feat: ensure only one instance is running (#38)

Author: sigoden

Cargo.toml

@@ -25,6 +25,7 @@ features = [
     "Win32_UI_Accessibility",
     "Win32_Graphics_Dwm",
     "Win32_Graphics_Gdi",
+    "Win32_Security",
     "Win32_System_LibraryLoader",
     "Win32_System_Console",
     "Win32_System_Registry",

src/main.rs

@@ -1,13 +1,17 @@
 #![windows_subsystem = "windows"]
 
-use anyhow::{anyhow, Result};
+use anyhow::{anyhow, bail, Result};
 use std::{
     fs::{File, OpenOptions},
     path::Path,
 };
 
 use ini::Ini;
-use window_switcher::{alert, start, utils::get_exe_folder, Config};
+use window_switcher::{
+    alert, start,
+    utils::{get_exe_folder, SingleInstance},
+    Config,
+};
 
 fn main() {
     if let Err(err) = run() {
@@ -27,6 +31,10 @@ fn run() -> Result<()> {
         })?;
         simple_logging::log_to(file, config.log_level);
     }
+    let instance = SingleInstance::create("WindowSwitcherMutex")?;
+    if !instance.is_single() {
+        bail!("Another instance is running. This instance will abort.")
+    }
     start(&config)
 }
 

src/utils.rs

@@ -1,13 +1,15 @@
 use anyhow::{anyhow, Result};
 use indexmap::IndexMap;
 use windows::core::{Error, PCWSTR, PWSTR};
-use windows::Win32::Foundation::{SetLastError, BOOL, ERROR_SUCCESS, HANDLE, HWND, LPARAM};
+use windows::Win32::Foundation::{
+    CloseHandle, SetLastError, BOOL, ERROR_ALREADY_EXISTS, ERROR_SUCCESS, HANDLE, HWND, LPARAM,
+};
 use windows::Win32::Graphics::Dwm::{DwmGetWindowAttribute, DWMWA_CLOAKED, DWM_CLOAKED_SHELL};
 use windows::Win32::System::Console::{AllocConsole, FreeConsole, GetConsoleWindow};
 use windows::Win32::System::LibraryLoader::GetModuleFileNameW;
 use windows::Win32::System::Threading::{
-    OpenProcess, QueryFullProcessImageNameW, PROCESS_NAME_WIN32, PROCESS_QUERY_INFORMATION,
-    PROCESS_VM_READ,
+    CreateMutexW, OpenProcess, QueryFullProcessImageNameW, ReleaseMutex, PROCESS_NAME_WIN32,
+    PROCESS_QUERY_INFORMATION, PROCESS_VM_READ,
 };
 use windows::Win32::UI::Controls::STATE_SYSTEM_INVISIBLE;
 use windows::Win32::UI::Input::KeyboardAndMouse::{RegisterHotKey, UnregisterHotKey, MOD_NOREPEAT};
@@ -321,3 +323,43 @@ impl CheckError for u16 {
 pub fn to_wstring(value: &str) -> Vec<u16> {
     value.encode_utf16().chain(Some(0)).collect::<Vec<u16>>()
 }
+
+/// A struct representing one running instance.
+pub struct SingleInstance {
+    handle: Option<HANDLE>,
+}
+
+unsafe impl Send for SingleInstance {}
+unsafe impl Sync for SingleInstance {}
+
+impl SingleInstance {
+    /// Returns a new SingleInstance object.
+    pub fn create(name: &str) -> Result<Self> {
+        let name = to_wstring(name);
+        let handle = unsafe { CreateMutexW(None, BOOL(1), PCWSTR(name.as_ptr())) }
+            .map_err(|err| anyhow!("Fail to setup single instance, {err}"))?;
+        let handle =
+            if windows::core::Error::from_win32().code() == ERROR_ALREADY_EXISTS.to_hresult() {
+                None
+            } else {
+                Some(handle)
+            };
+        Ok(SingleInstance { handle })
+    }
+
+    /// Returns whether this instance is single.
+    pub fn is_single(&self) -> bool {
+        self.handle.is_some()
+    }
+}
+
+impl Drop for SingleInstance {
+    fn drop(&mut self) {
+        if let Some(handle) = self.handle.take() {
+            unsafe {
+                ReleaseMutex(handle);
+                CloseHandle(handle);
+            }
+        }
+    }
+}