Scrolling functions

void vertical_scroll(char* buffer, int shift) {
    int i, j;
    char column[64];
    shift %= 64;
    for(i=0 ; i<16 ; i++) {
        for(j=0 ; j<64 ; j++) column[j] = buffer[(j<<4)+i];
        for(j=0 ; j<64 ; j++) buffer[(j<<4)+i] = column[(j-shift+64)&63];
    }
}

void horizontal_scroll(unsigned char* buffer, int shift) {
    int i, j;
    unsigned char line[16], Bshift, next;
    unsigned short word;
    shift %= 128;
    Bshift = 8-(shift&7);
    for(i=0 ; i<64 ; i++) {
        for(j=0 ; j<16 ; j++) line[j] = buffer[(i<<4)+((j-(shift>>3)+15)&15)];
        next = line[15];
        buffer[(i<<4)+15] = 0;
        for(j=15 ; j>0 ; j--) {
            word = next << Bshift;
            next = line[j-1];
            buffer[(i<<4)+j] |= *((char*)&word+1);
            buffer[(i<<4)+j-1] = *((char*)&word);
        }
        word = next << Bshift;
        buffer[(i<<4)] |= *((char*)&word+1);
        buffer[(i<<4)+15] |= *((char*)&word);
    }
}