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Code Issues Releases Activity

Simplified StringInstructionHandler by combining mnemonic and operands into a single dictionary and removing redundant switch statement

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This commit is contained in:
bird_egop 2025-04-13 23:24:14 +03:00
parent 00547ed273
commit 6827cb735e
1 changed files with 30 additions and 55 deletions
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85
X86Disassembler/X86/Handlers/String/StringInstructionHandler.cs
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@ -5,17 +5,17 @@ namespace X86Disassembler.X86.Handlers.String;
/// </summary>
public class StringInstructionHandler : InstructionHandler
{
// Dictionary mapping opcodes to their mnemonics
private static readonly Dictionary<byte, string> Mnemonics = new()
// Dictionary mapping opcodes to their mnemonics and operands
private static readonly Dictionary<byte, (string Mnemonic, string Operands)> StringInstructions = new()
{
{ 0xA4, "movs" }, // MOVSB
{ 0xA5, "movs" }, // MOVSD
{ 0xAA, "stos" }, // STOSB
{ 0xAB, "stos" }, // STOSD
{ 0xAC, "lods" }, // LODSB
{ 0xAD, "lods" }, // LODSD
{ 0xAE, "scas" }, // SCASB
{ 0xAF, "scas" } // SCASD
{ 0xA4, ("movs", "byte ptr [edi], byte ptr [esi]") }, // MOVSB
{ 0xA5, ("movs", "dword ptr [edi], dword ptr [esi]") }, // MOVSD
{ 0xAA, ("stos", "byte ptr [edi], al") }, // STOSB
{ 0xAB, ("stos", "dword ptr [edi], eax") }, // STOSD
{ 0xAC, ("lods", "al, byte ptr [esi]") }, // LODSB
{ 0xAD, ("lods", "eax, dword ptr [esi]") }, // LODSD
{ 0xAE, ("scas", "al, byte ptr [edi]") }, // SCASB
{ 0xAF, ("scas", "eax, dword ptr [edi]") } // SCASD
};
// REP/REPNE prefix opcodes
@ -41,7 +41,7 @@ public class StringInstructionHandler : InstructionHandler
public override bool CanHandle(byte opcode)
{
// Check if the opcode is a string instruction
if (Mnemonics.ContainsKey(opcode))
if (StringInstructions.ContainsKey(opcode))
{
return true;
}
@ -53,7 +53,7 @@ public class StringInstructionHandler : InstructionHandler
if (position < Length)
{
byte nextByte = CodeBuffer[position];
return Mnemonics.ContainsKey(nextByte);
return StringInstructions.ContainsKey(nextByte);
}
}
@ -70,12 +70,17 @@ public class StringInstructionHandler : InstructionHandler
{
// Check if this is a REP/REPNE prefix
bool hasRepPrefix = opcode == REP_PREFIX || opcode == REPNE_PREFIX;
string prefixString = opcode == REP_PREFIX ? "rep " : (opcode == REPNE_PREFIX ? "repne " : "");
string prefixString = "";
// If this is a REP/REPNE prefix, get the actual string instruction opcode
byte stringOpcode = opcode;
if (hasRepPrefix)
{
// Set the prefix string based on the prefix opcode
prefixString = opcode == REP_PREFIX ? "rep " : "repne ";
// Read the next byte (the actual string instruction opcode)
int position = Decoder.GetPosition();
if (position >= Length)
{
@ -83,55 +88,25 @@ public class StringInstructionHandler : InstructionHandler
}
stringOpcode = Decoder.ReadByte();
if (!Mnemonics.ContainsKey(stringOpcode))
if (!StringInstructions.ContainsKey(stringOpcode))
{
return false;
}
}
// Set the mnemonic
if (Mnemonics.TryGetValue(stringOpcode, out string? mnemonic))
// Get the mnemonic and operands for the string instruction
if (StringInstructions.TryGetValue(stringOpcode, out var instructionInfo))
{
instruction.Mnemonic = prefixString + mnemonic;
}
else
{
// This shouldn't happen if CanHandle is called first
return false;
// Set the mnemonic with the prefix if present
instruction.Mnemonic = prefixString + instructionInfo.Mnemonic;
// Set the operands
instruction.Operands = instructionInfo.Operands;
return true;
}
// Set the operands based on the string operation
switch (stringOpcode)
{
case 0xA4: // MOVSB
instruction.Operands = "byte ptr [edi], byte ptr [esi]";
break;
case 0xA5: // MOVSD
instruction.Operands = "dword ptr [edi], dword ptr [esi]";
break;
case 0xAA: // STOSB
instruction.Operands = "byte ptr [edi], al";
break;
case 0xAB: // STOSD
instruction.Operands = "dword ptr [edi], eax";
break;
case 0xAC: // LODSB
instruction.Operands = "al, byte ptr [esi]";
break;
case 0xAD: // LODSD
instruction.Operands = "eax, dword ptr [esi]";
break;
case 0xAE: // SCASB
instruction.Operands = "al, byte ptr [edi]";
break;
case 0xAF: // SCASD
instruction.Operands = "eax, dword ptr [edi]";
break;
default:
instruction.Operands = "??";
break;
}
return true;
// This shouldn't happen if CanHandle is called first
return false;
}
}