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;
{
// Create the xref stream!
/*
* 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.
*/
XRefStream xrefStream = new XRefStream(file);
// 2.1. Indirect objects.
IndirectObjects indirectObjects = file.IndirectObjects;
// Indirect objects serialization.
XRefEntry prevFreeEntry = null;
ObjectStream objectStream = null;
foreach (PdfIndirectObject indirectObject in indirectObjects)
{
if (indirectObject.IsCompressible())
{
if (objectStream == null ||
objectStream.Count >= ObjectStreamMaxEntryCount)
{
file.Register(objectStream = new ObjectStream());
}
indirectObject.Compress(objectStream);
}
prevFreeEntry = AddXRefEntry(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);
xrefStreamEntry = new XRefEntry(indirectObjects.Count, 0, (int)stream.Length, XRefEntry.UsageEnum.InUse);
/*
* NOTE: This xref stream indirect object is purposely temporary (i.e. not registered into
* the file's indirect objects collection).
*/
AddXRefEntry(new PdfIndirectObject(file, xrefStream, xrefStreamEntry), xrefStream, null, null);
}
// 3. Tail.
WriteTail(xrefStreamEntry.Offset);
}
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;
{
// Create the xref stream!
/*
* NOTE: Incremental xref information structure comprises multiple sections; this update adds
* a new section.
*/
XRefStream xrefStream = new XRefStream(file);
// 2.1. Indirect objects.
IndirectObjects indirectObjects = file.IndirectObjects;
// 2.1.1. Modified indirect objects serialization.
XRefEntry prevFreeEntry = null;
/*
* NOTE: Any uncompressed indirect object will be compressed.
*/
ObjectStream objectStream = null;
/*
* NOTE: Any previously-compressed indirect object will have its original object stream
* updated through a new extension object stream.
*/
IDictionary <int, ObjectStream> extensionObjectStreams = new Dictionary <int, ObjectStream>();
int indirectObjectsPrecompressCount = indirectObjects.Count;
foreach (PdfIndirectObject indirectObject in new List <PdfIndirectObject>(indirectObjects.ModifiedObjects.Values))
{
if (indirectObject.IsCompressible())
{
if (objectStream == null ||
objectStream.Count >= ObjectStreamMaxEntryCount)
{
file.Register(objectStream = new ObjectStream());
}
indirectObject.Compress(objectStream);
}
prevFreeEntry = AddXRefEntry(
indirectObject,
xrefStream,
prevFreeEntry,
extensionObjectStreams
);
}
// 2.1.2. Additional object streams serialization.
for (int index = indirectObjectsPrecompressCount, limit = indirectObjects.Count; index < limit; index++)
{
prevFreeEntry = AddXRefEntry(
indirectObjects[index],
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.
UpdateTrailer(xrefStream.Header, stream);
xrefStream.Header[PdfName.Prev] = PdfInteger.Get((int)parser.RetrieveXRefOffset());
AddXRefEntry(
/*
* 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, (int)stream.Length, XRefEntry.UsageEnum.InUse)
),
xrefStream,
null,
null
);
}
// 3. Tail.
WriteTail(xrefStreamEntry.Offset);
}
/**
* <summary>Adds an indirect object entry to the specified xref stream.</summary>
* <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(PdfIndirectObject indirectObject, XRefStream xrefStream, XRefEntry prevFreeEntry, IDictionary <int, ObjectStream> extensionObjectStreams)
{
XRefEntry xrefEntry = indirectObject.XrefEntry;
// Add the entry to the xref stream!
xrefStream[xrefEntry.Number] = xrefEntry;
// Serialize the entry contents!
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);
}