fgas/crt/fgas_stream.cpp

// 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

#include "xfa/fgas/crt/fgas_stream.h"

#if _FX_OS_ == _FX_WIN32_DESKTOP_ || _FX_OS_ == _FX_WIN32_MOBILE_ || \
    _FX_OS_ == _FX_WIN64_
#include <io.h>
#endif

#include <algorithm>
#include <memory>

#include "third_party/base/ptr_util.h"
#include "xfa/fgas/crt/fgas_codepage.h"

namespace {

class IFGAS_StreamImp {
 public:
  virtual ~IFGAS_StreamImp() {}

  virtual int32_t GetLength() const = 0;
  virtual int32_t Seek(FX_STREAMSEEK eSeek, int32_t iOffset) = 0;
  virtual int32_t GetPosition() = 0;
  virtual bool IsEOF() const = 0;
  virtual int32_t ReadData(uint8_t* pBuffer, int32_t iBufferSize) = 0;
  virtual int32_t ReadString(FX_WCHAR* pStr,
                             int32_t iMaxLength,
                             bool& bEOS) = 0;
  virtual int32_t WriteData(const uint8_t* pBuffer, int32_t iBufferSize) = 0;
  virtual int32_t WriteString(const FX_WCHAR* pStr, int32_t iLength) = 0;
  virtual void Flush() = 0;
  virtual bool SetLength(int32_t iLength) = 0;

 protected:
  IFGAS_StreamImp();

  uint32_t GetAccessModes() const { return m_dwAccess; }
  void SetAccessModes(uint32_t modes) { m_dwAccess = modes; }

 private:
  uint32_t m_dwAccess;
};

class CFGAS_FileStreamImp : public IFGAS_StreamImp {
 public:
  CFGAS_FileStreamImp();
  ~CFGAS_FileStreamImp() override;

  bool LoadFile(const FX_WCHAR* pszSrcFileName, uint32_t dwAccess);

  // IFGAS_StreamImp:
  int32_t GetLength() const override;
  int32_t Seek(FX_STREAMSEEK eSeek, int32_t iOffset) override;
  int32_t GetPosition() override;
  bool IsEOF() const override;
  int32_t ReadData(uint8_t* pBuffer, int32_t iBufferSize) override;
  int32_t ReadString(FX_WCHAR* pStr, int32_t iMaxLength, bool& bEOS) override;
  int32_t WriteData(const uint8_t* pBuffer, int32_t iBufferSize) override;
  int32_t WriteString(const FX_WCHAR* pStr, int32_t iLength) override;
  void Flush() override;
  bool SetLength(int32_t iLength) override;

 protected:
  FXSYS_FILE* m_hFile;
  int32_t m_iLength;
};

class CFGAS_BufferStreamImp : public IFGAS_StreamImp {
 public:
  CFGAS_BufferStreamImp();
  ~CFGAS_BufferStreamImp() override {}

  bool LoadBuffer(uint8_t* pData, int32_t iTotalSize, uint32_t dwAccess);

  // IFGAS_StreamImp:
  int32_t GetLength() const override;
  int32_t Seek(FX_STREAMSEEK eSeek, int32_t iOffset) override;
  int32_t GetPosition() override;
  bool IsEOF() const override;
  int32_t ReadData(uint8_t* pBuffer, int32_t iBufferSize) override;
  int32_t ReadString(FX_WCHAR* pStr, int32_t iMaxLength, bool& bEOS) override;
  int32_t WriteData(const uint8_t* pBuffer, int32_t iBufferSize) override;
  int32_t WriteString(const FX_WCHAR* pStr, int32_t iLength) override;
  void Flush() override {}
  bool SetLength(int32_t iLength) override { return false; }

 protected:
  uint8_t* m_pData;
  int32_t m_iTotalSize;
  int32_t m_iPosition;
  int32_t m_iLength;
};

class CFGAS_FileReadStreamImp : public IFGAS_StreamImp {
 public:
  CFGAS_FileReadStreamImp();
  ~CFGAS_FileReadStreamImp() override {}

  bool LoadFileRead(const CFX_RetainPtr<IFX_SeekableReadStream>& pFileRead,
                    uint32_t dwAccess);

  // IFGAS_StreamImp:
  int32_t GetLength() const override;
  int32_t Seek(FX_STREAMSEEK eSeek, int32_t iOffset) override;
  int32_t GetPosition() override { return m_iPosition; }
  bool IsEOF() const override;
  int32_t ReadData(uint8_t* pBuffer, int32_t iBufferSize) override;
  int32_t ReadString(FX_WCHAR* pStr, int32_t iMaxLength, bool& bEOS) override;
  int32_t WriteData(const uint8_t* pBuffer, int32_t iBufferSize) override {
    return 0;
  }
  int32_t WriteString(const FX_WCHAR* pStr, int32_t iLength) override {
    return 0;
  }
  void Flush() override {}
  bool SetLength(int32_t iLength) override { return false; }

 protected:
  CFX_RetainPtr<IFX_SeekableReadStream> m_pFileRead;
  int32_t m_iPosition;
  int32_t m_iLength;
};

class CFGAS_BufferReadStreamImp : public IFGAS_StreamImp {
 public:
  CFGAS_BufferReadStreamImp();
  ~CFGAS_BufferReadStreamImp() override;

  bool LoadBufferRead(const CFX_RetainPtr<IFX_BufferedReadStream>& pBufferRead,
                      int32_t iFileSize,
                      uint32_t dwAccess);

  // IFGAS_StreamImp:
  int32_t GetLength() const override;
  int32_t Seek(FX_STREAMSEEK eSeek, int32_t iOffset) override;
  int32_t GetPosition() override { return m_iPosition; }
  bool IsEOF() const override;
  int32_t ReadData(uint8_t* pBuffer, int32_t iBufferSize) override;
  int32_t ReadString(FX_WCHAR* pStr, int32_t iMaxLength, bool& bEOS) override;
  int32_t WriteData(const uint8_t* pBuffer, int32_t iBufferSize) override {
    return 0;
  }
  int32_t WriteString(const FX_WCHAR* pStr, int32_t iLength) override {
    return 0;
  }
  void Flush() override {}
  bool SetLength(int32_t iLength) override { return false; }

 private:
  CFX_RetainPtr<IFX_BufferedReadStream> m_pBufferRead;
  int32_t m_iPosition;
  int32_t m_iBufferSize;
};

class CFGAS_FileWriteStreamImp : public IFGAS_StreamImp {
 public:
  CFGAS_FileWriteStreamImp();
  ~CFGAS_FileWriteStreamImp() override {}

  bool LoadFileWrite(const CFX_RetainPtr<IFX_SeekableWriteStream>& pFileWrite,
                     uint32_t dwAccess);

