SIMD high performace xorcpy in C

In my current project I need a high performace xorcpy implemented in C. Here is my implementation to share and it is tested on my Xeon E5-2680 PC, it reaches almost 1.7GB/s.

#include <emmintrin.h>
...
__forceinline unsigned char* xorcpy(unsigned char* dst, const unsigned char* src, unsigned block_size)
{
    // Do the bulk of the copy a __m128i at a time, for faster speed
    __m128i* mto = (__m128i*)dst;
    const __m128i* mfrom = (__m128i*)(src);
    for(int i=(block_size / sizeof(__m128i) - 1); i>=0; i--)
    {
        __m128i xmm1 = _mm_loadu_si128(mto);
        __m128i xmm2 = _mm_loadu_si128(mfrom);

        xmm1 = _mm_xor_si128(xmm1, xmm2);     //  XOR 16 bytes
        _mm_storeu_si128(mto, xmm1);
        ++mto;
        ++mfrom;
    }

    // The rest bytes we have to do a byte a time though
    unsigned char* cto = (unsigned char*) mto;
    const unsigned char* cfrom = (const unsigned char*)mfrom;
    for(int i=(block_size % sizeof(__m128i)) - 1; i>=0; i--)
    {
        *cto++ ^= (*cfrom++);
    }
    return dst;
}

Share Brother HL-2130 through Lenovo Iomega EZ Media & Backup Center USB port

Recently I bought a Lenovo® EZ Media and Backup Center to share video and photos within my home network. I also have a Brother HL-2130 Mono Laser long time back which is connected to my PC USB port. Every time, when I want to print something, I have to keep my PC on. I am thinking is there a way to connect my Brother HL-2130 Mono Laser to Lenovo® EZ Media and Backup Center USB port, and sharing HL-2130 within my home network. I can print from any devices even from my iPad, Andaroid phone.

After few hours trying, I finally successfully share HL-2130 through Lenovo NAS USB port. This is the post I found from internet, and it gives the detailed steps.

http://forum.nas-central.org/viewtopic.php?f=279&t=8679

Here are the steps I followed to install HL-2130:

  1. In PC’s browser, go to http://lenovoez/manage/login.html?pg=/manage/diagnostics.html. Enable SSH login
  2. Download putty, and login your Lenovo NAS through SSH
  3. Connect HL-2130 to Lenovo NAS USB Port
  4. Issue command “/etc/init.d/cups start” to start CUPS service
  5. In PC’s browser, go to http://lenovoez:631/admin
  6. Click “Add Printer” and find Brother_HL-2130_series printer from local printers.
  7. In “Printers” tab, you will find Brother_HL-2130_series. Actually, the address for HL-2130 is http://lenovoez:631/printers/Brother_HL-2130_series
  8. Download latest HL-2130 Windows OS printer driver from http://support.brother.com/g/b/downloadtop.aspx?c=us_ot&lang=en&prod=hl2130_all
  9. Go back to PC, and Add new printer, give the printer address http://lenovoez:631/printers/Brother_HL-2130_series
  10. Click “Have a disk” and install HL-2130 printer driver.
  11. Follow the steps in the post to make cups to run every time the box reloads.