Path: utzoo!utgpu!water!watmath!clyde!rutgers!gatech!mcnc!decvax!decwrl!pyramid!prls!philabs!lamont!adam
From: adam@lamont.Columbia.edu (adam levin)
Newsgroups: comp.sys.amiga
Subject: Copying to chip RAM
Message-ID: <442@lamont.Columbia.edu>
Date: 26 Mar 88 00:17:34 GMT
Organization: Lamont-Doherty Geological Observatory N.Y.
Lines: 65


I have a 'C' array which needs to be in chip RAM.  The examples I have found
declare the array, AllocMem some chip RAM, and copy the array into it.
This is wasteful if all one has is chip RAM, or if the program was linked
with Manx's +C option.  I wrote the following routine, and I'd like to know
if this is a reasonable way to avoid the unnecessary copy.  Must I #include
the value of FAST_STARTS, or is it available in some system structure?


/*  MemType - Given a starting address and a length, returns
              either MEMF_CHIP, MEMF_FAST, or both.
              25-Mar-1988  aklevin
*/

#include <exec/types.h>
#include <exec/memory.h>

#define FAST_STARTS	0x80000L

ULONG
MemType(start, length)
ULONG start, length;
{
	if (start >= FAST_STARTS) return(MEMF_FAST);
	if (start + length < FAST_STARTS) return (MEMF_CHIP);
	else return (MEMF_FAST | MEMF_CHIP);
}	/* end MemType() */



/*  Here is a code fragment to show how I use MemType():  */

int i;
USHORT *varipointer, pointer[] = { 0x0000, 0x0c80,... 0x0202 };

if (MemType((ULONG)pointer, (ULONG)sizeof(pointer)) == MEMF_CHIP)
	/*  If it is already in chip RAM, use the existing pointer.  */
	varipointer = pointer;
else {
	/*  Otherwise, attempt to allocate chip RAM for it.  */
	varipointer = (USHORT *)AllocMem((long)sizeof(pointer), MEMF_CHIP|MEMF_CLEAR);
	/*  If chip RAM was successfully allocated, copy the array into it.  */
	if (varipointer) {
		for(i=0; i<sizeof(pointer)/sizeof(USHORT); i++)
			varipointer[i] = pointer[i];
	} /* end if */
	/*  Otherwise exit (I made up the NO_CHIP_RAM constant).  */
	else exit(NO_CHIP_RAM);
} /* end else */

/*  From here on I use varipointer to access the array.  */


/*  To deallocate the memory:  */

/*  If the varipointer exists, and is not the same as pointer,
	it was allocated, so deallocate.  */
if (varipointer && varipointer != pointer)
	FreeMem(varipointer, (long)sizeof(pointer));

-- 
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Post:   Lamont-Doherty Geological Observatory / Palisades, NY 10964
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