code: function getOffsets(size, total, delimiter) {
      if (total === 0) {
          return [];
      }
      if (total < size) {
          return [{ length: total, offset: 0 }];
      }
      const fullChunks = Math.floor(total / size);
      const delta = delimiter.length;
      const length = size + delta;
      const chunks = [];
      for (let chunk = 1; chunk < fullChunks; chunk += 1) {
          chunks.push({ length, offset: (chunk * size) - delta });
      }
      // First chunk doesn't need +/- delta.
      chunks.unshift({ offset: 0, length: size });
      // When last chunk is not full chunk size.
      const lastChunk = total % size;
      if (lastChunk > 0) {
          chunks.push({ offset: (fullChunks * size) - delta, length: lastChunk + delta });
      }
      return chunks;
  }
docs: [{offset, length}] of chunks `size` assuming `delimiter` for a file with `total` size.