Improve ValidateDictType().

Then use it in several places to de-duplicate some code.

-- avoid constructing temporary strings.
-- handle nullptr args on behalf of callers.
-- remove superfluous Get() call.

Change-Id: I0b847c7bca1cbb843456a2d1ae58a388ad958e1c
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/87592
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>

core/fpdfapi/parser/fpdf_parser_utility.cpp

diff --git a/core/fpdfapi/parser/fpdf_parser_utility.cpp b/core/fpdfapi/parser/fpdf_parser_utility.cpp
index 1396166..143551c 100644
--- a/core/fpdfapi/parser/fpdf_parser_utility.cpp
+++ b/core/fpdfapi/parser/fpdf_parser_utility.cpp
@@ -162,20 +162,20 @@
   return ret;
 }
 
-bool ValidateDictType(const CPDF_Dictionary* dict, const ByteString& type) {
+bool ValidateDictType(const CPDF_Dictionary* dict, ByteStringView type) {
   DCHECK(!type.IsEmpty());
-  return dict->GetNameFor("Type") == type;
+  return dict && dict->GetNameFor("Type") == type;
 }
 
 bool ValidateDictAllResourcesOfType(const CPDF_Dictionary* dict,
-                                    const ByteString& type) {
+                                    ByteStringView type) {
   if (!dict)
     return false;
 
   CPDF_DictionaryLocker locker(dict);
   for (const auto& it : locker) {
-    const CPDF_Dictionary* entry = ToDictionary(it.second.Get()->GetDirect());
-    if (!entry || !ValidateDictType(entry, type))
+    const CPDF_Dictionary* entry = ToDictionary(it.second->GetDirect());
+    if (!ValidateDictType(entry, type))
       return false;
   }
   return true;

core/fpdfapi/parser/fpdf_parser_utility.h

diff --git a/core/fpdfapi/parser/fpdf_parser_utility.h b/core/fpdfapi/parser/fpdf_parser_utility.h
index 3ef96c8..7f20a9d 100644
--- a/core/fpdfapi/parser/fpdf_parser_utility.h
+++ b/core/fpdfapi/parser/fpdf_parser_utility.h
@@ -55,13 +55,14 @@
 std::vector<float> ReadArrayElementsToVector(const CPDF_Array* pArray,
                                              size_t nCount);
 
-// Returns true if |dict| has a /Type name entry that matches |type|.
-bool ValidateDictType(const CPDF_Dictionary* dict, const ByteString& type);
+// Returns true if |dict| is non-null and has a /Type name entry that matches
+// |type|.
+bool ValidateDictType(const CPDF_Dictionary* dict, ByteStringView type);
 
 // Returns true if |dict| is non-null and all entries in |dict| are dictionaries
 // of |type|.
 bool ValidateDictAllResourcesOfType(const CPDF_Dictionary* dict,
-                                    const ByteString& type);
+                                    ByteStringView type);
 
 // Shorthand for ValidateDictAllResourcesOfType(dict, "Font").
 bool ValidateFontResourceDict(const CPDF_Dictionary* dict);

core/fpdfdoc/cpdf_bafontmap.cpp

diff --git a/core/fpdfdoc/cpdf_bafontmap.cpp b/core/fpdfdoc/cpdf_bafontmap.cpp
index 9ffba8a..db2f793 100644
--- a/core/fpdfdoc/cpdf_bafontmap.cpp
+++ b/core/fpdfdoc/cpdf_bafontmap.cpp
@@ -200,7 +200,7 @@
   for (const auto& it : locker) {
     const ByteString& csKey = it.first;
     CPDF_Dictionary* pElement = ToDictionary(it.second->GetDirect());
-    if (!pElement || pElement->GetNameFor("Type") != "Font")
+    if (!ValidateDictType(pElement, "Font"))
       continue;
 
     auto* pData = CPDF_DocPageData::FromDocument(m_pDocument.Get());

core/fpdfdoc/cpdf_interactiveform.cpp

diff --git a/core/fpdfdoc/cpdf_interactiveform.cpp b/core/fpdfdoc/cpdf_interactiveform.cpp
index df437c2..357b623 100644
--- a/core/fpdfdoc/cpdf_interactiveform.cpp
+++ b/core/fpdfdoc/cpdf_interactiveform.cpp
@@ -185,7 +185,7 @@
   for (const auto& it : locker) {
     const ByteString& csKey = it.first;
     const CPDF_Dictionary* pElement = ToDictionary(it.second->GetDirect());
-    if (!pElement || pElement->GetNameFor("Type") != "Font")
+    if (!ValidateDictType(pElement, "Font"))
       continue;
     if (pFont->GetFontDict() == pElement) {
       *csNameTag = csKey;
@@ -216,7 +216,7 @@
   for (const auto& it : locker) {
     const ByteString& csKey = it.first;
     CPDF_Dictionary* pElement = ToDictionary(it.second->GetDirect());
-    if (!pElement || pElement->GetNameFor("Type") != "Font")
+    if (!ValidateDictType(pElement, "Font"))
       continue;
 
     pFont = CPDF_DocPageData::FromDocument(pDocument)->GetFont(pElement);
@@ -321,7 +321,7 @@
   for (const auto& it : locker) {
     const ByteString& csKey = it.first;
     CPDF_Dictionary* pElement = ToDictionary(it.second->GetDirect());
-    if (!pElement || pElement->GetNameFor("Type") != "Font")
+    if (!ValidateDictType(pElement, "Font"))
       continue;
 
     auto* pData = CPDF_DocPageData::FromDocument(pDocument);
@@ -719,7 +719,7 @@
     return nullptr;
 
   CPDF_Dictionary* pElement = pFonts->GetDictFor(csAlias);
-  if (!pElement || pElement->GetNameFor("Type") != "Font")
+  if (!ValidateDictType(pElement, "Font"))
     return nullptr;
 
   return CPDF_DocPageData::FromDocument(m_pDocument)->GetFont(pElement);

xfa/fgas/font/cfgas_pdffontmgr.cpp

diff --git a/xfa/fgas/font/cfgas_pdffontmgr.cpp b/xfa/fgas/font/cfgas_pdffontmgr.cpp
index 7020121..a34bc98 100644
--- a/xfa/fgas/font/cfgas_pdffontmgr.cpp
+++ b/xfa/fgas/font/cfgas_pdffontmgr.cpp
@@ -12,6 +12,7 @@
 #include "core/fpdfapi/page/cpdf_docpagedata.h"
 #include "core/fpdfapi/parser/cpdf_dictionary.h"
 #include "core/fpdfapi/parser/cpdf_document.h"
+#include "core/fpdfapi/parser/fpdf_parser_utility.h"
 #include "core/fxge/fx_font.h"
 #include "third_party/base/check.h"
 #include "third_party/base/cxx17_backports.h"
@@ -61,7 +62,7 @@
       continue;
     }
     CPDF_Dictionary* pFontDict = ToDictionary(pObj->GetDirect());
-    if (!pFontDict || pFontDict->GetNameFor("Type") != "Font")
+    if (!ValidateDictType(pFontDict, "Font"))
       return nullptr;
 
     RetainPtr<CPDF_Font> pPDFFont = pData->GetFont(pFontDict);