public static void HtmlDecode(string value, TextWriter output)
{
if (value == null)
{
return;
}
if (output == null)
{
throw new ArgumentNullException("output");
}
if (!StringRequiresHtmlDecoding(value))
{
output.Write(value); // good as is
return;
}
UnicodeDecodingConformance decodeConformance = HtmlDecodeConformance;
int l = value.Length;
for (int i = 0; i < l; i++)
{
char ch = value[i];
if (ch == '&')
{
// We found a '&'. Now look for the next ';' or '&'. The idea is that
// if we find another '&' before finding a ';', then this is not an entity,
// and the next '&' might start a real entity (VSWhidbey 275184)
int index = value.IndexOfAny(_htmlEntityEndingChars, i + 1);
if (index > 0 && value[index] == ';')
{
string entity = value.Substring(i + 1, index - i - 1);
if (entity.Length > 1 && entity[0] == '#')
{
// The # syntax can be in decimal or hex, e.g.
// å --> decimal
// å --> same char in hex
// See http://www.w3.org/TR/REC-html40/charset.html#entities
bool parsedSuccessfully;
uint parsedValue;
if (entity[1] == 'x' || entity[1] == 'X')
{
parsedSuccessfully = UInt32.TryParse(entity.Substring(2), NumberStyles.AllowHexSpecifier, NumberFormatInfo.InvariantInfo, out parsedValue);
}
else
{
parsedSuccessfully = UInt32.TryParse(entity.Substring(1), NumberStyles.Integer, NumberFormatInfo.InvariantInfo, out parsedValue);
}
if (parsedSuccessfully)
{
switch (decodeConformance)
{
case UnicodeDecodingConformance.Strict:
// decoded character must be U+0000 .. U+10FFFF, excluding surrogates
parsedSuccessfully = ((parsedValue < HIGH_SURROGATE_START) || (LOW_SURROGATE_END < parsedValue && parsedValue <= UNICODE_PLANE16_END));
break;
case UnicodeDecodingConformance.Compat:
// decoded character must be U+0001 .. U+FFFF
// null chars disallowed for compat with 4.0
parsedSuccessfully = (0 < parsedValue && parsedValue <= UNICODE_PLANE00_END);
break;
case UnicodeDecodingConformance.Loose:
// decoded character must be U+0000 .. U+10FFFF
parsedSuccessfully = (parsedValue <= UNICODE_PLANE16_END);
break;
default:
Debug.Assert(false, "Should never get here!");
parsedSuccessfully = false;
break;
}
}
if (parsedSuccessfully)
{
if (parsedValue <= UNICODE_PLANE00_END)
{
// single character
output.Write((char)parsedValue);
}
else
{
// multi-character
char leadingSurrogate, trailingSurrogate;
ConvertSmpToUtf16(parsedValue, out leadingSurrogate, out trailingSurrogate);
output.Write(leadingSurrogate);
output.Write(trailingSurrogate);
}
i = index; // already looked at everything until semicolon
continue;
}
}
else
{
i = index; // already looked at everything until semicolon
char entityChar = HtmlEntities.Lookup(entity);
if (entityChar != (char)0)
{
ch = entityChar;
}
else
{
output.Write('&');
output.Write(entity);
output.Write(';');
continue;
}
}
}
}
output.Write(ch);
}
}
static WebUtility()
{
s_htmlDecodeConformance = UnicodeDecodingConformance.Strict;
s_htmlEncodeConformance = UnicodeEncodingConformance.Strict;
}
static WebUtility()
{
s_htmlDecodeConformance = UnicodeDecodingConformance.Strict;
s_htmlEncodeConformance = UnicodeEncodingConformance.Strict;
}