Fixed instruction boundary detection and added JGE instruction handler

X86Disassembler/X86/Handlers/Jump/JgeRel8Handler.cs

@@ -0,0 +1,67 @@
+namespace X86Disassembler.X86.Handlers.Jump;
+
+/// <summary>
+/// Handler for JGE rel8 instruction (0x7D)
+/// </summary>
+public class JgeRel8Handler : InstructionHandler
+{
+    /// <summary>
+    /// Initializes a new instance of the JgeRel8Handler class
+    /// </summary>
+    /// <param name="codeBuffer">The buffer containing the code to decode</param>
+    /// <param name="decoder">The instruction decoder that owns this handler</param>
+    /// <param name="length">The length of the buffer</param>
+    public JgeRel8Handler(byte[] codeBuffer, InstructionDecoder decoder, int length)
+        : base(codeBuffer, decoder, length)
+    {
+    }
+    
+    /// <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)
+    {
+        return opcode == 0x7D;
+    }
+    
+    /// <summary>
+    /// Decodes a JGE rel8 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)
+    {
+        // Save the original position for raw bytes calculation
+        int startPosition = Decoder.GetPosition();
+        
+        // Set the mnemonic
+        instruction.Mnemonic = "jge";
+        
+        if (startPosition >= Length)
+        {
+            instruction.Operands = "??";
+            instruction.RawBytes = new byte[] { opcode };
+            return true;
+        }
+        
+        // Read the relative offset
+        sbyte offset = (sbyte)CodeBuffer[startPosition];
+        Decoder.SetPosition(startPosition + 1);
+        
+        // Calculate the target address
+        // The target is calculated from the address of the next instruction (EIP + 2)
+        // EIP + 2 + offset
+        uint targetAddress = (uint)(instruction.Address + offset + 2);
+        
+        // Set the operands
+        instruction.Operands = $"0x{targetAddress:X8}";
+        
+        // Set the raw bytes
+        instruction.RawBytes = new byte[] { opcode, (byte)offset };
+        
+        return true;
+    }
+}