"
#include "libc/calls/cp.internal.h"
#include "libc/calls/internal.h"
#include "libc/calls/struct/flock.h"
#include "libc/calls/struct/flock.internal.h"
#include "libc/calls/syscall-nt.internal.h"
#include "libc/calls/syscall-sysv.internal.h"
#include "libc/dce.h"
#include "libc/intrin/describeflags.internal.h"
#include "libc/intrin/strace.internal.h"
#include "libc/intrin/weaken.h"
#include "libc/runtime/zipos.internal.h"
#include "libc/str/str.h"
#include "libc/sysv/consts/f.h"
#include "libc/sysv/errfuns.h"
/**
* Does things with file descriptor, e.g.
*
* CHECK_NE(-1, fcntl(fd, F_SETFD, FD_CLOEXEC));
*
* This function lets you duplicate file descriptors without running
* into an edge case where they take over stdio handles:
*
* CHECK_GE((newfd = fcntl(oldfd, F_DUPFD, 3)), 3);
* CHECK_GE((newfd = fcntl(oldfd, F_DUPFD_CLOEXEC, 3)), 3);
*
* This function implements file record locking, which lets independent
* processes (and on Linux 3.15+, threads too!) lock arbitrary ranges
* associated with a file. See `test/libc/calls/lock_test.c` and other
* locking related tests in that folder.
*
* On Windows, the Cosmopolitan Libc polyfill for POSIX advisory locks
* only implements enough of its nuances to support SQLite's needs. Some
* possibilities, e.g. punching holes in lock, will raise `ENOTSUP`.
*
* @param fd is the file descriptor
* @param cmd can be one of:
* - `F_GETFD` gets `FD_CLOEXEC` status of `fd
* - `F_SETFD` sets `FD_CLOEXEC` status of `arg` file descriptor
* - `F_GETFL` returns file descriptor status flags
* - `F_SETFL` sets file descriptor status flags
* - `O_NONBLOCK` may be changed
* - `O_APPEND` may be changed
* - `O_DIRECT` may be changed
* - `O_SEQUENTIAL` may be changed (no-op on non-Windows)
* - `O_RANDOM` may be changed (no-op on non-Windows)
* - Other bits (`O_ACCMODE`, `O_CREAT`, etc.) are ignored
* - `F_DUPFD` is like dup() but `arg` is a minimum result, e.g. 3
* - `F_DUPFD_CLOEXEC` ditto but sets `O_CLOEXEC` on returned fd
* - `F_SETLK` for record locking where `arg` is `struct flock *`
* - `F_SETLKW` ditto but waits for lock (SQLite avoids this)
* - `F_GETLK` to retrieve information about a record lock
* - `F_OFD_SETLK` for better non-blocking lock (Linux 3.15+ only)
* - `F_OFD_SETLKW` for better blocking lock (Linux 3.15+ only)
* - `F_OFD_GETLK` for better lock querying (Linux 3.15+ only)
* - `F_FULLFSYNC` on MacOS for fsync() with release barrier
* - `F_BARRIERFSYNC` on MacOS for fsync() with even more barriers
* - `F_SETNOSIGPIPE` on MacOS and NetBSD to control `SIGPIPE`
* - `F_GETNOSIGPIPE` on MacOS and NetBSD to control `SIGPIPE`
* - `F_GETPATH` on MacOS and NetBSD where arg is `char[PATH_MAX]`
* - `F_MAXFD` on NetBSD to get max open file descriptor
* - `F_NOCACHE` on MacOS to toggle data caching
* - `F_GETPIPE_SZ` on Linux to get pipe size
* - `F_SETPIPE_SZ` on Linux to set pipe size
* - `F_NOTIFY` raise `SIGIO` upon `fd` events in `arg` (Linux only)
* - `DN_ACCESS` for file access
* - `DN_MODIFY` for file modifications
* - `DN_CREATE` for file creations
