Add sign functionality

sign/pdfcatalog.go

@@ -0,0 +1,60 @@
+package sign
+
+import (
+	"errors"
+	"strconv"
+)
+
+func (context *SignContext) createCatalog() (catalog string, err error) {
+	catalog = strconv.Itoa(int(context.CatalogData.ObjectId)) + " 0 obj\n"
+	catalog += "<< /Type /Catalog"
+	catalog += " /Version /" + context.PDFReader.PDFVersion
+
+	root := context.PDFReader.Trailer().Key("Root")
+	root_keys := root.Keys()
+	found_pages := false
+	for _, key := range root_keys {
+		if key == "Pages" {
+			found_pages = true
+			break
+		}
+	}
+
+	if !found_pages {
+		return "", errors.New("Didn't find pages in PDF trailer Root.")
+	}
+
+	rootPtr := root.GetPtr()
+	context.CatalogData.RootString = strconv.Itoa(int(rootPtr.GetID())) + " " + strconv.Itoa(int(rootPtr.GetGen())) + " R"
+
+	pages := root.Key("Pages").GetPtr()
+	catalog += " /Pages " + strconv.Itoa(int(pages.GetID())) + " " + strconv.Itoa(int(pages.GetGen())) + " R"
+	catalog += " /AcroForm <<"
+	catalog += " /Fields [" + strconv.Itoa(int(context.SignData.ObjectId)) + " 0 R]"
+
+	if !context.SignData.Signature.Approval {
+		catalog += " /NeedAppearances false"
+	}
+
+	if context.SignData.Signature.CertType > 0 {
+		catalog += " /SigFlags 3"
+	} else {
+		catalog += " /SigFlags 1"
+	}
+
+	catalog += " >>"
+
+	// @todo: what do these do?
+	if !context.SignData.Signature.Approval {
+		if context.SignData.Signature.CertType > 0 {
+			//catalog += " /Perms << /DocMDP " + strconv.Itoa(int(context.SignData.ObjectId)) + " 0 R >>";
+		} else {
+			//catalog += " /Perms << /UR3 " + strconv.Itoa(int(context.SignData.ObjectId)) + " 0 R >>";
+		}
+	}
+
+	catalog += " >>"
+	catalog += "\nendobj\n"
+
+	return catalog, nil
+}