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Improve arena allocator a bit

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dcodeIO
2018-01-28 19:14:20 +01:00
parent 219ee81bc9
commit 78debee847
10 changed files with 1357 additions and 2733 deletions
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26
std/assembly/memory/arena.ts
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@ -1,23 +1,25 @@
// An simple arena allocator that provides a `clear_memory` function to reset
// everything to the initial state. A user must have to make sure that there
// a no more references to cleared memory.
// A simple arena allocator that provides a `clear_memory` function to reset
// the heap to its initial state. A user has to make sure that there are no
// more references to cleared memory afterwards. Always aligns to 8 bytes.
const ALIGN_LOG2: usize = 3;
const ALIGN_SIZE: usize = 1 << ALIGN_LOG2;
const ALIGN_MASK: usize = ALIGN_SIZE - 1;
var HEAP_OFFSET: usize = HEAP_BASE; // generated by the compiler
var HEAP_OFFSET: usize = HEAP_BASE;
export function allocate_memory(size: usize): usize {
if (!size) return 0;
var len: i32 = current_memory();
if (HEAP_OFFSET + size > <usize>len << 16)
if(grow_memory(max<i32>(<i32>ceil<f64>(<f64>size / 65536), len * 2 - len)) < 0)
unreachable();
var ptr: usize = HEAP_OFFSET;
if ((HEAP_OFFSET += size) & ALIGN_MASK) // align next offset
HEAP_OFFSET = (HEAP_OFFSET | ALIGN_MASK) + 1;
set_memory(ptr, 0, size);
var ptr = HEAP_OFFSET;
var off = (ptr + size + ALIGN_MASK) & ~ALIGN_MASK;
var avail = <usize>current_memory() << 16;
if (off > avail && grow_memory(
max(
(((off + 0xffff) & ~0xffff) - avail) >> 16, // minimum required pages
avail >> 16 // at least double memory
)
) < 0) unreachable(); // out of memory
HEAP_OFFSET = off;
return ptr;
}