Solar wrote:
Erm... I assume abusharaf got malloc() working allright, but wants to implement operator new() and operator delete(), the ones required by C++...
The new and delete operators shouldn't be that difficult, when you have a working malloc(). See the attached files. Remove the exception stuff if it gives you problems (it however should disable automaticly when supplying the parameter -fno-exceptions to GCC).
abuashraf wrote:
No Solar until now i didn't get "malloc()" and my real problem is about
it, and i don't know how malloc works...so i can't implement it.
it, and i don't know how malloc works...so i can't implement it.
Look at the links I gave you.
A very simple solution (but not very efficient in terms of speed) is to maintain a linked list with free chunks of memory and a linked list with used chunks of memory. When malloc() gets called with a size it has to search the linked list with free chunks for a chunk that is exactly the size or greater. Now remove the chunk from the list, split it up if it is greater than the size allocated, add the allocated chunk to the not-free linked list and eventually add the remaining free chunk to the free linked list. When free() gets called it gets a bit more complicated because of fragmentation. You remove the chunk from the not-free linked list and add it to the free linked-list, which should actually be sorted in terms of the memory position. Now see if the just inserted chunk is bound to the previous and/or next chunk and merge them if it does.
The algorithm is O(N) for N the number of allocated/free chunks, which is very bad for a memory allocator. But it works and it almost simple to implement.
When first initialized the linked list with free chunks has to be created. For that you have to know the available memory of your system. If booting using the multiboot standard (ie. GRUB) you can access this information. Just add the free memory blocks GRUBs tell you about to the linked list and that's it.
A lot of improvement can be made to the memory manager. Some of these improvements are discussed in the article I mentioned: http://gee.cs.oswego.edu/dl/html/malloc.html
Hope you get it to work.
| Attachments: |
File comment: C++ implementation of New. It is just calling malloc(), free() and abort() if failing (or throwing an exception).
new.cpp [1.12 KiB]
Downloaded 44 times |
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File comment: Header file for New. Only used when special calls are used. (Rename to no extension for proper C++ inclusion)
new.h [1.03 KiB]
Downloaded 71 times |
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