Mark CPDF_Object pointers as const in CPDF_ViewerPreferences.

Work up the short call stack and mark FPDF_PAGERANGE as an opaque const
pointer. Also fix CPDF_ViewerPreferences::GenericName() to return an
optional string.

Change-Id: I2356d38888fcff8d4da37dd3efc17b284ff90485
Reviewed-on: https://pdfium-review.googlesource.com/32174
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: dsinclair <dsinclair@chromium.org>

5 files changed, 38 insertions, 41 deletions

diff --git a/core/fpdfdoc/cpdf_viewerpreferences.cpp b/core/fpdfdoc/cpdf_viewerpreferences.cpp
index e7fb1416a8..3359d6344f 100644
--- a/core/fpdfdoc/cpdf_viewerpreferences.cpp
+++ b/core/fpdfdoc/cpdf_viewerpreferences.cpp
@@ -9,52 +9,50 @@
 #include "core/fpdfapi/parser/cpdf_document.h"
 #include "core/fpdfapi/parser/cpdf_name.h"
 
-CPDF_ViewerPreferences::CPDF_ViewerPreferences(CPDF_Document* pDoc)
+CPDF_ViewerPreferences::CPDF_ViewerPreferences(const CPDF_Document* pDoc)
     : m_pDoc(pDoc) {}
 
 CPDF_ViewerPreferences::~CPDF_ViewerPreferences() {}
 
 bool CPDF_ViewerPreferences::IsDirectionR2L() const {
-  CPDF_Dictionary* pDict = GetViewerPreferences();
+  const CPDF_Dictionary* pDict = GetViewerPreferences();
   return pDict ? pDict->GetStringFor("Direction") == "R2L" : false;
 }
 
 bool CPDF_ViewerPreferences::PrintScaling() const {
-  CPDF_Dictionary* pDict = GetViewerPreferences();
+  const CPDF_Dictionary* pDict = GetViewerPreferences();
   return pDict ? pDict->GetStringFor("PrintScaling") != "None" : true;
 }
 
 int32_t CPDF_ViewerPreferences::NumCopies() const {
-  CPDF_Dictionary* pDict = GetViewerPreferences();
+  const CPDF_Dictionary* pDict = GetViewerPreferences();
   return pDict ? pDict->GetIntegerFor("NumCopies") : 1;
 }
 
-CPDF_Array* CPDF_ViewerPreferences::PrintPageRange() const {
-  CPDF_Dictionary* pDict = GetViewerPreferences();
+const CPDF_Array* CPDF_ViewerPreferences::PrintPageRange() const {
+  const CPDF_Dictionary* pDict = GetViewerPreferences();
   return pDict ? pDict->GetArrayFor("PrintPageRange") : nullptr;
 }
 
 ByteString CPDF_ViewerPreferences::Duplex() const {
-  CPDF_Dictionary* pDict = GetViewerPreferences();
+  const CPDF_Dictionary* pDict = GetViewerPreferences();
   return pDict ? pDict->GetStringFor("Duplex") : ByteString("None");
 }
 
-bool CPDF_ViewerPreferences::GenericName(const ByteString& bsKey,
-                                         ByteString* bsVal) const {
-  ASSERT(bsVal);
-  CPDF_Dictionary* pDict = GetViewerPreferences();
+Optional<ByteString> CPDF_ViewerPreferences::GenericName(
+    const ByteString& bsKey) const {
+  const CPDF_Dictionary* pDict = GetViewerPreferences();
   if (!pDict)
-    return false;
+    return {};
 
   const CPDF_Name* pName = ToName(pDict->GetObjectFor(bsKey));
   if (!pName)
-    return false;
+    return {};
 
-  *bsVal = pName->GetString();
-  return true;
+  return pName->GetString();
 }
 
-CPDF_Dictionary* CPDF_ViewerPreferences::GetViewerPreferences() const {
+const CPDF_Dictionary* CPDF_ViewerPreferences::GetViewerPreferences() const {
   const CPDF_Dictionary* pDict = m_pDoc->GetRoot();
   return pDict ? pDict->GetDictFor("ViewerPreferences") : nullptr;
 }
diff --git a/core/fpdfdoc/cpdf_viewerpreferences.h b/core/fpdfdoc/cpdf_viewerpreferences.h
index a1884748e4..45e4390065 100644
--- a/core/fpdfdoc/cpdf_viewerpreferences.h
+++ b/core/fpdfdoc/cpdf_viewerpreferences.h
@@ -10,6 +10,7 @@
 #include "core/fxcrt/fx_string.h"
 #include "core/fxcrt/fx_system.h"
 #include "core/fxcrt/unowned_ptr.h"
+#include "third_party/base/optional.h"
 
 class CPDF_Array;
 class CPDF_Dictionary;
@@ -17,24 +18,22 @@ class CPDF_Document;
 
 class CPDF_ViewerPreferences {
  public:
-  explicit CPDF_ViewerPreferences(CPDF_Document* pDoc);
+  explicit CPDF_ViewerPreferences(const CPDF_Document* pDoc);
   ~CPDF_ViewerPreferences();
 
   bool IsDirectionR2L() const;
   bool PrintScaling() const;
   int32_t NumCopies() const;
-  CPDF_Array* PrintPageRange() const;
+  const CPDF_Array* PrintPageRange() const;
   ByteString Duplex() const;
 
