public static PdfXRefSection Parse(Lexer lexer)
{
int firstId = int.Parse(lexer.ReadToken(), CultureInfo.InvariantCulture);
int size = int.Parse(lexer.ReadToken(), CultureInfo.InvariantCulture);
var entries = new IPdfObject[size];
for (int i = 0; i < size; i++)
{
var entry = PdfXRefEntry.Parse(firstId + i, lexer);
// first entry must be free and have a gen 65535
// head of the linked list of free objects
if (i == 0)
{
if (entry.GenerationNumber != 65535)
{
throw new ParsingException($"The first xref entry must have generation number 65535. Was {entry.GenerationNumber}");
}
if (entry.InUse)
{
throw new ParsingException($"The first xref entry must be free");
}
}
entries[i] = entry;
}
return(new PdfXRefSection(firstId, size, entries));
}
public static PdfXRefSection Parse(PdfStream pdfStream)
{
var dictionary = pdfStream.StreamDictionary;
var type = dictionary["Type"] as PdfName;
if (type.Name != "XRef")
{
throw new ParsingException("A stream of type XRef is expected");
}
// W[1 2 1] (4 columns)
// W[1 3 1] (5 columns, larger indexes)
var w = dictionary["W"] as PdfArray;
int firstId = 0;
int size = 0;
if (dictionary.TryGetValue("Index", out IPdfObject indexObject))
{
var index = (PdfArray)indexObject;
firstId = ((PdfNumeric)index.Items[0]).ToInt32();
size = ((PdfNumeric)index.Items[1]).ToInt32();
}
else if (dictionary.TryGetValue("Size", out IPdfObject sizeObject))
{
size = ((PdfNumeric)sizeObject).ToInt32();
}
int items = w.Items.Count;
// for xref this shall always be 3
if (items != 3)
{
throw new ParsingException("The W[] parameter must contain 3 columns for an XRef");
}
int[] sizes = new int[w.Items.Count];
int bytesPerEntry = 0;
for (int i = 0; i < items; i++)
{
sizes[i] = ((PdfNumeric)w.Items[i]).ToInt32();
bytesPerEntry += sizes[i];
}
var decodedXRef = pdfStream.Decode();
// Use W[...] to build up the xref
int rowCount = decodedXRef.Length / bytesPerEntry;
if (size != rowCount)
{
throw new ParsingException("The number of refs inside the Index value must match the actual refs count present in the stream");
}
var entries = new IPdfObject[rowCount];
for (int row = 0; row < rowCount; row++)
{
var entry = PdfXRefEntry.Parse(firstId + row, decodedXRef, sizes, row, bytesPerEntry);
entries[row] = entry;
}
return(new PdfXRefSection(firstId, size, entries));
}
