This is wx's source:
// ----------------------------------------------------------------------------
// wxMemoryFSHandlerBase
// ----------------------------------------------------------------------------
class WXDLLIMPEXP_BASE wxMemoryFSHandlerBase : public wxFileSystemHandler
{
public:
wxMemoryFSHandlerBase();
virtual ~wxMemoryFSHandlerBase();
// Add file to list of files stored in memory. Stored data (bitmap, text or
// raw data) will be copied into private memory stream and available under
// name "memory:" + filename
static void AddFile(const wxString& filename, const wxString& textdata);
static void AddFile(const wxString& filename, const void *binarydata, size_t size);
static void AddFileWithMimeType(const wxString& filename,
const wxString& textdata,
const wxString& mimetype);
static void AddFileWithMimeType(const wxString& filename,
const void *binarydata, size_t size,
const wxString& mimetype);
// Remove file from memory FS and free occupied memory
static void RemoveFile(const wxString& filename);
virtual bool CanOpen(const wxString& location) wxOVERRIDE;
virtual wxFSFile* OpenFile(wxFileSystem& fs, const wxString& location) wxOVERRIDE;
virtual wxString FindFirst(const wxString& spec, int flags = 0) wxOVERRIDE;
virtual wxString FindNext() wxOVERRIDE;
protected:
// check that the given file is not already present in m_Hash; logs an
// error and returns false if it does exist
static bool CheckDoesntExist(const wxString& filename);
// the hash map indexed by the names of the files stored in the memory FS
static wxMemoryFSHash m_Hash;
// the file name currently being searched for, i.e. the argument of the
// last FindFirst() call or empty string if FindFirst() hasn't been called
// yet or FindNext() didn't find anything
wxString m_findArgument;
// iterator into m_Hash used by FindFirst/Next(), possibly m_Hash.end() or
// even invalid (can only be used when m_findArgument is not empty)
wxMemoryFSHash::const_iterator m_findIter;
};
// ----------------------------------------------------------------------------
// wxMemoryFSHandler
// ----------------------------------------------------------------------------
#if wxUSE_GUI
// add GUI-only operations to the base class
class WXDLLIMPEXP_CORE wxMemoryFSHandler : public wxMemoryFSHandlerBase
{
public:
// bring the base class versions into the scope, otherwise they would be
// inaccessible in wxMemoryFSHandler
// (unfortunately "using" can't be used as gcc 2.95 doesn't have it...)
static void AddFile(const wxString& filename, const wxString& textdata)
{
wxMemoryFSHandlerBase::AddFile(filename, textdata);
}
static void AddFile(const wxString& filename,
const void *binarydata,
size_t size)
{
wxMemoryFSHandlerBase::AddFile(filename, binarydata, size);
}
static void AddFileWithMimeType(const wxString& filename,
const wxString& textdata,
const wxString& mimetype)
{
wxMemoryFSHandlerBase::AddFileWithMimeType(filename,
textdata,
mimetype);
}
static void AddFileWithMimeType(const wxString& filename,
const void *binarydata, size_t size,
const wxString& mimetype)
{
wxMemoryFSHandlerBase::AddFileWithMimeType(filename,
binarydata, size,
mimetype);
}
#if wxUSE_IMAGE
static void AddFile(const wxString& filename,
const wxImage& image,
wxBitmapType type);
static void AddFile(const wxString& filename,
const wxBitmap& bitmap,
wxBitmapType type);
#endif // wxUSE_IMAGE
};
#else // !wxUSE_GUI
// just the same thing as the base class in wxBase
class WXDLLIMPEXP_BASE wxMemoryFSHandler : public wxMemoryFSHandlerBase
{
};
#endif // wxUSE_GUI/!wxUSE_GUI
Note that the function
static bool CheckDoesntExist(const wxString& filename);
But this function is protected, so we can't access it, this gives the dilemma：
1, if we try to remove a file which does not exists in the system, we get a log message from wx.
2, if we try to add a file which the same file already exists in the system, we also get a log message from wx.
So, how can we handle this? Do we need to always remove the file when a plugin is unloaded?
