Split FINIT/FNINIT handlers for proper instruction recognition

X86Disassembler/X86/Handlers/FloatingPoint/Control/FninitHandler.cs

@@ -0,0 +1,63 @@
+namespace X86Disassembler.X86.Handlers.FloatingPoint.Control;
+
+using X86Disassembler.X86.Operands;
+
+/// <summary>
+/// Handler for FNINIT instruction (DB E3) - Initialize FPU without checking for pending unmasked exceptions
+/// </summary>
+public class FninitHandler : InstructionHandler
+{
+    /// <summary>
+    /// Initializes a new instance of the FninitHandler class
+    /// </summary>
+    /// <param name="decoder">The instruction decoder that owns this handler</param>
+    public FninitHandler(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)
+    {
+        // FNINIT is DB E3
+        if (opcode != 0xDB) return false;
+
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
+        // Check if the next byte is E3
+        byte nextByte = Decoder.PeakByte();
+        return nextByte == 0xE3;
+    }
+    
+    /// <summary>
+    /// Decodes a FNINIT 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)
+    {
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
+        // Read the second byte of the opcode
+        byte secondByte = Decoder.ReadByte();
+        
+        // Set the instruction type
+        instruction.Type = InstructionType.Fninit;
+
+        // FINIT has no operands
+        instruction.StructuredOperands = [];
+
+        return true;
+    }
+}