Delphi TFileStream 打开模式与共享模式

  { TFileStream create mode }
  fmCreate = $FF00;         { Create a file with the given name. If a file with the given name exists, open the file in write mode.  }
  fmExclusive      = $0004; { when used with FileCreate, atomically creates the file only if it doesn't exist, fails otherwise }
  
  fmOpenRead       = $0000; { Open the file for reading only.   }
  fmOpenWrite      = $0001; { Open the file for writing only. Writing to the file completely replaces the current contents.   } 
  fmOpenReadWrite  = $0002; { Open the file to modify the current contents rather than replace them. }
  
  fmShareCompat    = $0000 platform; {  DOS compatibility mode is not portable, Sharing is compatible with the way FCBs are opened.   }
  fmShareExclusive = $0010; { Other applications can not open the file for any reason.    }
  fmShareDenyWrite = $0020; { Other applications can open the file for reading but not for writing.  }
  fmShareDenyRead  = $0030 platform; { Other applications can open the file for writing but not for reading, write-only not supported on all platforms }
  fmShareDenyNone  = $0040; { No attempt is made to prevent other applications from reading from or writing to the file }