FPDF_Creator can only create file through embedder-supplied callback.

core/include/fxcrt/fx_stream.h

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #ifndef CORE_INCLUDE_FXCRT_FX_STREAM_H_
 #define CORE_INCLUDE_FXCRT_FX_STREAM_H_
 
 #include "fx_string.h"
@@ skipping 60 matching lines @@
 
   virtual FX_BOOL Flush() = 0;
 
   virtual FX_BOOL WriteBlock(const void* pData,
                              FX_FILESIZE offset,
                              size_t size) = 0;
   virtual FX_BOOL WriteBlock(const void* pData, size_t size) {
     return WriteBlock(pData, GetSize(), size);
   }
 };
-IFX_FileWrite* FX_CreateFileWrite(const FX_CHAR* filename);
-IFX_FileWrite* FX_CreateFileWrite(const FX_WCHAR* filename);
 class IFX_StreamRead {
  public:
   virtual ~IFX_StreamRead() {}
 
   virtual void Release() = 0;
 
   virtual FX_BOOL IsEOF() = 0;
 
   virtual FX_FILESIZE GetPosition() = 0;
 
@@ skipping 79 matching lines @@
   virtual FX_BOOL ReadNextBlock(FX_BOOL bRestart = FALSE) = 0;
 
   virtual const uint8_t* GetBlockBuffer() = 0;
 
   virtual size_t GetBlockSize() = 0;
 
   virtual FX_FILESIZE GetBlockOffset() = 0;
 };
 
 #endif  // CORE_INCLUDE_FXCRT_FX_STREAM_H_