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>

9 files changed, 37 insertions, 36 deletions

diff --git a/core/fpdfapi/page/cpdf_streamparser.cpp b/core/fpdfapi/page/cpdf_streamparser.cpp
index 3c4e534116..e0c6e25aef 100644
--- a/core/fpdfapi/page/cpdf_streamparser.cpp
+++ b/core/fpdfapi/page/cpdf_streamparser.cpp
@@ -62,7 +62,7 @@ uint32_t PDF_DecodeInlineStream(const uint8_t* src_buf,
                                 uint32_t limit,
                                 int width,
                                 int height,
-                                CFX_ByteString& decoder,
+                                const CFX_ByteString& decoder,
                                 CPDF_Dictionary* pParam,
                                 uint8_t*& dest_buf,
                                 uint32_t& dest_size) {
diff --git a/core/fpdfapi/parser/cpdf_crypto_handler.cpp b/core/fpdfapi/parser/cpdf_crypto_handler.cpp
index 4fc7b3039b..ea09601b30 100644
--- a/core/fpdfapi/parser/cpdf_crypto_handler.cpp
+++ b/core/fpdfapi/parser/cpdf_crypto_handler.cpp
@@ -227,14 +227,14 @@ bool CPDF_CryptoHandler::CryptFinish(void* context,
   return true;
 }
 
-void CPDF_CryptoHandler::Decrypt(uint32_t objnum,
-                                 uint32_t gennum,
-                                 CFX_ByteString& str) {
+CFX_ByteString CPDF_CryptoHandler::Decrypt(uint32_t objnum,
+                                           uint32_t gennum,
+                                           const CFX_ByteString& str) {
   CFX_BinaryBuf dest_buf;
   void* context = DecryptStart(objnum, gennum);
   DecryptStream(context, str.raw_str(), str.GetLength(), dest_buf);
   DecryptFinish(context, dest_buf);
-  str = CFX_ByteString(dest_buf.GetBuffer(), dest_buf.GetSize());
+  return CFX_ByteString(dest_buf.GetBuffer(), dest_buf.GetSize());
 }
 
 void* CPDF_CryptoHandler::DecryptStart(uint32_t objnum, uint32_t gennum) {
diff --git a/core/fpdfapi/parser/cpdf_crypto_handler.h b/core/fpdfapi/parser/cpdf_crypto_handler.h
index 63a2590950..1e3890a55b 100644
--- a/core/fpdfapi/parser/cpdf_crypto_handler.h
+++ b/core/fpdfapi/parser/cpdf_crypto_handler.h
@@ -23,7 +23,9 @@ class CPDF_CryptoHandler {
             CPDF_SecurityHandler* pSecurityHandler);
   uint32_t DecryptGetSize(uint32_t src_size);
   void* DecryptStart(uint32_t objnum, uint32_t gennum);
-  void Decrypt(uint32_t objnum, uint32_t gennum, CFX_ByteString& str);
+  CFX_ByteString Decrypt(uint32_t objnum,
+                         uint32_t gennum,
+                         const CFX_ByteString& str);
   bool DecryptStream(void* context,
                      const uint8_t* src_buf,
                      uint32_t src_size,
diff --git a/core/fpdfapi/parser/cpdf_data_avail.cpp b/core/fpdfapi/parser/cpdf_data_avail.cpp
index 5a2db8861c..aa0b4fdad6 100644
--- a/core/fpdfapi/parser/cpdf_data_avail.cpp
+++ b/core/fpdfapi/parser/cpdf_data_avail.cpp
@@ -837,7 +837,7 @@ void CPDF_DataAvail::SetStartOffset(FX_FILESIZE dwOffset) {
   m_Pos = dwOffset;
 }
 
-bool CPDF_DataAvail::GetNextToken(CFX_ByteString& token) {
+bool CPDF_DataAvail::GetNextToken(CFX_ByteString* token) {
   uint8_t ch;
   if (!GetNextChar(ch))
     return false;
@@ -870,11 +870,9 @@ bool CPDF_DataAvail::GetNextToken(CFX_ByteString& token) {
 
         if (!PDFCharIsOther(ch) && !PDFCharIsNumeric(ch)) {
           m_Pos--;
-          CFX_ByteString ret(buffer, index);
-          token = ret;
+          *token = CFX_ByteString(buffer, index);
           return true;
         }
-
         if (index < sizeof(buffer))
           buffer[index++] = ch;
       }
@@ -895,9 +893,7 @@ bool CPDF_DataAvail::GetNextToken(CFX_ByteString& token) {
       else
         m_Pos--;
     }
-
-    CFX_ByteString ret(buffer, index);
-    token = ret;
+    *token = CFX_ByteString(buffer, index);
     return true;
   }
 
@@ -914,7 +910,7 @@ bool CPDF_DataAvail::GetNextToken(CFX_ByteString& token) {
     }
   }
 
-  token = CFX_ByteString(buffer, index);
+  *token = CFX_ByteString(buffer, index);
   return true;
 }
 
