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Improved tolerance against malformed hex-strings #225

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Merged
merged 1 commit into from
May 25, 2022
Merged

Improved tolerance against malformed hex-strings #225

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21 changes: 16 additions & 5 deletions PdfSharpCore/Pdf.IO/Lexer.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -562,15 +562,19 @@ public Symbol ScanHexadecimalString()
ScanNextChar(true);
break;
}
if (char.IsLetterOrDigit(_currChar))
if (IsHexChar(_currChar))
{
hex[0] = char.ToUpper(_currChar);
hex[1] = char.ToUpper(_nextChar);
int ch = int.Parse(new string(hex), NumberStyles.AllowHexSpecifier);
hex[0] = _currChar;
hex[1] = IsHexChar(_nextChar) ? _nextChar : ' ';
int ch = int.Parse(new string(hex), NumberStyles.HexNumber);
_token.Append(Convert.ToChar(ch));
ScanNextChar(true);
ScanNextChar(true);
if (_currChar != '>')
ScanNextChar(true);
}
else
// prevent endless loop in case _currChar is neither '>' nor a hex-char nor whitespace
ScanNextChar(true);
}
string chars = _token.ToString();
int count = chars.Length;
Expand All @@ -585,6 +589,13 @@ public Symbol ScanHexadecimalString()
return _symbol = Symbol.HexString;
}

internal static bool IsHexChar(char c)
{
return char.IsDigit(c) ||
(c >= 'A' && c <= 'F') ||
(c >= 'a' && c <= 'f');
}

/// <summary>
/// Move current position one character further in PDF stream.
/// </summary>
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