Adds the next chunk to this.
Adds the bytes defined by start and end-exclusive to this.
If isLast is true closes this.
Contrary to add the given chunk must not be held onto. Once the method
returns, it is safe to overwrite the data in it.
Source
void addSlice(List<int> chunk, int start, int end, bool isLast) {
add(chunk.sublist(start, end));
if (isLast) close();
}