4 files changed, 20 insertions, 19 deletions
diff --git a/core/fpdfapi/parser/cpdf_data_avail.cpp b/core/fpdfapi/parser/cpdf_data_avail.cpp
index 577b7e7a18..41d410a87b 100644
--- a/core/fpdfapi/parser/cpdf_data_avail.cpp
+++ b/core/fpdfapi/parser/cpdf_data_avail.cpp
@@ -499,15 +499,15 @@ CPDF_DataAvail::DocAvailStatus CPDF_DataAvail::CheckHeaderAndLinearized() {
     return DocAvailStatus::DataAvailable;
 
   const CPDF_ReadValidator::Session read_session(GetValidator().Get());
-  const int32_t header_offset = GetHeaderOffset(GetValidator());
+  const Optional<FX_FILESIZE> header_offset = GetHeaderOffset(GetValidator());
   if (GetValidator()->has_read_problems())
     return DocAvailStatus::DataNotAvailable;
 
-  if (header_offset == kInvalidHeaderOffset)
+  if (!header_offset)
     return DocAvailStatus::DataError;
 
   m_parser.m_pSyntax =
-      pdfium::MakeUnique<CPDF_SyntaxParser>(GetValidator(), header_offset);
+      pdfium::MakeUnique<CPDF_SyntaxParser>(GetValidator(), *header_offset);
   m_pLinearized = m_parser.ParseLinearizedHeader();
   if (GetValidator()->has_read_problems())
     return DocAvailStatus::DataNotAvailable;
diff --git a/core/fpdfapi/parser/cpdf_parser.cpp b/core/fpdfapi/parser/cpdf_parser.cpp
index ba8974a0de..e93f293f84 100644
--- a/core/fpdfapi/parser/cpdf_parser.cpp
+++ b/core/fpdfapi/parser/cpdf_parser.cpp
@@ -121,13 +121,13 @@ void CPDF_Parser::ShrinkObjectMap(uint32_t objnum) {
 
 bool CPDF_Parser::InitSyntaxParser(
     const RetainPtr<CPDF_ReadValidator>& validator) {
-  const int32_t header_offset = GetHeaderOffset(validator);
-  if (header_offset == kInvalidHeaderOffset)
+  const Optional<FX_FILESIZE> header_offset = GetHeaderOffset(validator);
+  if (!header_offset)
     return false;
-  if (validator->GetSize() < header_offset + kPDFHeaderSize)
+  if (validator->GetSize() < *header_offset + kPDFHeaderSize)
     return false;
 
-  m_pSyntax = pdfium::MakeUnique<CPDF_SyntaxParser>(validator, header_offset);
+  m_pSyntax = pdfium::MakeUnique<CPDF_SyntaxParser>(validator, *header_offset);
   return ParseFileVersion();
 }
 
diff --git a/core/fpdfapi/parser/fpdf_parser_utility.cpp b/core/fpdfapi/parser/fpdf_parser_utility.cpp
index 3c99415d21..83c967d8c2 100644
--- a/core/fpdfapi/parser/fpdf_parser_utility.cpp
+++ b/core/fpdfapi/parser/fpdf_parser_utility.cpp
@@ -71,17 +71,18 @@ const char PDF_CharType[256] = {
     'R', 'R', 'R', 'R', 'R', 'R', 'R', 'R', 'R', 'R', 'R', 'R', 'R', 'R', 'R',
     'R', 'R', 'R', 'R', 'R', 'R', 'R', 'W'};
 
-int32_t GetHeaderOffset(const RetainPtr<IFX_SeekableReadStream>& pFile) {
-  const size_t kBufSize = 4;
+Optional<FX_FILESIZE> GetHeaderOffset(
+    const RetainPtr<IFX_SeekableReadStream>& pFile) {
+  static constexpr size_t kBufSize = 4;
   uint8_t buf[kBufSize];
-  for (int32_t offset = 0; offset <= 1024; ++offset) {
+  for (FX_FILESIZE offset = 0; offset <= 1024; ++offset) {
     if (!pFile->ReadBlock(buf, offset, kBufSize))
-      return kInvalidHeaderOffset;
+      return {};
 
     if (memcmp(buf, "%PDF", 4) == 0)
       return offset;
   }
-  return kInvalidHeaderOffset;
+  return {};
 }
 
 int32_t GetDirectInteger(const CPDF_Dictionary* pDict, const ByteString& key) {
@@ -114,7 +115,7 @@ ByteString PDF_NameDecode(const ByteStringView& bstr) {
 }
 
 ByteString PDF_NameEncode(const ByteString& orig) {
-  uint8_t* src_buf = (uint8_t*)orig.c_str();
+  const uint8_t* src_buf = reinterpret_cast<const uint8_t*>(orig.c_str());
   int src_len = orig.GetLength();
   int dest_len = 0;
   int i;
diff --git a/core/fpdfapi/parser/fpdf_parser_utility.h b/core/fpdfapi/parser/fpdf_parser_utility.h
index 7529fbc484..5fe9b5d4a9 100644
--- a/core/fpdfapi/parser/fpdf_parser_utility.h
+++ b/core/fpdfapi/parser/fpdf_parser_utility.h
@@ -11,10 +11,11 @@
 
 #include "core/fxcrt/fx_string.h"
 #include "core/fxcrt/retain_ptr.h"
+#include "third_party/base/optional.h"
 
-class IFX_SeekableReadStream;
 class CPDF_Dictionary;
 class CPDF_Object;
+class IFX_SeekableReadStream;
 
 // Use the accessors below instead of directly accessing PDF_CharType.
 extern const char PDF_CharType[256];
@@ -36,12 +37,11 @@ inline bool PDFCharIsLineEnding(uint8_t c) {
   return c == '\r' || c == '\n';
 }
 
-constexpr int32_t kInvalidHeaderOffset = -1;
-
-// On success, return a positive offset value to the PDF header.. If the header
+// On success, return a positive offset value to the PDF header. If the header
 // cannot be found, or if there is an error reading from |pFile|, then return
-// |kInvalidHeaderOffset|.
-int32_t GetHeaderOffset(const RetainPtr<IFX_SeekableReadStream>& pFile);
+// nullopt.
+Optional<FX_FILESIZE> GetHeaderOffset(
+    const RetainPtr<IFX_SeekableReadStream>& pFile);
 
 int32_t GetDirectInteger(const CPDF_Dictionary* pDict, const ByteString& key);