@@ -948,8 +944,9 @@ bool CPDF_DataAvail::CheckCrossRefItem(DownloadHints* pHints) {
   int32_t iSize = 0;
   CFX_ByteString token;
   while (1) {
-    if (!GetNextToken(token)) {
-      iSize = (int32_t)(m_Pos + 512 > m_dwFileLen ? m_dwFileLen - m_Pos : 512);
+    if (!GetNextToken(&token)) {
+      iSize = static_cast<int32_t>(
+          m_Pos + 512 > m_dwFileLen ? m_dwFileLen - m_Pos : 512);
       pHints->AddSegment(m_Pos, iSize);
       return false;
     }
@@ -983,8 +980,9 @@ bool CPDF_DataAvail::CheckAllCrossRefStream(DownloadHints* pHints) {
 bool CPDF_DataAvail::CheckCrossRef(DownloadHints* pHints) {
   int32_t iSize = 0;
   CFX_ByteString token;
-  if (!GetNextToken(token)) {
-    iSize = (int32_t)(m_Pos + 512 > m_dwFileLen ? m_dwFileLen - m_Pos : 512);
+  if (!GetNextToken(&token)) {
+    iSize = static_cast<int32_t>(m_Pos + 512 > m_dwFileLen ? m_dwFileLen - m_Pos
+                                                           : 512);
     pHints->AddSegment(m_Pos, iSize);
     return false;
   }
@@ -995,8 +993,9 @@ bool CPDF_DataAvail::CheckCrossRef(DownloadHints* pHints) {
   }
 
