/// <summary>
/// This will parse a PDF HEX string with fail fast semantic meaning that we stop if a not allowed character is found.
/// This is necessary in order to detect malformed input and be able to skip to next object start.
/// We assume starting '<' was already read.
/// </summary>
private static CosString ParseHexString(IRandomAccessRead reader)
{
var sBuf = new StringBuilder();
while (true)
{
int c = reader.Read();
if (ReadHelper.IsHexDigit((char)c))
{
sBuf.Append((char)c);
}
else if (c == '>')
{
break;
}
else if (c < 0)
{
throw new IOException("Missing closing bracket for hex string. Reached EOS.");
}
else if (c == ' ' || c == '\n' || c == '\t' || c == '\r' || c == '\b' || c == '\f')
{
}
else
{
// if invalid chars was found: discard last
// hex character if it is not part of a pair
if (sBuf.Length % 2 != 0)
{
sBuf.Remove(sBuf.Length - 1, 1);
}
// read till the closing bracket was found
do
{
c = reader.Read();
}while (c != '>' && c >= 0);
// might have reached EOF while looking for the closing bracket
// this can happen for malformed PDFs only. Make sure that there is
// no endless loop.
if (c < 0)
{
throw new IOException("Missing closing bracket for hex string. Reached EOS.");
}
// exit loop
break;
}
}
return(CosString.ParseHex(sBuf.ToString()));
}
public CosName Parse([NotNull] IRandomAccessRead reader)
{
if (reader == null)
{
throw new ArgumentNullException(nameof(reader));
}
ReadHelper.ReadExpectedChar(reader, '/');
using (var memoryStream = new MemoryStream())
using (var writer = new BinaryWriter(memoryStream))
{
int c = reader.Read();
while (c != -1)
{
byte ch = (byte)c;
if (ch == '#')
{
int ch1 = reader.Read();
int ch2 = reader.Read();
// Prior to PDF v1.2, the # was not a special character. Also,
// it has been observed that various PDF tools do not follow the
// spec with respect to the # escape, even though they report
// PDF versions of 1.2 or later. The solution here is that we
// interpret the # as an escape only when it is followed by two
// valid hex digits.
if (ReadHelper.IsHexDigit((char)ch1) && ReadHelper.IsHexDigit((char)ch2))
{
string hex = "" + (char)ch1 + (char)ch2;
try
{
var byteToWrite = (byte)Convert.ToInt32(hex, 16);
writer.Write(byteToWrite);
}
catch (FormatException e)
{
throw new IOException("Error: expected hex digit, actual='" + hex + "'", e);
}
c = reader.Read();
}
else
{
// check for premature EOF
if (ch2 == -1 || ch1 == -1)
{
//LOG.error("Premature EOF in BaseParser#parseCosName");
c = -1;
break;
}
reader.Unread(ch2);
c = ch1;
writer.Write(ch);
}
}
else if (ReadHelper.IsEndOfName(ch))
{
break;
}
else
{
writer.Write(ch);
c = reader.Read();
}
}
if (c != -1)
{
reader.Unread(c);
}
byte[] bytes = memoryStream.ToArray();
var str = ReadHelper.IsValidUtf8(bytes) ? Encoding.UTF8.GetString(memoryStream.ToArray()) : Encoding.GetEncoding("windows-1252").GetString(memoryStream.ToArray());
return(CosName.Create(str));
}
}
