Initial project import

tools/v/vlib/os/filelock/lib.v

@@ -0,0 +1,74 @@
+module filelock
+
+import time
+
+// LockMode describes whether an existing file lock is shared/read or exclusive/write.
+pub enum LockMode {
+	shared
+	exclusive
+}
+
+// LockOptions configures how `new_file` locks an existing file.
+@[params]
+pub struct LockOptions {
+pub:
+	mode  LockMode = .exclusive
+	start u64
+	len   u64
+}
+
+enum LockTarget {
+	sidecar
+	file
+}
+
+pub struct FileLock {
+	name   string
+	mode   LockMode = .exclusive
+	start  u64
+	len    u64
+	target LockTarget = .sidecar
+mut:
+	fd i64
+}
+
+// new creates a sidecar lock file that is removed again when the lock is released.
+pub fn new(file_name string) FileLock {
+	return FileLock{
+		name: file_name
+		fd:   -1
+	}
+}
+
+// new_file creates a lock for an existing file path using OS-level file locking.
+pub fn new_file(path string, options LockOptions) FileLock {
+	return FileLock{
+		name:   path
+		mode:   options.mode
+		start:  options.start
+		len:    options.len
+		target: .file
+		fd:     -1
+	}
+}
+
+// wait_acquire keeps trying to acquire the lock until `timeout` expires.
+pub fn (mut l FileLock) wait_acquire(timeout time.Duration) bool {
+	fin := time.now().add(timeout)
+	for time.now() < fin {
+		if l.try_acquire() {
+			return true
+		}
+		time.sleep(1 * time.millisecond)
+	}
+	return false
+}
+
+// release unlocks the file and closes the underlying file descriptor or handle.
+pub fn (mut l FileLock) release() bool {
+	if l.fd != -1 {
+		l.close_lock()
+		return true
+	}
+	return false
+}