  // IFGAS_StreamImp:
  int32_t GetLength() const override;
  int32_t Seek(FX_STREAMSEEK eSeek, int32_t iOffset) override;
  int32_t GetPosition() override { return m_iPosition; }
  bool IsEOF() const override;
  int32_t ReadData(uint8_t* pBuffer, int32_t iBufferSize) override { return 0; }
  int32_t ReadString(FX_WCHAR* pStr, int32_t iMaxLength, bool& bEOS) override {
    return 0;
  }
  int32_t WriteData(const uint8_t* pBuffer, int32_t iBufferSize) override;
  int32_t WriteString(const FX_WCHAR* pStr, int32_t iLength) override;
  void Flush() override;
  bool SetLength(int32_t iLength) override { return false; }

 protected:
  CFX_RetainPtr<IFX_SeekableWriteStream> m_pFileWrite;
  int32_t m_iPosition;
};

enum FX_STREAMTYPE {
  FX_SREAMTYPE_Unknown = 0,
  FX_STREAMTYPE_File,
  FX_STREAMTYPE_Buffer,
  FX_STREAMTYPE_Stream,
  FX_STREAMTYPE_BufferRead,
};

class CFGAS_Stream : public IFGAS_Stream {
 public:
  template <typename T, typename... Args>
  friend CFX_RetainPtr<T> pdfium::MakeRetain(Args&&... args);

  bool LoadFile(const FX_WCHAR* pszSrcFileName, uint32_t dwAccess);
  bool LoadBuffer(uint8_t* pData, int32_t iTotalSize, uint32_t dwAccess);
  bool LoadFileRead(const CFX_RetainPtr<IFX_SeekableReadStream>& pFileRead,
                    uint32_t dwAccess);
  bool LoadFileWrite(const CFX_RetainPtr<IFX_SeekableWriteStream>& pFileWrite,
                     uint32_t dwAccess);
  bool LoadBufferRead(const CFX_RetainPtr<IFX_BufferedReadStream>& pBufferRead,
                      int32_t iFileSize,
                      uint32_t dwAccess);

  // IFGAS_Stream
  uint32_t GetAccessModes() const override;
  int32_t GetLength() const override;
  int32_t Seek(FX_STREAMSEEK eSeek, int32_t iOffset) override;
  int32_t GetPosition() override;
  bool IsEOF() const override;
  int32_t ReadData(uint8_t* pBuffer, int32_t iBufferSize) override;
  int32_t ReadString(FX_WCHAR* pStr, int32_t iMaxLength, bool& bEOS) override;
  int32_t WriteData(const uint8_t* pBuffer, int32_t iBufferSize) override;
  int32_t WriteString(const FX_WCHAR* pStr, int32_t iLength) override;
  void Flush() override;
  bool SetLength(int32_t iLength) override;
  int32_t GetBOM(uint8_t bom[4]) const override;
  uint16_t GetCodePage() const override;
  uint16_t SetCodePage(uint16_t wCodePage) override;
  CFX_RetainPtr<IFGAS_Stream> CreateSharedStream(uint32_t dwAccess,
                                                 int32_t iOffset,
                                                 int32_t iLength) override;

 protected:
  CFGAS_Stream();
  ~CFGAS_Stream() override;

  FX_STREAMTYPE m_eStreamType;
  IFGAS_StreamImp* m_pStreamImp;
  uint32_t m_dwAccess;
  int32_t m_iTotalSize;
  int32_t m_iPosition;
  int32_t m_iStart;
  int32_t m_iLength;
  int32_t m_iRefCount;
};

class CFGAS_TextStream : public IFGAS_Stream {
 public:
  template <typename T, typename... Args>
  friend CFX_RetainPtr<T> pdfium::MakeRetain(Args&&... args);

  // IFGAS_Stream
  uint32_t GetAccessModes() const override;
  int32_t GetLength() const override;
  int32_t Seek(FX_STREAMSEEK eSeek, int32_t iOffset) override;
  int32_t GetPosition() override;
  bool IsEOF() const override;
  int32_t ReadData(uint8_t* pBuffer, int32_t iBufferSize) override;
  int32_t ReadString(FX_WCHAR* pStr, int32_t iMaxLength, bool& bEOS) override;
  int32_t WriteData(const uint8_t* pBuffer, int32_t iBufferSize) override;
  int32_t WriteString(const FX_WCHAR* pStr, int32_t iLength) override;
  void Flush() override;
  bool SetLength(int32_t iLength) override;
  int32_t GetBOM(uint8_t bom[4]) const override;
  uint16_t GetCodePage() const override;
  uint16_t SetCodePage(uint16_t wCodePage) override;
  CFX_RetainPtr<IFGAS_Stream> CreateSharedStream(uint32_t dwAccess,
                                                 int32_t iOffset,
                                                 int32_t iLength) override;

 protected:
  explicit CFGAS_TextStream(const CFX_RetainPtr<IFGAS_Stream>& pStream);
  ~CFGAS_TextStream() override;

  void InitStream();

  uint16_t m_wCodePage;
  int32_t m_wBOMLength;
  uint32_t m_dwBOM;
  uint8_t* m_pBuf;
  int32_t m_iBufSize;
  CFX_RetainPtr<IFGAS_Stream> m_pStreamImp;
};

class CFGAS_FileRead : public IFX_SeekableReadStream {
 public:
  static CFX_RetainPtr<CFGAS_FileRead> Create(
      const CFX_RetainPtr<IFGAS_Stream>& pStream);

  explicit CFGAS_FileRead(const CFX_RetainPtr<IFGAS_Stream>& pStream);
  ~CFGAS_FileRead() override;

  // IFX_SeekableReadStream
  FX_FILESIZE GetSize() override;
  bool ReadBlock(void* buffer, FX_FILESIZE offset, size_t size) override;

 protected:
  CFX_RetainPtr<IFGAS_Stream> m_pStream;
};

int32_t FileLength(FXSYS_FILE* file) {
  ASSERT(file);
#if _FX_OS_ == _FX_WIN32_DESKTOP_ || _FX_OS_ == _FX_WIN64_
  return _filelength(_fileno(file));
#else
  int32_t iPos = FXSYS_ftell(file);
  FXSYS_fseek(file, 0, FXSYS_SEEK_END);
  int32_t iLen = FXSYS_ftell(file);
  FXSYS_fseek(file, iPos, FXSYS_SEEK_SET);
  return iLen;
#endif
}

bool FileSetSize(FXSYS_FILE* file, int32_t size) {
  ASSERT(file);
#if _FX_OS_ == _FX_WIN32_DESKTOP_ || _FX_OS_ == _FX_WIN64_
  return _chsize(_fileno(file), size) == 0;
#elif _FX_OS_ == _FX_WIN32_MOBILE_
  HANDLE hFile = _fileno(file);
  uint32_t dwPos = ::SetFilePointer(hFile, 0, 0, FILE_CURRENT);
  ::SetFilePointer(hFile, size, 0, FILE_BEGIN);
  bool bRet = ::SetEndOfFile(hFile);
  ::SetFilePointer(hFile, (int32_t)dwPos, 0, FILE_BEGIN);
  return bRet;
#else
  return false;
#endif
}

}  // namespace

// static
CFX_RetainPtr<IFGAS_Stream> IFGAS_Stream::CreateStream(
    const CFX_RetainPtr<IFX_SeekableReadStream>& pFileRead,
    uint32_t dwAccess) {
  auto pSR = pdfium::MakeRetain<CFGAS_Stream>();
  if (!pSR->LoadFileRead(pFileRead, dwAccess))
    return nullptr;

  if (dwAccess & FX_STREAMACCESS_Text)
    return pdfium::MakeRetain<CFGAS_TextStream>(pSR);

  return pSR;
}

// static
CFX_RetainPtr<IFGAS_Stream> IFGAS_Stream::CreateStream(
    const CFX_RetainPtr<IFX_SeekableWriteStream>& pFileWrite,
    uint32_t dwAccess) {
  auto pSR = pdfium::MakeRetain<CFGAS_Stream>();
  if (!pSR->LoadFileWrite(pFileWrite, dwAccess))
    return nullptr;

  if (dwAccess & FX_STREAMACCESS_Text)
    return pdfium::MakeRetain<CFGAS_TextStream>(pSR);

