diff --git a/core/fpdfapi/font/cpdf_cidfont.cpp b/core/fpdfapi/font/cpdf_cidfont.cpp
index b25b728..b73e0b8 100644
--- a/core/fpdfapi/font/cpdf_cidfont.cpp
+++ b/core/fpdfapi/font/cpdf_cidfont.cpp
@@ -736,8 +736,8 @@
 }
 
 uint32_t CPDF_CIDFont::GetNextChar(const ByteStringView& pString,
-                                   size_t& offset) const {
-  return m_pCMap->GetNextChar(pString, offset);
+                                   size_t* pOffset) const {
+  return m_pCMap->GetNextChar(pString, pOffset);
 }
 
 int CPDF_CIDFont::GetCharSize(uint32_t charcode) const {
diff --git a/core/fpdfapi/font/cpdf_cidfont.h b/core/fpdfapi/font/cpdf_cidfont.h
index 43c1184..ab074fb 100644
--- a/core/fpdfapi/font/cpdf_cidfont.h
+++ b/core/fpdfapi/font/cpdf_cidfont.h
@@ -47,7 +47,7 @@
   uint32_t GetCharWidthF(uint32_t charcode) override;
   FX_RECT GetCharBBox(uint32_t charcode) override;
   uint32_t GetNextChar(const ByteStringView& pString,
-                       size_t& offset) const override;
+                       size_t* pOffset) const override;
   size_t CountChar(const ByteStringView& pString) const override;
   int AppendChar(char* str, uint32_t charcode) const override;
   bool IsVertWriting() const override;
diff --git a/core/fpdfapi/font/cpdf_cmap.cpp b/core/fpdfapi/font/cpdf_cmap.cpp
index f3ef829..ee8f264 100644
--- a/core/fpdfapi/font/cpdf_cmap.cpp
+++ b/core/fpdfapi/font/cpdf_cmap.cpp
@@ -338,7 +338,8 @@
 }
 
 uint32_t CPDF_CMap::GetNextChar(const ByteStringView& pString,
-                                size_t& offset) const {
+                                size_t* pOffset) const {
+  size_t& offset = *pOffset;
   auto pBytes = pString.span();
   switch (m_CodingScheme) {
     case OneByte: {
@@ -422,7 +423,7 @@
       size_t count = 0;
       size_t offset = 0;
       while (offset < pString.GetLength()) {
-        GetNextChar(pString, offset);
+        GetNextChar(pString, &offset);
         count++;
       }
       return count;
diff --git a/core/fpdfapi/font/cpdf_cmap.h b/core/fpdfapi/font/cpdf_cmap.h
index 781f0f9..b3c09d5 100644
--- a/core/fpdfapi/font/cpdf_cmap.h
+++ b/core/fpdfapi/font/cpdf_cmap.h
@@ -62,7 +62,7 @@
   uint16_t CIDFromCharCode(uint32_t charcode) const;
 
   int GetCharSize(uint32_t charcode) const;
-  uint32_t GetNextChar(const ByteStringView& pString, size_t& offset) const;
+  uint32_t GetNextChar(const ByteStringView& pString, size_t* pOffset) const;
   size_t CountChar(const ByteStringView& pString) const;
   int AppendChar(char* str, uint32_t charcode) const;
 
diff --git a/core/fpdfapi/font/cpdf_font.cpp b/core/fpdfapi/font/cpdf_font.cpp
index a243ceb..f75f696 100644
--- a/core/fpdfapi/font/cpdf_font.cpp
+++ b/core/fpdfapi/font/cpdf_font.cpp
@@ -275,7 +275,7 @@
   size_t offset = 0;
   uint32_t width = 0;
   while (offset < pString.GetLength())
-    width += GetCharWidthF(GetNextChar(pString, offset));
+    width += GetCharWidthF(GetNextChar(pString, &offset));
   return width;
 }
 
@@ -330,13 +330,13 @@
 }
 
 uint32_t CPDF_Font::GetNextChar(const ByteStringView& pString,
-                                size_t& offset) const {
+                                size_t* pOffset) const {
   if (pString.IsEmpty())
     return 0;
 
-  uint8_t ch = offset < pString.GetLength() ? pString[offset++]
-                                            : pString[pString.GetLength() - 1];
-  return static_cast<uint32_t>(ch);
+  size_t& offset = *pOffset;
+  return offset < pString.GetLength() ? pString[offset++]
+                                      : pString[pString.GetLength() - 1];
 }
 
 bool CPDF_Font::IsStandardFont() const {
diff --git a/core/fpdfapi/font/cpdf_font.h b/core/fpdfapi/font/cpdf_font.h
index 0174a67..f5d0bac 100644
--- a/core/fpdfapi/font/cpdf_font.h
+++ b/core/fpdfapi/font/cpdf_font.h
@@ -54,7 +54,7 @@
   virtual bool IsVertWriting() const;
   virtual bool IsUnicodeCompatible() const;
   virtual uint32_t GetNextChar(const ByteStringView& pString,
-                               size_t& offset) const;
+                               size_t* pOffset) const;
   virtual size_t CountChar(const ByteStringView& pString) const;
   virtual int AppendChar(char* buf, uint32_t charcode) const;
   virtual int GlyphFromCharCode(uint32_t charcode, bool* pVertGlyph) = 0;
diff --git a/core/fpdfapi/page/cpdf_textobject.cpp b/core/fpdfapi/page/cpdf_textobject.cpp
index 9da96f5..84428fe 100644
--- a/core/fpdfapi/page/cpdf_textobject.cpp
+++ b/core/fpdfapi/page/cpdf_textobject.cpp
@@ -165,7 +165,7 @@
     size_t offset = 0;
     while (offset < segment.GetLength()) {
       ASSERT(index < m_CharCodes.size());
-      m_CharCodes[index++] = pFont->GetNextChar(segment, offset);
+      m_CharCodes[index++] = pFont->GetNextChar(segment, &offset);
     }
     if (i != nSegs - 1) {
       m_CharPos[index - 1] = kernings[i];
diff --git a/core/fpdfapi/render/cpdf_textrenderer.cpp b/core/fpdfapi/render/cpdf_textrenderer.cpp
index 7aeddf0..dd25d03 100644
--- a/core/fpdfapi/render/cpdf_textrenderer.cpp
+++ b/core/fpdfapi/render/cpdf_textrenderer.cpp
@@ -94,7 +94,7 @@
   positions.resize(nChars - 1);
   float cur_pos = 0;
   for (int i = 0; i < nChars; i++) {
-    codes[i] = pFont->GetNextChar(str.AsStringView(), offset);
+    codes[i] = pFont->GetNextChar(str.AsStringView(), &offset);
     if (i)
       positions[i - 1] = cur_pos;
     cur_pos += pFont->GetCharWidthF(codes[i]) * font_size / 1000;