1 files changed, 82 insertions, 0 deletions
diff --git a/src/libstd/sys/wasm/rwlock.rs b/src/libstd/sys/wasm/rwlock.rs
new file mode 100644
index 00000000000..8b06f541674
--- /dev/null
+++ b/src/libstd/sys/wasm/rwlock.rs
@@ -0,0 +1,82 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use cell::UnsafeCell;
+
+pub struct RWLock {
+    mode: UnsafeCell<isize>,
+}
+
+unsafe impl Send for RWLock {}
+unsafe impl Sync for RWLock {} // no threads on wasm
+
+impl RWLock {
+    pub const fn new() -> RWLock {
+        RWLock {
+            mode: UnsafeCell::new(0),
+        }
+    }
+
+    #[inline]
+    pub unsafe fn read(&self) {
+        let mode = self.mode.get();
+        if *mode >= 0 {
+            *mode += 1;
+        } else {
+            panic!("rwlock locked for writing");
+        }
+    }
+
+    #[inline]
+    pub unsafe fn try_read(&self) -> bool {
+        let mode = self.mode.get();
+        if *mode >= 0 {
+            *mode += 1;
+            true
+        } else {
+            false
+        }
+    }
+
+    #[inline]
+    pub unsafe fn write(&self) {
+        let mode = self.mode.get();
+        if *mode == 0 {
+            *mode = -1;
+        } else {
+            panic!("rwlock locked for reading")
+        }
+    }
+
+    #[inline]
+    pub unsafe fn try_write(&self) -> bool {
+        let mode = self.mode.get();
+        if *mode == 0 {
+            *mode = -1;
+            true
+        } else {
+            false
+        }
+    }
+
+    #[inline]
+    pub unsafe fn read_unlock(&self) {
+        *self.mode.get() -= 1;
+    }
+
+    #[inline]
+    pub unsafe fn write_unlock(&self) {
+        *self.mode.get() += 1;
+    }
+
+    #[inline]
+    pub unsafe fn destroy(&self) {
+    }
+}