Hi Tomas On Tue, Sep 25, 2012 at 7:09 PM, Graeme Russ <graeme.r...@gmail.com> wrote:
> We should implement each of malloc(), free(), calloc(), and realloc(). > > Don't worry about reclaiming and reusing space with a proper free() > implementation. Remember, all memory allocated on the early heap must be > relocated anyway. > > Maybe if you add a size_t value immediately before the allocated space which > stores the block size. So: > > size_t *bytes_ptr = ptr; > bytes_ptr--; > size_t bytes = *bytes_ptr; > > gives you the block size I've been thinking about this a bit more, and for the sake of 4 bytes, this additional 'size' member could be quite handy: - We effectively end up with a linked-list of allocated blocks - free() could set the high bit to tag the block as 'de-allocated' - When a block is relocated into the permanent heap, free() should be called on the source (early heap) block - We can call a 'cleanup' function after early heap is no longer needed and check that every block has the high bit set - We can re-use blocks by scanning for a tagged block with the same size (usefull for drivers that allocate temporary buffers which are always the same size) - If there are no early heaps with enough space for a given malloc operation, but there is a tagged block that is larger than the requested size, we can split tagged blocks Remebering back to when I suggested a list of relocation helpers (one for each allocated block), I think we can implement that as an additional field in the block header (stretching the header to 8 bytes). This can come later. Regards, Graeme _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
