Commodore Amiga A500 Technical Reference Manual page 157

janus.h-the software data structures for the j a m s 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 t o 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