Initial project import

tools/v/vlib/os/filelock/lib_nix.c.v

@@ -0,0 +1,92 @@
+module filelock
+
+#include <sys/file.h>
+#insert "@VEXEROOT/vlib/os/filelock/filelock_helpers.h"
+
+fn C.unlink(&char) i32
+fn C.open(&char, i32, i32) i32
+fn C.close(i32) i32
+fn C.flock(i32, i32) i32
+fn C.v_filelock_lock(i32, i32, i32, u64, u64) i32
+fn C.v_filelock_unlock(i32, u64, u64) i32
+
+fn (l &FileLock) open_lock() int {
+	if l.target == .file {
+		return open_existing_file(l.name, l.mode)
+	}
+	return open_lockfile(l.name)
+}
+
+fn open_lockfile(path string) int {
+	mut fd := C.open(&char(path.str), C.O_CREAT | C.O_RDONLY, 0o644)
+	if fd == -1 {
+		fd = C.open(&char(path.str), C.O_RDONLY, 0)
+	}
+	return fd
+}
+
+fn open_existing_file(path string, mode LockMode) int {
+	flags := if mode == .shared { C.O_RDONLY } else { C.O_RDWR }
+	return C.open(&char(path.str), flags, 0)
+}
+
+fn (l &FileLock) lock_fd(fd int, immediate bool) bool {
+	if l.target == .file {
+		return C.v_filelock_lock(fd, int(l.mode == .exclusive), int(immediate), l.start, l.len) == 0
+	}
+	flags := if immediate { C.LOCK_EX | C.LOCK_NB } else { C.LOCK_EX }
+	return C.flock(fd, flags) == 0
+}
+
+fn (mut l FileLock) close_lock() {
+	if l.fd == -1 {
+		return
+	}
+	fd := int(l.fd)
+	if l.target == .file {
+		C.v_filelock_unlock(fd, l.start, l.len)
+		C.close(fd)
+	} else {
+		C.close(fd)
+		C.unlink(&char(l.name.str))
+	}
+	l.fd = -1
+}
+
+// acquire blocks until the lock is acquired.
+pub fn (mut l FileLock) acquire() ! {
+	if l.fd != -1 {
+		return error_with_code('lock already acquired by this instance', 1)
+	}
+	fd := l.open_lock()
+	if fd == -1 {
+		msg := if l.target == .file {
+			'cannot open file ${l.name}'
+		} else {
+			'cannot create lock file ${l.name}'
+		}
+		return error_with_code(msg, -1)
+	}
+	if !l.lock_fd(fd, false) {
+		C.close(fd)
+		return error_with_code('cannot lock ${l.name}', -2)
+	}
+	l.fd = fd
+}
+
+// try_acquire tries to acquire the lock without blocking.
+pub fn (mut l FileLock) try_acquire() bool {
+	if l.fd != -1 {
+		return true
+	}
+	fd := l.open_lock()
+	if fd == -1 {
+		return false
+	}
+	if !l.lock_fd(fd, true) {
+		C.close(fd)
+		return false
+	}
+	l.fd = fd
+	return true
+}