  return pSR;
}

// static
CFX_RetainPtr<IFGAS_Stream> IFGAS_Stream::CreateStream(uint8_t* pData,
                                                       int32_t length,
                                                       uint32_t dwAccess) {
  auto pSR = pdfium::MakeRetain<CFGAS_Stream>();
  if (!pSR->LoadBuffer(pData, length, dwAccess))
    return nullptr;

  if (dwAccess & FX_STREAMACCESS_Text)
    return pdfium::MakeRetain<CFGAS_TextStream>(pSR);

  return pSR;
}

IFGAS_StreamImp::IFGAS_StreamImp() : m_dwAccess(0) {}

CFGAS_FileStreamImp::CFGAS_FileStreamImp() : m_hFile(nullptr), m_iLength(0) {}

CFGAS_FileStreamImp::~CFGAS_FileStreamImp() {
  if (m_hFile)
    FXSYS_fclose(m_hFile);
}

bool CFGAS_FileStreamImp::LoadFile(const FX_WCHAR* pszSrcFileName,
                                   uint32_t dwAccess) {
  ASSERT(!m_hFile);
  ASSERT(pszSrcFileName && FXSYS_wcslen(pszSrcFileName) > 0);
#if _FX_OS_ == _FX_WIN32_DESKTOP_ || _FX_OS_ == _FX_WIN32_MOBILE_ || \
    _FX_OS_ == _FX_WIN64_
  const FX_WCHAR* wsMode;
  if (dwAccess & FX_STREAMACCESS_Write) {
    if (dwAccess & FX_STREAMACCESS_Append) {
      wsMode = L"a+b";
    } else if (dwAccess & FX_STREAMACCESS_Truncate) {
      wsMode = L"w+b";
    } else {
      wsMode = L"r+b";
    }
  } else {
    wsMode = L"rb";
  }
  m_hFile = FXSYS_wfopen(pszSrcFileName, wsMode);

  if (!m_hFile) {
    if (dwAccess & FX_STREAMACCESS_Write) {
      if (dwAccess & FX_STREAMACCESS_Create)
        m_hFile = FXSYS_wfopen(pszSrcFileName, L"w+b");

      if (!m_hFile) {
        m_hFile = FXSYS_wfopen(pszSrcFileName, L"r+b");
        if (!m_hFile)
          return false;

        if (dwAccess & FX_STREAMACCESS_Truncate)
          FileSetSize(m_hFile, 0);
      }
    } else {
      return false;
    }
  }
#else
  const FX_CHAR* wsMode = "rb";
  if (dwAccess & FX_STREAMACCESS_Write) {
    if (dwAccess & FX_STREAMACCESS_Append) {
      wsMode = "a+b";
    } else if (dwAccess & FX_STREAMACCESS_Truncate) {
      wsMode = "w+b";
    } else {
      wsMode = "r+b";
    }
  }
  CFX_ByteString szFileName = CFX_ByteString::FromUnicode(pszSrcFileName);
  m_hFile = FXSYS_fopen(szFileName.c_str(), wsMode);
  if (!m_hFile) {
    if (dwAccess & FX_STREAMACCESS_Write) {
      if (dwAccess & FX_STREAMACCESS_Create) {
        m_hFile = FXSYS_fopen(szFileName.c_str(), "w+b");
      }
      if (!m_hFile) {
        m_hFile = FXSYS_fopen(szFileName.c_str(), "r+b");
        if (!m_hFile) {
          return false;
        }
        if (dwAccess & FX_STREAMACCESS_Truncate) {
          FileSetSize(m_hFile, 0);
        }
      }
    } else {
      return false;
    }
  }
#endif
  SetAccessModes(dwAccess);
  if ((dwAccess & (FX_STREAMACCESS_Write | FX_STREAMACCESS_Truncate)) ==
      (FX_STREAMACCESS_Write | FX_STREAMACCESS_Truncate)) {
    m_iLength = 0;
  } else {
    m_iLength = FileLength(m_hFile);
  }
  return true;
}
int32_t CFGAS_FileStreamImp::GetLength() const {
  ASSERT(m_hFile);
  return m_iLength;
}
int32_t CFGAS_FileStreamImp::Seek(FX_STREAMSEEK eSeek, int32_t iOffset) {
  ASSERT(m_hFile);
  FXSYS_fseek(m_hFile, iOffset, eSeek);
  return FXSYS_ftell(m_hFile);
}
int32_t CFGAS_FileStreamImp::GetPosition() {
  ASSERT(m_hFile);
  return FXSYS_ftell(m_hFile);
}
bool CFGAS_FileStreamImp::IsEOF() const {
  ASSERT(m_hFile);
  return FXSYS_ftell(m_hFile) >= m_iLength;
}
int32_t CFGAS_FileStreamImp::ReadData(uint8_t* pBuffer, int32_t iBufferSize) {
  ASSERT(m_hFile);
  ASSERT(pBuffer && iBufferSize > 0);
  return FXSYS_fread(pBuffer, 1, iBufferSize, m_hFile);
}
int32_t CFGAS_FileStreamImp::ReadString(FX_WCHAR* pStr,
                                        int32_t iMaxLength,
                                        bool& bEOS) {
  ASSERT(m_hFile);
  ASSERT(pStr && iMaxLength > 0);
  if (m_iLength <= 0) {
    return 0;
  }
  int32_t iPosition = FXSYS_ftell(m_hFile);
  int32_t iLen = std::min((m_iLength - iPosition) / 2, iMaxLength);
  if (iLen <= 0) {
    return 0;
  }
  iLen = FXSYS_fread(pStr, 2, iLen, m_hFile);
  int32_t iCount = 0;
  while (*pStr != L'\0' && iCount < iLen) {
    pStr++, iCount++;
  }
  iPosition += iCount * 2;
  if (FXSYS_ftell(m_hFile) != iPosition) {
    FXSYS_fseek(m_hFile, iPosition, 0);
  }
  bEOS = (iPosition >= m_iLength);
  return iCount;
}
int32_t CFGAS_FileStreamImp::WriteData(const uint8_t* pBuffer,
                                       int32_t iBufferSize) {
  ASSERT(m_hFile && (GetAccessModes() & FX_STREAMACCESS_Write) != 0);
  ASSERT(pBuffer && iBufferSize > 0);
  int32_t iRet = FXSYS_fwrite(pBuffer, 1, iBufferSize, m_hFile);
  if (iRet != 0) {
    int32_t iPos = FXSYS_ftell(m_hFile);
    if (iPos > m_iLength) {
      m_iLength = iPos;
    }
  }
  return iRet;
}
int32_t CFGAS_FileStreamImp::WriteString(const FX_WCHAR* pStr,
                                         int32_t iLength) {
  ASSERT(m_hFile && (GetAccessModes() & FX_STREAMACCESS_Write) != 0);
  ASSERT(pStr && iLength > 0);
  int32_t iRet = FXSYS_fwrite(pStr, 2, iLength, m_hFile);
  if (iRet != 0) {
    int32_t iPos = FXSYS_ftell(m_hFile);
    if (iPos > m_iLength) {
      m_iLength = iPos;
    }
  }
  return iRet;
}
void CFGAS_FileStreamImp::Flush() {
  ASSERT(m_hFile && (GetAccessModes() & FX_STREAMACCESS_Write) != 0);
  FXSYS_fflush(m_hFile);
}
bool CFGAS_FileStreamImp::SetLength(int32_t iLength) {
  ASSERT(m_hFile && (GetAccessModes() & FX_STREAMACCESS_Write) != 0);
  bool bRet = FileSetSize(m_hFile, iLength);
  m_iLength = FileLength(m_hFile);
  return bRet;
}

