大文件写：

大文件写：HttpSM::set_next_stateHttpSM::do_cache_prepare_writeHttpSM::do_cache_prepare_actionHttpCacheSM::open_write1.  CacheProcessor::open_write  --> 22.  Cache::open_write  --> 3 //new_CacheVC3.  CacheVC::callcont  --> 44.  CacheVC::openWriteMain  --> 5,65.  CacheVC::calluser  --> 46.  CacheVC::handleWrite  --> 7(write every fragment except the last one),8(write the last fragment done ),11(write head to cache done)    CacheVC::handleWriteLock7.  CacheVC::openWriteWriteDone  --> 48.  CacheVC::openWriteCloseDataDone  --> 9(dir_insert,write last fragment of the body done)9.  CacheVC::openWriteCloseHead  --> 1010. CacheVC::updateVector  --> 611. CacheVC::openWriteCloseHeadDone --> 12(dir_insert,use first_key for head)12. CacheVC::openWriteCloseDir  --> 1313. free_CacheVC对于大文件的读写，程序逻辑相对要复杂一些。结合小文件写以及第一章最后对大文件的存储策略的描述，大文件写有以下几点不同：(1) 大文件是先写body的fragment，写完所有fragment后，再写head。head使用object生成的first_key作为它的key值找到对应的索引保存相关元信息，而对于fragment，第一个fragment使用随机数算法生成一个数作为它的key值，从第二个开始，每个fragment都是以前一个fragment的key值作为种子，通过随机数算法生成一个key值。(2) 如果一个body被分成了几个fragment，则写第一个至倒数第二个fragment结束后程序逻辑走到openWriteWriteDone，而写最后一个fragment结束后程序逻辑走到openWriteCloseDataDone，代表写body完成。

4.4M文件的写流程：HttpSM::do_cache_prepare_writeHttpSM::do_cache_prepare_actionHttpCacheSM::open_writeCacheProcessor::open_writeCache::open_writenew_CacheVCrand_CacheKeyCacheVC::callcontCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::handleWriteLockCacheVC::handleWriteVol::aggWriteCacheVC::openWriteWriteDonenext_CacheKeyCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::handleWriteLockCacheVC::handleWriteVol::aggWriteCacheVC::openWriteWriteDonenext_CacheKeyCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::handleWriteLockCacheVC::handleWriteVol::aggWriteCacheVC::openWriteWriteDonenext_CacheKeyCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::handleWriteLockCacheVC::handleWriteVol::aggWriteCacheVC::openWriteWriteDonenext_CacheKeyCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteMainCacheVC::calluserCacheVC::openWriteCloseCacheVC::handleWriteLockCacheVC::handleWriteVol::aggWriteCacheVC::openWriteCloseDataDonenext_CacheKeyCacheVC::openWriteCloseHeadCacheVC::updateVectorCacheVC::handleWriteVol::aggWriteCacheVC::openWriteCloseHeadDoneCacheVC::openWriteCloseDirfree_CacheVC