// COPY: Copied from libcore.net.UriCodec
/// <param name="convertPlus">true to convert '+' to ' '.</param>
public static string Decode(string s, bool convertPlus, Encoding charset)
{
if (s.IndexOf('%') == -1 && (!convertPlus || s.IndexOf('+') == -1))
{
return s;
}
StringBuilder result = new StringBuilder(s.Length);
ByteArrayOutputStream @out = new ByteArrayOutputStream();
for (int i = 0; i < s.Length; )
{
char c = s[i];
if (c == '%')
{
do
{
if (i + 2 >= s.Length)
{
throw new ArgumentException("Incomplete % sequence at: " + i);
}
int d1 = HexToInt(s[i + 1]);
int d2 = HexToInt(s[i + 2]);
if (d1 == -1 || d2 == -1)
{
throw new ArgumentException("Invalid % sequence " + Sharpen.Runtime.Substring(s,
i, i + 3) + " at " + i);
}
@out.Write(unchecked((byte)((d1 << 4) + d2)));
i += 3;
}
while (i < s.Length && s[i] == '%');
result.Append(charset.GetString(@out.ToByteArray()));
@out.Reset();
}
else
{
if (convertPlus && c == '+')
{
c = ' ';
}
result.Append(c);
i++;
}
}
return result.ToString();
}