CFGAS_FileReadStreamImp::CFGAS_FileReadStreamImp()
    : m_pFileRead(nullptr), m_iPosition(0), m_iLength(0) {}

bool CFGAS_FileReadStreamImp::LoadFileRead(
    const CFX_RetainPtr<IFX_SeekableReadStream>& pFileRead,
    uint32_t dwAccess) {
  ASSERT(!m_pFileRead && pFileRead);
  if (dwAccess & FX_STREAMACCESS_Write)
    return false;

  m_pFileRead = pFileRead;
  m_iLength = m_pFileRead->GetSize();
  return true;
}

int32_t CFGAS_FileReadStreamImp::GetLength() const {
  return m_iLength;
}
int32_t CFGAS_FileReadStreamImp::Seek(FX_STREAMSEEK eSeek, int32_t iOffset) {
  switch (eSeek) {
    case FX_STREAMSEEK_Begin:
      m_iPosition = iOffset;
      break;
    case FX_STREAMSEEK_Current:
      m_iPosition += iOffset;
      break;
    case FX_STREAMSEEK_End:
      m_iPosition = m_iLength + iOffset;
      break;
  }
  if (m_iPosition < 0) {
    m_iPosition = 0;
  } else if (m_iPosition >= m_iLength) {
    m_iPosition = m_iLength;
  }
  return m_iPosition;
}
bool CFGAS_FileReadStreamImp::IsEOF() const {
  return m_iPosition >= m_iLength;
}
int32_t CFGAS_FileReadStreamImp::ReadData(uint8_t* pBuffer,
                                          int32_t iBufferSize) {
  ASSERT(m_pFileRead);
  ASSERT(pBuffer && iBufferSize > 0);
  if (iBufferSize > m_iLength - m_iPosition) {
    iBufferSize = m_iLength - m_iPosition;
  }
  if (m_pFileRead->ReadBlock(pBuffer, m_iPosition, iBufferSize)) {
    m_iPosition += iBufferSize;
    return iBufferSize;
  }
  return 0;
}
int32_t CFGAS_FileReadStreamImp::ReadString(FX_WCHAR* pStr,
                                            int32_t iMaxLength,
                                            bool& bEOS) {
  ASSERT(m_pFileRead);
  ASSERT(pStr && iMaxLength > 0);
  iMaxLength = ReadData((uint8_t*)pStr, iMaxLength * 2) / 2;
  if (iMaxLength <= 0) {
    return 0;
  }
  int32_t i = 0;
  while (i < iMaxLength && pStr[i] != L'\0') {
    ++i;
  }
  bEOS = (m_iPosition >= m_iLength) || pStr[i] == L'\0';
  return i;
}

CFGAS_BufferReadStreamImp::CFGAS_BufferReadStreamImp()
    : m_iPosition(0), m_iBufferSize(0) {}

CFGAS_BufferReadStreamImp::~CFGAS_BufferReadStreamImp() {}

bool CFGAS_BufferReadStreamImp::LoadBufferRead(
    const CFX_RetainPtr<IFX_BufferedReadStream>& pBufferRead,
    int32_t iFileSize,
    uint32_t dwAccess) {
  ASSERT(!m_pBufferRead && pBufferRead);
  if (dwAccess & FX_STREAMACCESS_Write)
    return false;

  m_pBufferRead = pBufferRead;
  m_iBufferSize = iFileSize;
  if (m_iBufferSize >= 0)
    return true;

  if (!m_pBufferRead->ReadNextBlock(true))
    return false;

  m_iBufferSize = m_pBufferRead->GetBlockSize();
  while (!m_pBufferRead->IsEOF()) {
    m_pBufferRead->ReadNextBlock(false);
    m_iBufferSize += m_pBufferRead->GetBlockSize();
  }
  return true;
}
int32_t CFGAS_BufferReadStreamImp::GetLength() const {
  return m_iBufferSize;
}
int32_t CFGAS_BufferReadStreamImp::Seek(FX_STREAMSEEK eSeek, int32_t iOffset) {
  int32_t iLength = GetLength();
  switch (eSeek) {
    case FX_STREAMSEEK_Begin:
      m_iPosition = iOffset;
      break;
    case FX_STREAMSEEK_Current:
      m_iPosition += iOffset;
      break;
    case FX_STREAMSEEK_End:
      m_iPosition = iLength + iOffset;
      break;
  }
  if (m_iPosition < 0) {
    m_iPosition = 0;
  } else if (m_iPosition >= iLength) {
    m_iPosition = iLength;
  }
  return m_iPosition;
}
bool CFGAS_BufferReadStreamImp::IsEOF() const {
  return m_pBufferRead ? m_pBufferRead->IsEOF() : true;
}
int32_t CFGAS_BufferReadStreamImp::ReadData(uint8_t* pBuffer,
                                            int32_t iBufferSize) {
  ASSERT(m_pBufferRead);
  ASSERT(pBuffer && iBufferSize > 0);
  int32_t iLength = GetLength();
  if (m_iPosition >= iLength) {
    return 0;
  }
  if (iBufferSize > iLength - m_iPosition) {
    iBufferSize = iLength - m_iPosition;
  }
  uint32_t dwBlockOffset = m_pBufferRead->GetBlockOffset();
  uint32_t dwBlockSize = m_pBufferRead->GetBlockSize();
  if (m_iPosition < (int32_t)dwBlockOffset) {
    if (!m_pBufferRead->ReadNextBlock(true)) {
      return 0;
    }
    dwBlockOffset = m_pBufferRead->GetBlockOffset();
    dwBlockSize = m_pBufferRead->GetBlockSize();
  }
  while (m_iPosition < (int32_t)dwBlockOffset ||
         m_iPosition >= (int32_t)(dwBlockOffset + dwBlockSize)) {
    if (m_pBufferRead->IsEOF() || !m_pBufferRead->ReadNextBlock(false)) {
      break;
    }
    dwBlockOffset = m_pBufferRead->GetBlockOffset();
    dwBlockSize = m_pBufferRead->GetBlockSize();
  }
  if (m_iPosition < (int32_t)dwBlockOffset ||
      m_iPosition >= (int32_t)(dwBlockOffset + dwBlockSize)) {
    return 0;
  }
  const uint8_t* pBufferTmp = m_pBufferRead->GetBlockBuffer();
  uint32_t dwOffsetTmp = m_iPosition - dwBlockOffset;
  uint32_t dwCopySize =
      std::min(iBufferSize, (int32_t)(dwBlockSize - dwOffsetTmp));
  FXSYS_memcpy(pBuffer, pBufferTmp + dwOffsetTmp, dwCopySize);
  dwOffsetTmp = dwCopySize;
  iBufferSize -= dwCopySize;
  while (iBufferSize > 0) {
    if (!m_pBufferRead->ReadNextBlock(false)) {
      break;
    }
    dwBlockOffset = m_pBufferRead->GetBlockOffset();
    dwBlockSize = m_pBufferRead->GetBlockSize();
    pBufferTmp = m_pBufferRead->GetBlockBuffer();
    dwCopySize = std::min((uint32_t)iBufferSize, dwBlockSize);
    FXSYS_memcpy(pBuffer + dwOffsetTmp, pBufferTmp, dwCopySize);
    dwOffsetTmp += dwCopySize;
    iBufferSize -= dwCopySize;
  }
  m_iPosition += dwOffsetTmp;
  return dwOffsetTmp;
}
int32_t CFGAS_BufferReadStreamImp::ReadString(FX_WCHAR* pStr,
                                              int32_t iMaxLength,
                                              bool& bEOS) {
  ASSERT(m_pBufferRead);
  ASSERT(pStr && iMaxLength > 0);
  iMaxLength = ReadData((uint8_t*)pStr, iMaxLength * 2) / 2;
  if (iMaxLength <= 0) {
    return 0;
  }
  int32_t i = 0;
  while (i < iMaxLength && pStr[i] != L'\0') {
    ++i;
  }
  bEOS = (m_iPosition >= GetLength()) || pStr[i] == L'\0';
  return i;
}
CFGAS_FileWriteStreamImp::CFGAS_FileWriteStreamImp()
    : m_pFileWrite(nullptr), m_iPosition(0) {}

