1 files changed, 95 insertions, 0 deletions
diff --git a/third_party/rust/jobserver/src/wasm.rs b/third_party/rust/jobserver/src/wasm.rs
new file mode 100644
index 0000000000..3793bd67cc
--- /dev/null
+++ b/third_party/rust/jobserver/src/wasm.rs
@@ -0,0 +1,95 @@
+use std::io;
+use std::process::Command;
+use std::sync::{Arc, Condvar, Mutex};
+use std::thread::{Builder, JoinHandle};
+
+#[derive(Debug)]
+pub struct Client {
+    inner: Arc<Inner>,
+}
+
+#[derive(Debug)]
+struct Inner {
+    count: Mutex<usize>,
+    cvar: Condvar,
+}
+
+#[derive(Debug)]
+pub struct Acquired(());
+
+impl Client {
+    pub fn new(limit: usize) -> io::Result<Client> {
+        Ok(Client {
+            inner: Arc::new(Inner {
+                count: Mutex::new(limit),
+                cvar: Condvar::new(),
+            }),
+        })
+    }
+
+    pub unsafe fn open(_s: &str) -> Option<Client> {
+        None
+    }
+
+    pub fn acquire(&self) -> io::Result<Acquired> {
+        let mut lock = self.inner.count.lock().unwrap_or_else(|e| e.into_inner());
+        while *lock == 0 {
+            lock = self
+                .inner
+                .cvar
+                .wait(lock)
+                .unwrap_or_else(|e| e.into_inner());
+        }
+        *lock -= 1;
+        Ok(Acquired(()))
+    }
+
+    pub fn release(&self, _data: Option<&Acquired>) -> io::Result<()> {
+        let mut lock = self.inner.count.lock().unwrap_or_else(|e| e.into_inner());
+        *lock += 1;
+        drop(lock);
+        self.inner.cvar.notify_one();
+        Ok(())
+    }
+
+    pub fn string_arg(&self) -> String {
+        panic!(
+            "On this platform there is no cross process jobserver support,
+             so Client::configure is not supported."
+        );
+    }
+
+    pub fn available(&self) -> io::Result<usize> {
+        let lock = self.inner.count.lock().unwrap_or_else(|e| e.into_inner());
+        Ok(*lock)
+    }
+
+    pub fn configure(&self, _cmd: &mut Command) {
+        unreachable!();
+    }
+}
+
+#[derive(Debug)]
+pub struct Helper {
+    thread: JoinHandle<()>,
+}
+
+pub(crate) fn spawn_helper(
+    client: crate::Client,
+    state: Arc<super::HelperState>,
+    mut f: Box<dyn FnMut(io::Result<crate::Acquired>) + Send>,
+) -> io::Result<Helper> {
+    let thread = Builder::new().spawn(move || {
+        state.for_each_request(|_| f(client.acquire()));
+    })?;
+
+    Ok(Helper { thread: thread })
+}
+
+impl Helper {
+    pub fn join(self) {
+        // TODO: this is not correct if the thread is blocked in
+        // `client.acquire()`.
+        drop(self.thread.join());
+    }
+}