Pancake Memory LIFO Queue

Pancake Memory LIFO Queue

An alternative memory management scheme such as pancaking can be utilized. This is where a base (or sub-base) level is set and the next available memory pointer is merely advanced by the amount of memory needed. There is no memory-free function as memory is merely disposed of by resetting the memory available back to its original base (in essence, abandoning the memory), then merely making sure the base is on a 16-byte alignment. This is like a bottom based processor stack. A free memory pointer is preset to the bottom of the stack at the physical base level of that memory. As data is loaded into memory, the free pointer is moved higher up in memory. When it is decided it is time to release that memory, all allocated objects are instantly thrown away by merely resetting the free pointer to the base level again. Console games sometimes use this method to keep code space from having to deal with individual deallocations.

Obviously, since there is no need for reallocations, or freeing of memory, then there is no need for a header either.

There are other schemes. Just make sure your memory is 16-byte aligned. Now that any possible memory allocation alignment problems have been taken care of up front, it is time to move on to the good stuff.

When one orders "all you can eat" pancakes, either a short stack or a tall stack is delivered to your table. If you have not finished eating the stack of pancakes and the server brings you more, you do not pick them all up and place them under your older pancakes; you have them placed on top of those already on your plate. So this would be considered a LIFO (last in, first out) system. Those new pancakes will be the first to be eaten, will they not?

Well, a computer stack is like that. Memory is typically allocated from the bottom up, and data in that memory is low address to high address oriented. The computer stack starts from the top of memory and works its way down, and hopefully the two ends do not meet or boom! That is why you have to watch recursive functions; if they "curse" too much, they run out of memory. We will go into a little more depth as we discuss the PUSH and POP instructions.



32.64-Bit 80X86 Assembly Language Architecture
32/64-Bit 80x86 Assembly Language Architecture
ISBN: 1598220020
EAN: 2147483647
Year: 2003
Pages: 191

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