improved 8-byte strrev

gistfile1.c

void strrev(char *strStart, const int len){
    
    char* strEnd = strStart + len;
    
    while (strStart <= (strEnd -= 8)){
        
        __uint64_t buf = *(__uint64_t*)strStart;
        
        *(__uint64_t*)strStart = *(__uint64_t*)strEnd;
        __asm__ ("bswap %0" : "=r" (*(__uint64_t*)strStart) : "0" (*(__uint64_t*)strStart));
        
        *(__uint64_t*)strEnd = buf;
        __asm__ ("bswap %0" : "=r" (*(__uint64_t*)strEnd) : "0" (*(__uint64_t*)strEnd));
        
       
        strStart += 8;
        
    }
    
    strEnd += (8 > len ? 7 : 8);
    
    // do the rest of the modulo 8 bytes
    while (strStart < strEnd) {
        char charBuf = *strStart;
        *strStart = *strEnd;
        *strEnd = charBuf;
        
        --strEnd;
        ++strStart;
    }
    
}