add std.event.RwLock and a few more std changes

 * add std.event.RwLock and std.event.RwLocked
 * std.debug.warn does its printing locked
 * add std.Mutex, however it's currently implemented as a spinlock
 * rename std.event.Group.cancelAll to std.event.Group.deinit and change
   the docs and assumptions.
 * add std.HashMap.clone

1 files changed, 27 insertions, 0 deletions

diff --git a/std/mutex.zig b/std/mutex.zig
new file mode 100644
index 0000000000..6aee87d1d7
--- /dev/null
+++ b/std/mutex.zig
@@ -0,0 +1,27 @@
+const std = @import("index.zig");
+const builtin = @import("builtin");
+const AtomicOrder = builtin.AtomicOrder;
+const AtomicRmwOp = builtin.AtomicRmwOp;
+const assert = std.debug.assert;
+
+/// TODO use syscalls instead of a spinlock
+pub const Mutex = struct {
+    lock: u8, // TODO use a bool
+
+    pub const Held = struct {
+        mutex: *Mutex,
+
+        pub fn release(self: Held) void {
+            assert(@atomicRmw(u8, &self.mutex.lock, builtin.AtomicRmwOp.Xchg, 0, AtomicOrder.SeqCst) == 1);
+        }
+    };
+
+    pub fn init() Mutex {
+        return Mutex{ .lock = 0 };
+    }
+
+    pub fn acquire(self: *Mutex) Held {
+        while (@atomicRmw(u8, &self.lock, builtin.AtomicRmwOp.Xchg, 1, AtomicOrder.SeqCst) != 0) {}
+        return Held{ .mutex = self };
+    }
+};