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      = $; { when used with FileCreate, atomically creates the file only if it doesn't exist, fails otherwise }

  fmOpenRead       = $; { Open the file for reading only.   }
  fmOpenWrite      = $; { Open the file for writing only. Writing to the file completely replaces the current contents.   }
  fmOpenReadWrite  = $; { Open the file to modify the current contents rather than replace them. }

  fmShareCompat    = $ platform; {  DOS compatibility mode is not portable, Sharing is compatible with the way FCBs are opened.   }
  fmShareExclusive = $; { Other applications can not open the file for any reason.    }
  fmShareDenyWrite = $; { Other applications can open the file for reading but not for writing.  }
  fmShareDenyRead  = $ platform; { Other applications can open the file for writing but not for reading, write-only not supported on all platforms }
  fmShareDenyNone  = $; { No attempt is made to prevent other applications from reading from or writing to the file }