Re: Quick question about AUXMOVE

["Bill Buckels" <bbuckels@mts.net>]

"Bill Buckels" <bbuckels@mts.net> wrote:

 > Not anything especially special (the usual things) except not to 
overwrite anything when you are moving your data around...

And if you are loading data from disk to share between programs or overlays 
and you don't want to duplicate loading something that is already in memory 
(in the interests of efficiency) you likely will want to establish a 
tracking method for what you already have loaded... fwiw here is another of 
my core routines from Aztec C that does exactly that:

(refer to my memory map illustration at 
http://www.appleoldies.ca/apmap.gif )

/* the address of 2048 in main memory is used             */
/* for the ems signature which reserves 40 bytes          */
/* this is the first line of the text screen page 2       */
/* the ems buffer start is set to 0x0C00 in aux memory    */

/* this is the area directly above the secondary page of video ram    */
/* the auxilliary memory map for the apple 2C indicates that areas    */
/* below this have memory "holes" which are reserved or assigned even */
/* though zero page and the hardware stack finish at 0x200            */

/* in Main Memory... */
/* a 4000 byte buffer is used above where we store the font   */
/* at 0x0C00+1096+24 =4192 as a temporary IO buffer           */
/* to transfer the data to the upper ram banks                */
/* this avoids text screen page 2 and is below the prodos load address */


#include <stdio.h>
#include <fcntl.h>
#include <prodos.h>
#include <sgtty.h>
#include <device.h>
#include <sysfunc.h>


/* loads a library file */
emslode(name,libsize)
char *name;
unsigned libsize;
{
   int fh;
   int emscheck();
   unsigned int i;
   unsigned packet, straggler;
   unsigned himem,lomem;

   /* don't load the library if it's too big...               */
   /* don't load the library if it's in high memory already   */
   /* step 1... get the signature... this is the library name */
   /* if the library is already in memory this will likely be there  */
   /* when we exit we erase this to make sure. */

   /* step 2... compare and return -2 if it's already there */
   /* otherwise continue */

   if(libsize>46080)return -3;

   if(emscheck(name)!=0)return -2;

   if((fh = open(name,O_RDONLY,0xC3))==-1)
   {
    emsoff();
    return -1;
    }

   packet=    libsize/4000;         /* primary number of reads */
   straggler= libsize%4000;         /* remainder of reads      */

   himem = 0x0C00;
   lomem = 0x0C00+1096+24;

   /* do the bulk of the work and then the remainder */


   i=0;
   while(i<packet)
   {
   read(fh,(char *)lomem,4000);
   maintoaux(lomem,lomem+4000-1,himem);
   himem+=4000;
   i++;
   }

   if(straggler>0)
   {
   read(fh,(char *)lomem,straggler);
   maintoaux(lomem,lomem+straggler-1,himem);
   }
   close(fh);

   strcpy((char *)2048,name);
   /* Step 3... now do the signature... and return */
   return 0;

}



/* sign off the upper memory at 2048  */
/* the apple has no standard for this */
/* unlike the IBM LIM convention      */

emscheck(name)
char *name;
{
   char *sigbuf=(char *)2048;
   int target;

   unsigned int i;

   /* don't load the library if it's in high memory already   */
   /* step 1... get the signature... this is the library name */
   /* if the library is already in memory this will likely be there  */
   /* when we exit we erase this to make sure. */

   target=strlen(name);

   /* step 2... compare and return -2 if it's already there */
   /* otherwise return 0 */

   i=0;
   while(i<target)
   {
     if(name[i]!=sigbuf[i])return 0;
     i++;
     }

   return -2;
}


/* don't care what's there... unsign the ems when we leave */
/* that way we're not tripping over ourselves...           */
/* all we need to do is put zeros there...                 */
/* names don't contain zeros...                            */

emsoff()
{
   char *signoff=(char *)2048;
   int i=0;

   while(i++<40)*signoff++=0;
}