/* See if a dictionary is a structure element.
We identify it by the S and P elements, which are
required, and by making sure that the Type element,
if present, has a value of "StructElem".
*/
private boolean isStructElem(PdfDictionary elem) throws PdfException {
try {
PdfObject typ = elem.get("Type");
if (typ != null) {
if (!"StructElem".equals(((PdfSimpleObject) typ).getStringValue())) {
return false;
}
}
PdfObject s = _module.resolveIndirectObject(elem.get("S"));
// The structure type is supposed to be one of
// a list of known structure types, or else is
// mapped to one through the role map dictionary.
// For the moment, just make sure it's a name.
if (!(s instanceof PdfSimpleObject)) {
return false;
}
Token tok = ((PdfSimpleObject) s).getToken();
if (!(tok instanceof Name)) {
return false;
}
// It appears that there really isn't a requirement
// to have structure types belong to the standard types.
// Conditionalize this code out, pending more info.
boolean checkStandardTypes = false;
String st = ((Name) tok).getValue();
st = _tree.dereferenceStructType(st);
if (!StdStructTypes.includes(st)) {
if (checkStandardTypes) {
throw new PdfInvalidException("Non-standard structure type name");
}
} else {
// The structure type is a standard one.
}
// The parent reference must be an indirect reference.
// The documentation says it must refer to another
// structure element dictionary, but it seems that it
// must also be able to refer to the structure tree root.
// I'll allow both.
PdfObject pref = elem.get("P");
if (!(pref instanceof PdfIndirectObj)) {
return false;
}
// Make sure it refers to a dictionary (at least).
PdfDictionary p = (PdfDictionary) _module.resolveIndirectObject(pref);
PdfSimpleObject ptype = (PdfSimpleObject) p.get("Type");
if (ptype != null) {
String typename = ptype.getStringValue();
if (!"StructTreeRoot".equals(typename) && !"StructElem".equals(typename)) {
return false;
}
}
// Passed all tests.
return true;
} catch (Exception e) {
// Some assumption was violated
return false;
}
}
/* Determine if a dictionary is an object reference dictionary,
as in table 9.12. */
private boolean isObjectRef(PdfDictionary dict) {
try {
PdfSimpleObject typeObj = (PdfSimpleObject) dict.get("Type");
if (!typeObj.getStringValue().equals("OBJR")) {
return false;
}
// An Obj entry is required. Must be an indirect object.
PdfObject obj = _module.resolveIndirectObject(dict.get("Obj"));
if (obj == null) {
return false;
}
return true;
} catch (Exception e) {
return false;
}
}
/* Determine if a dictionary is a marked content dictionary.
See Table 9.11 in the PDF 1.4 book. */
private boolean isMarkedContent(PdfDictionary dict) {
try {
PdfSimpleObject typeObj = (PdfSimpleObject) dict.get("Type");
if (!typeObj.getStringValue().equals("MCR")) {
return false;
}
// An MCID entry is required.
PdfSimpleObject mcidObj = (PdfSimpleObject) _module.resolveIndirectObject(dict.get("MCID"));
if (mcidObj == null) {
return false;
}
return true;
} catch (Exception e) {
return false;
}
}
/* Check if an attribute dictionary is reasonable. */
private void checkAttribute(PdfDictionary attr) throws PdfException {
try {
// Must have an entry named "O", whose value is a name.
PdfSimpleObject plugin = (PdfSimpleObject) attr.get("O");
Name tok = (Name) plugin.getToken();
// If it has a Placement entry with a value other than
// "Inline", then we allow block level attributes.
PdfSimpleObject placement = (PdfSimpleObject) attr.get("Placement");
if (placement != null && !"Inline".equals(placement.getStringValue())) {
_structIsInline = false;
}
// Though I don't think the Adobe PDF bible actually
// says so, it appears that the "attributes" are
// simply other keys in the attribute dictionary.
// Remember if we see attributes that can't go in BLSE's;
// we'll check later if we're actually in a BLSE.
if (attrIsBlockLevel(attr)) {
_attrIsBlock = true;
}
} catch (Exception e) {
throw new PdfInvalidException("Invalid attribute in document structure");
}
}
/* Walk through the page tree and check all Resources dictionaries
that we find. Along the way, we check several things:
Color spaces. Any Separation and DeviceN resources we
find must have an AlternateSpace of DeviceGray or
DeviceCMYK.
Extended graphic states.
XObjects.
*/
private boolean resourcesOK() {
PageTreeNode docTreeRoot = _module.getDocumentTree();
try {
docTreeRoot.startWalk();
DocNode docNode;
for (; ; ) {
docNode = docTreeRoot.nextDocNode();
if (docNode == null) {
break;
}
// Check for node-level resources
PdfDictionary rsrc = docNode.getResources();
if (rsrc != null) {
// Check extended graphics state.
PdfDictionary gs = (PdfDictionary) _module.resolveIndirectObject(rsrc.get("ExtGState"));
if (!extGStateOK(gs)) {
return false;
}
// Check XObjects.
PdfDictionary xo = (PdfDictionary) _module.resolveIndirectObject(rsrc.get("XObject"));
if (!xObjectsOK(xo)) {
return false;
}
}
// Check content streams for resources
if (docNode instanceof PageObject) {
List streams = ((PageObject) docNode).getContentStreams();
if (streams != null) {
Iterator iter = streams.listIterator();
while (iter.hasNext()) {
PdfStream stream = (PdfStream) iter.next();
PdfDictionary dict = stream.getDict();
PdfDictionary rs = (PdfDictionary) dict.get("Resources");
if (rs != null) {
PdfDictionary gs =
(PdfDictionary) _module.resolveIndirectObject(rs.get("ExtGState"));
if (!extGStateOK(gs)) {
return false;
}
PdfDictionary xo = (PdfDictionary) _module.resolveIndirectObject(rs.get("XObject"));
if (!xObjectsOK(xo)) {
return false;
}
}
// Also check for filters, to make sure
// there aren't any forbidden LZW filters.
PdfObject filters = dict.get("Filter");
if (!filterOK(filters, true, true)) {
return false;
}
// External streams are also forbidden.
if (dict.get("F") != null) {
return false;
}
}
}
// Also check page objects for annotations --
// in particular, TrapNet annotations.
PdfArray annots = ((PageObject) docNode).getAnnotations();
if (annots != null) {
Vector annVec = annots.getContent();
for (int i = 0; i < annVec.size(); i++) {
PdfDictionary annDict =
(PdfDictionary) _module.resolveIndirectObject((PdfObject) annVec.elementAt(i));
PdfSimpleObject subtypeObj = (PdfSimpleObject) annDict.get("Subtype");
if ("TrapNet".equals(subtypeObj.getStringValue())) {
// FontFauxing must be absent or 0-length
PdfArray ff = (PdfArray) annDict.get("FontFauxing");
if (ff != null) {
Vector ffVec = ff.getContent();
if (ffVec.size() > 0) {
return false; // a faux pas
}
}
}
}
}
}
}
} catch (Exception e) {
return false;
}
return true; // passed all tests
}
