Commodore Amiga A500 - Page 157

janus.h-the software data structures for the jams board
Copyright
0 1986, Commodore Amiga Inc., All rights reserved
/* all bytes described here are described in the byte order of the
* 8088. Note that words and longwords in these structures will be
* accessed from the word access space to preserve the byte order in
* a word - the 8088 will access longwords by reversing the words:
* like a 68000 access to the word access memory.
*/
/* JanusMemHead - a data structure roughly analogous to an exec
mem chunk.
* It is used to keep track of memory used between the 8088 and the
68000.
*/
struct JanusMemHead [
UBYTE jmhLock; /* lock byte between
processors
*/
UBYTE jmhpad0;
APTR jmh68000Base; /* rptr's are relative to this */
UWORD jmh8088Segment; /* segment base for 8088 */
RPTR jmhFirst; /* offset to first free chunk *l
RPTR jmhMax: /* max allowable index */
UWORD jmhFree: /* total number of free
bytes
-1 *l
l:
/* JanusMemChunk - keep track of individualy freed chunks of
memory.
* Memory Chunks are longword aligned in this memory.
*l
struct JanusMemChunk [
RPTR jmc-Next;
UWORD jmc-Size;
l:
/* rptr to next free chunk */
/* size of chunk -1 */
#ifdef undef
this stuff
is saved for future use, but is not yet thought out
/* JanusList - an RPTWExec style list header.
*/
struct JanusList [
RPTR jl-Head;
RPTR jl-Tail;
RPTR
jl-TailPred:
UBYTE j l-Lock; /* lock byte between
processors