-  // Gets the entry for |bsKey|. If the entry exists and it is of type name,
-  // then this method writes the value into |bsVal| and returns true. Otherwise
-  // returns false and |bsVal| is untouched. |bsVal| must not be NULL.
-  bool GenericName(const ByteString& bsKey, ByteString* bsVal) const;
+  // Gets the entry for |bsKey|.
+  Optional<ByteString> GenericName(const ByteString& bsKey) const;
 
  private:
-  CPDF_Dictionary* GetViewerPreferences() const;
+  const CPDF_Dictionary* GetViewerPreferences() const;
 
-  UnownedPtr<CPDF_Document> const m_pDoc;
+  UnownedPtr<const CPDF_Document> const m_pDoc;
 };
 
 #endif  // CORE_FPDFDOC_CPDF_VIEWERPREFERENCES_H_
diff --git a/fpdfsdk/cpdfsdk_helpers.h b/fpdfsdk/cpdfsdk_helpers.h
index 0cd2617412..214fa72ab1 100644
--- a/fpdfsdk/cpdfsdk_helpers.h
+++ b/fpdfsdk/cpdfsdk_helpers.h
@@ -154,11 +154,11 @@ inline const CPDF_ContentMarkItem* CPDFContentMarkItemFromFPDFPageObjectMark(
   return reinterpret_cast<const CPDF_ContentMarkItem*>(mark);
 }
 
-inline FPDF_PAGERANGE FPDFPageRangeFromCPDFArray(CPDF_Array* range) {
+inline FPDF_PAGERANGE FPDFPageRangeFromCPDFArray(const CPDF_Array* range) {
   return reinterpret_cast<FPDF_PAGERANGE>(range);
 }
-inline CPDF_Array* CPDFArrayFromFPDFPageRange(FPDF_PAGERANGE range) {
-  return reinterpret_cast<CPDF_Array*>(range);
+inline const CPDF_Array* CPDFArrayFromFPDFPageRange(FPDF_PAGERANGE range) {
+  return reinterpret_cast<const CPDF_Array*>(range);
 }
 
 inline FPDF_PATHSEGMENT FPDFPathSegmentFromFXPathPoint(
diff --git a/fpdfsdk/fpdf_view.cpp b/fpdfsdk/fpdf_view.cpp
index 22cb62ea6e..6c4ad6020e 100644
--- a/fpdfsdk/fpdf_view.cpp
+++ b/fpdfsdk/fpdf_view.cpp
@@ -243,11 +243,11 @@ FPDF_EXPORT int FPDF_CALLCONV FPDF_GetFormType(FPDF_DOCUMENT document) {
   if (!pRoot)
     return FORMTYPE_NONE;
 
-  CPDF_Dictionary* pAcroForm = pRoot->GetDictFor("AcroForm");
+  const CPDF_Dictionary* pAcroForm = pRoot->GetDictFor("AcroForm");
   if (!pAcroForm)
     return FORMTYPE_NONE;
 
-  CPDF_Object* pXFA = pAcroForm->GetObjectFor("XFA");
+  const CPDF_Object* pXFA = pAcroForm->GetObjectFor("XFA");
   if (!pXFA)
     return FORMTYPE_ACRO_FORM;
 
@@ -978,7 +978,7 @@ FPDF_EXPORT int FPDF_CALLCONV FPDF_GetPageSizeByIndex(FPDF_DOCUMENT document,
 
 FPDF_EXPORT FPDF_BOOL FPDF_CALLCONV
 FPDF_VIEWERREF_GetPrintScaling(FPDF_DOCUMENT document) {
-  CPDF_Document* pDoc = CPDFDocumentFromFPDFDocument(document);
+  const CPDF_Document* pDoc = CPDFDocumentFromFPDFDocument(document);
   if (!pDoc)
     return true;
   CPDF_ViewerPreferences viewRef(pDoc);
@@ -987,7 +987,7 @@ FPDF_VIEWERREF_GetPrintScaling(FPDF_DOCUMENT document) {
 
