// IsHexEncoding
//
// Determines whether a substring has the URI hex encoding format of '%'
// followed by 2 hexadecimal characters
//
// Inputs:
// <argument> pattern
// String to check
//
// <argument> index
// Offset in <pattern> at which to check substring for hex encoding
//
// Assumes:
// 0 <= <index> < <pattern>.Length
//
// Returns:
// true if <pattern>[<index>] is hex encoded, else false
//
// Throws:
// Nothing
public static bool IsHexEncoding(string pattern, int index)
{
if ((pattern.Length - index) < 3)
{
return(false);
}
if ((pattern[index] == '%') && UriShim.EscapedAscii(pattern[index + 1], pattern[index + 2]) != c_DummyChar)
{
return(true);
}
return(false);
}
// Transforms a character into its hexadecimal representation.
public static string HexEscape(char character)
{
if (character > '\xff')
{
throw new ArgumentOutOfRangeException(nameof(character));
}
char[] chars = new char[3];
int pos = 0;
UriShim.EscapeAsciiChar(character, chars, ref pos);
return(new string(chars));
}
// HexUnescape
//
// Converts a substring of the form "%XX" to the single character represented
// by the hexadecimal value XX. If the substring s[Index] does not conform to
// the hex encoding format then the character at s[Index] is returned
//
// Inputs:
// <argument> pattern
// String from which to read the hexadecimal encoded substring
//
// <argument> index
// Offset within <pattern> from which to start reading the hexadecimal
// encoded substring
//
// Outputs:
// <argument> index
// Incremented to the next character position within the string. This
// may be EOS if this was the last character/encoding within <pattern>
//
// Returns:
// Either the converted character if <pattern>[<index>] was hex encoded, or
// the character at <pattern>[<index>]
//
// Throws:
// ArgumentOutOfRangeException
public static char HexUnescape(string pattern, ref int index)
{
if ((index < 0) || (index >= pattern.Length))
{
throw new ArgumentOutOfRangeException(nameof(index));
}
if ((pattern[index] == '%') &&
(pattern.Length - index >= 3))
{
char ret = UriShim.EscapedAscii(pattern[index + 1], pattern[index + 2]);
if (ret != c_DummyChar)
{
index += 3;
return(ret);
}
}
return(pattern[index++]);
}