/// <summary>Gets the best encoding available for the specified charset request.</summary>
/// <param name="acceptableCharsets">
/// The Accept-Charset header value (eg: "iso-8859-5, unicode-1-1;q=0.8").
/// </param>
/// <param name="mediaType">The media type used to compute the default encoding for the payload.</param>
/// <param name="utf8Encoding">The encoding to use for UTF-8 charsets; we use the one without the BOM.</param>
/// <param name="defaultEncoding">The encoding to use if no encoding could be computed from the <paramref name="acceptableCharsets"/> or <paramref name="mediaType"/>.</param>
/// <returns>An Encoding object appropriate to the specifed charset request.</returns>
internal static Encoding EncodingFromAcceptableCharsets(string acceptableCharsets, MediaType mediaType, Encoding utf8Encoding, Encoding defaultEncoding)
{
DebugUtils.CheckNoExternalCallers();
Debug.Assert(mediaType != null, "mediaType != null");
// Determines the appropriate encoding mapping according to
// RFC 2616.14.2 (http://tools.ietf.org/html/rfc2616#section-14.2).
Encoding result = null;
if (!string.IsNullOrEmpty(acceptableCharsets))
{
// PERF: in the future if we find that computing the encoding from the accept charsets is
// too expensive we could introduce a cache of original strings to resolved encoding.
CharsetPart[] parts = new List <CharsetPart>(AcceptCharsetParts(acceptableCharsets)).ToArray();
// NOTE: List<T>.Sort uses an unstable sort algorithm; if charsets have the same quality value
// we want to pick the first one specified so we need a stable sort.
KeyValuePair <int, CharsetPart>[] sortedParts = parts.StableSort(delegate(CharsetPart x, CharsetPart y)
{
return(y.Quality - x.Quality);
});
foreach (KeyValuePair <int, CharsetPart> sortedPart in sortedParts)
{
CharsetPart part = sortedPart.Value;
if (part.Quality > 0)
{
// When UTF-8 is specified, select the version that doesn't use the BOM.
if (String.Compare("utf-8", part.Charset, StringComparison.OrdinalIgnoreCase) == 0)
{
result = utf8Encoding;
break;
}
else
{
result = GetEncodingFromCharsetName(part.Charset);
if (result != null)
{
break;
}
// If the charset is not supported it is ignored so other possible charsets are evaluated.
}
}
}
}
// No Charset was specifed, or if charsets were specified, no valid charset was found.
// Returning a different charset is also valid. Get the default encoding for the media type.
if (result == null)
{
result = mediaType.SelectEncoding();
if (result == null)
{
return(defaultEncoding);
}
}
return(result);
}
internal static Encoding EncodingFromAcceptableCharsets(string acceptableCharsets, MediaType mediaType, Encoding utf8Encoding, Encoding defaultEncoding)
{
Encoding encodingFromCharsetName = null;
if (!string.IsNullOrEmpty(acceptableCharsets))
{
foreach (KeyValuePair <int, CharsetPart> pair in new List <CharsetPart>(AcceptCharsetParts(acceptableCharsets)).ToArray().StableSort <CharsetPart>((x, y) => y.Quality - x.Quality))
{
CharsetPart part = pair.Value;
if (part.Quality > 0)
{
if (string.Compare("utf-8", part.Charset, StringComparison.OrdinalIgnoreCase) == 0)
{
encodingFromCharsetName = utf8Encoding;
break;
}
encodingFromCharsetName = GetEncodingFromCharsetName(part.Charset);
if (encodingFromCharsetName != null)
{
break;
}
}
}
}
if (encodingFromCharsetName == null)
{
encodingFromCharsetName = mediaType.SelectEncoding();
if (encodingFromCharsetName == null)
{
return(defaultEncoding);
}
}
return(encodingFromCharsetName);
}
