Cleanup string passing in core/fpdf*

Return strings where possible.
Add missing consts to strings passed by ref.
Convert non-const cases to pointers.
Rename a few methods to be clearer.

Change-Id: I86569bc1744f539e6dd67fc73649b272c016328c
Reviewed-on: https://pdfium-review.googlesource.com/3951
Commit-Queue: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Nicolás Peña <npm@chromium.org>

11 files changed, 68 insertions, 71 deletions

diff --git a/core/fpdfdoc/cpdf_defaultappearance.cpp b/core/fpdfdoc/cpdf_defaultappearance.cpp
index 1873c1ae58..28213aa33b 100644
--- a/core/fpdfdoc/cpdf_defaultappearance.cpp
+++ b/core/fpdfdoc/cpdf_defaultappearance.cpp
@@ -36,20 +36,19 @@ CFX_ByteString CPDF_DefaultAppearance::GetFontString() {
   return csFont;
 }
 
-void CPDF_DefaultAppearance::GetFont(CFX_ByteString& csFontNameTag,
-                                     float& fFontSize) {
-  csFontNameTag = "";
-  fFontSize = 0;
+CFX_ByteString CPDF_DefaultAppearance::GetFont(float* fFontSize) {
+  *fFontSize = 0.0f;
   if (m_csDA.IsEmpty())
-    return;
+    return CFX_ByteString();
 
+  CFX_ByteString csFontNameTag;
   CPDF_SimpleParser syntax(m_csDA.AsStringC());
   if (syntax.FindTagParamFromStart("Tf", 2)) {
     csFontNameTag = CFX_ByteString(syntax.GetWord());
     csFontNameTag.Delete(0, 1);
-    fFontSize = FX_atof(syntax.GetWord());
+    *fFontSize = FX_atof(syntax.GetWord());
   }
-  csFontNameTag = PDF_NameDecode(csFontNameTag);
+  return PDF_NameDecode(csFontNameTag);
 }
 
 bool CPDF_DefaultAppearance::HasColor(PaintOperation nOperation) {
diff --git a/core/fpdfdoc/cpdf_defaultappearance.h b/core/fpdfdoc/cpdf_defaultappearance.h
index 0edc18c31f..3be06e294d 100644
--- a/core/fpdfdoc/cpdf_defaultappearance.h
+++ b/core/fpdfdoc/cpdf_defaultappearance.h
@@ -29,7 +29,7 @@ class CPDF_DefaultAppearance {
 
   bool HasFont();
   CFX_ByteString GetFontString();
-  void GetFont(CFX_ByteString& csFontNameTag, float& fFontSize);
+  CFX_ByteString GetFont(float* fFontSize);
 
   bool HasColor(PaintOperation nOperation = PaintOperation::FILL);
   CFX_ByteString GetColorString(
diff --git a/core/fpdfdoc/cpdf_docjsactions.cpp b/core/fpdfdoc/cpdf_docjsactions.cpp
index a7fcdfd071..c0e7a78fd6 100644
--- a/core/fpdfdoc/cpdf_docjsactions.cpp
+++ b/core/fpdfdoc/cpdf_docjsactions.cpp
@@ -16,11 +16,12 @@ int CPDF_DocJSActions::CountJSActions() const {
   return name_tree.GetCount();
 }
 
-CPDF_Action CPDF_DocJSActions::GetJSAction(int index,
-                                           CFX_ByteString& csName) const {
+CPDF_Action CPDF_DocJSActions::GetJSActionAndName(
+    int index,
+    CFX_ByteString* csName) const {
   ASSERT(m_pDocument);
   CPDF_NameTree name_tree(m_pDocument, "JavaScript");
-  CPDF_Object* pAction = name_tree.LookupValue(index, csName);
+  CPDF_Object* pAction = name_tree.LookupValueAndName(index, csName);
   return ToDictionary(pAction) ? CPDF_Action(pAction->GetDict())
                                : CPDF_Action();
 }
diff --git a/core/fpdfdoc/cpdf_docjsactions.h b/core/fpdfdoc/cpdf_docjsactions.h
index 8a8d03d364..16b6be3d69 100644
--- a/core/fpdfdoc/cpdf_docjsactions.h
+++ b/core/fpdfdoc/cpdf_docjsactions.h
@@ -17,7 +17,7 @@ class CPDF_DocJSActions {
   explicit CPDF_DocJSActions(CPDF_Document* pDoc);
 