* - `DN_DELETE` for file deletions
* - `DN_RENAME` for file renames
* - `DN_ATTRIB` for file attribute changes
* - `DN_MULTISHOT` bitwise or for realtime signals (non-coalesced)
* @param arg can be FD_CLOEXEC, etc. depending
* @return 0 on success, or -1 w/ errno
* @raise EBADF if `fd` isn't a valid open file descriptor
* @raise EINVAL if `cmd` is unknown or unsupported by os
* @raise EINVAL if `cmd` is invalid or unsupported by os
* @raise EPERM if pledge() is in play w/o `stdio` or `flock` promise
* @raise ENOLCK if `F_SETLKW` would have exceeded `RLIMIT_LOCKS`
* @raise EPERM if `cmd` is `F_SETOWN` and we weren't authorized
* @raise ESRCH if `cmd` is `F_SETOWN` and process group not found
* @raise ENOTSUP on Windows if locking operation isn't supported yet
* @raise EDEADLK if `cmd` was `F_SETLKW` and waiting would deadlock
* @raise EMFILE if `cmd` is `F_DUPFD` or `F_DUPFD_CLOEXEC` and
* `RLIMIT_NOFILE` would be exceeded
* @cancelationpoint when `cmd` is `F_SETLKW` or `F_OFD_SETLKW`
* @asyncsignalsafe
* @restartable
*/
int fcntl(int fd, int cmd, ...) {
int rc;
va_list va;
uintptr_t arg;
va_start(va, cmd);
arg = va_arg(va, uintptr_t);
va_end(va);
if (fd >= 0) {
if (cmd >= 0) {
if (fd < g_fds.n && g_fds.p[fd].kind == kFdZip) {
rc = _weaken(__zipos_fcntl)(fd, cmd, arg);
} else if (!IsWindows()) {
if (cmd == F_SETLKW || cmd == F_OFD_SETLKW) {
BEGIN_CANCELATION_POINT;
rc = sys_fcntl(fd, cmd, arg, __sys_fcntl_cp);
END_CANCELATION_POINT;
} else {
rc = sys_fcntl(fd, cmd, arg, __sys_fcntl);
if (rc != -1 && (cmd == F_DUPFD || cmd == F_DUPFD_CLOEXEC) &&
__isfdkind(rc, kFdZip)) {
_weaken(__zipos_postdup)(fd, rc);
}
}
} else {
rc = sys_fcntl_nt(fd, cmd, arg);
}
} else {
rc = einval();
}
} else {
rc = ebadf();
}
#if SYSDEBUG
if (rc != -1 && cmd == F_GETFL) {
STRACE("fcntl(%d, F_GETFL) → %s", fd, DescribeOpenFlags(rc));
} else if (cmd == F_SETFL) {
STRACE("fcntl(%d, F_SETFL, %s) → %d% m", fd, DescribeOpenFlags(arg), rc);
} else if (cmd == F_GETFD || //
cmd == F_GETOWN || //
cmd == F_FULLFSYNC || //
cmd == F_BARRIERFSYNC || //
cmd == F_MAXFD) {
STRACE("fcntl(%d, %s) → %d% m", fd, DescribeFcntlCmd(cmd), rc);
} else if (cmd == F_GETFL) {
STRACE("fcntl(%d, %s) → %s% m", fd, DescribeFcntlCmd(cmd),
DescribeOpenFlags(rc));
} else if (cmd == F_SETLK || //
cmd == F_SETLKW || //
cmd == F_GETLK || //
((SupportsLinux() || SupportsXnu()) && //
cmd != -1 && //
(cmd == F_OFD_SETLK || //
cmd == F_OFD_SETLKW || //
cmd == F_OFD_GETLK))) {
STRACE("fcntl(%d, %s, %s) → %d% m", fd, DescribeFcntlCmd(cmd),
DescribeFlock(cmd, (struct flock *)arg), rc);
} else if ((SupportsNetbsd() || SupportsXnu()) && cmd != -1 &&
cmd == F_GETPATH) {
STRACE("fcntl(%d, %s, [%s]) → %d% m", fd, DescribeFcntlCmd(cmd),
!rc ? (const char *)arg : "n/a", rc);
} else if (SupportsLinux() && cmd != -1 && cmd == F_NOTIFY) {
STRACE("fcntl(%d, %s, %s) → %d% m", fd, DescribeFcntlCmd(cmd),
DescribeDnotifyFlags(arg), rc);
} else {
STRACE("fcntl(%d, %s, %ld) → %d% m", fd, DescribeFcntlCmd(cmd), arg, rc);
}
#endif
return rc;
}
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