pdfviewer: don't crash when trailer is missing

experimental/PdfViewer/pdfparser/native/SkNativeParsedPDF.cpp

 #include "SkNativeParsedPDF.h"
 #include "SkPdfNativeTokenizer.h"
 #include "SkPdfBasics.h"
 #include "SkPdfObject.h"
 
 #include <stdio.h>
 #include <string.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 
@@ skipping 49 matching lines @@
 
 SkNativeParsedPDF* gDoc = NULL;
 
 // TODO(edisonn): NYI
 // TODO(edisonn): 3 constructuctors from URL, from stream, from file ...
 // TODO(edisonn): write one that accepts errors in the file and ignores/fixis them
 // TODO(edisonn): testing:
 // 1) run on a lot of file
 // 2) recoverable corupt file: remove endobj, endsteam, remove other keywords, use other white spaces, insert comments randomly, ...
 // 3) irrecoverable corrupt file
-SkNativeParsedPDF::SkNativeParsedPDF(const char* path) : fAllocator(new SkPdfAllocator()) {
+SkNativeParsedPDF::SkNativeParsedPDF(const char* path)
+        : fAllocator(new SkPdfAllocator())
+        , fRootCatalogRef(NULL)
+        , fRootCatalog(NULL) {
     gDoc = this;
     FILE* file = fopen(path, "r");
     fContentLength = getFileSize(path);
     fFileContent = new unsigned char[fContentLength + 1];
     fread(fFileContent, fContentLength, 1, file);
     fFileContent[fContentLength] = '\0';
     fclose(file);
     file = NULL;
 
     unsigned char* eofLine = lineHome(fFileContent, fFileContent + fContentLength - 1);
     unsigned char* xrefByteOffsetLine = previousLineHome(fFileContent, eofLine);
     unsigned char* xrefstartKeywordLine = previousLineHome(fFileContent, xrefByteOffsetLine);
 
     if (strcmp((char*)xrefstartKeywordLine, "startxref") != 0) {
         // TODO(edisonn): report/issue
     }
 
     long xrefByteOffset = atol((const char*)xrefByteOffsetLine);
 
     bool storeCatalog = true;
     while (xrefByteOffset >= 0) {
         unsigned char* trailerStart = readCrossReferenceSection(fFileContent + xrefByteOffset, xrefstartKeywordLine);
         xrefByteOffset = readTrailer(trailerStart, xrefstartKeywordLine, storeCatalog);
         storeCatalog = false;
     }
 
     // TODO(edisonn): warn/error expect fObjects[fRefCatalogId].fGeneration == fRefCatalogGeneration
     // TODO(edisonn): security, verify that SkPdfCatalogDictionary is indeed using mapper
     // load catalog
-    fRootCatalog = (SkPdfCatalogDictionary*)resolveReference(fRootCatalogRef);
-    SkPdfPageTreeNodeDictionary* tree = fRootCatalog->Pages(this);
 
-    fillPages(tree);
+    if (fRootCatalogRef) {
+        fRootCatalog = (SkPdfCatalogDictionary*)resolveReference(fRootCatalogRef);
+        SkPdfPageTreeNodeDictionary* tree = fRootCatalog->Pages(this);
+
+        fillPages(tree);
+    } else {
+        // TODO(edisonn): corrupted pdf, read it from beginning and rebuild (xref, trailer, or just reall all objects)
+        // 0 pages
+    }
 
     // now actually read all objects if we want, or do it lazyly
     // and resolve references?... or not ...
 }
 
 // TODO(edisonn): NYI
 SkNativeParsedPDF::~SkNativeParsedPDF() {
     delete[] fFileContent;
     delete fAllocator;
 }
@@ skipping 50 matching lines @@
     }
     // TODO(edisonn): it should never get here? there is no trailer?
     return current;
 }
 
 long SkNativeParsedPDF::readTrailer(unsigned char* trailerStart, unsigned char* trailerEnd, bool storeCatalog) {
     unsigned char* current = ignoreLine(trailerStart, trailerEnd);  // TODO(edisonn): verify next keyord is "trailer" use nextObject here
 
     SkPdfObject token;
     current = nextObject(current, trailerEnd, &token, fAllocator);
+    if (!token.isDictionary()) {
+        return -1;
+    }
     SkPdfFileTrailerDictionary* trailer = (SkPdfFileTrailerDictionary*)&token;
+    if (!trailer->valid()) {
+        return -1;
+    }
 
     if (storeCatalog) {
         const SkPdfObject* ref = trailer->Root(NULL);
         if (ref == NULL || !ref->isReference()) {
             // TODO(edisonn): oops, we have to fix the corrup pdf file
             return -1;
         }
         fRootCatalogRef = ref;
     }
 
@@ skipping 210 matching lines @@
             } else {
                 fObjects[id].fResolvedReference = resolveReference(fObjects[id].fObj);
             }
         }
 
         return fObjects[id].fResolvedReference;
     }
     // TODO(edisonn): fix the mess with const, probably we need to remove it pretty much everywhere
     return (SkPdfObject*)ref;
 }