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    <p>(I'm assuming you're on Windows, since using U+FEFF as a signature in UTF-8 files is mostly a Windows thing and should simply be avoided elsewhere)</p> <p>You could open the file as a UTF-8 file and then check to see if the first character is U+FEFF. You can do this by opening a normal char based fstream and then use wbuffer_convert to treat it as a series of code units in another encoding. VS2010 doesn't yet have great support for char32_t so the following uses UTF-16 in wchar_t.</p> <pre><code>std::fstream fs(filename); std::wbuffer_convert&lt;std::codecvt_utf8_utf16&lt;wchar_t&gt;,wchar_t&gt; wb(fs.rdbuf()); std::wistream is(&amp;wb); // if you don't do this on the stack remember to destroy the objects in reverse order of creation. is, then wb, then fs. std::wistream::int_type ch = is.get(); const std::wistream::int_type ZERO_WIDTH_NO_BREAK_SPACE = 0xFEFF if(ZERO_WIDTH_NO_BREAK_SPACE != ch) is.putback(ch); // now the stream can be passed around and used without worrying about the extra character in the stream. int i; readFromStream&lt;int&gt;(is,i); </code></pre> <p>Remember that this should be done on the file stream as a whole, not inside readFromFile on your stringstream, because ignoring U+FEFF should only be done if it's the very first character in the whole file, if at all. It shouldn't be done anywhere else.</p> <p>On the other hand, if you're happy using a char based stream and just want to skip U+FEFF if present then James Kanze suggestion seems good so here's an implementation:</p> <pre><code>std::fstream fs(filename); char a,b,c; a = fs.get(); b = fs.get(); c = fs.get(); if (a != (char)0xEF || b != (char)0xBB || c != (char)0xBF) { fs.seekg(0); } else { std::cerr &lt;&lt; "Warning: file contains the so-called 'UTF-8 signature'\n"; } </code></pre> <hr> <p>Additionally if you want to use <code>wchar_t</code> internally the <code>codecvt_utf8_utf16</code> and <code>codecvt_utf8</code> facets have a mode that can consume 'BOMs' for you. The only problem is that <code>wchar_t</code> is widely recognized to be worthless these days* and so you probably shouldn't do this.</p> <pre><code>std::wifstream fin(filename); fin.imbue(std::locale(fin.getloc(), new std::codecvt_utf8_utf16&lt;wchar_t, 0x10FFFF, std::consume_header)); </code></pre> <p><sub>* <code>wchar_t</code> is worthless because it is specified to do just one thing; provide a fixed size data type that can represent any code point in a locale's character repertoire. It does not provide a common representation <em>between</em> locales (i.e., the same <code>wchar_t</code> value can be different characters in different locales so you cannot necessarily convert to <code>wchar_t</code>, switch to another locale, and then convert back to <code>char</code> in order to do <code>iconv</code>-like encoding conversions.)</sub></p> <p><sub>The fixed sized representation itself is worthless for two reasons; first, many code points have semantic meanings and so understanding text means you have to process multiple code points anyway. Secondly, some platforms such as Windows use UTF-16 as the <code>wchar_t</code> encoding, which means a single <code>wchar_t</code> isn't even necessarily a code point value. (Whether using UTF-16 this way is even conformant to the standard is ambiguous. The standard requires that every character supported by a locale be representable as a single <code>wchar_t</code> value; If no locale supports any character outside the BMP then UTF-16 could be seen as conformant.)</sub></p>
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