static string DecodeComponent(string s, int from, int toExcluded, Encoding charset, bool isPath)
{
int len = toExcluded - from;
if (len <= 0)
{
return(StringUtil.EmptyString);
}
int firstEscaped = -1;
for (int i = from; i < toExcluded; i++)
{
char c = s[i];
if (c == HttpConstants.PercentChar || c == HttpConstants.PlusSignChar && !isPath)
{
firstEscaped = i;
break;
}
}
if (firstEscaped == -1)
{
return(s.Substring(from, len));
}
// Each encoded byte takes 3 characters (e.g. "%20")
int decodedCapacity = (toExcluded - firstEscaped) / 3;
var byteBuf = new byte[decodedCapacity];
int idx;
var strBuf = StringBuilderManager.Allocate(len);
_ = strBuf.Append(s, from, firstEscaped - from);
for (int i = firstEscaped; i < toExcluded; i++)
{
char c = s[i];
if (c != HttpConstants.PercentChar)
{
_ = strBuf.Append(c != HttpConstants.PlusSignChar || isPath ? c : StringUtil.Space);
continue;
}
idx = 0;
do
{
if (i + 3 > toExcluded)
{
StringBuilderManager.Free(strBuf); ThrowHelper.ThrowArgumentException_UnterminatedEscapeSeq(i, s);
}
byteBuf[idx++] = StringUtil.DecodeHexByte(s, i + 1);
i += 3;
}while (i < toExcluded && s[i] == HttpConstants.PercentChar);
i--;
_ = strBuf.Append(charset.GetString(byteBuf, 0, idx));
}
return(StringBuilderManager.ReturnAndFree(strBuf));
}