附加数据文件与Firefox扩展 [英] Append data to file with firefox extension

问题描述

我试图建立一个Firefox扩展，我想定期在文件中写东西。所以我想要一个文件，我添加新的字符串。下面的代码写入文件，但最后文件只包含我写的最后一个字符串，而不是以前的字符串。

$ mydir = null;
mylog = null;
mystream = null;

函数initFolder（）{
var dirSvc = Components.classes [@ mozilla.org/file/directory_service;1]
.getService（Components.interfaces.nsIProperties） ;
mydir = dirSvc.get（ProfD，Components.interfaces.nsILocalFile）;
mydir.append（mylogFolder）;
if（！mydir.exists（））
mydir.create（mydir.DIRECTORY_TYPE，0700）;

var fileName =logFile.txt;
mylog = mydir.clone（）;
mylog.append（fileName）;
mylog.createUnique（Components.interfaces.nsIFile.NORMAL_FILE_TYPE，0777）;


函数mywriteFile（aData）{
//初始化流
mystream = Components.classes [@ mozilla.org/network/safe-file-output -stream; 1\" ]。
createInstance（Components.interfaces.nsIFileOutputStream）;
尝试{
mystream.init（mylog，0x02 | 0x10，0777，0）; //这些标志附加文件？
} catch（e）{
dump（exception：+ e +\\\
）;
}

//转换为UTF-8
var converter = Components.classes [@ mozilla.org/intl/scriptableunicodeconverter]。
createInstance（Components.interfaces.nsIScriptableUnicodeConverter）;
converter.charset =UTF-8;
var convertedData = converter.ConvertFromUnicode（aData）;
convertedData + = converter.Finish（）;
尝试{
mystream.write（convertedData，convertedData.length）;
} catch（e）{
dump（exception：+ e +\\\
）;


$ b函数close（）{
if（mystream instanceof Components.interfaces.nsISafeOutputStream）{
mystream.finish（）;
} else {
mystream.close（）;


$ b window.addEventListener（load，function（）{initFolder（）;}，false）;
window.addEventListener（unload，function（）{close（）;}，false）;


有什么建议？

解决方案

安全文件输出流安全的原因是它将数据写入一个临时文件，并在您调用stream.finish（）时仅将其复制到实际文件中。所以任何现有的数据都会丢失。如果你想追加你将不得不使用一个不同的组件（普通的老@ mozilla.org /网络/文件输出流; 1应该正常工作）。

I'm trying to build a firefox extension and i want to write things periodically in a file. So i want a file in which i append new strings. The following code writes the file but at the end the file contains only the last string i wrote and not the previous.

Can you help me?

mydir=null;
mylog=null;
mystream=null;

function initFolder() {
var dirSvc = Components.classes["@mozilla.org/file/directory_service;1"]
           .getService(Components.interfaces.nsIProperties);
 mydir = dirSvc.get("ProfD", Components.interfaces.nsILocalFile);
 mydir.append("mylogFolder");
 if (!mydir.exists())
    mydir.create(mydir.DIRECTORY_TYPE, 0700);

 var fileName = "logFile.txt";
 mylog = mydir.clone();
 mylog.append(fileName);
 mylog.createUnique(Components.interfaces.nsIFile.NORMAL_FILE_TYPE, 0777);
}

function mywriteFile(aData) { 
  // init stream
  mystream = Components.classes["@mozilla.org/network/safe-file-output-stream;1"].
             createInstance(Components.interfaces.nsIFileOutputStream);
  try {
    mystream.init(mylog, 0x02 | 0x10, 0777, 0); //these flags to append file?
  } catch (e) {
    dump("exception: " + e + "\n");
  }

  // convert to UTF-8
  var converter = Components.classes["@mozilla.org/intl/scriptableunicodeconverter"].
                createInstance(Components.interfaces.nsIScriptableUnicodeConverter);
  converter.charset = "UTF-8";
  var convertedData = converter.ConvertFromUnicode(aData);
  convertedData += converter.Finish();
  try {
    mystream.write(convertedData, convertedData.length);
  } catch (e) {
dump("exception: " + e + "\n");
  }
}

function close() {
  if (mystream instanceof Components.interfaces.nsISafeOutputStream) {
     mystream.finish();
  } else {
     mystream.close();
  }
}

window.addEventListener("load", function(){ initFolder(); }, false);
window.addEventListener("unload", function(){close(); }, false);

Any suggestions?

解决方案

The reason the "safe" file output stream is safe is that it writes the data to a temporary file and only copies it over to the actual file when you call stream.finish(). So any existing data is lost. If you want to append you'll have to use a different component (plain old "@mozilla.org/network/file-output-stream;1" should work fine).

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