Extern in .cpp files is a code smell.

core/include/fpdfapi/fpdf_parser.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_FPDFAPI_FPDF_PARSER_H_
 #define CORE_INCLUDE_FPDFAPI_FPDF_PARSER_H_
 
 #include "../fxcrt/fx_system.h"
@@ skipping 783 matching lines @@
 };
 
 CFX_WideString FPDF_FileSpec_GetWin32Path(const CPDF_Object* pFileSpec);
 void FPDF_FileSpec_SetWin32Path(CPDF_Object* pFileSpec,
                                 const CFX_WideString& fullpath);
 
 void FlateEncode(const uint8_t* src_buf,
                  FX_DWORD src_size,
                  uint8_t*& dest_buf,
                  FX_DWORD& dest_size);
+void FlateEncode(const uint8_t* src_buf,
+                 FX_DWORD src_size,
+                 int predictor,
+                 int Colors,
+                 int BitsPerComponent,
+                 int Columns,
+                 uint8_t*& dest_buf,
+                 FX_DWORD& dest_size);
 FX_DWORD FlateDecode(const uint8_t* src_buf,
                      FX_DWORD src_size,
                      uint8_t*& dest_buf,
                      FX_DWORD& dest_size);
 FX_DWORD RunLengthDecode(const uint8_t* src_buf,
                          FX_DWORD src_size,
                          uint8_t*& dest_buf,
                          FX_DWORD& dest_size);
+FX_BOOL IsSignatureDict(const CPDF_Dictionary* pDict);
+
 class CPDF_NumberTree {
  public:
   CPDF_NumberTree(CPDF_Dictionary* pRoot) { m_pRoot = pRoot; }
 
   CPDF_Object* LookupValue(int num);
 
  protected:
   CPDF_Dictionary* m_pRoot;
 };
 
@@ skipping 83 matching lines @@
   PDF_DATAAVAIL_PAGE,
   PDF_DATAAVAIL_PAGE_LATERLOAD,
   PDF_DATAAVAIL_RESOURCES,
   PDF_DATAAVAIL_DONE,
   PDF_DATAAVAIL_ERROR,
   PDF_DATAAVAIL_LOADALLFILE,
   PDF_DATAAVAIL_TRAILER_APPEND
 };
 
 #endif  // CORE_INCLUDE_FPDFAPI_FPDF_PARSER_H_