Fixed regression from span refactor

Author: CoreyKaylor

src/LightningDB.Tests/CursorTests.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Text;
 using LightningDB.Native;
 using Xunit;
 using static System.Text.Encoding;
@@ -225,5 +226,27 @@ public void ShouldMoveNextMultiple()
                 Assert.Equal(original, result);
             }
         }
+
+        [Fact]
+        public void ShouldAdvanceKeyToClosestWhenKeyNotFound()
+        {
+            var keys = new List<string>
+            {
+                "one",
+                "two/1",
+                "two/2",
+                "two/3"
+            };
+            _db = _txn.OpenDatabase(configuration: new DatabaseConfiguration { Flags = DatabaseOpenFlags.DuplicatesFixed | DatabaseOpenFlags.Create });
+            foreach (var key in keys)
+            {
+                _txn.Put(_db, Encoding.UTF8.GetBytes(key), null);
+            }
+
+            using var cursor = _txn.CreateCursor(_db);
+            cursor.MoveTo(UTF8.GetBytes("two"));
+            var result = cursor.GetCurrent().Key.CopyToNewArray();
+            Assert.Equal("two/1", UTF8.GetString(result));
+        }
     }
 }

src/LightningDB/LightningCursor.cs

@@ -246,11 +246,15 @@ private bool Get(CursorOperation operation, byte[] key)
         private unsafe bool Get(CursorOperation operation, ReadOnlySpan<byte> key)
         {
             _currentValue = default;
-#warning should this update _currentKey?
             fixed (byte* keyPtr = key)
             {
                 var findKey = new MDBValue(key.Length, keyPtr);
-                return mdb_cursor_get(_handle, ref findKey, ref _currentValue, operation) == 0;
+                var found = mdb_cursor_get(_handle, ref findKey, ref _currentValue, operation) == 0;
+                if (found)
+                {
+                    _currentKey = findKey;
+                }
+                return found;
             }
         }