Convenience methods for cursor navigation

krisskross · krisskross · commit 22008de0641d · 2016-06-29T21:37:20.000+02:00
diff --git a/src/main/java/org/lmdbjava/Cursor.java b/src/main/java/org/lmdbjava/Cursor.java
@@ -230,6 +230,34 @@ public boolean seek(final SeekOp op) {
     return true;
   }
 
+  /**
+   * Position at first key/data item
+   */
+  public boolean first() {
+    return seek(SeekOp.MDB_FIRST);
+  }
+
+  /**
+   * Position at last key/data item
+   */
+  public boolean last() {
+    return seek(SeekOp.MDB_LAST);
+  }
+
+  /**
+   * Position at next data item
+   */
+  public boolean next() {
+    return seek(SeekOp.MDB_NEXT);
+  }
+
+  /**
+   * Position at previous data item
+   */
+  public boolean prev() {
+    return seek(SeekOp.MDB_PREV);
+  }
+
   private void checkNotClosed() throws ClosedException {
     if (closed) {
       throw new ClosedException();
diff --git a/src/main/java/org/lmdbjava/SeekOp.java b/src/main/java/org/lmdbjava/SeekOp.java
@@ -77,6 +77,7 @@ public enum SeekOp {
    * Position at first data item of next key
    */
   MDB_NEXT_NODUP(11),
+
   /**
    * Position at previous data item
    */
diff --git a/src/test/java/org/lmdbjava/CursorTest.java b/src/test/java/org/lmdbjava/CursorTest.java
@@ -350,4 +350,35 @@ private <T> Env<T> makeEnv(final BufferProxy<T> proxy) {
       throw new RuntimeException(e);
     }
   }
+
+  @Test
+  public void cursorFirstLastNextPrev() {
+    final Env<ByteBuffer> env = makeEnv(PROXY_OPTIMAL);
+    final Dbi<ByteBuffer> db = env.openDbi(DB_1, MDB_CREATE);
+    try (final Txn<ByteBuffer> txn = env.txnWrite()) {
+      // populate data
+      final Cursor<ByteBuffer> c = db.openCursor(txn);
+      c.put(createBb(1), createBb(2), MDB_NOOVERWRITE);
+      c.put(createBb(3), createBb(4));
+      c.put(createBb(5), createBb(6));
+      c.put(createBb(7), createBb(8));
+
+      assertThat(c.first(), is(true));
+      assertThat(txn.key().getInt(0), is(1));
+      assertThat(txn.val().getInt(0), is(2));
+
+      assertThat(c.last(), is(true));
+      assertThat(txn.key().getInt(0), is(7));
+      assertThat(txn.val().getInt(0), is(8));
+
+      assertThat(c.prev(), is(true));
+      assertThat(txn.key().getInt(0), is(5));
+      assertThat(txn.val().getInt(0), is(6));
+
+      assertThat(c.first(), is(true));
+      assertThat(c.next(), is(true));
+      assertThat(txn.key().getInt(0), is(3));
+      assertThat(txn.val().getInt(0), is(4));
+    }
+  }
 }