bool CFGAS_FileWriteStreamImp::LoadFileWrite(
    const CFX_RetainPtr<IFX_SeekableWriteStream>& pFileWrite,
    uint32_t dwAccess) {
  ASSERT(!m_pFileWrite && pFileWrite);
  if (dwAccess & FX_STREAMACCESS_Read)
    return false;

  if (dwAccess & FX_STREAMACCESS_Append)
    m_iPosition = pFileWrite->GetSize();

  m_pFileWrite = pFileWrite;
  return true;
}

int32_t CFGAS_FileWriteStreamImp::GetLength() const {
  if (!m_pFileWrite)
    return 0;

  return (int32_t)m_pFileWrite->GetSize();
}
int32_t CFGAS_FileWriteStreamImp::Seek(FX_STREAMSEEK eSeek, int32_t iOffset) {
  int32_t iLength = GetLength();
  switch (eSeek) {
    case FX_STREAMSEEK_Begin:
      m_iPosition = iOffset;
      break;
    case FX_STREAMSEEK_Current:
      m_iPosition += iOffset;
      break;
    case FX_STREAMSEEK_End:
      m_iPosition = iLength + iOffset;
      break;
  }
  if (m_iPosition < 0) {
    m_iPosition = 0;
  } else if (m_iPosition >= iLength) {
    m_iPosition = iLength;
  }
  return m_iPosition;
}
bool CFGAS_FileWriteStreamImp::IsEOF() const {
  return m_iPosition >= GetLength();
}
int32_t CFGAS_FileWriteStreamImp::WriteData(const uint8_t* pBuffer,
                                            int32_t iBufferSize) {
  if (!m_pFileWrite) {
    return 0;
  }
  if (m_pFileWrite->WriteBlock(pBuffer, m_iPosition, iBufferSize)) {
    m_iPosition += iBufferSize;
  }
  return iBufferSize;
}
int32_t CFGAS_FileWriteStreamImp::WriteString(const FX_WCHAR* pStr,
                                              int32_t iLength) {
  return WriteData((const uint8_t*)pStr, iLength * sizeof(FX_WCHAR));
}
void CFGAS_FileWriteStreamImp::Flush() {
  if (m_pFileWrite) {
    m_pFileWrite->Flush();
  }
}
CFGAS_BufferStreamImp::CFGAS_BufferStreamImp()
    : m_pData(nullptr), m_iTotalSize(0), m_iPosition(0), m_iLength(0) {}

bool CFGAS_BufferStreamImp::LoadBuffer(uint8_t* pData,
                                       int32_t iTotalSize,
                                       uint32_t dwAccess) {
  ASSERT(!m_pData && pData && iTotalSize > 0);
  SetAccessModes(dwAccess);
  m_pData = pData;
  m_iTotalSize = iTotalSize;
  m_iPosition = 0;
  m_iLength = (dwAccess & FX_STREAMACCESS_Write) != 0 ? 0 : iTotalSize;
  return true;
}
int32_t CFGAS_BufferStreamImp::GetLength() const {
  ASSERT(m_pData);
  return m_iLength;
}
int32_t CFGAS_BufferStreamImp::Seek(FX_STREAMSEEK eSeek, int32_t iOffset) {
  ASSERT(m_pData);
  if (eSeek == FX_STREAMSEEK_Begin) {
    m_iPosition = iOffset;
  } else if (eSeek == FX_STREAMSEEK_Current) {
    m_iPosition += iOffset;
  } else if (eSeek == FX_STREAMSEEK_End) {
    m_iPosition = m_iLength + iOffset;
  }
  if (m_iPosition > m_iLength) {
    m_iPosition = m_iLength;
  }
  if (m_iPosition < 0) {
    m_iPosition = 0;
  }
  return m_iPosition;
}
int32_t CFGAS_BufferStreamImp::GetPosition() {
  ASSERT(m_pData);
  return m_iPosition;
}
bool CFGAS_BufferStreamImp::IsEOF() const {
  ASSERT(m_pData);
  return m_iPosition >= m_iLength;
}
int32_t CFGAS_BufferStreamImp::ReadData(uint8_t* pBuffer, int32_t iBufferSize) {
  ASSERT(m_pData);
  ASSERT(pBuffer && iBufferSize > 0);
  int32_t iLen = std::min(m_iLength - m_iPosition, iBufferSize);
  if (iLen <= 0) {
    return 0;
  }
  FXSYS_memcpy(pBuffer, m_pData + m_iPosition, iLen);
  m_iPosition += iLen;
  return iLen;
}
int32_t CFGAS_BufferStreamImp::ReadString(FX_WCHAR* pStr,
                                          int32_t iMaxLength,
                                          bool& bEOS) {
  ASSERT(m_pData);
  ASSERT(pStr && iMaxLength > 0);
  int32_t iLen = std::min((m_iLength - m_iPosition) / 2, iMaxLength);
  if (iLen <= 0) {
    return 0;
  }
  const FX_WCHAR* pSrc = (const FX_WCHAR*)(FX_CHAR*)(m_pData + m_iPosition);
  int32_t iCount = 0;
  while (*pSrc && iCount < iLen) {
    *pStr++ = *pSrc++;
    iCount++;
  }
  m_iPosition += iCount * 2;
  bEOS = (*pSrc == L'\0') || (m_iPosition >= m_iLength);
  return iCount;
}
int32_t CFGAS_BufferStreamImp::WriteData(const uint8_t* pBuffer,
                                         int32_t iBufferSize) {
  ASSERT(m_pData && (GetAccessModes() & FX_STREAMACCESS_Write) != 0);
  ASSERT(pBuffer && iBufferSize > 0);
  int32_t iLen = std::min(m_iTotalSize - m_iPosition, iBufferSize);
  if (iLen <= 0) {
    return 0;
  }
  FXSYS_memcpy(m_pData + m_iPosition, pBuffer, iLen);
  m_iPosition += iLen;
  if (m_iPosition > m_iLength) {
    m_iLength = m_iPosition;
  }
  return iLen;
}
int32_t CFGAS_BufferStreamImp::WriteString(const FX_WCHAR* pStr,
                                           int32_t iLength) {
  ASSERT(m_pData && (GetAccessModes() & FX_STREAMACCESS_Write) != 0);
  ASSERT(pStr && iLength > 0);
  int32_t iLen = std::min((m_iTotalSize - m_iPosition) / 2, iLength);
  if (iLen <= 0) {
    return 0;
  }
  FXSYS_memcpy(m_pData + m_iPosition, pStr, iLen * 2);
  m_iPosition += iLen * 2;
  if (m_iPosition > m_iLength) {
    m_iLength = m_iPosition;
  }
  return iLen;
}

