locks around observable list's access

[mobile-ledger.git] / app / src / main / java / net / ktnx / mobileledger / utils / LockHolder.java

diff --git a/app/src/main/java/net/ktnx/mobileledger/utils/LockHolder.java b/app/src/main/java/net/ktnx/mobileledger/utils/LockHolder.java
new file mode 100644 (file)
index 0000000..f0c976d
--- /dev/null
+++ b/app/src/main/java/net/ktnx/mobileledger/utils/LockHolder.java
@@ -0,0 +1,46 @@
+/*
+ * Copyright © 2019 Damyan Ivanov.
+ * This file is part of MoLe.
+ * MoLe is free software: you can distribute it and/or modify it
+ * under the term of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your opinion), any later version.
+ *
+ * MoLe is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License terms for details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with MoLe. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package net.ktnx.mobileledger.utils;
+
+import java.io.Closeable;
+import java.util.concurrent.locks.Lock;
+
+public class LockHolder implements Closeable {
+    private Lock rLock, wLock;
+    LockHolder(Lock rLock) {
+        this.rLock = rLock;
+        this.wLock = null;
+    }
+    public LockHolder(Lock rLock, Lock wLock) {
+        this.rLock = rLock;
+        this.wLock = wLock;
+    }
+    @Override
+    public void close() {
+        if (wLock != null) wLock.unlock();
+        if (rLock != null) rLock.unlock();
+    }
+    public void downgrade() {
+        if (rLock == null) throw new IllegalStateException("no locks are held");
+
+        if (wLock == null) return;
+
+        wLock.unlock();
+        wLock = null;
+    }
+}