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>

2 files changed, 21 insertions, 24 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_