add misc handlers, cleanup and fixes

X86Disassembler/X86/Handlers/Add/AddAxImmHandler.cs

@@ -0,0 +1,71 @@
+using X86Disassembler.X86.Operands;
+
+namespace X86Disassembler.X86.Handlers.Add;
+
+/// <summary>
+/// Handler for ADD AX, imm16 instruction (0x05 with 0x66 prefix)
+/// </summary>
+public class AddAxImmHandler : InstructionHandler
+{
+    /// <summary>
+    /// Initializes a new instance of the AddAxImmHandler class
+    /// </summary>
+    /// <param name="decoder">The instruction decoder that owns this handler</param>
+    public AddAxImmHandler(InstructionDecoder decoder)
+        : base(decoder)
+    {
+    }
+
+    /// <summary>
+    /// Checks if this handler can decode the given opcode
+    /// </summary>
+    /// <param name="opcode">The opcode to check</param>
+    /// <returns>True if this handler can decode the opcode</returns>
+    public override bool CanHandle(byte opcode)
+    {
+        // ADD AX, imm16 is encoded as 0x05 with 0x66 prefix
+        if (opcode != 0x05)
+        {
+            return false;
+        }
+
+        // Only handle when the operand size prefix is present
+        return Decoder.HasOperandSizePrefix();
+    }
+
+    /// <summary>
+    /// Decodes an ADD AX, imm16 instruction
+    /// </summary>
+    /// <param name="opcode">The opcode of the instruction</param>
+    /// <param name="instruction">The instruction object to populate</param>
+    /// <returns>True if the instruction was successfully decoded</returns>
+    public override bool Decode(byte opcode, Instruction instruction)
+    {
+        // Set the instruction type
+        instruction.Type = InstructionType.Add;
+
+        // Check if we have enough bytes for the immediate value
+        if (!Decoder.CanReadUShort())
+        {
+            return false;
+        }
+
+        // Read the immediate value
+        ushort imm16 = Decoder.ReadUInt16();
+
+        // Create the AX register operand
+        var axOperand = OperandFactory.CreateRegisterOperand(RegisterIndex.A, 16);
+
+        // Create the immediate operand
+        var immOperand = OperandFactory.CreateImmediateOperand(imm16);
+
+        // Set the structured operands
+        instruction.StructuredOperands = 
+        [
+            axOperand,
+            immOperand
+        ];
+
+        return true;
+    }
+}