private CosBase ParseObjectFromFile(long offset, IRandomAccessRead reader,
CosObjectKey key,
CosObjectPool pool,
bool isLenientParsing)
{
reader.Seek(offset);
var objectNumber = ObjectHelper.ReadObjectNumber(reader);
var objectGeneration = ObjectHelper.ReadGenerationNumber(reader);
ReadHelper.ReadExpectedString(reader, "obj", true);
if (objectNumber != key.Number || objectGeneration != key.Generation)
{
throw new InvalidOperationException($"Xref for {key} points to object {objectNumber} {objectGeneration} at {offset}");
}
ReadHelper.SkipSpaces(reader);
var baseObject = baseParser.Parse(reader, pool);
var endObjectKey = ReadHelper.ReadString(reader);
var atStreamStart = string.Equals(endObjectKey, "stream");
if (atStreamStart)
{
var streamStartBytes = OtherEncodings.StringAsLatin1Bytes(endObjectKey);
reader.Rewind(streamStartBytes.Length);
baseObject = ReadNormalObjectStream(reader, baseObject, offset, isLenientParsing, out endObjectKey);
}
if (!string.Equals(endObjectKey, "endobj"))
{
var message =
$"Object ({objectNumber}:{objectGeneration}) at offset {offset} does not end with \'endobj\' but with \'{endObjectKey}\'";
if (isLenientParsing)
{
log.Warn(message);
}
else
{
throw new InvalidOperationException(message);
}
}
return(baseObject);
}
private bool CheckXRefStreamOffset(IRandomAccessRead source, long startXRefOffset, bool isLenient, CosObjectPool pool)
{
// repair mode isn't available in non-lenient mode
if (!isLenient || startXRefOffset == 0)
{
return(true);
}
// seek to offset-1
source.Seek(startXRefOffset - 1);
int nextValue = source.Read();
// the first character has to be a whitespace, and then a digit
if (ReadHelper.IsWhitespace(nextValue))
{
ReadHelper.SkipSpaces(source);
if (ReadHelper.IsDigit(source))
{
try
{
// it's a XRef stream
ObjectHelper.ReadObjectNumber(source);
ObjectHelper.ReadGenerationNumber(source);
ReadHelper.ReadExpectedString(source, "obj", true);
// check the dictionary to avoid false positives
PdfDictionary dict = dictionaryParser.Parse(source, baseParser, pool);
source.Seek(startXRefOffset);
if (dict.IsType(CosName.XREF))
{
return(true);
}
}
catch (Exception ex)
{
log.Error("Couldn't read the xref stream object.", ex);
// there wasn't an object of a xref stream
source.Seek(startXRefOffset);
}
}
}
return(false);
}
