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Assembly and C#

Started by Degorath Mar 6, 2008 at 4:25 AM 2 replies 1.3k views

Original Post

Mar 6, 2008 at 4:25 AM

I have a string in Hex (very very very long) which needs to be converted into a byte array in C#. To do this takes around 2 minutes for 145KB (if error checking is disabled. If not, 5 minutes). What I would really like to do is use an assembly routine which will probably do it in a few seconds. What I would like to know is; is it possible to run an assembly routine from C# code? (The .COM file takes the string as input and returns the result) Thanks...

Daedalus AI

Mar 6, 2008 at 4:34 AM

I'm not sure, but you might be able to use P/Invoke.

Have a look at that!

Basically, it's a good way of including non-managed code into your C# from what I can remember.

guardian24

Mar 6, 2008 at 4:58 AM

Look at this horror for machine code in C++/CLI:

delegate Int32 DoubleNum(Int32 x);unsigned char pNative[] ={0x55, // push ebp0x8B, 0xEC, // mov ebp,esp0x8B, 0x45, 0x08, // mov eax,dword ptr [arg]0x03, 0x45, 0x08, // add eax,dword ptr [arg]0x5D, // pop ebp0xC3 // ret};DoubleNum^ pDoubleNum = (DoubleNum^)Marshal::GetDelegateForFunctionPointer((IntPtr)pNative, DoubleNum::typeid);Console::WriteLine(pDoubleNum(19));

ToohrVyk

Mar 6, 2008 at 5:04 AM

What you would really like to do is write an efficient routine in C#.

My computer isn't top-of-the-line, but it still manages to generate 145k bytes in less than 400 milliseconds without any special optimization effort on my part...

byte [] output = new byte[input.Length / 2];byte a = 0; int i = 0;foreach (char c in input){  byte x = hex(c);  if (i % 2 == 0) a = x;  else output[i/2] = (byte)(a * 16 + x);  ++i;}

Where hex uses a straightforward switch statement to return the 0-15 value of an 0-9A-Fa-f character.

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