public void setFileFromOffset(final long fileFromOffset) {
        this.FileFromOffset = fileFromOffset;
    }
File header:
<pre>
  magic bytes       first log index   file from offset       reserved
  [0x20 0x20]      [... 8 bytes...]   [... 8 bytes...]   [... 8 bytes...]
<pre>
@author hzh (642256541@qq.com)
jraft-extension/java-log-storage-impl/src/main/java/com/alipay/sofa/jraft/storage/file/FileHeader.java