OCCT

// Copyright (c) 2021 OPEN CASCADE SAS
//
// This file is part of Open CASCADE Technology software library.
//
// This library is free software; you can redistribute it and/or modify it under
// the terms of the GNU Lesser General Public License version 2.1 as published
// by the Free Software Foundation, with special exception defined in the file
// OCCT_LGPL_EXCEPTION.txt. Consult the file LICENSE_LGPL_21.txt included in OCCT
// distribution for complete text of the license and disclaimer of any warranty.
//
// Alternatively, this file may be used under the terms of Open CASCADE
// commercial license or contractual agreement.

#ifndef _OSD_CachedFileSystem_HeaderFile
#define _OSD_CachedFileSystem_HeaderFile

#include <OSD_FileSystem.hxx>

//! File system keeping last stream created by linked file system
//! (OSD_FileSystem::DefaultFileSystem() by default) to be reused for opening a stream with the same
//! URL. Note that as file is kept in opened state, application will need destroying this object to
//! ensure all files being closed. This interface could be handy in context of reading numerous
//! objects pointing to the same file (at different offset). Make sure to create a dedicated
//! OSD_CachedFileSystem for each working thread to avoid data races.
class OSD_CachedFileSystem : public OSD_FileSystem
{
  DEFINE_STANDARD_RTTIEXT(OSD_CachedFileSystem, OSD_FileSystem)
public:
  //! Constructor.
  Standard_EXPORT OSD_CachedFileSystem(
    const occ::handle<OSD_FileSystem>& theLinkedFileSystem = occ::handle<OSD_FileSystem>());

  //! Return linked file system; initialized with OSD_FileSystem::DefaultFileSystem() by default.
  const occ::handle<OSD_FileSystem>& LinkedFileSystem() const { return myLinkedFS; }

  //! Sets linked file system.
  void SetLinkedFileSystem(const occ::handle<OSD_FileSystem>& theLinkedFileSystem)
  {
    myLinkedFS = theLinkedFileSystem;
  }

  //! Returns TRUE if URL defines a supported protocol.
  Standard_EXPORT bool IsSupportedPath(const TCollection_AsciiString& theUrl) const override;

  //! Returns TRUE if current input stream is opened for reading operations.
  Standard_EXPORT bool IsOpenIStream(const std::shared_ptr<std::istream>& theStream) const override;

  //! Returns TRUE if current output stream is opened for writing operations.
  Standard_EXPORT bool IsOpenOStream(const std::shared_ptr<std::ostream>& theStream) const override;

  //! Opens stream for specified file URL for reading operations or returns previously created
  //! stream pointing to the same URL.
  Standard_EXPORT std::shared_ptr<std::istream> OpenIStream(
    const TCollection_AsciiString&       theUrl,
    const std::ios_base::openmode        theParams,
    const int64_t                        theOffset,
    const std::shared_ptr<std::istream>& theOldStream) override;

  //! Opens stream for specified file URL for writing operations (std::ostream) by calling parent's
  //! method.
  Standard_EXPORT std::shared_ptr<std::ostream> OpenOStream(
    const TCollection_AsciiString& theUrl,
    const std::ios_base::openmode  theMode) override;

  //! Opens stream buffer for specified file URL.
  Standard_EXPORT std::shared_ptr<std::streambuf> OpenStreamBuffer(
    const TCollection_AsciiString& theUrl,
    const std::ios_base::openmode  theMode,
    const int64_t                  theOffset     = 0,
    int64_t*                       theOutBufSize = nullptr) override;

protected:
  // Auxiliary structure to save shared stream with path to it.
  struct OSD_CachedStream
  {
    TCollection_AsciiString         Url;
    std::shared_ptr<std::istream>   Stream;
    std::shared_ptr<std::streambuf> StreamBuf;

    void Reset()
    {
      Stream.reset();
      StreamBuf.reset();
    }
  };

protected:
  OSD_CachedStream            myStream;   //!< active cached stream
  occ::handle<OSD_FileSystem> myLinkedFS; //!< linked file system to open files
};

#endif // _OSD_CachedFileSystem_HeaderFile