how to create an nsIFile object using URIs

Question

I'm making extension for firefox, and I want to my extension open a file like "file:///home/blahblah/foo.txt" and then put content of this file in text area. Its easy with files "http://", but i cant do this with "file://"

Answer 1

when working with local files you have to really "load" them:

 var file = Components.classes["@mozilla.org/file/local;1"]
           .createInstance(Components.interfaces.nsILocalFile);
 file.initWithPath("/home/blahblah/foo.txt");
 if ( file.exists() == false ) {
  dup.value = “File does not exist”;
 }
 var istream = Components.classes["@mozilla.org/network/file-input-stream;1"]
  .createInstance(Components.interfaces.nsIFileInputStream);
 istream.init(file, 0x01, 4, null);
 var fileScriptableIO = Components.classes["@mozilla.org/scriptableinputstream;1"].createInstance(Components.interfaces.nsIScriptableInputStream); 
 fileScriptableIO.init(istream);
 // parse the xml into our internal document
 istream.QueryInterface(Components.interfaces.nsILineInputStream); 
 var fileContent = "";
 var csize = 0; 
 while ((csize = fileScriptableIO.available()) != 0)
 {
  fileContent += fileScriptableIO.read( csize );
 }
 fileScriptableIO.close();  
 istream.close();

fileContent contains the content as string

Answer 2

If you have the URI string for the file (rather than the local path or nsIFile object) then you can also use XMLHttpRequest to read the file's contents.