   int CountJSActions() const;
-  CPDF_Action GetJSAction(int index, CFX_ByteString& csName) const;
+  CPDF_Action GetJSActionAndName(int index, CFX_ByteString* csName) const;
   CPDF_Action GetJSAction(const CFX_ByteString& csName) const;
   int FindJSAction(const CFX_ByteString& csName) const;
   CPDF_Document* GetDocument() const { return m_pDocument; }
diff --git a/core/fpdfdoc/cpdf_formcontrol.cpp b/core/fpdfdoc/cpdf_formcontrol.cpp
index b8a11cc204..d8d6854b82 100644
--- a/core/fpdfdoc/cpdf_formcontrol.cpp
+++ b/core/fpdfdoc/cpdf_formcontrol.cpp
@@ -280,10 +280,9 @@ CPDF_DefaultAppearance CPDF_FormControl::GetDefaultAppearance() {
 }
 
 CPDF_Font* CPDF_FormControl::GetDefaultControlFont() {
-  CPDF_DefaultAppearance cDA = GetDefaultAppearance();
-  CFX_ByteString csFontNameTag;
   float fFontSize;
-  cDA.GetFont(csFontNameTag, fFontSize);
+  CPDF_DefaultAppearance cDA = GetDefaultAppearance();
+  CFX_ByteString csFontNameTag = cDA.GetFont(&fFontSize);
   if (csFontNameTag.IsEmpty())
     return nullptr;
 
diff --git a/core/fpdfdoc/cpdf_interform.cpp b/core/fpdfdoc/cpdf_interform.cpp
index 1192e6e556..ebe5079f3b 100644
--- a/core/fpdfdoc/cpdf_interform.cpp
+++ b/core/fpdfdoc/cpdf_interform.cpp
@@ -55,7 +55,7 @@ CFX_WideString GetFieldValue(const CPDF_Dictionary& pFieldDict,
 void AddFont(CPDF_Dictionary*& pFormDict,
              CPDF_Document* pDocument,
              const CPDF_Font* pFont,
-             CFX_ByteString& csNameTag);
+             CFX_ByteString* csNameTag);
 
 void InitDict(CPDF_Dictionary*& pFormDict, CPDF_Document* pDocument) {
   if (!pDocument)
@@ -70,27 +70,24 @@ void InitDict(CPDF_Dictionary*& pFormDict, CPDF_Document* pDocument) {
   CFX_ByteString csDA;
   if (!pFormDict->KeyExist("DR")) {
     CFX_ByteString csBaseName;
-    CFX_ByteString csDefault;
     uint8_t charSet = CPDF_InterForm::GetNativeCharSet();
     CPDF_Font* pFont = CPDF_InterForm::AddStandardFont(pDocument, "Helvetica");
-    if (pFont) {
-      AddFont(pFormDict, pDocument, pFont, csBaseName);
-      csDefault = csBaseName;
-    }
+    if (pFont)
+      AddFont(pFormDict, pDocument, pFont, &csBaseName);
+
     if (charSet != FXFONT_ANSI_CHARSET) {
       CFX_ByteString csFontName =
           CPDF_InterForm::GetNativeFont(charSet, nullptr);
       if (!pFont || csFontName != "Helvetica") {
         pFont = CPDF_InterForm::AddNativeFont(pDocument);
         if (pFont) {
-          csBaseName = "";
-          AddFont(pFormDict, pDocument, pFont, csBaseName);
-          csDefault = csBaseName;
+          csBaseName.clear();
+          AddFont(pFormDict, pDocument, pFont, &csBaseName);
         }
       }
     }
     if (pFont)
-      csDA = "/" + PDF_NameEncode(csDefault) + " 0 Tf";
+      csDA = "/" + PDF_NameEncode(csBaseName) + " 0 Tf";
   }
   if (!csDA.IsEmpty())
     csDA += " ";
@@ -102,7 +99,7 @@ void InitDict(CPDF_Dictionary*& pFormDict, CPDF_Document* pDocument) {
 
 CPDF_Font* GetFont(CPDF_Dictionary* pFormDict,
                    CPDF_Document* pDocument,
-                   CFX_ByteString csNameTag) {
+                   const CFX_ByteString& csNameTag) {
   CFX_ByteString csAlias = PDF_NameDecode(csNameTag);
   if (!pFormDict || csAlias.IsEmpty())
     return nullptr;
@@ -127,7 +124,7 @@ CPDF_Font* GetFont(CPDF_Dictionary* pFormDict,
 CPDF_Font* GetNativeFont(CPDF_Dictionary* pFormDict,
                          CPDF_Document* pDocument,
                          uint8_t charSet,
-                         CFX_ByteString& csNameTag) {
+                         CFX_ByteString* csNameTag) {
   if (!pFormDict)
     return nullptr;
 
