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