analloc

This is a completely stand-alone memory allocator which uses Buddy memory allocation under the hood. The point of analloc is to provide a flexible, lightweight allocator to operating system kernels.

Usage

Initializing analloc is a simple matter. The usage is roughly as follows:

• Reserve a chunk of physical memory for use with analloc. This chunk may begin with some pre-allocated memory.
• Allocate some memory for an analloc_t structure. This memory may be part of the pre-allocated memory in the physical memory chunk you plan to use for analloc.
• Call analloc_with_chunk(). You pass in
  • a pointer to the analloc_t structure
  • a pointer to the absolute beginning of the buffer
  • the number of bytes used by your pre-allocated data at the beginning of the buffer. If you use another location to store the analloc_t, this may very well be 0.
  • the page size. This specifies the minimum amount of bytes the user should be able to allocate. See the note on Page Size below for more.
• Calculate the number of bytes actually used by analloc. This is equal to context->page << context->depth where context is your analloc_t.

To allocate some data, use analloc_alloc(), to free data use analloc_free(), and to resize data, use analloc_realloc().

Things to Note

Page Size

When you initialize an allocator, you specify a page argument. Whenever a call to analloc_alloc() or analloc_realloc() succeeds, the allocated chunk of memory will have length of the form 2^n * page where n is some non-negative integer. This means, for instance, that if your page size is 4096, and you try to allocate 4097 bytes, you will be given a chunk of 8192 bytes. This will not be a problem in my operating system, where mainly single pages will be allocated at once.

Synchronization

The analloc_t structure is designed for single-threaded access. If you plan on having multiple threads all capable of allocating memory (as I do in my OS), you will need a separate mutex system.

I don't want to store the damn size

Call analloc_mem_size and pass in a pointer to get its size. I still encourage keeping track of sizes if you can, since that reduces clock cycles.

License

This software is under the GNU GPL v1.