@@ -157,8 +154,8 @@ CPDF_Font* GetNativeFont(CPDF_Dictionary* pFormDict,
     if (!pSubst)
       continue;
 
-    if (pSubst->m_Charset == (int)charSet) {
-      csNameTag = csKey;
+    if (pSubst->m_Charset == static_cast<int>(charSet)) {
+      *csNameTag = csKey;
       return pFind;
     }
   }
@@ -167,7 +164,7 @@ CPDF_Font* GetNativeFont(CPDF_Dictionary* pFormDict,
 
 bool FindFont(CPDF_Dictionary* pFormDict,
               const CPDF_Font* pFont,
-              CFX_ByteString& csNameTag) {
+              CFX_ByteString* csNameTag) {
   if (!pFormDict || !pFont)
     return false;
 
@@ -189,7 +186,7 @@ bool FindFont(CPDF_Dictionary* pFormDict,
     if (pElement->GetStringFor("Type") != "Font")
       continue;
     if (pFont->GetFontDict() == pElement) {
-      csNameTag = csKey;
+      *csNameTag = csKey;
       return true;
     }
   }
@@ -200,7 +197,7 @@ bool FindFont(CPDF_Dictionary* pFormDict,
               CPDF_Document* pDocument,
               CFX_ByteString csFontName,
               CPDF_Font*& pFont,
-              CFX_ByteString& csNameTag) {
+              CFX_ByteString* csNameTag) {
   if (!pFormDict)
     return false;
 
@@ -211,6 +208,7 @@ bool FindFont(CPDF_Dictionary* pFormDict,
   CPDF_Dictionary* pFonts = pDR->GetDictFor("Font");
   if (!pFonts)
     return false;
+
   if (csFontName.GetLength() > 0)
     csFontName.Remove(' ');
 
@@ -232,7 +230,7 @@ bool FindFont(CPDF_Dictionary* pFormDict,
     csBaseFont = pFont->GetBaseFont();
     csBaseFont.Remove(' ');
     if (csBaseFont == csFontName) {
-      csNameTag = csKey;
+      *csNameTag = csKey;
       return true;
     }
   }
@@ -242,15 +240,15 @@ bool FindFont(CPDF_Dictionary* pFormDict,
 void AddFont(CPDF_Dictionary*& pFormDict,
              CPDF_Document* pDocument,
              const CPDF_Font* pFont,
-             CFX_ByteString& csNameTag) {
+             CFX_ByteString* csNameTag) {
   if (!pFont)
     return;
   if (!pFormDict)
     InitDict(pFormDict, pDocument);
 
   CFX_ByteString csTag;
-  if (FindFont(pFormDict, pFont, csTag)) {
-    csNameTag = csTag;
+  if (FindFont(pFormDict, pFont, &csTag)) {
+    *csNameTag = csTag;
     return;
   }
   if (!pFormDict)
@@ -264,27 +262,27 @@ void AddFont(CPDF_Dictionary*& pFormDict,
   if (!pFonts)
     pFonts = pDR->SetNewFor<CPDF_Dictionary>("Font");
 
-  if (csNameTag.IsEmpty())
-    csNameTag = pFont->GetBaseFont();
+  if (csNameTag->IsEmpty())
+    *csNameTag = pFont->GetBaseFont();
 
-  csNameTag.Remove(' ');
-  csNameTag = CPDF_InterForm::GenerateNewResourceName(pDR, "Font", 4,
-                                                      csNameTag.c_str());
-  pFonts->SetNewFor<CPDF_Reference>(csNameTag, pDocument,
+  csNameTag->Remove(' ');
+  *csNameTag = CPDF_InterForm::GenerateNewResourceName(pDR, "Font", 4,
+                                                       csNameTag->c_str());
+  pFonts->SetNewFor<CPDF_Reference>(*csNameTag, pDocument,
                                     pFont->GetFontDict()->GetObjNum());
 }
 
 CPDF_Font* AddNativeFont(CPDF_Dictionary*& pFormDict,
                          CPDF_Document* pDocument,
                          uint8_t charSet,
-                         CFX_ByteString& csNameTag) {
+                         CFX_ByteString* csNameTag) {
   if (!pFormDict)
     InitDict(pFormDict, pDocument);
 