// static
CFX_RetainPtr<IFGAS_Stream> IFGAS_Stream::CreateTextStream(
    const CFX_RetainPtr<IFGAS_Stream>& pBaseStream) {
  ASSERT(pBaseStream);
  return pdfium::MakeRetain<CFGAS_TextStream>(pBaseStream);
}

CFGAS_TextStream::CFGAS_TextStream(const CFX_RetainPtr<IFGAS_Stream>& pStream)
    : m_wCodePage(FX_CODEPAGE_DefANSI),
      m_wBOMLength(0),
      m_dwBOM(0),
      m_pBuf(nullptr),
      m_iBufSize(0),
      m_pStreamImp(pStream) {
  ASSERT(m_pStreamImp);
  InitStream();
}

CFGAS_TextStream::~CFGAS_TextStream() {
  if (m_pBuf)
    FX_Free(m_pBuf);
}

void CFGAS_TextStream::InitStream() {
  int32_t iPosition = m_pStreamImp->GetPosition();
  m_pStreamImp->Seek(FX_STREAMSEEK_Begin, 0);
  m_pStreamImp->ReadData((uint8_t*)&m_dwBOM, 3);
#if _FX_ENDIAN_ == _FX_LITTLE_ENDIAN_
  m_dwBOM &= 0x00FFFFFF;
  if (m_dwBOM == 0x00BFBBEF) {
    m_wBOMLength = 3;
    m_wCodePage = FX_CODEPAGE_UTF8;
  } else {
    m_dwBOM &= 0x0000FFFF;
    if (m_dwBOM == 0x0000FFFE) {
      m_wBOMLength = 2;
      m_wCodePage = FX_CODEPAGE_UTF16BE;
    } else if (m_dwBOM == 0x0000FEFF) {
      m_wBOMLength = 2;
      m_wCodePage = FX_CODEPAGE_UTF16LE;
    } else {
      m_wBOMLength = 0;
      m_dwBOM = 0;
      m_wCodePage = FXSYS_GetACP();
    }
  }
#else
  m_dwBOM &= 0xFFFFFF00;
  if (m_dwBOM == 0xEFBBBF00) {
    m_wBOMLength = 3;
    m_wCodePage = FX_CODEPAGE_UTF8;
  } else {
    m_dwBOM &= 0xFFFF0000;
    if (m_dwBOM == 0xFEFF0000) {
      m_wBOMLength = 2;
      m_wCodePage = FX_CODEPAGE_UTF16BE;
    } else if (m_dwBOM == 0xFFFE0000) {
      m_wBOMLength = 2;
      m_wCodePage = FX_CODEPAGE_UTF16LE;
    } else {
      m_wBOMLength = 0;
      m_dwBOM = 0;
      m_wCodePage = FXSYS_GetACP();
    }
  }
#endif
  m_pStreamImp->Seek(FX_STREAMSEEK_Begin, std::max(m_wBOMLength, iPosition));
}

uint32_t CFGAS_TextStream::GetAccessModes() const {
  return m_pStreamImp->GetAccessModes() | FX_STREAMACCESS_Text;
}

int32_t CFGAS_TextStream::GetLength() const {
  return m_pStreamImp->GetLength();
}

int32_t CFGAS_TextStream::Seek(FX_STREAMSEEK eSeek, int32_t iOffset) {
  return m_pStreamImp->Seek(eSeek, iOffset);
}

int32_t CFGAS_TextStream::GetPosition() {
  return m_pStreamImp->GetPosition();
}

bool CFGAS_TextStream::IsEOF() const {
  return m_pStreamImp->IsEOF();
}

int32_t CFGAS_TextStream::ReadData(uint8_t* pBuffer, int32_t iBufferSize) {
  return m_pStreamImp->ReadData(pBuffer, iBufferSize);
}

int32_t CFGAS_TextStream::WriteData(const uint8_t* pBuffer,
                                    int32_t iBufferSize) {
  return m_pStreamImp->WriteData(pBuffer, iBufferSize);
}

void CFGAS_TextStream::Flush() {
  m_pStreamImp->Flush();
}

bool CFGAS_TextStream::SetLength(int32_t iLength) {
  return m_pStreamImp->SetLength(iLength);
}

uint16_t CFGAS_TextStream::GetCodePage() const {
  return m_wCodePage;
}

CFX_RetainPtr<IFGAS_Stream> CFGAS_TextStream::CreateSharedStream(
    uint32_t dwAccess,
    int32_t iOffset,
    int32_t iLength) {
  CFX_RetainPtr<IFGAS_Stream> pSR =
      m_pStreamImp->CreateSharedStream(dwAccess, iOffset, iLength);
  if (!pSR)
    return nullptr;

  if (dwAccess & FX_STREAMACCESS_Text)
    return pdfium::MakeRetain<CFGAS_TextStream>(pSR);

  return pSR;
}

int32_t CFGAS_TextStream::GetBOM(uint8_t bom[4]) const {
  if (m_wBOMLength < 1)
    return 0;

  *(uint32_t*)bom = m_dwBOM;
  return m_wBOMLength;
}

uint16_t CFGAS_TextStream::SetCodePage(uint16_t wCodePage) {
  if (m_wBOMLength > 0)
    return m_wCodePage;

  uint16_t v = m_wCodePage;
  m_wCodePage = wCodePage;
  return v;
}

int32_t CFGAS_TextStream::ReadString(FX_WCHAR* pStr,
                                     int32_t iMaxLength,
                                     bool& bEOS) {
  ASSERT(pStr && iMaxLength > 0);
  if (!m_pStreamImp) {
    return -1;
  }
  int32_t iLen;
  if (m_wCodePage == FX_CODEPAGE_UTF16LE ||
      m_wCodePage == FX_CODEPAGE_UTF16BE) {
    int32_t iBytes = iMaxLength * 2;
    iLen = m_pStreamImp->ReadData((uint8_t*)pStr, iBytes);
    iMaxLength = iLen / 2;
    if (sizeof(FX_WCHAR) > 2) {
      FX_UTF16ToWChar(pStr, iMaxLength);
    }
#if _FX_ENDIAN_ == _FX_BIG_ENDIAN_
    if (m_wCodePage == FX_CODEPAGE_UTF16LE) {
      FX_SwapByteOrder(pStr, iMaxLength);
    }
#else
    if (m_wCodePage == FX_CODEPAGE_UTF16BE) {
      FX_SwapByteOrder(pStr, iMaxLength);
    }
#endif
  } else {
    int32_t pos = m_pStreamImp->GetPosition();
    int32_t iBytes = iMaxLength;
    iBytes = std::min(iBytes, m_pStreamImp->GetLength() - pos);
    if (iBytes > 0) {
      if (!m_pBuf) {
        m_pBuf = FX_Alloc(uint8_t, iBytes);
        m_iBufSize = iBytes;
      } else if (iBytes > m_iBufSize) {
        m_pBuf = FX_Realloc(uint8_t, m_pBuf, iBytes);
        m_iBufSize = iBytes;
      }
      iLen = m_pStreamImp->ReadData(m_pBuf, iBytes);
      int32_t iSrc = iLen;
      int32_t iDecode = FX_DecodeString(m_wCodePage, (const FX_CHAR*)m_pBuf,
                                        &iSrc, pStr, &iMaxLength, true);
      m_pStreamImp->Seek(FX_STREAMSEEK_Current, iSrc - iLen);
      if (iDecode < 1) {
        return -1;
      }
    } else {
      iMaxLength = 0;
    }
  }
  bEOS = m_pStreamImp->IsEOF();
  return iMaxLength;
}

int32_t CFGAS_TextStream::WriteString(const FX_WCHAR* pStr, int32_t iLength) {
  ASSERT(pStr && iLength > 0);
  if ((m_pStreamImp->GetAccessModes() & FX_STREAMACCESS_Write) == 0)
    return -1;

  if (m_wCodePage == FX_CODEPAGE_UTF8) {
    int32_t len = iLength;
    CFX_UTF8Encoder encoder;
    while (len-- > 0) {
      encoder.Input(*pStr++);
    }
    CFX_ByteStringC bsResult = encoder.GetResult();
    m_pStreamImp->WriteData((const uint8_t*)bsResult.c_str(),
                            bsResult.GetLength());
  }
  return iLength;
}

