/**
* <summary>Serializes the file trailer [PDF:1.6:3.4.4].</summary>
* <param name="startxref">Byte offset from the beginning of the file to the beginning
* of the last cross-reference section.</param>
* <param name="xrefSize">Total number of entries in the file's cross-reference table,
* as defined by the combination of the original section and all update sections.</param>
* <param name="parser">File parser.</param>
*/
private void WriteTrailer(
long startxref,
int xrefSize,
FileParser parser
)
{
// 1. Header.
stream.Write(TrailerChunk);
// 2. Body.
// Update its entries:
PdfDictionary trailer = file.Trailer;
UpdateTrailer(trailer, stream);
// * Size
trailer[PdfName.Size] = PdfInteger.Get(xrefSize);
// * Prev
if (parser == null)
{
trailer.Remove(PdfName.Prev);
} // [FIX:0.0.4:5] It (wrongly) kept the 'Prev' entry of multiple-section xref tables.
else
{
trailer[PdfName.Prev] = PdfInteger.Get((int)parser.RetrieveXRefOffset());
}
// Serialize its contents!
trailer.WriteTo(stream, file); stream.Write(Chunk.LineFeed);
// 3. Tail.
WriteTail(startxref);
}
/**
* <summary>Retrieves the file information.</summary>
*/
public FileInfo ReadInfo()
{
//TODO:hybrid xref table/stream
Version version = Version.Get(parser.RetrieveVersion());
PdfDictionary trailer = null;
SortedDictionary <int, XRefEntry> xrefEntries = new SortedDictionary <int, XRefEntry>();
{
long sectionOffset = parser.RetrieveXRefOffset();
while (sectionOffset > -1)
{
// Move to the start of the xref section!
parser.Seek(sectionOffset);
PdfDictionary sectionTrailer;
if (parser.GetToken(1).Equals(Keyword.XRef)) // XRef-table section.
{
// Looping sequentially across the subsections inside the current xref-table section...
while (true)
{
/*
* NOTE: Each iteration of this block represents the scanning of one subsection.
* We get its bounds (first and last object numbers within its range) and then collect
* its entries.
*/
// 1. First object number.
parser.MoveNext();
if ((parser.TokenType == PostScriptParser.TokenTypeEnum.Keyword) &&
parser.Token.Equals(Keyword.Trailer)) // XRef-table section ended.
{
break;
}
else if (parser.TokenType != PostScriptParser.TokenTypeEnum.Integer)
{
throw new PostScriptParseException("Neither object number of the first object in this xref subsection nor end of xref section found.", parser);
}
// Get the object number of the first object in this xref-table subsection!
int startObjectNumber = (int)parser.Token;
// 2. Last object number.
parser.MoveNext();
if (parser.TokenType != PostScriptParser.TokenTypeEnum.Integer)
{
throw new PostScriptParseException("Number of entries in this xref subsection not found.", parser);
}
// Get the object number of the last object in this xref-table subsection!
int endObjectNumber = (int)parser.Token + startObjectNumber;
// 3. XRef-table subsection entries.
for (int index = startObjectNumber; index < endObjectNumber; index++)
{
if (xrefEntries.ContainsKey(index)) // Already-defined entry.
{
// Skip to the next entry!
parser.MoveNext(3);
continue;
}
// Get the indirect object offset!
int offset = (int)parser.GetToken(1);
// Get the object generation number!
int generation = (int)parser.GetToken(1);
// Get the usage tag!
XRefEntry.UsageEnum usage;
{
string usageToken = (string)parser.GetToken(1);
if (usageToken.Equals(Keyword.InUseXrefEntry, StringComparison.Ordinal))
{
usage = XRefEntry.UsageEnum.InUse;
}
else if (usageToken.Equals(Keyword.FreeXrefEntry, StringComparison.Ordinal))
{
usage = XRefEntry.UsageEnum.Free;
}
else
{
throw new PostScriptParseException("Invalid xref entry.", parser);
}
}
// Define entry!
xrefEntries[index] = new XRefEntry(
index,
generation,
offset,
usage
);
}
}
// Get the previous trailer!
sectionTrailer = (PdfDictionary)parser.ParsePdfObject(1);
}
else // XRef-stream section.
{
XRefStream stream = (XRefStream)parser.ParsePdfObject(3); // Gets the xref stream skipping the indirect-object header.
// XRef-stream subsection entries.
foreach (XRefEntry xrefEntry in stream.Values)
{
if (xrefEntries.ContainsKey(xrefEntry.Number)) // Already-defined entry.
{
continue;
}
// Define entry!
xrefEntries[xrefEntry.Number] = xrefEntry;
}
// Get the previous trailer!
sectionTrailer = stream.Header;
}
if (trailer == null)
{
trailer = sectionTrailer;
}
// Get the previous xref-table section's offset!
PdfInteger prevXRefOffset = (PdfInteger)sectionTrailer[PdfName.Prev];
sectionOffset = (prevXRefOffset != null ? prevXRefOffset.IntValue : -1);
}
}
return(new FileInfo(version, trailer, xrefEntries));
}
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);
}