assemblyscript/std/impl/heap.ts

/// <reference path="../../assembly.d.ts" />

const ALIGN_LOG2: usize = 3;
const ALIGN_SIZE: usize = 1 << ALIGN_LOG2;
const ALIGN_MASK: usize = ALIGN_SIZE - 1;

let HEAP_OFFSET: usize = HEAP_START; // HEAP_START is a constant generated by the compiler

@global()
@struct()
class Heap {

  static allocate(size: usize): usize {
    const ptr: usize = HEAP_OFFSET;
    assert(ptr + size <= (<usize>current_memory() << 16));
    if (((HEAP_OFFSET += size) & ALIGN_MASK) != 0) // align next offset
      HEAP_OFFSET = (HEAP_OFFSET | ALIGN_MASK) + 1;
    return ptr;
  }

  static dispose(ptr: usize): void {
    // just a big chunk of non-disposable memory for now
  }

  static get used(): usize {
    return HEAP_OFFSET - HEAP_START;
  }

  static get free(): usize {
    return (<usize>current_memory() << 16) - HEAP_OFFSET;
  }

  static get size(): usize {
    return (<usize>current_memory() << 16) - HEAP_START;
  }

  private constructor() {}
}