// Dynamic arenas. export arena, arena_with_size; import list; type chunk = {data: [u8], mut fill: uint}; type arena = {mut chunks: list::list<@chunk>}; fn chunk(size: uint) -> @chunk { @{ data: vec::from_elem(size, 0u8), mut fill: 0u } } fn arena_with_size(initial_size: uint) -> arena { ret {mut chunks: list::cons(chunk(initial_size), @list::nil)}; } fn arena() -> arena { arena_with_size(32u) } impl arena for arena { unsafe fn alloc(n_bytes: uint) -> &self.T { let mut head = list::head(self.chunks); if head.fill + n_bytes > vec::len(head.data) { // Allocate a new chunk. let new_min_chunk_size = uint::max(n_bytes, vec::len(head.data)); head = chunk(uint::next_power_of_two(new_min_chunk_size)); self.chunks = list::cons(head, @self.chunks); } let start = vec::unsafe::to_ptr(head.data); let p = ptr::offset(start, head.fill); head.fill += n_bytes; ret unsafe::reinterpret_cast(p); } }