pdfviewer: readobject can return null, and catalog can be null

experimental/PdfViewer/pdfparser/native/SkPdfNativeDoc.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkPdfNativeDoc.h"
 
 #include <stdio.h>
@@ skipping 122 matching lines @@
             readTrailer(trailerStart, xrefstartKeywordLine, storeCatalog, &xrefByteOffset, false);
             storeCatalog = false;
         }
     }
 
     // TODO(edisonn): warn/error expect fObjects[fRefCatalogId].fGeneration == fRefCatalogGeneration
     // TODO(edisonn): security, verify that SkPdfCatalogDictionary is indeed using mapper
 
     if (fRootCatalogRef) {
         fRootCatalog = (SkPdfCatalogDictionary*)resolveReference(fRootCatalogRef);
-        if (fRootCatalog->isDictionary() && fRootCatalog->valid()) {
+        if (fRootCatalog != NULL && fRootCatalog->isDictionary() && fRootCatalog->valid()) {
             SkPdfPageTreeNodeDictionary* tree = fRootCatalog->Pages(this);
             if (tree && tree->isDictionary() && tree->valid()) {
                 fillPages(tree);
             }
         }
     }
 
     if (pages() == 0) {
         // TODO(edisonn): probably it would be better to return NULL and make a clean document.
         loadWithoutXRef();
@@ skipping 61 matching lines @@
             SkPdfNativeObject* obj = object(i);
             SkPdfNativeObject* root = (obj && obj->isDictionary()) ? obj->get("Root") : NULL;
             if (root && root->isReference()) {
                 fRootCatalogRef = root;
             }
         }
     }
 
     if (fRootCatalogRef) {
         fRootCatalog = (SkPdfCatalogDictionary*)resolveReference(fRootCatalogRef);
-        if (fRootCatalog->isDictionary() && fRootCatalog->valid()) {
+        if (fRootCatalog != NULL && fRootCatalog->isDictionary() && fRootCatalog->valid()) {
             SkPdfPageTreeNodeDictionary* tree = fRootCatalog->Pages(this);
             if (tree && tree->isDictionary() && tree->valid()) {
                 fillPages(tree);
             }
         }
     }
 
 
 }
 
@@ skipping 340 matching lines @@
         // here unless we check for resolved reference on next line.
         // Determine if the pdf is corrupted, or we have a bug here.
 
         // Avoids recursive calls
         fObjects[id].fIsReferenceResolved = true;
 
         if (fObjects[id].fObj == NULL) {
             fObjects[id].fObj = readObject(id);
         }
 
-        if (fObjects[id].fResolvedReference == NULL) {
+        if (fObjects[id].fObj != NULL && fObjects[id].fResolvedReference == NULL) {
             if (!fObjects[id].fObj->isReference()) {
                 fObjects[id].fResolvedReference = fObjects[id].fObj;
             } else {
                 fObjects[id].fResolvedReference = resolveReference(fObjects[id].fObj);
             }
         }
 
         return fObjects[id].fResolvedReference;
     }
 
     return (SkPdfNativeObject*)ref;
 }
 
 size_t SkPdfNativeDoc::bytesUsed() const {
     return fAllocator->bytesUsed() +
            fContentLength +
            fObjects.count() * sizeof(PublicObjectEntry) +
            fPages.count() * sizeof(SkPdfPageObjectDictionary*) +
            sizeof(*this);
 }