From b5deadbeea24f46588376ae230a517e4a2d51766 Mon Sep 17 00:00:00 2001
From: oddcoder <ahmedsoliman@oddcoder.com>
Date: Sun, 21 Jun 2020 12:30:11 +0200
Subject: [PATCH] Add (POSIX defined) struct flock
struct flock is posix defined locking mechanism on *nix platform
Example usage (copied from https://gavv.github.io/articles/file-locks/) :
#include <fcntl.h>
struct flock fl;
memset(&fl, 0, sizeof(fl));
// lock in shared mode
fl.l_type = F_RDLCK;
// lock entire file
fl.l_whence = SEEK_SET; // offset base is start of the file
fl.l_start = 0; // starting offset is zero
fl.l_len = 0; // len is zero, which is a special value representing end
// of file (no matter how large the file grows in future)
fl.l_pid = 0; // F_SETLK(W) ignores it; F_OFD_SETLK(W) requires it to be zero
// F_SETLKW specifies blocking mode
if (fcntl(fd, F_SETLKW, &fl) == -1) {
exit(1);
}
// atomically upgrade shared lock to exclusive lock, but only
// for bytes in range [10; 15)
//
// after this call, the process will hold three lock regions:
// [0; 10) - shared lock
// [10; 15) - exclusive lock
// [15; SEEK_END) - shared lock
fl.l_type = F_WRLCK;
fl.l_start = 10;
fl.l_len = 5;
// F_SETLKW specifies non-blocking mode
if (fcntl(fd, F_SETLK, &fl) == -1) {
exit(1);
}
// release lock for bytes in range [10; 15)
fl.l_type = F_UNLCK;
if (fcntl(fd, F_SETLK, &fl) == -1) {
exit(1);
}
// close file and release locks for all regions
// remember that locks are released when process calls close()
// on any descriptor for a lock file
close(fd);
---
src/header/fcntl/mod.rs | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/src/header/fcntl/mod.rs b/src/header/fcntl/mod.rs
index f7b20a56..1e9975c6 100644
--- a/src/header/fcntl/mod.rs
+++ b/src/header/fcntl/mod.rs
@@ -32,7 +32,14 @@ pub const F_UNLCK: c_int = 2;
pub unsafe extern "C" fn creat(path: *const c_char, mode: mode_t) -> c_int {
sys_open(path, O_WRONLY | O_CREAT | O_TRUNC, mode)
}
-
+#[repr(C)]
+pub struct flock {
+ pub l_type: c_short,
+ pub l_whence: c_short,
+ pub l_start: off_t,
+ pub l_len: off_t,
+ pub l_pid: pid_t,
+}
#[no_mangle]
pub extern "C" fn sys_fcntl(fildes: c_int, cmd: c_int, arg: c_int) -> c_int {
Sys::fcntl(fildes, cmd, arg)
@@ -43,3 +50,6 @@ pub unsafe extern "C" fn sys_open(path: *const c_char, oflag: c_int, mode: mode_
let path = CStr::from_ptr(path);
Sys::open(path, oflag, mode)
}
+
+#[no_mangle]
+pub unsafe extern "C" fn cbindgen_stupid_struct_user_for_fcntl(a: flock) {}
--
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