io/text-streams

Experimental

Provides streams for reading and writing text.

function readTextFromFile(filename) {
  var fileIO = require("sdk/io/file");
  var text = null;
  if (fileIO.exists(filename)) {
    var TextReader = fileIO.open(filename, "r");
    if (!TextReader.closed) {
      text = TextReader.read();
      TextReader.close();
    }
  }
  return text;
}
function writeTextToFile(text, filename) {
  var fileIO = require("sdk/io/file");
  var TextWriter = fileIO.open(filename, "w");
  if (!TextWriter.closed) {
    TextWriter.write(text);
    TextWriter.close();
  }
}

Globals

Constructors

TextReader(inputStream, charset)

Creates a buffered input stream that reads text from a backing stream using a given text encoding.

You can also create TextReader objects using io/file's open() function.

Parameters

inputStream : stream
The backing stream, an nsIInputStream. It must already be opened.

charset : string
inputStream is expected to be in the character encoding named by this value. If not specified, "UTF-8" is assumed. See nsICharsetConverterManager.idl for documentation on how to determine other valid values for this.

TextWriter(outputStream, charset)

Creates a buffered output stream that writes text to a backing stream using a given text encoding.

You can also create TextWriter objects using io/file's open() function.

Parameters

outputStream : stream
The backing stream, an nsIOutputStream. It must already be opened.

charset : string
Text will be written to outputStream using the character encoding named by this value. If not specified, "UTF-8" is assumed. See nsICharsetConverterManager.idl for documentation on how to determine other valid values for this.

TextReader

Methods

close()

Closes both the stream and its backing stream.

read(numChars)

Reads and returns a string from the stream. If the stream is closed, an exception is thrown.

Parameters

numChars : number
The number of characters to read. If not given, the remainder of the stream is read.

Returns

string : The string read. If the stream is at the end, the empty string is returned.

Properties

closed

True if the stream is closed.

TextWriter

Methods

close()

Flushes the backing stream's buffer and closes both the stream and the backing stream. If the stream is already closed, an exception is thrown.

flush()

Flushes the backing stream's buffer.

write(str)

Writes a string to the stream. If the stream is closed, an exception is thrown.

Parameters

str : string
The string to write.

writeAsync(str, callback)

Writes a string on a background thread. After the write completes, the backing stream's buffer is flushed, and both the stream and the backing stream are closed, also on the background thread. If the stream is already closed, an exception is thrown immediately.

Parameters

str : string
The string to write.

callback : callback
callback, if given, must be a function. It's called as callback(error) when the write completes. error is an Error object or undefined if there was no error. Inside callback, this is the TextWriter object.

Properties

closed

True if the stream is closed.

Document Tags and Contributors

Contributors to this page: wbamberg, backy0175
Last updated by: wbamberg,