: Hello,
: Can someone give me some pointers on how to implement a doubly linked list while still staying in the 8086 arch. (16-bit). Yes, this is for a class project.
http://www.cs.uakron.edu/~margush/306/PRG4.html
: Thanks.
:
If you know C, write it out in C first and convert (no, I DON'T mean -S). Converting to and from C/ASM is something I've gotten fairly good at. Either way, if you can't implement it in C (assuming you DO know C) then you won't be able to in assembly. The assembly should flow right from the C source when you finish.
Whether you follow my advice (if relevant) or not here is some more.
*Preliminary note: I don't target 8086 and I'm not going to really bother making sure this is 8086 compatible. Nothing I'm going to write is going to be inconvertible. *
Basically, you'll have some structure that holds a next and a prev pointer and whatever data. So, let's say it holds WORDs. You might have something like the following (using the syntax of your assembler, this is TASM/MASM syntax)...
NODE STRUCT
data dw ? ;the data
next dw ? ;next near pointer
prev dw ? ;prev near pointer
NODE ENDS
From there you just need to think of what you have to do for a linked-list.
eg
Insert at head
Here's some quick C assuming an analogous structure...
node->next=head;
node->prev=NULL;
head->prev=node;
head=node;
and a possible assembly interpretation (TASM syntax, though it will probably work with MASM, others will likely need some fixing)
;si=node di=head
mov [si].NODE.next, di
mov [si].NODE.prev, 0
mov [di].NODE.prev, si
mov di, si
You can see how this flows straight from the C.
Compatibility notes (if you are using a different assembler)
The most general (ie least features needed of the assembler) way to rewrite this would be to replace the STRUCT with a set of symbolic constants that evaluated to the proper offset (in this case it would look like the following in TASM... (the names aren't important)
NODE_DATA=0
NODE_NEXT=2
NODE_PREV=4
)
Then to use it you'd simply add (this is all TASM does behind the scenes). Once again, what it might look like in TASM.
mov [si].NODE.next,di
is now
mov [si+NODE_NEXT],di
"We can't do nothing and think someone else will make it right."
-Kyoto Now, Bad Religion
