1 files changed, 128 insertions, 0 deletions
diff --git a/services/common/app_services_logger/src/lib.rs b/services/common/app_services_logger/src/lib.rs
new file mode 100644
index 0000000000..92125b62c4
--- /dev/null
+++ b/services/common/app_services_logger/src/lib.rs
@@ -0,0 +1,128 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! This provides a XPCOM service to send app services logs to the desktop
+
+#[macro_use]
+extern crate cstr;
+
+#[macro_use]
+extern crate xpcom;
+
+use golden_gate::log::LogSink;
+use nserror::{nsresult, NS_OK};
+use nsstring::nsAString;
+use once_cell::sync::Lazy;
+use std::os::raw::c_char;
+use std::{
+    collections::HashMap,
+    sync::{
+        atomic::{AtomicBool, Ordering},
+        RwLock,
+    },
+};
+use xpcom::{
+    interfaces::{mozIAppServicesLogger, mozIServicesLogSink, nsIObserverService, nsISupports},
+    RefPtr,
+};
+
+/// A flag that's set after we register our observer to clear the map of loggers
+/// on shutdown.
+static SHUTDOWN_OBSERVED: AtomicBool = AtomicBool::new(false);
+
+#[xpcom(implement(mozIAppServicesLogger), nonatomic)]
+pub struct AppServicesLogger {}
+
+pub static LOGGERS_BY_TARGET: Lazy<RwLock<HashMap<String, LogSink>>> = Lazy::new(|| {
+    let h: HashMap<String, LogSink> = HashMap::new();
+    let m = RwLock::new(h);
+    m
+});
+
+impl AppServicesLogger {
+    xpcom_method!(register => Register(target: *const nsAString, logger: *const mozIServicesLogSink));
+    fn register(&self, target: &nsAString, logger: &mozIServicesLogSink) -> Result<(), nsresult> {
+        let log_sink_logger = LogSink::with_logger(Some(logger))?;
+
+        ensure_observing_shutdown();
+
+        LOGGERS_BY_TARGET
+            .write()
+            .unwrap()
+            .insert(target.to_string(), log_sink_logger);
+        Ok(())
+    }
+
+    pub fn is_app_services_logger_registered(target: String) -> bool {
+        match LOGGERS_BY_TARGET.read() {
+            Ok(loggers_by_target) => loggers_by_target.contains_key(&target),
+            Err(_e) => false,
+        }
+    }
+}
+
+// Import the `NS_IsMainThread` symbol from Gecko...
+extern "C" {
+    fn NS_IsMainThread() -> bool;
+}
+
+/// Registers an observer to clear the loggers map on `xpcom-shutdown`. This
+/// function must be called from the main thread, because the observer service
+//// is main thread-only.
+fn ensure_observing_shutdown() {
+    assert!(unsafe { NS_IsMainThread() });
+    // If we've already registered our observer, bail. Relaxed ordering is safe
+    // here and below, because we've asserted we're only called from the main
+    // thread, and only check the flag here.
+    if SHUTDOWN_OBSERVED.load(Ordering::Relaxed) {
+        return;
+    }
+    if let Ok(service) = xpcom::components::Observer::service::<nsIObserverService>() {
+        let observer = ShutdownObserver::allocate(InitShutdownObserver {});
+        let rv = unsafe {
+            service.AddObserver(observer.coerce(), cstr!("xpcom-shutdown").as_ptr(), false)
+        };
+        // If we fail to register the observer now, or fail to get the observer
+        // service, the flag will remain `false`, and we'll try again on the
+        // next call to `ensure_observing_shutdown`.
+        SHUTDOWN_OBSERVED.store(rv.succeeded(), Ordering::Relaxed);
+    }
+}
+
+#[xpcom(implement(nsIObserver), nonatomic)]
+struct ShutdownObserver {}
+
+impl ShutdownObserver {
+    xpcom_method!(observe => Observe(_subject: *const nsISupports, topic: *const c_char, _data: *const u16));
+    /// Remove our shutdown observer and clear the map.
+    fn observe(
+        &self,
+        _subject: &nsISupports,
+        topic: *const c_char,
+        _data: *const u16,
+    ) -> Result<(), nsresult> {
+        LOGGERS_BY_TARGET.write().unwrap().clear();
+        if let Ok(service) = xpcom::components::Observer::service::<nsIObserverService>() {
+            // Ignore errors, since we're already shutting down.
+            let _ = unsafe { service.RemoveObserver(self.coerce(), topic) };
+        }
+        Ok(())
+    }
+}
+
+/// The constructor for an `AppServicesLogger` service. This uses C linkage so that it
+/// can be called from C++. See `AppServicesLoggerComponents.h` for the C++
+/// constructor that's passed to the component manager.
+///
+/// # Safety
+///
+/// This function is unsafe because it dereferences `result`.
+#[no_mangle]
+pub unsafe extern "C" fn NS_NewAppServicesLogger(
+    result: *mut *const mozIAppServicesLogger,
+) -> nsresult {
+    let logger = AppServicesLogger::allocate(InitAppServicesLogger {});
+    RefPtr::new(logger.coerce::<mozIAppServicesLogger>()).forget(&mut *result);
+    NS_OK
+}