CFGAS_Stream::CFGAS_Stream()
    : m_eStreamType(FX_SREAMTYPE_Unknown),
      m_pStreamImp(nullptr),
      m_dwAccess(0),
      m_iTotalSize(0),
      m_iPosition(0),
      m_iStart(0),
      m_iLength(0),
      m_iRefCount(1) {}

CFGAS_Stream::~CFGAS_Stream() {
  if (m_eStreamType != FX_STREAMTYPE_Stream)
    delete m_pStreamImp;
}

bool CFGAS_Stream::LoadFile(const FX_WCHAR* pszSrcFileName, uint32_t dwAccess) {
  if (m_eStreamType != FX_SREAMTYPE_Unknown || m_pStreamImp)
    return false;

  if (!pszSrcFileName || FXSYS_wcslen(pszSrcFileName) < 1)
    return false;

  std::unique_ptr<CFGAS_FileStreamImp> pImp(new CFGAS_FileStreamImp());
  if (!pImp->LoadFile(pszSrcFileName, dwAccess))
    return false;

  m_pStreamImp = pImp.release();
  m_eStreamType = FX_STREAMTYPE_File;
  m_dwAccess = dwAccess;
  m_iLength = m_pStreamImp->GetLength();
  return true;
}

bool CFGAS_Stream::LoadFileRead(
    const CFX_RetainPtr<IFX_SeekableReadStream>& pFileRead,
    uint32_t dwAccess) {
  if (m_eStreamType != FX_SREAMTYPE_Unknown || m_pStreamImp)
    return false;

  if (!pFileRead)
    return false;

  std::unique_ptr<CFGAS_FileReadStreamImp> pImp(new CFGAS_FileReadStreamImp());
  if (!pImp->LoadFileRead(pFileRead, dwAccess))
    return false;

  m_pStreamImp = pImp.release();
  m_eStreamType = FX_STREAMTYPE_File;
  m_dwAccess = dwAccess;
  m_iLength = m_pStreamImp->GetLength();
  return true;
}

bool CFGAS_Stream::LoadFileWrite(
    const CFX_RetainPtr<IFX_SeekableWriteStream>& pFileWrite,
    uint32_t dwAccess) {
  if (m_eStreamType != FX_SREAMTYPE_Unknown || m_pStreamImp)
    return false;

  if (!pFileWrite)
    return false;

  auto pImp = pdfium::MakeUnique<CFGAS_FileWriteStreamImp>();
  if (!pImp->LoadFileWrite(pFileWrite, dwAccess))
    return false;

  m_pStreamImp = pImp.release();
  m_eStreamType = FX_STREAMTYPE_File;
  m_dwAccess = dwAccess;
  m_iLength = m_pStreamImp->GetLength();
  return true;
}

bool CFGAS_Stream::LoadBuffer(uint8_t* pData,
                              int32_t iTotalSize,
                              uint32_t dwAccess) {
  if (m_eStreamType != FX_SREAMTYPE_Unknown || m_pStreamImp)
    return false;

  if (!pData || iTotalSize < 1)
    return false;

  std::unique_ptr<CFGAS_BufferStreamImp> pImp(new CFGAS_BufferStreamImp());
  if (!pImp->LoadBuffer(pData, iTotalSize, dwAccess))
    return false;

  m_pStreamImp = pImp.release();
  m_eStreamType = FX_STREAMTYPE_Buffer;
  m_dwAccess = dwAccess;
  m_iLength = m_pStreamImp->GetLength();
  return true;
}

bool CFGAS_Stream::LoadBufferRead(
    const CFX_RetainPtr<IFX_BufferedReadStream>& pBufferRead,
    int32_t iFileSize,
    uint32_t dwAccess) {
  if (m_eStreamType != FX_SREAMTYPE_Unknown || m_pStreamImp)
    return false;

  if (!pBufferRead)
    return false;

  auto pImp = pdfium::MakeUnique<CFGAS_BufferReadStreamImp>();
  if (!pImp->LoadBufferRead(pBufferRead, iFileSize, dwAccess))
    return false;

  m_pStreamImp = pImp.release();
  m_eStreamType = FX_STREAMTYPE_BufferRead;
  m_dwAccess = dwAccess;
  m_iLength = m_pStreamImp->GetLength();
  return true;
}

uint32_t CFGAS_Stream::GetAccessModes() const {
  return m_dwAccess;
}

int32_t CFGAS_Stream::GetLength() const {
  if (!m_pStreamImp) {
    return -1;
  }
  if (m_eStreamType == FX_STREAMTYPE_File ||
      m_eStreamType == FX_STREAMTYPE_Buffer) {
    return m_pStreamImp->GetLength();
  }
  return m_iLength;
}
int32_t CFGAS_Stream::Seek(FX_STREAMSEEK eSeek, int32_t iOffset) {
  if (!m_pStreamImp) {
    return -1;
  }
  if (m_eStreamType == FX_STREAMTYPE_File ||
      m_eStreamType == FX_STREAMTYPE_Buffer) {
    return m_iPosition = m_pStreamImp->Seek(eSeek, iOffset);
  }
  int32_t iEnd = m_iStart + m_iLength;
  int32_t iPosition = m_iStart + iOffset;
  if (eSeek == FX_STREAMSEEK_Begin) {
    m_iPosition = iPosition;
  } else if (eSeek == FX_STREAMSEEK_Current) {
    m_iPosition += iOffset;
  } else if (eSeek == FX_STREAMSEEK_End) {
    m_iPosition = iEnd + iOffset;
  }
  if (m_iPosition > iEnd) {
    m_iPosition = iEnd;
  }
  if (m_iPosition < m_iStart) {
    m_iPosition = m_iStart;
  }
  return m_iPosition - m_iStart;
}
int32_t CFGAS_Stream::GetPosition() {
  if (!m_pStreamImp) {
    return -1;
  }
  if (m_eStreamType == FX_STREAMTYPE_File ||
      m_eStreamType == FX_STREAMTYPE_Buffer) {
    return m_iPosition = m_pStreamImp->GetPosition();
  }
  return m_iPosition - m_iStart;
}
bool CFGAS_Stream::IsEOF() const {
  if (!m_pStreamImp) {
    return true;
  }
  if (m_eStreamType == FX_STREAMTYPE_File ||
      m_eStreamType == FX_STREAMTYPE_Buffer) {
    return m_pStreamImp->IsEOF();
  }
  return m_iPosition >= m_iStart + m_iLength;
}
int32_t CFGAS_Stream::ReadData(uint8_t* pBuffer, int32_t iBufferSize) {
  ASSERT(pBuffer && iBufferSize > 0);
  if (!m_pStreamImp) {
    return -1;
  }
  int32_t iLen = std::min(m_iStart + m_iLength - m_iPosition, iBufferSize);
  if (iLen <= 0) {
    return 0;
  }
  if (m_pStreamImp->GetPosition() != m_iPosition) {
    m_pStreamImp->Seek(FX_STREAMSEEK_Begin, m_iPosition);
  }
  iLen = m_pStreamImp->ReadData(pBuffer, iLen);
  m_iPosition = m_pStreamImp->GetPosition();
  return iLen;
}
int32_t CFGAS_Stream::ReadString(FX_WCHAR* pStr,
                                 int32_t iMaxLength,
                                 bool& bEOS) {
  ASSERT(pStr && iMaxLength > 0);
  if (!m_pStreamImp) {
    return -1;
  }
  int32_t iEnd = m_iStart + m_iLength;
  int32_t iLen = iEnd - m_iPosition;
  iLen = std::min(iEnd / 2, iMaxLength);
  if (iLen <= 0) {
    return 0;
  }
  if (m_pStreamImp->GetPosition() != m_iPosition) {
    m_pStreamImp->Seek(FX_STREAMSEEK_Begin, m_iPosition);
  }
  iLen = m_pStreamImp->ReadString(pStr, iLen, bEOS);
  m_iPosition = m_pStreamImp->GetPosition();
  if (iLen > 0 && m_iPosition >= iEnd) {
    bEOS = true;
  }
  return iLen;
}

