source: buchla-68k/orig/GEMDOS/BLT.C

/*
   =============================================================================
        blt.c -- block image transfer functions for the Atari
        Version 1 -- 1988-08-15 -- D.N. Lynx Crowe
   =============================================================================
*/

#include "osbind.h"

extern short    gl_hres;                /* horizontal resolution */

cpy_raster(src, dst, width )
register short  *src, *dst, width;
{
        if ((long)src > (long)dst) {

                while (width--)
                        *dst++ = *src++;

        } else {

                while (width--)
                        *(dst + width) = *(src + width);
        }
}

cpy_block(src_x, src_y, src_w, src_h, dst_x, dst_y )
short src_x, src_y;
register short src_w, src_h;
short dst_x, dst_y;
{
        register short  *pbase, *src_base, *dst_base;

        pbase = (short *)Physbase();

        if (src_y > dst_y) {

                (long)src_base = (long)pbase + (src_y * gl_hres) + src_x;
                (long)dst_base = (long)pbase + (dst_y * gl_hres) + dst_x;

                while (src_h--) {

                        cpy_raster(src_base, dst_base, src_w);
                        src_base += gl_hres;
                        dst_base += gl_hres;
                }

        } else {

                (long)src_base = (long)pbase + ((src_y + src_h) * gl_hres);
                (long)dst_base = (long)pbase + ((dst_y + src_h) * gl_hres);

                while (src_h--) {

                        cpy_raster(src_base, dst_base, src_w);
                        src_base -= gl_hres;
                        dst_base -= gl_hres;
                }
        }
}