/// <summary>
/// Creates a new instance of the PdfDocument class from the IO stream.
/// </summary>
/// <param name="stream">The <see cref="Stream"/> on which to open the PdfDocument.</param>
/// <returns></returns>
public static PdfDocument Open(Stream stream)
{
if (stream == null)
{
throw new ArgumentNullException(nameof(stream));
}
if (!stream.CanRead)
{
throw new ArgumentException("Cannot read stream", nameof(stream));
}
var document = new PdfDocument(stream);
using (var reader = new PdfReader(stream))
{
// Check header
document.pdfVersion = PdfVersion.FromReader(reader);
// Check trailer
reader.Position = reader.GetXRefPosition();
// Read Cross-Reference Table
IPdfTrailer trailer;
IXRefSection xrefSection;
char fisrtChar;
do
{
fisrtChar = reader.Peek();
if (fisrtChar == XRefSection.StartKeyword[0])
{
// Cross-Reference Section
xrefSection = XRefSection.FromReader(reader);
trailer = PdfTrailer.FromReader(reader);
}
else if (char.IsDigit(fisrtChar))
{
// Cross-Reference Stream
var xrefStream = XRefStream.FromReader(reader);
trailer = xrefStream;
xrefSection = xrefStream;
}
else
{
throw new FormatException("Invalid Cross-Reference section.");
}
if (document.xrefTable == null)
{
// Initialize document's Cross-Reference Table
document.xrefTable = new XRefTable(xrefSection, trailer.Size);
}
else
{
// Register section
document.xrefTable.AddSection(xrefSection);
}
// Keep instance of last trailer
if (document.trailer == null)
{
document.trailer = trailer;
}
// Seek to previous trailer
if (trailer.Prev.HasValue)
{
reader.Position = trailer.Prev.Value;
}
}while (trailer.Prev != null);
}
return(document);
}
