Stack Allocator FAQ.
Written by Alex Verstak.
License: use at your own risk.
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Q1: What is stack allocator?
A1: It's the most primitive memory manager I know of.

Q2: How does it generally perform?
A2: Good locality, no fragmentation, guaranteed speed O(1).

Q3: What is it for?
A3: It's for managing physical RAM.

Q4: Why stack allocator for RAM?
A4: It has several advantages:
1. Quick allocation/deallocation.
2. No headers for free or used blocks, only a small fixed-size stack.
3. Convenient block size 4K.
4. Good locality.

Q5: Why not use stack allocator for all physical RAM?
A5: Because it supports only one block size.

Q6: Why not use stack allocator for virtual RAM?
A6: See Q5.

Q7: What cookies does it have?
Q7: There are some:
1. Deallocation at fixed address.
2. It never touches RAM being managed.
3. Therefore, one can easily cut out the regions with no RAM.

Q8: Can I have several stack allocators?
A8: No.

Q9: How long is a page?
A9: 4KB by default. You can change it to 8, 16, etc by defining
ALLOCATION_GRANULARITY=1, 2, etc.

Q10: How dumb-proof is it?
A10: Not at all. Only minimal error checking.

Q11: How to compile it?
A11: I hope, any ANSI C compiler will do. I used GCC 2.8.1. Code uses
two include files: assert.h for assert and stdio.h for printf.

Q12: How to integrate it in OS?
A12: It needs access to several static variables and a tree.
Re-entrancy is not allowed. Calling convention is, well, C.
The routines won't eat more than 128 bytes of stack.

Q13: Example, please!!!
A13:
#include "stack-a.h"
                                         //Suggested Initialization
int s=stacka_size(16384*1024);           //get tree size for 16MB
buddy_init((char*)0x74000,0x1000000,0x1000000);
                                         //initialize 16MB starting at 16MB,
                                         //use RAM at 0x74000 for stack
stacka_free_at(0x1000000,0x800000);      //free RAM 16MB-24MB
stacka_free_at(0x1c00000,0x400000);      //free RAM 28MB-32MB
...
#ifdef DEBUG
stacka_stat();                           //print statistics
#endif
...                                      //Suggested Runtime
void *f=stacka_alloc(4096);              //allocate page for VM
stacka_free(f);                          //...and free it

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end of stack allocator  FAQ