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Code Issues Releases Activity

Simplified FnstswHandler by using CanReadByte for boundary checking and improving code readability

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This commit is contained in:
bird_egop 2025-04-13 23:45:26 +03:00
parent ec1aa4a124
commit 7ab388f26d
1 changed files with 18 additions and 8 deletions
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26
X86Disassembler/X86/Handlers/FloatingPoint/FnstswHandler.cs
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@ -1,7 +1,7 @@
namespace X86Disassembler.X86.Handlers.FloatingPoint;
/// <summary>
/// Handler for FNSTSW instruction (0xDFE0)
/// Handler for FNSTSW AX instruction (0xDF 0xE0)
/// </summary>
public class FnstswHandler : InstructionHandler
{
@ -11,11 +11,11 @@ public class FnstswHandler : InstructionHandler
/// <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 FnstswHandler(byte[] codeBuffer, InstructionDecoder decoder, int length)
public FnstswHandler(byte[] codeBuffer, InstructionDecoder decoder, int length)
: base(codeBuffer, decoder, length)
{
}
/// <summary>
/// Checks if this handler can decode the given opcode
/// </summary>
@ -26,8 +26,12 @@ public class FnstswHandler : InstructionHandler
// FNSTSW is a two-byte opcode (0xDF 0xE0)
if (opcode == 0xDF)
{
int position = Decoder.GetPosition();
if (position < Length && CodeBuffer[position] == 0xE0)
if (!Decoder.CanReadByte())
{
return false;
}
if (CodeBuffer[Decoder.GetPosition()] == 0xE0)
{
return true;
}
@ -44,15 +48,21 @@ public class FnstswHandler : InstructionHandler
/// <returns>True if the instruction was successfully decoded</returns>
public override bool Decode(byte opcode, Instruction instruction)
{
int position = Decoder.GetPosition();
// Check if we can read the second byte of the opcode
if (!Decoder.CanReadByte())
{
return false;
}
if (position >= Length || CodeBuffer[position] != 0xE0)
// Verify the second byte is 0xE0
byte secondByte = CodeBuffer[Decoder.GetPosition()];
if (secondByte != 0xE0)
{
return false;
}
// Skip the second byte of the opcode
Decoder.SetPosition(position + 1);
Decoder.ReadByte(); // Consume the 0xE0 byte
// Set the mnemonic and operands
instruction.Mnemonic = "fnstsw";