* Fixed index size length calculation on CollectionIndex.GetLength()

* Fixed some typos on exception messages and comments

LiteDB/Client/SqlParser/Commands/Create.cs

@@ -9,7 +9,7 @@ namespace LiteDB
     internal partial class SqlParser
     {
         /// <summary>
-        /// CREATE [ UNQIUE ] INDEX {indexName} ON {collection} ({indexExpr})
+        /// CREATE [ UNIQUE ] INDEX {indexName} ON {collection} ({indexExpr})
         /// </summary>
         private BsonDataReader ParseCreate()
         {

LiteDB/Engine/Engine/Index.cs

@@ -20,7 +20,7 @@ public bool EnsureIndex(string collection, string name, BsonExpression expressio
 
             if (name.Length > INDEX_NAME_MAX_LENGTH) throw LiteException.InvalidIndexName(name, collection, "MaxLength = " + INDEX_NAME_MAX_LENGTH);
             if (!name.IsWord()) throw LiteException.InvalidIndexName(name, collection, "Use only [a-Z$_]");
-            if (name.StartsWith("$")) throw LiteException.InvalidIndexName(name, collection, "Index name can't starts with `$`");
+            if (name.StartsWith("$")) throw LiteException.InvalidIndexName(name, collection, "Index name can't start with `$`");
             if (expression.IsScalar == false && unique) throw new LiteException(0, "Multikey index expression do not support unique option");
 
             if (expression.Source == "$._id") return false; // always exists

LiteDB/Engine/Pages/DataPage.cs

@@ -103,8 +103,9 @@ public IEnumerable<PageAddress> GetBlocks()
         };
 
         /// <summary>
-        /// Get page index slot on FreeDataPageID
+        /// Returns the slot the page should be in, given the <paramref name="freeBytes"/> it has
         /// </summary>
+        /// <returns>A slot number between 0 and 4</returns>
         public static byte FreeIndexSlot(int freeBytes)
         {
             ENSURE(freeBytes >= 0, "freeBytes must be positive");
@@ -118,9 +119,10 @@ public static byte FreeIndexSlot(int freeBytes)
         }
 
         /// <summary>
-        /// Get minimum slot with space enough for your data content
-        /// Returns -1 if no space guaranteed (more than 90%)
+        /// Returns the slot where there is a page with enough space for <paramref name="length"/> bytes of data.
+        /// Returns -1 if no space guaranteed (more than 90% of a DataPage net size)
         /// </summary>
+        /// <returns>A slot number between -1 and 3</returns>
         public static int GetMinimumIndexSlot(int length)
         {
             return FreeIndexSlot(length) - 1;

LiteDB/Engine/Services/IndexService.cs

@@ -30,10 +30,10 @@ public IndexService(Snapshot snapshot, Collation collation)
         /// </summary>
         public CollectionIndex CreateIndex(string name, string expr, bool unique)
         {
-            // get how many butes needed fore each head/tail (both has same size)
+            // get how many bytes needed for each head/tail (both has same size)
             var bytesLength = IndexNode.GetNodeLength(MAX_LEVEL_LENGTH, BsonValue.MinValue, out var keyLength);
 
-            // get a new empty page (each index contains your own linked nodes)
+            // get a new empty page (each index contains its own linked nodes)
             var indexPage = _snapshot.NewPage<IndexPage>();
 
             // create index ref

LiteDB/Engine/Services/SnapShot.cs

@@ -252,7 +252,7 @@ public DataPage GetFreeDataPage(int bytesLength)
             // get minimum slot to check for free page. Returns -1 if need NewPage
             var startSlot = DataPage.GetMinimumIndexSlot(length);
 
-            // check for avaiable re-usable page
+            // check for available re-usable page
             for (int currentSlot = startSlot; currentSlot >= 0; currentSlot--)
             {
                 var freePageID = _collectionPage.FreeDataPageList[currentSlot];
@@ -263,15 +263,15 @@ public DataPage GetFreeDataPage(int bytesLength)
                 var page = this.GetPage<DataPage>(freePageID);
 
                 ENSURE(page.PageListSlot == currentSlot, "stored slot must be same as called");
-                ENSURE(page.FreeBytes >= length, "ensure selected page has space enougth for this content");
+                ENSURE(page.FreeBytes >= length, "ensure selected page has space enough for this content");
 
                 // mark page page as dirty
                 page.IsDirty = true;
 
                 return page;
             }
 
-            // if not page free list page avaiable, create new page
+            // if there is no re-usable page, create a new one
             return this.NewPage<DataPage>();
         }
 

LiteDB/Engine/Structures/CollectionIndex.cs

@@ -127,7 +127,7 @@ public static int GetLength(string name, string expr)
                 PageAddress.SIZE + // Head
                 PageAddress.SIZE + // Tail
                 1 + // MaxLevel
-                (PAGE_FREE_LIST_SLOTS * PageAddress.SIZE); // FreeListPage
+                4; // FreeListPage
         }
     }
 }