diff --git a/core/fpdfapi/parser/cpdf_stream.cpp b/core/fpdfapi/parser/cpdf_stream.cpp
index 1ef1cdf..7fd6556 100644
--- a/core/fpdfapi/parser/cpdf_stream.cpp
+++ b/core/fpdfapi/parser/cpdf_stream.cpp
@@ -42,7 +42,7 @@
 }
 
 CPDF_Stream::CPDF_Stream(std::unique_ptr<uint8_t, FxFreeDeleter> pData,
-                         uint32_t size,
+                         size_t size,
                          RetainPtr<CPDF_Dictionary> pDict)
     : m_pDict(std::move(pDict)) {
   TakeData(std::move(pData), size);
@@ -147,14 +147,15 @@
 }
 
 void CPDF_Stream::TakeData(std::unique_ptr<uint8_t, FxFreeDeleter> pData,
-                           uint32_t size) {
+                           size_t size) {
   m_bMemoryBased = true;
   m_pFile = nullptr;
   m_pDataBuf = std::move(pData);
   m_dwSize = size;
   if (!m_pDict)
     m_pDict = pdfium::MakeRetain<CPDF_Dictionary>();
-  m_pDict->SetNewFor<CPDF_Number>("Length", static_cast<int>(size));
+  m_pDict->SetNewFor<CPDF_Number>("Length",
+                                  pdfium::base::checked_cast<int>(size));
 }
 
 void CPDF_Stream::SetDataFromStringstream(fxcrt::ostringstream* stream) {
@@ -168,7 +169,7 @@
 
 bool CPDF_Stream::ReadRawData(FX_FILESIZE offset,
                               uint8_t* buf,
-                              uint32_t size) const {
+                              size_t size) const {
   if (!m_bMemoryBased && m_pFile)
     return m_pFile->ReadBlockAtOffset(buf, offset, size);
 
diff --git a/core/fpdfapi/parser/cpdf_stream.h b/core/fpdfapi/parser/cpdf_stream.h
index eaf2696..497db20 100644
--- a/core/fpdfapi/parser/cpdf_stream.h
+++ b/core/fpdfapi/parser/cpdf_stream.h
@@ -34,20 +34,19 @@
   bool WriteTo(IFX_ArchiveStream* archive,
                const CPDF_Encryptor* encryptor) const override;
 
-  uint32_t GetRawSize() const { return m_dwSize; }
+  size_t GetRawSize() const { return m_dwSize; }
   // Will be null in case when stream is not memory based.
   // Use CPDF_StreamAcc to data access in all cases.
   uint8_t* GetInMemoryRawData() const { return m_pDataBuf.get(); }
 
-  // Copies span into internally-owned buffer.
+  // Copies span or stream into internally-owned buffer.
   void SetData(pdfium::span<const uint8_t> pData);
-
-  void TakeData(std::unique_ptr<uint8_t, FxFreeDeleter> pData, uint32_t size);
-
   void SetDataFromStringstream(fxcrt::ostringstream* stream);
 
+  void TakeData(std::unique_ptr<uint8_t, FxFreeDeleter> pData, size_t size);
+
   // Set data and remove "Filter" and "DecodeParms" fields from stream
-  // dictionary.
+  // dictionary. Copies span or stream into internally-owned buffer.
   void SetDataAndRemoveFilter(pdfium::span<const uint8_t> pData);
   void SetDataFromStringstreamAndRemoveFilter(fxcrt::ostringstream* stream);
 
@@ -56,7 +55,7 @@
   void InitStreamFromFile(const RetainPtr<IFX_SeekableReadStream>& pFile,
                           RetainPtr<CPDF_Dictionary> pDict);
 
-  bool ReadRawData(FX_FILESIZE offset, uint8_t* pBuf, uint32_t buf_size) const;
+  bool ReadRawData(FX_FILESIZE offset, uint8_t* pBuf, size_t buf_size) const;
 
   bool IsMemoryBased() const { return m_bMemoryBased; }
   bool HasFilter() const;
@@ -66,7 +65,7 @@
   CPDF_Stream(pdfium::span<const uint8_t> pData,
               RetainPtr<CPDF_Dictionary> pDict);
   CPDF_Stream(std::unique_ptr<uint8_t, FxFreeDeleter> pData,
-              uint32_t size,
+              size_t size,
               RetainPtr<CPDF_Dictionary> pDict);
   ~CPDF_Stream() override;
 
@@ -75,7 +74,7 @@
       std::set<const CPDF_Object*>* pVisited) const override;
 
   bool m_bMemoryBased = true;
-  uint32_t m_dwSize = 0;
+  size_t m_dwSize = 0;
   RetainPtr<CPDF_Dictionary> m_pDict;
   std::unique_ptr<uint8_t, FxFreeDeleter> m_pDataBuf;
   RetainPtr<IFX_SeekableReadStream> m_pFile;