   CFX_ByteString csTemp;
-  CPDF_Font* pFont = GetNativeFont(pFormDict, pDocument, charSet, csTemp);
+  CPDF_Font* pFont = GetNativeFont(pFormDict, pDocument, charSet, &csTemp);
   if (pFont) {
-    csNameTag = csTemp;
+    *csNameTag = csTemp;
     return pFont;
   }
   CFX_ByteString csFontName = CPDF_InterForm::GetNativeFont(charSet, nullptr);
@@ -565,7 +563,7 @@ CFieldTree::Node* CFieldTree::FindNode(const CFX_WideString& full_name) {
 
 CPDF_Font* AddNativeInterFormFont(CPDF_Dictionary*& pFormDict,
                                   CPDF_Document* pDocument,
-                                  CFX_ByteString& csNameTag) {
+                                  CFX_ByteString* csNameTag) {
   uint8_t charSet = CPDF_InterForm::GetNativeCharSet();
   return AddNativeFont(pFormDict, pDocument, charSet, csNameTag);
 }
diff --git a/core/fpdfdoc/cpdf_interform.h b/core/fpdfdoc/cpdf_interform.h
index 6c464f023d..74e5b10864 100644
--- a/core/fpdfdoc/cpdf_interform.h
+++ b/core/fpdfdoc/cpdf_interform.h
@@ -29,7 +29,7 @@ class IPDF_FormNotify;
 
 CPDF_Font* AddNativeInterFormFont(CPDF_Dictionary*& pFormDict,
                                   CPDF_Document* pDocument,
-                                  CFX_ByteString& csNameTag);
+                                  CFX_ByteString* csNameTag);
 
 class CPDF_InterForm {
  public:
diff --git a/core/fpdfdoc/cpdf_nametree.cpp b/core/fpdfdoc/cpdf_nametree.cpp
index b8d1eb0ab1..5ecdb4863b 100644
--- a/core/fpdfdoc/cpdf_nametree.cpp
+++ b/core/fpdfdoc/cpdf_nametree.cpp
@@ -78,7 +78,7 @@ CPDF_Object* SearchNameNode(CPDF_Dictionary* pNode,
 CPDF_Object* SearchNameNode(CPDF_Dictionary* pNode,
                             size_t nIndex,
                             size_t& nCurIndex,
-                            CFX_ByteString& csName,
+                            CFX_ByteString* csName,
                             CPDF_Array** ppFind,
                             int nLevel = 0) {
   if (nLevel > nMaxRecursion)
@@ -93,7 +93,7 @@ CPDF_Object* SearchNameNode(CPDF_Dictionary* pNode,
     }
     if (ppFind)
       *ppFind = pNames;
-    csName = pNames->GetStringAt((nIndex - nCurIndex) * 2);
+    *csName = pNames->GetStringAt((nIndex - nCurIndex) * 2);
     return pNames->GetDirectObjectAt((nIndex - nCurIndex) * 2 + 1);
   }
   CPDF_Array* pKids = pNode->GetArrayFor("Kids");
@@ -164,10 +164,12 @@ int CPDF_NameTree::GetIndex(const CFX_ByteString& csName) const {
   return nIndex;
 }
 
-CPDF_Object* CPDF_NameTree::LookupValue(int nIndex,
-                                        CFX_ByteString& csName) const {
+CPDF_Object* CPDF_NameTree::LookupValueAndName(int nIndex,
+                                               CFX_ByteString* csName) const {
+  *csName = CFX_ByteString();
   if (!m_pRoot)
     return nullptr;
+
   size_t nCurIndex = 0;
   return SearchNameNode(m_pRoot, nIndex, nCurIndex, csName, nullptr);
 }
@@ -175,6 +177,7 @@ CPDF_Object* CPDF_NameTree::LookupValue(int nIndex,
 CPDF_Object* CPDF_NameTree::LookupValue(const CFX_ByteString& csName) const {
   if (!m_pRoot)
     return nullptr;
+
   size_t nIndex = 0;
   return SearchNameNode(m_pRoot, csName, nIndex, nullptr);
 }
diff --git a/core/fpdfdoc/cpdf_nametree.h b/core/fpdfdoc/cpdf_nametree.h
index d6763ad987..7a792aef59 100644
--- a/core/fpdfdoc/cpdf_nametree.h
+++ b/core/fpdfdoc/cpdf_nametree.h
@@ -19,7 +19,7 @@ class CPDF_NameTree {
   explicit CPDF_NameTree(CPDF_Dictionary* pRoot) : m_pRoot(pRoot) {}
   CPDF_NameTree(CPDF_Document* pDoc, const CFX_ByteString& category);
 
