ES6 Sample

buffer.js

import { Primitive } from 'primitive';

let Buffer = Primitive.extend((Super) => {

  return {
    init (ArrayType, itemSize, pageSize) {
      this.used = new Set();
      this.freeByteIndices = [];
      this.pages = [];
      this.itemSize = itemSize;
      this.pageSize = pageSize || itemSize * 100;

      if (this.pageSize < this.itemSize) {
        throw new Error('Invalid page size (cannot be less than item size).');
      }

      this.maxAllocatedItems = 0;
      this.ArrayType = ArrayType;
      this.itemInitializerValues = this.allocate();
    },
    get itemByteLength () {
      return this.itemSize * this.ArrayType.BYTES_PER_ELEMENT;
    },
    get lastItemByteIndex () {
      return ((this.maxAllocatedItems - 1) * this.itemByteLength) % this.pageByteLength;
    },
    get pageByteLength () {
      return this.pageSize * this.ArrayType.BYTES_PER_ELEMENT;
    },
    get currentPageIsFull () {
      return this.lastItemByteIndex >= this.pageByteLength - this.itemByteLength;
    },
    get currentPage () {
      return this.pages[this.currentPageIndex];
    },
    get currentPageIndex () {
      return this.pages.length - 1;
    },
    get numberOfPages () {
      return this.pages.length;
    },
    get itemsPerPage () {
      return Math.floor(this.pageSize / this.itemSize);
    },
    allocate () {
      let page;
      let itemByteIndex;
      let item;

      if (this.freeByteIndices.length) {
        itemByteIndex = this.freeByteIndices.pop();
        page = this.pages[this.freeByteIndices.pop()];
      }

      if (itemByteIndex === undefined) {
        if (!this.pages.length || this.currentPageIsFull) {
          this.pages.push(new ArrayBuffer(this.pageByteLength));
        }

        ++this.maxAllocatedItems;
        itemByteIndex = this.lastItemByteIndex
        page = this.currentPage;
      }

      item = new this.ArrayType(page, itemByteIndex, this.itemSize);
      item.bufferByteIndex = itemByteIndex;
      item.pageIndex = this.currentPageIndex;

      return item;
    },
    free (item) {
      this.freeByteIndices.push(item.pageIndex, item.bufferByteIndex);
      item.set(this.itemInitializerValues);
      item.free = true;
    }
  };
});

export { Buffer }