new handlers and test fixes

X86Disassembler/X86/Handlers/Neg/NegRm8Handler.cs

@@ -0,0 +1,65 @@
+using X86Disassembler.X86.Operands;
+
+namespace X86Disassembler.X86.Handlers.Neg;
+
+/// <summary>
+/// Handler for NEG r/m8 instruction (0xF6 /3)
+/// </summary>
+public class NegRm8Handler : InstructionHandler
+{
+    /// <summary>
+    /// Initializes a new instance of the NegRm8Handler class
+    /// </summary>
+    /// <param name="decoder">The instruction decoder that owns this handler</param>
+    public NegRm8Handler(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)
+    {
+        if (opcode != 0xF6)
+            return false;
+
+        // Check if the reg field of the ModR/M byte is 3 (NEG)
+        if (!Decoder.CanReadByte())
+            return false;
+
+        var reg = ModRMDecoder.PeakModRMReg();
+
+        return reg == 3; // 3 = NEG
+    }
+
+    /// <summary>
+    /// Decodes a NEG r/m8 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.Neg;
+
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
+        var (_, _, _, operand) = ModRMDecoder.ReadModRM8();
+
+        // Set the structured operands
+        // NEG has only one operand
+        instruction.StructuredOperands = 
+        [
+            operand
+        ];
+
+        return true;
+    }
+}