 FPDF_EXPORT int FPDF_CALLCONV
 FPDF_VIEWERREF_GetNumCopies(FPDF_DOCUMENT document) {
-  CPDF_Document* pDoc = CPDFDocumentFromFPDFDocument(document);
+  const CPDF_Document* pDoc = CPDFDocumentFromFPDFDocument(document);
   if (!pDoc)
     return 1;
   CPDF_ViewerPreferences viewRef(pDoc);
@@ -996,7 +996,7 @@ FPDF_VIEWERREF_GetNumCopies(FPDF_DOCUMENT document) {
 
 FPDF_EXPORT FPDF_PAGERANGE FPDF_CALLCONV
 FPDF_VIEWERREF_GetPrintPageRange(FPDF_DOCUMENT document) {
-  CPDF_Document* pDoc = CPDFDocumentFromFPDFDocument(document);
+  const CPDF_Document* pDoc = CPDFDocumentFromFPDFDocument(document);
   if (!pDoc)
     return nullptr;
   CPDF_ViewerPreferences viewRef(pDoc);
@@ -1020,7 +1020,7 @@ FPDF_VIEWERREF_GetPrintPageRangeElement(FPDF_PAGERANGE pagerange,
 
 FPDF_EXPORT FPDF_DUPLEXTYPE FPDF_CALLCONV
 FPDF_VIEWERREF_GetDuplex(FPDF_DOCUMENT document) {
-  CPDF_Document* pDoc = CPDFDocumentFromFPDFDocument(document);
+  const CPDF_Document* pDoc = CPDFDocumentFromFPDFDocument(document);
   if (!pDoc)
     return DuplexUndefined;
   CPDF_ViewerPreferences viewRef(pDoc);
@@ -1039,18 +1039,18 @@ FPDF_VIEWERREF_GetName(FPDF_DOCUMENT document,
                        FPDF_BYTESTRING key,
                        char* buffer,
                        unsigned long length) {
-  CPDF_Document* pDoc = CPDFDocumentFromFPDFDocument(document);
+  const CPDF_Document* pDoc = CPDFDocumentFromFPDFDocument(document);
   if (!pDoc)
     return 0;
 
   CPDF_ViewerPreferences viewRef(pDoc);
-  ByteString bsVal;
-  if (!viewRef.GenericName(key, &bsVal))
+  Optional<ByteString> bsVal = viewRef.GenericName(key);
+  if (!bsVal)
     return 0;
 
-  unsigned long dwStringLen = bsVal.GetLength() + 1;
+  unsigned long dwStringLen = bsVal->GetLength() + 1;
   if (buffer && length >= dwStringLen)
-    memcpy(buffer, bsVal.c_str(), dwStringLen);
+    memcpy(buffer, bsVal->c_str(), dwStringLen);
   return dwStringLen;
 }
 
@@ -1066,7 +1066,7 @@ FPDF_CountNamedDests(FPDF_DOCUMENT document) {
 
   CPDF_NameTree nameTree(pDoc, "Dests");
   pdfium::base::CheckedNumeric<FPDF_DWORD> count = nameTree.GetCount();
-  CPDF_Dictionary* pDest = pRoot->GetDictFor("Dests");
+  const CPDF_Dictionary* pDest = pRoot->GetDictFor("Dests");
   if (pDest)
     count += pDest->GetCount();
 
@@ -1161,7 +1161,7 @@ FPDF_EXPORT FPDF_DEST FPDF_CALLCONV FPDF_GetNamedDest(FPDF_DOCUMENT document,
   CPDF_NameTree nameTree(pDoc, "Dests");
   int count = nameTree.GetCount();
   if (index >= count) {
-    CPDF_Dictionary* pDest = pRoot->GetDictFor("Dests");
+    const CPDF_Dictionary* pDest = pRoot->GetDictFor("Dests");
     if (!pDest)
       return nullptr;
 
diff --git a/public/fpdfview.h b/public/fpdfview.h
index 7758facc39..66813d8bb4 100644
--- a/public/fpdfview.h
+++ b/public/fpdfview.h
@@ -49,7 +49,7 @@ typedef struct fpdf_page_t__* FPDF_PAGE;
 typedef struct fpdf_pagelink_t__* FPDF_PAGELINK;
 typedef struct fpdf_pageobject_t__* FPDF_PAGEOBJECT;  // (text, path, etc.)
 typedef const struct fpdf_pageobjectmark_t__* FPDF_PAGEOBJECTMARK;
-typedef struct fpdf_pagerange_t__* FPDF_PAGERANGE;
+typedef const struct fpdf_pagerange_t__* FPDF_PAGERANGE;
 typedef const struct fpdf_pathsegment_t* FPDF_PATHSEGMENT;
 typedef void* FPDF_RECORDER;  // Passed into skia.
 typedef struct fpdf_schhandle_t__* FPDF_SCHHANDLE;