int32_t CFGAS_Stream::WriteData(const uint8_t* pBuffer, int32_t iBufferSize) {
  ASSERT(pBuffer && iBufferSize > 0);
  if (!m_pStreamImp) {
    return -1;
  }
  if ((m_dwAccess & FX_STREAMACCESS_Write) == 0) {
    return -1;
  }
  int32_t iLen = iBufferSize;
  if (m_eStreamType == FX_STREAMTYPE_Stream) {
    iLen = std::min(m_iStart + m_iTotalSize - m_iPosition, iBufferSize);
    if (iLen <= 0) {
      return 0;
    }
  }
  int32_t iEnd = m_iStart + m_iLength;
  if (m_pStreamImp->GetPosition() != m_iPosition) {
    m_pStreamImp->Seek(FX_STREAMSEEK_Begin, m_iPosition);
  }
  iLen = m_pStreamImp->WriteData(pBuffer, iLen);
  m_iPosition = m_pStreamImp->GetPosition();
  if (m_iPosition > iEnd) {
    m_iLength = m_iPosition - m_iStart;
  }
  return iLen;
}
int32_t CFGAS_Stream::WriteString(const FX_WCHAR* pStr, int32_t iLength) {
  ASSERT(pStr && iLength > 0);
  if (!m_pStreamImp) {
    return -1;
  }
  if ((m_dwAccess & FX_STREAMACCESS_Write) == 0) {
    return -1;
  }
  int32_t iLen = iLength;
  if (m_eStreamType == FX_STREAMTYPE_Stream) {
    iLen = std::min((m_iStart + m_iTotalSize - m_iPosition) / 2, iLength);
    if (iLen <= 0) {
      return 0;
    }
  }
  int32_t iEnd = m_iStart + m_iLength;
  if (m_pStreamImp->GetPosition() != m_iPosition) {
    m_pStreamImp->Seek(FX_STREAMSEEK_Begin, m_iPosition);
  }
  iLen = m_pStreamImp->WriteString(pStr, iLen);
  m_iPosition = m_pStreamImp->GetPosition();
  if (m_iPosition > iEnd) {
    m_iLength = m_iPosition - m_iStart;
  }
  return iLen;
}
void CFGAS_Stream::Flush() {
  if (!m_pStreamImp) {
    return;
  }
  if ((m_dwAccess & FX_STREAMACCESS_Write) == 0) {
    return;
  }
  m_pStreamImp->Flush();
}
bool CFGAS_Stream::SetLength(int32_t iLength) {
  if (!m_pStreamImp) {
    return false;
  }
  if ((m_dwAccess & FX_STREAMACCESS_Write) == 0) {
    return false;
  }
  return m_pStreamImp->SetLength(iLength);
}
int32_t CFGAS_Stream::GetBOM(uint8_t bom[4]) const {
  if (!m_pStreamImp) {
    return -1;
  }
  return 0;
}
uint16_t CFGAS_Stream::GetCodePage() const {
#if _FX_ENDIAN_ == _FX_LITTLE_ENDIAN_
  return FX_CODEPAGE_UTF16LE;
#else
  return FX_CODEPAGE_UTF16BE;
#endif
}
uint16_t CFGAS_Stream::SetCodePage(uint16_t wCodePage) {
#if _FX_ENDIAN_ == _FX_LITTLE_ENDIAN_
  return FX_CODEPAGE_UTF16LE;
#else
  return FX_CODEPAGE_UTF16BE;
#endif
}

CFX_RetainPtr<IFGAS_Stream> CFGAS_Stream::CreateSharedStream(uint32_t dwAccess,
                                                             int32_t iOffset,
                                                             int32_t iLength) {
  ASSERT(iLength > 0);
  if (!m_pStreamImp)
    return nullptr;

  if ((m_dwAccess & FX_STREAMACCESS_Text) != 0 &&
      (dwAccess & FX_STREAMACCESS_Text) == 0) {
    return nullptr;
  }
  if ((m_dwAccess & FX_STREAMACCESS_Write) == 0 &&
      (dwAccess & FX_STREAMACCESS_Write) != 0) {
    return nullptr;
  }
  int32_t iStart = m_iStart + iOffset;
  int32_t iTotal = m_iStart + m_iLength;
  if (iStart < m_iStart || iStart >= iTotal)
    return nullptr;

  int32_t iEnd = iStart + iLength;
  if (iEnd < iStart || iEnd > iTotal)
    return nullptr;

  auto pShared = pdfium::MakeRetain<CFGAS_Stream>();
  pShared->m_eStreamType = FX_STREAMTYPE_Stream;
  pShared->m_pStreamImp = m_pStreamImp;
  pShared->m_dwAccess = dwAccess;
  pShared->m_iTotalSize = iLength;
  pShared->m_iPosition = iStart;
  pShared->m_iStart = iStart;
  pShared->m_iLength = (dwAccess & FX_STREAMACCESS_Write) != 0 ? 0 : iLength;
  if (dwAccess & FX_STREAMACCESS_Text)
    return IFGAS_Stream::CreateTextStream(pShared);

  return pShared;
}

CFX_RetainPtr<IFX_SeekableReadStream> IFGAS_Stream::MakeSeekableReadStream() {
  return CFGAS_FileRead::Create(CFX_RetainPtr<IFGAS_Stream>(this));
}

CFX_RetainPtr<CFGAS_FileRead> CFGAS_FileRead::Create(
    const CFX_RetainPtr<IFGAS_Stream>& pStream) {
  return pdfium::MakeRetain<CFGAS_FileRead>(pStream);
}

CFGAS_FileRead::CFGAS_FileRead(const CFX_RetainPtr<IFGAS_Stream>& pStream)
    : m_pStream(pStream) {
  ASSERT(m_pStream);
}

CFGAS_FileRead::~CFGAS_FileRead() {}

FX_FILESIZE CFGAS_FileRead::GetSize() {
  return (FX_FILESIZE)m_pStream->GetLength();
}

bool CFGAS_FileRead::ReadBlock(void* buffer, FX_FILESIZE offset, size_t size) {
  m_pStream->Seek(FX_STREAMSEEK_Begin, (int32_t)offset);
  int32_t iLen = m_pStream->ReadData((uint8_t*)buffer, (int32_t)size);
  return iLen == (int32_t)size;
}