Data update

Task/Truncate-a-file/FutureBasic/truncate-a-file.basic

@@ -0,0 +1,43 @@
+include "NSLog.incl"
+
+void local fn ShowFileContents( fileURL as CFURLRef )
+  CFStringRef string = fn StringWithContentsOfURL( fileURL, NSUTF8StringEncoding, NULL )
+  NSLog(@"%@",string)
+end fn
+
+void local fn TruncateFile( fileURL as CFURLRef, length as UInt64 )
+  ErrorRef err = NULL
+  FileHandleRef fh = fn FileHandleForUpdatingURL( fileURL, @err )
+  if ( !fh )
+    NSLog(@"%@",err)
+    return
+  end if
+
+  UInt64 offset
+  fn FileHandleSeekToEnd( fh, @offset, NULL )
+  if ( length >= offset )
+    NSLog(@"Error: Truncate length is not less than file length.")
+    return
+  end if
+
+  if ( fn FileHandleTruncateAtOffset( fh, length, @err ) )
+    fn ShowFileContents( fileURL )
+  else
+    NSLog(@"%@",err)
+  end if
+end fn
+
+void local fn Doit
+  // create
+  CFURLRef desktopURL = fn FileManagerURLForDirectory( NSDesktopDirectory, NSUserDomainMask )
+  CFURLRef fileURL = fn URLByAppendingPathComponent( desktopURL, @"MyFile.txt" )
+  fn StringWriteToURL( @"abcdefghijklmnopqrstuvwxyz", fileURL, YES, NSUTF8StringEncoding, NULL )
+  fn ShowFileContents( fileURL )
+
+  // truncate
+  fn TruncateFile( fileURL, 13 )
+end fn
+
+fn DoIt
+
+HandleEvents