Make ListReadKeysWithCount use idiomatic code instead of needless readHead and direct input parsing.

Author: prvyk

libs/server/Resp/RespServerSession.cs

@@ -1188,43 +1188,6 @@ ReadOnlySpan<byte> GetUpperCaseCommand(out bool success)
             return result;
         }
 
-        public ArgSlice GetCommandAsArgSlice(out bool success)
-        {
-            if (bytesRead - readHead < 6)
-            {
-                success = false;
-                return default;
-            }
-
-            Debug.Assert(*(recvBufferPtr + readHead) == '$');
-            int psize = *(recvBufferPtr + readHead + 1) - '0';
-            readHead += 2;
-            while (*(recvBufferPtr + readHead) != '\r')
-            {
-                psize = psize * 10 + *(recvBufferPtr + readHead) - '0';
-                if (bytesRead - readHead < 1)
-                {
-                    success = false;
-                    return default;
-                }
-                readHead++;
-            }
-            if (bytesRead - readHead < 2 + psize + 2)
-            {
-                success = false;
-                return default;
-            }
-            Debug.Assert(*(recvBufferPtr + readHead + 1) == '\n');
-
-            var result = new ArgSlice(recvBufferPtr + readHead + 2, psize);
-            Debug.Assert(*(recvBufferPtr + readHead + 2 + psize) == '\r');
-            Debug.Assert(*(recvBufferPtr + readHead + 2 + psize + 1) == '\n');
-
-            readHead += 2 + psize + 2;
-            success = true;
-            return result;
-        }
-
         /// <summary>
         /// Attempt to kill this session.
         ///

libs/server/Transaction/TxnKeyManager.cs

@@ -378,7 +378,7 @@ private int ListObjectKeys(RespCommand command)
                 RespCommand.LINSERT => SingleKey(StoreType.Object, LockType.Exclusive),
                 RespCommand.LLEN => SingleKey(StoreType.Object, LockType.Shared),
                 RespCommand.LMOVE => ListKeys(2, StoreType.Object, LockType.Exclusive),
-                RespCommand.LMPOP => ListReadKeysWithCount(LockType.Exclusive),
+                RespCommand.LMPOP => ListReadKeysWithCount(LockType.Exclusive, mandatoryArgs: 1),
                 RespCommand.LPOP => SingleKey(StoreType.Object, LockType.Exclusive),
                 RespCommand.LPOS => SingleKey(StoreType.Object, LockType.Shared),
                 RespCommand.LPUSH => SingleKey(StoreType.Object, LockType.Exclusive),
@@ -487,17 +487,20 @@ private int ListKeys(int inputCount, StoreType storeType, LockType type)
         /// <summary>
         /// Returns a list of keys for LMPOP command
         /// </summary>
-        private int ListReadKeysWithCount(LockType type, bool isObject = true)
+        private int ListReadKeysWithCount(LockType type, bool isObject = true, int mandatoryArgs = 0)
         {
-            var numKeysArg = respSession.GetCommandAsArgSlice(out var success);
-            if (!success) return -2;
+            if (respSession.parseState.Count == 0)
+                return -2;
 
-            if (!NumUtils.TryParse(numKeysArg.ReadOnlySpan, out int numKeys)) return -2;
+            if (!respSession.parseState.TryGetInt(0, out var numKeys))
+                return -2;
 
-            for (var i = 0; i < numKeys; i++)
+            if (numKeys + mandatoryArgs + 1 > respSession.parseState.Count)
+                return -2;
+
+            for (var i = 1; i < numKeys + 1; i++)
             {
-                var key = respSession.GetCommandAsArgSlice(out success);
-                if (!success) return -2;
+                var key = respSession.parseState.GetArgSliceByRef(i);
                 SaveKeyEntryToLock(key, isObject, type);
                 SaveKeyArgSlice(key);
             }