public virtual PdfObject Visit(
XRefStream obj,
object data
)
{
return(obj);
}
public override PdfObject Visit(
XRefStream obj,
object data
)
{
throw new NotSupportedException();
}
public virtual PdfObject Visit(
XRefStream obj,
object data
)
{
return obj;
}
public override PdfObject Visit(
XRefStream obj,
object data
)
{
throw new NotSupportedException();
}
/// <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);
}
protected override void WriteIncremental(
)
{
// 1. Original content (header, body and previous trailer).
FileParser parser = file.Reader.Parser;
stream.Write(parser.Stream);
// 2. Body update (modified indirect objects insertion).
XRefEntry xrefStreamEntry;
{
// 2.1. Content indirect objects.
IndirectObjects indirectObjects = file.IndirectObjects;
// Create the xref stream!
/*
NOTE: Incremental xref information structure comprises multiple sections; this update adds
a new section.
*/
XRefStream xrefStream = new XRefStream(file);
XRefEntry prevFreeEntry = null;
/*
NOTE: Extension object streams are necessary to update original object streams whose
entries have been modified.
*/
IDictionary<int,ObjectStream> extensionObjectStreams = new Dictionary<int,ObjectStream>();
foreach(PdfIndirectObject indirectObject in new List<PdfIndirectObject>(indirectObjects.ModifiedObjects.Values))
{
prevFreeEntry = AddXRefEntry(
indirectObject.XrefEntry,
indirectObject,
xrefStream,
prevFreeEntry,
extensionObjectStreams
);
}
foreach(ObjectStream extensionObjectStream in extensionObjectStreams.Values)
{
prevFreeEntry = AddXRefEntry(
extensionObjectStream.Container.XrefEntry,
extensionObjectStream.Container,
xrefStream,
prevFreeEntry,
null
);
}
if(prevFreeEntry != null)
{prevFreeEntry.Offset = 0;} // Links back to the first free object. NOTE: The first entry in the table (object number 0) is always free.
// 2.2. XRef stream.
/*
NOTE: This xref stream indirect object is purposely temporary (i.e. not registered into the
file's indirect objects collection).
*/
new PdfIndirectObject(
file,
xrefStream,
xrefStreamEntry = new XRefEntry(indirectObjects.Count, 0)
);
UpdateTrailer(xrefStream.Header, stream);
xrefStream.Header[PdfName.Prev] = PdfInteger.Get((int)parser.RetrieveXRefOffset());
AddXRefEntry(
xrefStreamEntry,
xrefStream.Container,
xrefStream,
null,
null
);
}
// 3. Tail.
WriteTail(xrefStreamEntry.Offset);
}
/**
<summary>Adds an indirect object entry to the specified xref stream.</summary>
<param name="xrefEntry">Indirect object's xref entry.</param>
<param name="indirectObject">Indirect object.</param>
<param name="xrefStream">XRef stream.</param>
<param name="prevFreeEntry">Previous free xref entry.</param>
<param name="extensionObjectStreams">Object streams used in incremental updates to extend
modified ones.</param>
<returns>Current free xref entry.</returns>
*/
private XRefEntry AddXRefEntry(
XRefEntry xrefEntry,
PdfIndirectObject indirectObject,
XRefStream xrefStream,
XRefEntry prevFreeEntry,
IDictionary<int,ObjectStream> extensionObjectStreams
)
{
xrefStream[xrefEntry.Number] = xrefEntry;
switch(xrefEntry.Usage)
{
case XRefEntry.UsageEnum.InUse:
{
int offset = (int)stream.Length;
// Add entry content!
indirectObject.WriteTo(stream, file);
// Set entry content's offset!
xrefEntry.Offset = offset;
}
break;
case XRefEntry.UsageEnum.InUseCompressed:
/*
NOTE: Serialization is delegated to the containing object stream.
*/
if(extensionObjectStreams != null) // Incremental update.
{
int baseStreamNumber = xrefEntry.StreamNumber;
PdfIndirectObject baseStreamIndirectObject = file.IndirectObjects[baseStreamNumber];
if(baseStreamIndirectObject.IsOriginal()) // Extension stream needed in order to preserve the original object stream.
{
// Get the extension object stream associated to the original object stream!
ObjectStream extensionObjectStream;
if(!extensionObjectStreams.TryGetValue(baseStreamNumber, out extensionObjectStream))
{
file.Register(extensionObjectStream = new ObjectStream());
// Link the extension to the base object stream!
extensionObjectStream.BaseStream = (ObjectStream)baseStreamIndirectObject.DataObject;
extensionObjectStreams[baseStreamNumber] = extensionObjectStream;
}
// Insert the data object into the extension object stream!
extensionObjectStream[xrefEntry.Number] = indirectObject.DataObject;
// Update the data object's xref entry!
xrefEntry.StreamNumber = extensionObjectStream.Reference.ObjectNumber;
xrefEntry.Offset = XRefEntry.UndefinedOffset; // Internal object index unknown (to set on object stream serialization -- see ObjectStream).
}
}
break;
case XRefEntry.UsageEnum.Free:
if(prevFreeEntry != null)
{prevFreeEntry.Offset = xrefEntry.Number;} // Object number of the next free object.
prevFreeEntry = xrefEntry;
break;
default:
throw new NotSupportedException();
}
return prevFreeEntry;
}
protected override void WriteStandard(
)
{
// 1. Header [PDF:1.6:3.4.1].
WriteHeader();
// 2. Body [PDF:1.6:3.4.2,3,7].
XRefEntry xrefStreamEntry;
{
// 2.1. Content indirect objects.
IndirectObjects indirectObjects = file.IndirectObjects;
// Create the xref stream indirect object!
/*
NOTE: Standard xref information structure comprises just one section; the xref stream is
generated on-the-fly and kept volatile not to interfere with the existing file structure.
*/
/*
NOTE: This xref stream indirect object is purposely temporary (i.e. not registered into the
file's indirect objects collection).
*/
XRefStream xrefStream = new XRefStream(file);
new PdfIndirectObject(
file,
xrefStream,
xrefStreamEntry = new XRefEntry(indirectObjects.Count, 0)
);
XRefEntry prevFreeEntry = null;
foreach(PdfIndirectObject indirectObject in indirectObjects)
{
prevFreeEntry = AddXRefEntry(
indirectObject.XrefEntry,
indirectObject,
xrefStream,
prevFreeEntry,
null
);
}
prevFreeEntry.Offset = 0; // Links back to the first free object. NOTE: The first entry in the table (object number 0) is always free.
// 2.2. XRef stream.
UpdateTrailer(xrefStream.Header, stream);
AddXRefEntry(
xrefStreamEntry,
xrefStream.Container,
xrefStream,
null,
null
);
}
// 3. Tail.
WriteTail(xrefStreamEntry.Offset);
}
