fileLock

fn fileLock(userdata: ?*anyopaque, file: File, lock: File.Lock) File.LockError!void {
    if (native_os == .wasi) return error.FileLocksUnsupported;
    const t: *Threaded = @ptrCast(@alignCast(userdata));
    _ = t;

    if (is_windows) {
        const exclusive = switch (lock) {
            .none => {
                // To match the non-Windows behavior, unlock
                var io_status_block: windows.IO_STATUS_BLOCK = undefined;
                while (true) switch (windows.ntdll.NtUnlockFile(
                    file.handle,
                    &io_status_block,
                    &windows_lock_range_off,
                    &windows_lock_range_len,
                    0,
                )) {
                    .SUCCESS => return,
                    .CANCELLED => continue,
                    .RANGE_NOT_LOCKED => return,
                    .ACCESS_VIOLATION => |err| return windows.statusBug(err), // bad io_status_block pointer
                    else => |status| return windows.unexpectedStatus(status),
                };
            },
            .shared => false,
            .exclusive => true,
        };
        var io_status_block: windows.IO_STATUS_BLOCK = undefined;
        const syscall: Syscall = try .start();
        while (true) switch (windows.ntdll.NtLockFile(
            file.handle,
            null,
            null,
            null,
            &io_status_block,
            &windows_lock_range_off,
            &windows_lock_range_len,
            null,
            .FALSE,
            .fromBool(exclusive),
        )) {
            .SUCCESS => return syscall.finish(),
            .CANCELLED => {
                try syscall.checkCancel();
                continue;
            },
            .INSUFFICIENT_RESOURCES => return syscall.fail(error.SystemResources),
            .LOCK_NOT_GRANTED => |err| return syscall.ntstatusBug(err), // passed FailImmediately=false
            .ACCESS_VIOLATION => |err| return syscall.ntstatusBug(err), // bad io_status_block pointer
            else => |status| return syscall.unexpectedNtstatus(status),
        };
    }

    const operation: i32 = switch (lock) {
        .none => posix.LOCK.UN,
        .shared => posix.LOCK.SH,
        .exclusive => posix.LOCK.EX,
    };
    const syscall: Syscall = try .start();
    while (true) {
        switch (posix.errno(posix.system.flock(file.handle, operation))) {
            .SUCCESS => return syscall.finish(),
            .INTR => {
                try syscall.checkCancel();
                continue;
            },
            else => |e| {
                syscall.finish();
                switch (e) {
                    .BADF => |err| return errnoBug(err),
                    .INVAL => |err| return errnoBug(err), // invalid parameters
                    .NOLCK => return error.SystemResources,
                    .AGAIN => |err| return errnoBug(err),
                    .OPNOTSUPP => return error.FileLocksUnsupported,
                    else => |err| return posix.unexpectedErrno(err),
                }
            },
        }
    }
}