/*
 open source routing machine
 Copyright (C) Dennis Luxen, others 2010

 This program is free software; you can redistribute it and/or modify
 it under the terms of the GNU AFFERO General Public License as published by
 the Free Software Foundation; either version 3 of the License, or
 any later version.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU Affero General Public License
 along with this program; if not, write to the Free Software
 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 or see http://www.gnu.org/licenses/agpl.txt.
 */

#include "CRC32.h"

CRC32::CRC32() : crc(0) {
    crcFunction = detectBestCRC32C();
}

unsigned CRC32::SoftwareBasedCRC32(char *str, unsigned len, unsigned crc) {
    boost::crc_optimal<32, 0x1EDC6F41, 0x0, 0x0, true, true> CRC32_Processor;
    CRC32_Processor.process_bytes( str, len);
    return CRC32_Processor.checksum();
}

unsigned CRC32::SSEBasedCRC32( char *str, unsigned len, unsigned crc) {
    unsigned q=len/sizeof(unsigned),
            r=len%sizeof(unsigned),
            *p=(unsigned*)str/*, crc*/;

    //crc=0;
    while (q--) {
        __asm__ __volatile__(
                ".byte 0xf2, 0xf, 0x38, 0xf1, 0xf1;"
                :"=S"(crc)
                 :"0"(crc), "c"(*p)
        );
        ++p;
    }

    str=(char*)p;
    while (r--) {
        __asm__ __volatile__(
                ".byte 0xf2, 0xf, 0x38, 0xf1, 0xf1;"
                :"=S"(crc)
                 :"0"(crc), "c"(*str)
        );
        ++str;
    }
    return crc;
}

CRC32::CRC32CFunctionPtr CRC32::detectBestCRC32C() {
    static const int SSE42_BIT = 20;
    unsigned ecx = cpuid(1);
    bool hasSSE42 = ecx & (1 << SSE42_BIT);
    if (hasSSE42) {
        std::cout << "sse based" << std::endl;
        return &CRC32::SSEBasedCRC32; //crc32 hardware accelarated;
    } else {
        std::cout << "softbased" << std::endl;
        return &CRC32::SoftwareBasedCRC32; //crc32cSlicingBy8;
    }
}

unsigned CRC32::cpuid(unsigned functionInput) {
    unsigned eax;
    unsigned ebx;
    unsigned ecx;
    unsigned edx;
    asm("cpuid" : "=a" (eax), "=b" (ebx), "=c" (ecx), "=d" (edx) : "a" (functionInput));
    return ecx;
}

unsigned CRC32::operator()(char *str, unsigned len){
    crc =((*this).*(crcFunction))(str, len, crc);
    return crc;
}