Resolve TODOs where we don't cache records during StepFirst/Next/Prev…

…/Last (#408) * Cache btrieve records during StepFirst/Next/Previous/Last * s/GetBtrieveRecord/GetAndCacheBtrieveRecord/g
mbbsemu · Feb 21, 2021 · 35070e9 · 35070e9
1 parent 1de6866
commit 35070e9
Showing 1 changed file with 28 additions and 16 deletions.
diff --git a/MBBSEmu/Btrieve/BtrieveFileProcessor.cs b/MBBSEmu/Btrieve/BtrieveFileProcessor.cs
@@ -350,22 +350,24 @@ public int GetRecordCount()
         /// </summary>
         private bool StepFirst()
         {
-            // TODO consider grabbing data at the same time and prepopulating the cache
-            var cmd = GetSqliteCommand("SELECT id FROM data_t ORDER BY id LIMIT 1");
+            var cmd = GetSqliteCommand("SELECT id, data FROM data_t ORDER BY id LIMIT 1");
             using var reader = cmd.ExecuteReader();
 
-            Position = reader.Read() ? (uint)reader.GetInt32(0) : 0;
+            if (!reader.Read())
+                return false;
+
+            Position = (uint)reader.GetInt32(0);
+            GetAndCacheBtrieveRecord(Position, reader, ordinal: 1);
             reader.Close();
-            return Position > 0;
+            return true;
         }
 
         /// <summary>
         ///     Sets Position to the offset of the next logical Record in the loaded Btrieve File.
         /// </summary>
         private bool StepNext()
         {
-            // TODO consider grabbing data at the same time and prepopulating the cache
-            var cmd = GetSqliteCommand("SELECT id FROM data_t WHERE id > @position ORDER BY id LIMIT 1");
+            var cmd = GetSqliteCommand("SELECT id, data FROM data_t WHERE id > @position ORDER BY id LIMIT 1");
             cmd.Parameters.AddWithValue("@position", Position);
             using var reader = cmd.ExecuteReader();
             try
@@ -374,6 +376,7 @@ private bool StepNext()
                     return false;
 
                 Position = (uint)reader.GetInt32(0);
+                GetAndCacheBtrieveRecord(Position, reader, ordinal: 1);
                 return true;
             }
             finally
@@ -387,7 +390,7 @@ private bool StepNext()
         /// </summary>
         private bool StepPrevious()
         {
-            var cmd = GetSqliteCommand("SELECT id FROM data_t WHERE id < @position ORDER BY id DESC LIMIT 1");
+            var cmd = GetSqliteCommand("SELECT id, data FROM data_t WHERE id < @position ORDER BY id DESC LIMIT 1");
             cmd.Parameters.AddWithValue("@position", Position);
             using var reader = cmd.ExecuteReader();
             try
@@ -396,6 +399,7 @@ private bool StepPrevious()
                     return false;
 
                 Position = (uint)reader.GetInt32(0);
+                GetAndCacheBtrieveRecord(Position, reader, 1);
                 return true;
             }
             finally
@@ -409,11 +413,14 @@ private bool StepPrevious()
         /// </summary>
         private bool StepLast()
         {
-            // TODO consider grabbing data at the same time and prepopulating the cache
-            var cmd = GetSqliteCommand("SELECT id FROM data_t ORDER BY id DESC LIMIT 1");
+            var cmd = GetSqliteCommand("SELECT id, data FROM data_t ORDER BY id DESC LIMIT 1");
             using var reader = cmd.ExecuteReader();
 
-            Position = reader.Read() ? (uint)reader.GetInt32(0) : 0;
+            if (!reader.Read())
+                return false;
+
+            Position = (uint)reader.GetInt32(0);
+            GetAndCacheBtrieveRecord(Position, reader, 1);
             reader.Close();
             return Position > 0;
         }
@@ -424,6 +431,16 @@ private bool StepLast()
         /// <returns></returns>
         public byte[] GetRecord() => GetRecord(Position)?.Data;
 
+        private BtrieveRecord GetAndCacheBtrieveRecord(uint id, SqliteDataReader reader, int ordinal)
+        {
+            using var stream = reader.GetStream(ordinal);
+            var data = BtrieveUtil.ReadEntireStream(stream);
+
+            var record = new BtrieveRecord(id, data);
+            _cache[id] = record;
+            return record;
+        }
+
         /// <summary>
         ///     Returns the Record at the specified Offset, while also updating Position to match.
         /// </summary>
@@ -442,12 +459,7 @@ public BtrieveRecord GetRecord(uint offset)
                 if (!reader.Read())
                     return null;
 
-                using var stream = reader.GetStream(0);
-                var data = BtrieveUtil.ReadEntireStream(stream);
-
-                record = new BtrieveRecord(offset, data);
-                _cache[offset] = record;
-                return record;
+                return GetAndCacheBtrieveRecord(offset, reader, 0);
             }
             finally
             {