From a02bc60b31b36b42dc86344bec5719d11183f571 Mon Sep 17 00:00:00 2001
From: Justin Heister <justin.heister@youdevise.com>
Date: Tue, 10 Mar 2020 09:47:04 +0000
Subject: [PATCH] Add support for listing Dbi flags

---
 src/main/java/org/lmdbjava/Dbi.java     | 28 +++++++++++++++++++++++++
 src/main/java/org/lmdbjava/Library.java |  2 +-
 src/test/java/org/lmdbjava/DbiTest.java | 12 +++++++++++
 3 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/src/main/java/org/lmdbjava/Dbi.java b/src/main/java/org/lmdbjava/Dbi.java
index d402a282..eccefd5f 100644
--- a/src/main/java/org/lmdbjava/Dbi.java
+++ b/src/main/java/org/lmdbjava/Dbi.java
@@ -20,10 +20,15 @@
 
 package org.lmdbjava;
 
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Comparator;
+import java.util.List;
+
 import static java.util.Objects.requireNonNull;
 import static jnr.ffi.Memory.allocateDirect;
+
+import jnr.ffi.NativeType;
 import static jnr.ffi.NativeType.ADDRESS;
 import jnr.ffi.Pointer;
 import jnr.ffi.byref.PointerByReference;
@@ -489,6 +494,29 @@ public Stat stat(final Txn<T> txn) {
         stat.f5_ms_entries.longValue());
   }
 
+  /*
+  * Return DbiFlags for this Dbi.
+  *
+  * @param txn transaction handle (not null; not committed)
+  * @return the list of flags this Dbi was created with
+  */
+  public List<DbiFlags> listFlags(final Txn<T> txn) {
+    final Pointer resultPtr = allocateDirect(RUNTIME, NativeType.UINT);
+    checkRc(LIB.mdb_dbi_flags(txn.pointer(), ptr, resultPtr));
+
+    final int flags = resultPtr.getInt(0);
+
+    final List<DbiFlags> result = new ArrayList<>();
+
+    for (final DbiFlags flag : DbiFlags.values()) {
+      if (MaskedFlag.isSet(flags, flag)) {
+        result.add(flag);
+      }
+    }
+
+    return result;
+  }
+
   private void clean() {
     if (cleaned) {
       return;
diff --git a/src/main/java/org/lmdbjava/Library.java b/src/main/java/org/lmdbjava/Library.java
index 3cb44fae..60ac2fbc 100644
--- a/src/main/java/org/lmdbjava/Library.java
+++ b/src/main/java/org/lmdbjava/Library.java
@@ -222,7 +222,7 @@ int mdb_cursor_put(@In Pointer cursor, @In Pointer key, @In Pointer data,
 
     void mdb_dbi_close(@In Pointer env, @In Pointer dbi);
 
-    int mdb_dbi_flags(@In Pointer txn, @In Pointer dbi, int flags);
+    int mdb_dbi_flags(@In Pointer txn, @In Pointer dbi, @Out Pointer flags);
 
     int mdb_dbi_open(@In Pointer txn, @In byte[] name, int flags,
                      @In Pointer dbiPtr);
diff --git a/src/test/java/org/lmdbjava/DbiTest.java b/src/test/java/org/lmdbjava/DbiTest.java
index 5d454cb8..c36be6bf 100644
--- a/src/test/java/org/lmdbjava/DbiTest.java
+++ b/src/test/java/org/lmdbjava/DbiTest.java
@@ -49,6 +49,7 @@
 import static org.hamcrest.CoreMatchers.nullValue;
 import static org.hamcrest.MatcherAssert.assertThat;
 import org.hamcrest.Matchers;
+import static org.hamcrest.Matchers.containsInAnyOrder;
 import static org.hamcrest.Matchers.hasSize;
 import static org.hamcrest.collection.IsEmptyCollection.empty;
 import org.junit.After;
@@ -62,6 +63,7 @@
 import org.lmdbjava.Dbi.DbFullException;
 import static org.lmdbjava.DbiFlags.MDB_CREATE;
 import static org.lmdbjava.DbiFlags.MDB_DUPSORT;
+import static org.lmdbjava.DbiFlags.MDB_REVERSEKEY;
 import org.lmdbjava.Env.MapFullException;
 import static org.lmdbjava.Env.create;
 import static org.lmdbjava.EnvFlags.MDB_NOSUBDIR;
@@ -474,4 +476,14 @@ public void testParallelWritesStress() {
           }
         });
   }
+
+  @Test
+  public void listsFlags() {
+    final Dbi<ByteBuffer> dbi = env.openDbi(DB_1, MDB_CREATE, MDB_DUPSORT, MDB_REVERSEKEY);
+
+    try (Txn<ByteBuffer> txn = env.txnRead()) {
+      final List<DbiFlags> flags = dbi.listFlags(txn);
+      assertThat(flags, containsInAnyOrder(MDB_DUPSORT, MDB_REVERSEKEY));
+    }
+  }
 }