Add wxSecretStore

Add a new class allowing to store passwords and other sensitive information
using the OS-provided facilities.

Add implementations for all the main platforms, documentation and a new sample
(which contains an ad hoc unit test as the real unit test for this class would
probably be a bad idea as it wouldn't run in non-interactive contexts and
could show OS level dialog boxes if it did).

include/wx/private/secretstore.h

@@ -0,0 +1,93 @@
+///////////////////////////////////////////////////////////////////////////////
+// Name:        wx/private/secretstore.h
+// Purpose:     Classes used in wxSecretStore implementation only.
+// Author:      Vadim Zeitlin
+// Created:     2016-05-27
+// Copyright:   (c) 2016 Vadim Zeitlin <vadim@wxwidgets.org>
+// Licence:     wxWindows licence
+///////////////////////////////////////////////////////////////////////////////
+
+#ifndef _WX_PRIVATE_SECRETSTORE_H_
+#define _WX_PRIVATE_SECRETSTORE_H_
+
+#include "wx/object.h"          // wxRefCounter
+
+// Both of the implementation classes here are ref-counted so that the
+// corresponding public objects could be copied cheaply and, in the case of
+// wxSecretValue, also to avoid having the secret in more than one place in
+// memory at a time.
+
+// ----------------------------------------------------------------------------
+// Class holding wxSecretValue data
+// ----------------------------------------------------------------------------
+
+// This is a common base class for our own and libsecret-based implementations.
+class wxSecretValueImpl : public wxRefCounter
+{
+public:
+    wxSecretValueImpl()
+    {
+    }
+
+    virtual size_t GetSize() const = 0;
+    virtual const void *GetData() const = 0;
+};
+
+// Trivial common implementation of wxSecretValueImpl used under MSW and OS X.
+#if defined(__WINDOWS__) || defined(__DARWIN__)
+
+class wxSecretValueGenericImpl : public wxSecretValueImpl
+{
+public:
+    wxSecretValueGenericImpl(size_t size, const void *data)
+        : m_size(size),
+          m_data(new char[size])
+    {
+        memcpy(m_data, data, size);
+    }
+
+    virtual ~wxSecretValueGenericImpl()
+    {
+        if ( m_data )
+        {
+            wxSecretValue::Wipe(m_size, m_data);
+            delete [] m_data;
+        }
+    }
+
+    virtual size_t GetSize() const wxOVERRIDE { return m_size; }
+    virtual const void *GetData() const wxOVERRIDE { return m_data; }
+
+private:
+    const size_t m_size;
+    char* const m_data;
+};
+
+#endif // MSW or OSX
+
+// ----------------------------------------------------------------------------
+// Base class for wxSecretStore implementations
+// ----------------------------------------------------------------------------
+
+// All its methods are similar to the methods of the public class except that
+// they work with the implementation rather than public objects and they all
+// take an extra "wxString&" output parameter which is filled with the low
+// level error message in case of an error. This message will be logged by
+// wxSecretStore itself, wxSecretStoreImpl methods shouldn't do any logging on
+// their own.
+class wxSecretStoreImpl : public wxRefCounter
+{
+public:
+    virtual bool Save(const wxString& service,
+                      const wxString& user,
+                      const wxSecretValueImpl& secret,
+                      wxString& errmsg) = 0;
+    virtual wxSecretValueImpl* Load(const wxString& service,
+                                    const wxString& user,
+                                    wxString& errmsg) const = 0;
+    virtual bool Delete(const wxString& service,
+                        const wxString& user,
+                        wxString& errmsg) = 0;
+};
+
+#endif // _WX_PRIVATE_SECRETSTORE_H_