Reading textual data - Archive of obsolete content
it can be used like nsilineinputstream, except that it supports non-ascii characters, and has no problems with charsets with embedded nulls (like utf-16 and utf-32).
...set = /* the character encoding you want, using utf-8 here */ "utf-8"; // this assumes that 'file' is a variable that contains the file you want to read, as an nsifile var fis = components.classes["@mozilla.org/network/file-input-stream;1"] .createinstance(components.interfaces.nsifileinputstream); fis.init(file, -1, -1, 0); var lis = fis.queryinterface(components.interfaces.nsilineinputstream); var linedata = {}; var cont; do { cont = lis.readline(linedata); var line = converter.converttounicode(linedata.value); // now you can do something with line } while (cont); fis.close(); see also writing textual data joel on software: the absolute minimum every software developer absolutely, positively must know about unicode and character sets ...

File I/O - Archive of obsolete content
createinstance(components.interfaces.nsifileinputstream); istream.init(file, 0x01, 0444, 0); istream.queryinterface(components.interfaces.nsilineinputstream); // read lines into array var line = {}, lines = [], hasmore; do { hasmore = istream.readline(line); lines.push(line.value); } while(hasmore); istream.close(); // do something with read data alert(lines); reading a binary file for instance, to get the data in a png file: var ios = components.classes["@mozilla.org/network/io-service;1"].

XPCOM Stream Guide
nsconverteroutputstream @mozilla.org/intl/converter-output-stream;1 nsiconverteroutputstream .init(stream, charset, buffersize, replacechar) additional stream interfaces the nsilineinputstream interface supports a .readline() method for reading a single line from an input stream.