Fix subtle issues in opj_skip_from_memory and add unit tests.

core/src/fxcodec/codec/codec_int.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_SRC_FXCODEC_CODEC_CODEC_INT_H_
+#define CORE_SRC_FXCODEC_CODEC_CODEC_INT_H_
+
 #include <limits.h>
 #include <list>
+
+#include "../../../include/fxcodec/fx_codec.h"
 #include "../jbig2/JBig2_Context.h"
+#include "../fx_libopenjpeg/libopenjpeg20/openjpeg.h"  // For OPJ_SIZE_T.
+
 class CCodec_BasicModule : public ICodec_BasicModule
 {
 public:
     virtual FX_BOOL     RunLengthEncode(const FX_BYTE* src_buf, FX_DWORD src_size, FX_LPBYTE& dest_buf,
                                     FX_DWORD& dest_size);
     virtual FX_BOOL     A85Encode(const FX_BYTE* src_buf, FX_DWORD src_size, FX_LPBYTE& dest_buf,
                               FX_DWORD& dest_size);
     virtual ICodec_ScanlineDecoder*     CreateRunLengthDecoder(FX_LPCBYTE src_buf, FX_DWORD src_size, int width, int height,
             int nComps, int bpc);
 };
@@ skipping 245 matching lines @@
                                     FX_LPCBYTE global_data, FX_DWORD global_size, FX_LPBYTE dest_buf, FX_DWORD dest_pitch, IFX_Pause* pPause);
 
     FXCODEC_STATUS              StartDecode(void* pJbig2Context, IFX_FileRead* file_ptr,
                                     FX_DWORD& width, FX_DWORD& height, FX_DWORD& pitch, FX_LPBYTE& dest_buf, IFX_Pause* pPause);
     FXCODEC_STATUS              ContinueDecode(void* pJbig2Context, IFX_Pause* pPause);
     void                                DestroyJbig2Context(void* pJbig2Context);
     CPDF_Jbig2Interface m_Module;
     std::list<CJBig2_CachePair> m_SymbolDictCache;
 private:
 };
+
+struct DecodeData {
+public:
+    DecodeData(unsigned char* src_data, OPJ_SIZE_T src_size) :
+        src_data(src_data), src_size(src_size), offset(0) {
+    }
+    unsigned char* src_data;
+    OPJ_SIZE_T     src_size;
+    OPJ_SIZE_T     offset;
+};
+
+/* Wrappers for C-style callbacks. */
+OPJ_SIZE_T opj_read_from_memory (void* p_buffer, OPJ_SIZE_T nb_bytes,  void* p_user_data);
+OPJ_SIZE_T opj_write_from_memory (void* p_buffer, OPJ_SIZE_T nb_bytes, void* p_user_data);
+OPJ_OFF_T opj_skip_from_memory (OPJ_OFF_T nb_bytes, void* p_user_data);
+OPJ_BOOL opj_seek_from_memory (OPJ_OFF_T nb_bytes, void* p_user_data);
+
+#endif  // CORE_SRC_FXCODEC_CODEC_CODEC_INT_H_