Thread: copying buffers

  1. #1
    h ֆhr s Nor's Avatar
    Join Date
    Nov 2001

    copying buffers

    blowfish requires data come in 64 bit blocks

    now should i use a loop to copy the data or memcpy() ???

    // NAME: blf_padData 
    //    pads data into 64-bit blocks
    //    void*        data    buffer you want to pad
    //    unsigned int  len    length in bits(uchar)
    //    int  &NumofBlocks    place to store num of 64 bit blocks
    unsigned long* blf_padData( void* data, const unsigned int len, int &NumofBlocks){
        unsigned int w,x,y,z;    //counters
        unsigned char* d;        //pointer to cast data into;
        unsigned long* pdata = 0;//pointer to the padded data.
        unsigned long  temp;
        if (!data)
            return NULL;
        d = (unsigned char*)data;
        //get the size of the buffer needed
        NumofBlocks = len/8;    //64-bit blocks
        if (0 != len%8)         //if it doesnt fit perfect then add a block
        //make the buffer
        pdata = (unsigned long*) malloc( 8 * NumofBlocks);    //8 = sizeof(unsigned long)*2  64-bit blocks
            w = 0;
        if (!pdata)
            return NULL;
        //copy all of data into pdata               
        for(x = 0, z = 0; x < NumofBlocks; x++){
            for(int loopc = 0; loopc < 2; loopc++){
                temp = 0x00000000;     
                for(y = 0; y < 4; y++){
                    temp <<= 8;        
                    if(z < len)
                        temp = temp | d[z];                 
                pdata[w] = temp;
        //memset(pdata, 0, 8*NumofBlocks);
        //memcpy( pdata, data, len);
        return pdata;
    Try to help all less knowledgeable than yourself, within
    the limits provided by time, complexity and tolerance.
    - Nor

  2. #2
    Toaster Zach L.'s Avatar
    Join Date
    Aug 2001
    memcpy should be faster.
    The word rap as it applies to music is the result of a peculiar phonological rule which has stripped the word of its initial voiceless velar stop.

  3. #3
    Registered User
    Join Date
    May 2003
    std::copy is the preferred way.

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