/// <exception cref="System.IO.IOException"/>
public override int Read(char[] cbuf, int off, int len)
{
var readAhead = 0;
var read = 0;
var pos = off;
var readAheadBuffer = new char[BufferSize];
var available = true;
while (available && read < len)
{
available = base.Read(readAheadBuffer, readAhead, 1) == 1;
if (available)
{
var c = ProcessChar(readAheadBuffer[readAhead]);
if (_state == StateStart)
{
// replace control chars with space
if (Utils.IsControlChar(c))
{
c = ' ';
}
cbuf[pos++] = c;
readAhead = 0;
read++;
}
else
{
if (_state == StateError)
{
Unread(readAheadBuffer, 0, readAhead + 1);
readAhead = 0;
}
else
{
readAhead++;
}
}
}
else
{
if (readAhead > 0)
{
// handles case when file ends within excaped sequence
Unread(readAheadBuffer, 0, readAhead);
_state = StateError;
readAhead = 0;
available = true;
}
}
}
return(read > 0 || available ? read : -1);
}
/// <summary>Processes numeric escaped chars to find out if they are a control character.</summary>
/// <param name="ch">a char</param>
/// <returns>Returns the char directly or as replacement for the escaped sequence.</returns>
private char ProcessChar(char ch)
{
switch (_state)
{
case StateStart:
{
if (ch == '&')
{
_state = StateAmp;
}
return ch;
}
case StateAmp:
{
_state = ch == '#' ? StateHash : StateError;
return ch;
}
case StateHash:
{
if (ch == 'x')
{
_control = 0;
_digits = 0;
_state = StateHex;
}
else
{
if ('0' <= ch && ch <= '9')
{
_control = ch - '0';
_digits = 1;
_state = StateDig1;
}
else
{
_state = StateError;
}
}
return ch;
}
case StateDig1:
{
if ('0' <= ch && ch <= '9')
{
_control = _control*10 + (ch - '0');
_digits++;
_state = _digits <= 5 ? StateDig1 : StateError;
}
else
{
// sequence too long
if (ch == ';' && Utils.IsControlChar((char)_control))
{
_state = StateStart;
return (char)_control;
}
_state = StateError;
}
return ch;
}
case StateHex:
{
if (('0' <= ch && ch <= '9') || ('a' <= ch && ch <= 'f') || ('A' <= ch && ch <= 'F'))
{
_control = _control*16 + Convert.ToInt32(ch.ToString(), fromBase: 16);
_digits++;
_state = _digits <= 4 ? StateHex : StateError;
}
else
{
// sequence too long
if (ch == ';' && Utils.IsControlChar((char)_control))
{
_state = StateStart;
return (char)_control;
}
_state = StateError;
}
return ch;
}
case StateError:
{
_state = StateStart;
return ch;
}
default:
{
// not reachable
return ch;
}
}
}