   while (1) {
-    if (!GetNextToken(token)) {
-      iSize = (int32_t)(m_Pos + 512 > m_dwFileLen ? m_dwFileLen - m_Pos : 512);
+    if (!GetNextToken(&token)) {
+      iSize = static_cast<int32_t>(
+          m_Pos + 512 > m_dwFileLen ? m_dwFileLen - m_Pos : 512);
       pHints->AddSegment(m_Pos, iSize);
       m_docStatus = PDF_DATAAVAIL_CROSSREF_ITEM;
       return false;
diff --git a/core/fpdfapi/parser/cpdf_data_avail.h b/core/fpdfapi/parser/cpdf_data_avail.h
index 65638cff0b..62c5d49c9d 100644
--- a/core/fpdfapi/parser/cpdf_data_avail.h
+++ b/core/fpdfapi/parser/cpdf_data_avail.h
@@ -156,7 +156,7 @@ class CPDF_DataAvail final {
   int32_t CheckCrossRefStream(DownloadHints* pHints, FX_FILESIZE& xref_offset);
   bool IsLinearizedFile(uint8_t* pData, uint32_t dwLen);
   void SetStartOffset(FX_FILESIZE dwOffset);
-  bool GetNextToken(CFX_ByteString& token);
+  bool GetNextToken(CFX_ByteString* token);
   bool GetNextChar(uint8_t& ch);
   std::unique_ptr<CPDF_Object> ParseIndirectObjectAt(
       FX_FILESIZE pos,
diff --git a/core/fpdfapi/parser/cpdf_stream_acc.cpp b/core/fpdfapi/parser/cpdf_stream_acc.cpp
index 77ef2ff2bc..fe333e4d2b 100644
--- a/core/fpdfapi/parser/cpdf_stream_acc.cpp
+++ b/core/fpdfapi/parser/cpdf_stream_acc.cpp
@@ -43,7 +43,7 @@ void CPDF_StreamAcc::LoadAllData(bool bRawAccess,
     m_pData = pSrcData;
     m_dwSize = dwSrcSize;
   } else if (!PDF_DataDecode(pSrcData, dwSrcSize, m_pStream->GetDict(), m_pData,
-                             m_dwSize, m_ImageDecoder, m_pImageParam,
+                             m_dwSize, &m_ImageDecoder, m_pImageParam,
                              estimated_size, bImageAcc)) {
     m_pData = pSrcData;
     m_dwSize = dwSrcSize;
diff --git a/core/fpdfapi/parser/cpdf_syntax_parser.cpp b/core/fpdfapi/parser/cpdf_syntax_parser.cpp
index 73bf56d206..1c84b859db 100644
--- a/core/fpdfapi/parser/cpdf_syntax_parser.cpp
+++ b/core/fpdfapi/parser/cpdf_syntax_parser.cpp
@@ -405,13 +405,13 @@ std::unique_ptr<CPDF_Object> CPDF_SyntaxParser::GetObject(
   if (word == "(") {
     CFX_ByteString str = ReadString();
     if (m_pCryptoHandler && bDecrypt)
-      m_pCryptoHandler->Decrypt(objnum, gennum, str);
+      str = m_pCryptoHandler->Decrypt(objnum, gennum, str);
     return pdfium::MakeUnique<CPDF_String>(m_pPool, str, false);
   }
   if (word == "<") {
     CFX_ByteString str = ReadHexString();
     if (m_pCryptoHandler && bDecrypt)
-      m_pCryptoHandler->Decrypt(objnum, gennum, str);
+      str = m_pCryptoHandler->Decrypt(objnum, gennum, str);
     return pdfium::MakeUnique<CPDF_String>(m_pPool, str, true);
   }
   if (word == "[") {
@@ -526,17 +526,17 @@ std::unique_ptr<CPDF_Object> CPDF_SyntaxParser::GetObjectForStrict(
   if (word == "(") {
     CFX_ByteString str = ReadString();
     if (m_pCryptoHandler)
-      m_pCryptoHandler->Decrypt(objnum, gennum, str);
+      str = m_pCryptoHandler->Decrypt(objnum, gennum, str);
     return pdfium::MakeUnique<CPDF_String>(m_pPool, str, false);
   }
   if (word == "<") {
     CFX_ByteString str = ReadHexString();
     if (m_pCryptoHandler)
-      m_pCryptoHandler->Decrypt(objnum, gennum, str);
+      str = m_pCryptoHandler->Decrypt(objnum, gennum, str);
     return pdfium::MakeUnique<CPDF_String>(m_pPool, str, true);
   }
   if (word == "[") {
-    std::unique_ptr<CPDF_Array> pArray = pdfium::MakeUnique<CPDF_Array>();
+    auto pArray = pdfium::MakeUnique<CPDF_Array>();
     while (std::unique_ptr<CPDF_Object> pObj =
                GetObject(pObjList, objnum, gennum, true)) {
       pArray->Add(std::move(pObj));
diff --git a/core/fpdfapi/parser/fpdf_parser_decode.cpp b/core/fpdfapi/parser/fpdf_parser_decode.cpp
index a1698aedde..cc8b507025 100644
--- a/core/fpdfapi/parser/fpdf_parser_decode.cpp
+++ b/core/fpdfapi/parser/fpdf_parser_decode.cpp
@@ -327,7 +327,7 @@ bool PDF_DataDecode(const uint8_t* src_buf,
                     const CPDF_Dictionary* pDict,
                     uint8_t*& dest_buf,
                     uint32_t& dest_size,
-                    CFX_ByteString& ImageEncoding,
+                    CFX_ByteString* ImageEncoding,
                     CPDF_Dictionary*& pImageParms,
                     uint32_t last_estimated_size,
                     bool bImageAcc) {
@@ -362,8 +362,8 @@ bool PDF_DataDecode(const uint8_t* src_buf,
     int offset = -1;
     if (decoder == "FlateDecode" || decoder == "Fl") {
       if (bImageAcc && i == nSize - 1) {
-        ImageEncoding = "FlateDecode";
-        dest_buf = (uint8_t*)last_buf;
+        *ImageEncoding = "FlateDecode";
+        dest_buf = last_buf;
         dest_size = last_size;
         pImageParms = pParam;
         return true;
@@ -379,8 +379,8 @@ bool PDF_DataDecode(const uint8_t* src_buf,
       offset = HexDecode(last_buf, last_size, new_buf, new_size);
     } else if (decoder == "RunLengthDecode" || decoder == "RL") {
       if (bImageAcc && i == nSize - 1) {
-        ImageEncoding = "RunLengthDecode";
-        dest_buf = (uint8_t*)last_buf;
+        *ImageEncoding = "RunLengthDecode";
+        dest_buf = last_buf;
         dest_size = last_size;
         pImageParms = pParam;
         return true;
@@ -395,9 +395,9 @@ bool PDF_DataDecode(const uint8_t* src_buf,
       } else if (decoder == "CCF") {
         decoder = "CCITTFaxDecode";
       }
-      ImageEncoding = decoder;
+      *ImageEncoding = decoder;
       pImageParms = pParam;
-      dest_buf = (uint8_t*)last_buf;
+      dest_buf = last_buf;
       dest_size = last_size;
       if (CPDF_Array* pDecoders = pDecoder->AsArray())
         pDecoders->RemoveAt(i + 1, pDecoders->GetCount() - i - 1);
@@ -413,7 +413,7 @@ bool PDF_DataDecode(const uint8_t* src_buf,
     last_buf = new_buf;
     last_size = new_size;
   }
-  ImageEncoding = "";
+  *ImageEncoding = "";
   pImageParms = nullptr;
   dest_buf = last_buf;
   dest_size = last_size;
diff --git a/core/fpdfapi/parser/fpdf_parser_decode.h b/core/fpdfapi/parser/fpdf_parser_decode.h
index 0c74e41058..955a8cfb32 100644
--- a/core/fpdfapi/parser/fpdf_parser_decode.h
+++ b/core/fpdfapi/parser/fpdf_parser_decode.h
@@ -87,7 +87,7 @@ bool PDF_DataDecode(const uint8_t* src_buf,
                     const CPDF_Dictionary* pDict,
                     uint8_t*& dest_buf,
                     uint32_t& dest_size,
-                    CFX_ByteString& ImageEncoding,
+                    CFX_ByteString* ImageEncoding,
                     CPDF_Dictionary*& pImageParms,
                     uint32_t estimated_size,
                     bool bImageAcc);