Merge branch 'master' into future

src/main/java/carpet/script/utils/GlocalFlag.java

@@ -0,0 +1,68 @@
+package carpet.script.utils;
+
+import java.util.function.Supplier;
+
+public class GlocalFlag extends ThreadLocal<Boolean>
+{
+    private final boolean initial;
+
+    public GlocalFlag(boolean initial)
+    {
+        this.initial = initial;
+    }
+
+    @Override
+    public Boolean initialValue()
+    {
+        return initial;
+    }
+
+    /**
+     * Allows to thread-safely wrap a call while disabling a global flag and setting it back up right after.
+     * @param action - callback to invoke when the wrapping is all setup
+     * @param <T> - returned value of that action, whatever that might be
+     * @return result of the action
+     */
+    public <T> T getWhileDisabled(Supplier<T> action)
+    {
+        return whileValueReturn(!initial, action);
+    }
+
+    private <T> T whileValueReturn(boolean what, Supplier<T> action)
+    {
+        T result;
+        boolean previous;
+        synchronized (this)
+        {
+            previous = get();
+            set(what);
+        }
+        try
+        {
+            result = action.get();
+        }
+        finally
+        {
+            set(previous);
+        }
+        return result;
+    }
+
+    public boolean runIfEnabled(Runnable action)
+    {
+        synchronized (this)
+        {
+            if (get() != initial) return false;
+            set(!initial);
+        }
+        try
+        {
+            action.run();
+        }
+        finally
+        {
+            set(initial);
+        }
+        return true;
+    }
+}