断点续传时in.skip

断点续传里用到的一个重要方法就是inputstream的skip方法，但是在使用的时候有一点需要注意，就是skip不能保证你的输入流准确的跳过count个字节。

看看这个方法的介绍是怎么说的

 

Skips at most {@code byteCount} bytes in this stream. The number of actual
* bytes skipped may be anywhere between 0 and {@code byteCount}. 

Note the "at most" in the description of this method: this method may
* choose to skip fewer bytes than requested. Callers should <i>always</i>
* check the return value.

 所以单纯的只是 in.skip(count)是不行的，改成

int skip = (int) in.skip(m_currentBlockPos);

                    while(skip<m_currentBlockPos){

                        m_currentBlockPos-=skip;
                        skip = (int) in.skip(m_currentBlockPos);
                    }

 解决问题！