Reworked cursor api to be more in line with native lib

Added Span<byte> overloads for cursor methods
Added more test coverage

src/LightningDB.Tests/DatabaseTests.cs

@@ -89,7 +89,7 @@ public void NamedDatabaseNameExistsInMaster()
                 using (var cursor = tx.CreateCursor(db))
                 {
                     cursor.MoveNext();
-                    Assert.Equal("customdb", UTF8.GetString(cursor.Current.Key.CopyToNewArray()));
+                    Assert.Equal("customdb", UTF8.GetString(cursor.GetCurrent().key.CopyToNewArray()));
                 }
             }
         }

src/LightningDB.Tests/TestHelperExtensions.cs

@@ -1,4 +1,5 @@
-using System.Linq;
+using System;
+using System.Linq;
 using System.Collections.Generic;
 
 namespace LightningDB.Tests
@@ -46,5 +47,15 @@ public static IEnumerable<IEnumerable<T>> Split<T>(this IEnumerable<T> list, int
                 .GroupBy(x => x.Index / parts)
                 .Select(x => x.Select(v => v.Value));
         }
+
+        public static void RunCursorScenario(this LightningEnvironment env, 
+            Action<LightningTransaction, LightningDatabase, LightningCursor> scenario,
+            DatabaseOpenFlags flags = DatabaseOpenFlags.Create, TransactionBeginFlags transactionFlags = TransactionBeginFlags.None)
+        {
+            using var tx = env.BeginTransaction(transactionFlags);
+            using var db = tx.OpenDatabase(configuration: new DatabaseConfiguration { Flags = flags });
+            using var cursor = tx.CreateCursor(db);
+            scenario(tx, db, cursor);
+        }
     }
 }

src/LightningDB.Tests/TransactionTests.cs

@@ -1,7 +1,6 @@
 using System;
 using System.Linq;
 using System.Collections.Generic;
-using LightningDB.Native;
 using Xunit;
 using System.Runtime.InteropServices;
 
@@ -53,7 +52,7 @@ public void CanCountTransactionEntries()
     }
 
 
-        [Collection("SharedFileSystem")]
+    [Collection("SharedFileSystem")]
     public class TransactionTests : IDisposable
     {
         private LightningEnvironment _env;
@@ -216,8 +215,8 @@ public void TransactionShouldSupportCustomComparer()
             using (var c = txn.CreateCursor(db))
             {
                 int order = 0;
-                while (c.MoveNext())
-                    Assert.Equal(keysSorted[order++], BitConverter.ToInt32(c.Current.Key.CopyToNewArray(), 0));
+                while (c.MoveNext() == MDBResultCode.Success)
+                    Assert.Equal(keysSorted[order++], BitConverter.ToInt32(c.GetCurrent().key.CopyToNewArray(), 0));
             }
         }
 
@@ -243,8 +242,8 @@ public void TransactionShouldSupportCustomDupSorter()
             {
                 int order = 0;
 
-                while (c.MoveNext())
-                    Assert.Equal(valuesSorted[order++], BitConverter.ToInt32(c.Current.Value.CopyToNewArray(), 0));
+                while (c.MoveNext() == MDBResultCode.Success)
+                    Assert.Equal(valuesSorted[order++], BitConverter.ToInt32(c.GetCurrent().value.CopyToNewArray(), 0));
             }
         }
     }

src/LightningDB/CursorOperation.cs

@@ -93,6 +93,6 @@ public enum CursorOperation
         /// <summary>
         /// Position at first key greater than or equal to specified key.
         /// </summary>
-        SetRange
+        SetRange,
     }
 }

src/LightningDB/GetResult.cs

@@ -45,7 +45,7 @@ public enum GetResultCode
 
         /// <summary>
         /// Failure. The requested key was found, but the provided buffer was
-        /// too small to contain the full value. No data has been retrived.
+        /// too small to contain the full value. No data has been retrieved.
         /// The Get operation should be retried with a buffer at least the 
         /// length represented in GetResult.Length
         /// <para>
@@ -58,7 +58,7 @@ public enum GetResultCode
 
         /// <summary>
         /// Failure. The requested key was not found in the database. No data has 
-        /// been retrived.
+        /// been retrieved.
         /// <para>
         ///     GetResult.Length has no meaning for this result. It's value
         ///     is set to zero.