-  CPDF_Object* LookupValue(int nIndex, CFX_ByteString& csName) const;
+  CPDF_Object* LookupValueAndName(int nIndex, CFX_ByteString* csName) const;
   CPDF_Object* LookupValue(const CFX_ByteString& csName) const;
   CPDF_Array* LookupNamedDest(CPDF_Document* pDoc, const CFX_ByteString& sName);
 
diff --git a/core/fpdfdoc/cpvt_fontmap.cpp b/core/fpdfdoc/cpvt_fontmap.cpp
index 283f60011b..17ce673fde 100644
--- a/core/fpdfdoc/cpvt_fontmap.cpp
+++ b/core/fpdfdoc/cpvt_fontmap.cpp
@@ -25,25 +25,23 @@ CPVT_FontMap::CPVT_FontMap(CPDF_Document* pDoc,
 
 CPVT_FontMap::~CPVT_FontMap() {}
 
-void CPVT_FontMap::GetAnnotSysPDFFont(CPDF_Document* pDoc,
-                                      const CPDF_Dictionary* pResDict,
-                                      CPDF_Font*& pSysFont,
-                                      CFX_ByteString& sSysFontAlias) {
+CPDF_Font* CPVT_FontMap::GetAnnotSysPDFFont(CPDF_Document* pDoc,
+                                            const CPDF_Dictionary* pResDict,
+                                            CFX_ByteString* sSysFontAlias) {
   if (!pDoc || !pResDict)
-    return;
+    return nullptr;
 
-  CFX_ByteString sFontAlias;
   CPDF_Dictionary* pFormDict = pDoc->GetRoot()->GetDictFor("AcroForm");
   CPDF_Font* pPDFFont = AddNativeInterFormFont(pFormDict, pDoc, sSysFontAlias);
   if (!pPDFFont)
-    return;
+    return nullptr;
 
   CPDF_Dictionary* pFontList = pResDict->GetDictFor("Font");
-  if (pFontList && !pFontList->KeyExist(sSysFontAlias)) {
-    pFontList->SetNewFor<CPDF_Reference>(sSysFontAlias, pDoc,
+  if (pFontList && !pFontList->KeyExist(*sSysFontAlias)) {
+    pFontList->SetNewFor<CPDF_Reference>(*sSysFontAlias, pDoc,
                                          pPDFFont->GetFontDict()->GetObjNum());
   }
-  pSysFont = pPDFFont;
+  return pPDFFont;
 }
 
 CPDF_Font* CPVT_FontMap::GetPDFFont(int32_t nFontIndex) {
@@ -52,8 +50,8 @@ CPDF_Font* CPVT_FontMap::GetPDFFont(int32_t nFontIndex) {
       return m_pDefFont;
     case 1:
       if (!m_pSysFont) {
-        GetAnnotSysPDFFont(m_pDocument, m_pResDict, m_pSysFont,
-                           m_sSysFontAlias);
+        m_pSysFont =
+            GetAnnotSysPDFFont(m_pDocument, m_pResDict, &m_sSysFontAlias);
       }
       return m_pSysFont;
     default:
@@ -67,12 +65,12 @@ CFX_ByteString CPVT_FontMap::GetPDFFontAlias(int32_t nFontIndex) {
       return m_sDefFontAlias;
     case 1:
       if (!m_pSysFont) {
-        GetAnnotSysPDFFont(m_pDocument, m_pResDict, m_pSysFont,
-                           m_sSysFontAlias);
+        m_pSysFont =
+            GetAnnotSysPDFFont(m_pDocument, m_pResDict, &m_sSysFontAlias);
       }
       return m_sSysFontAlias;
     default:
-      return "";
+      return CFX_ByteString();
   }
 }
 
diff --git a/core/fpdfdoc/cpvt_fontmap.h b/core/fpdfdoc/cpvt_fontmap.h
index 98e390f409..6080010cac 100644
--- a/core/fpdfdoc/cpvt_fontmap.h
+++ b/core/fpdfdoc/cpvt_fontmap.h
@@ -33,10 +33,9 @@ class CPVT_FontMap : public IPVT_FontMap {
   int32_t CharCodeFromUnicode(int32_t nFontIndex, uint16_t word) override;
   int32_t CharSetFromUnicode(uint16_t word, int32_t nOldCharset) override;
 
-  static void GetAnnotSysPDFFont(CPDF_Document* pDoc,
-                                 const CPDF_Dictionary* pResDict,
-                                 CPDF_Font*& pSysFont,
-                                 CFX_ByteString& sSysFontAlias);
+  static CPDF_Font* GetAnnotSysPDFFont(CPDF_Document* pDoc,
+                                       const CPDF_Dictionary* pResDict,
+                                       CFX_ByteString* sSysFontAlias);
 
  private:
   CPDF_Document* const m_pDocument;