First implementation of per-chunk CRC32 check. This is triggered

- by the right-click+Force Check on files.
- when a global hash on a downloaded file does not match the announced hash.

When a CRC map check is ordered, the CRC map is requested to one of the sources for the current file download.
When received, all downloaded chunks are checked w.r.t the reference CRC and marked as not done if the CRCs do not match.
The exchange of CRC32 map and requests has been tested, as well as CRC map checking during download (force check).

To be implemented soon:
    - caching of CRC32 maps (although these are fast to compute)
    - CRC32 map packets for normal downloads. For now these work only for turtle tunnels.
    - handling of errors if the CRC never comes. For now, the download will stay stuck in "Checking..." mode.

So, don't play too much with the force check feature for now...





git-svn-id: http://svn.code.sf.net/p/retroshare/code/trunk@3310 b45a01b8-16f6-495d-af2f-9b41ad6348cc

libretroshare/src/ft/fttransfermodule.h

@@ -144,6 +144,8 @@ public:
   bool cancelFileTransferUpward();
   bool completeFileTransfer();
   bool isCheckingHash() ;
+  void forceCheck() ;
+  void addCRC32Map(const CRC32Map& map) ;
 
   //interface to multiplex module
   bool recvFileData(std::string peerId, uint64_t offset, 
@@ -189,7 +191,10 @@ private:
   double desiredRate;
   double actualRate;
 
-  CRC32Map _crc32map ;
+  CRC32Map _crcmap ;
+  uint32_t _crcmap_state ;
+  time_t   _crcmap_last_asked_time ;
+  int 	  _crcmap_last_source_id ;
 
   ftFileStatus mFileStatus; //used for pause/resume file transfer