Proj version agnostic context storage

Sponsored by ICSM

src/core/CMakeLists.txt

@@ -284,6 +284,7 @@ SET(QGIS_CORE_SRCS
   qgsprojectstorage.cpp
   qgsprojectstorageregistry.cpp
   qgsprojectversion.cpp
+  qgsprojutils.cpp
   qgsproperty.cpp
   qgspropertycollection.cpp
   qgspropertytransformer.cpp
@@ -940,6 +941,7 @@ SET(QGIS_CORE_HDRS
   qgsprojectstorageregistry.h
   qgsprojecttranslator.h
   qgsprojectversion.h
+  qgsprojutils.h
   qgsproperty.h
   qgsproperty_p.h
   qgspropertycollection.h

src/core/qgsprojutils.cpp

@@ -0,0 +1,67 @@
+/***************************************************************************
+                             qgsprojutils.h
+                             -------------------
+    begin                : March 2019
+    copyright            : (C) 2019 by Nyall Dawson
+    email                : nyall dot dawson at gmail dot com
+***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+#include "qgsprojutils.h"
+
+#if PROJ_VERSION_MAJOR>=6
+#include <proj.h>
+#else
+#include <proj_api.h>
+#endif
+
+
+#ifdef USE_THREAD_LOCAL
+thread_local QgsProjContext QgsProjContext::sProjContext;
+#else
+QThreadStorage< QgsProjContext * > QgsProjContext::sProjContext;
+#endif
+
+QgsProjContext::QgsProjContext()
+{
+#if PROJ_VERSION_MAJOR>=6
+  mContext = proj_context_create();
+#else
+  mContext = pj_ctx_alloc();
+#endif
+}
+
+QgsProjContext::~QgsProjContext()
+{
+#if PROJ_VERSION_MAJOR>=6
+  proj_context_destroy( mContext );
+#else
+  pj_ctx_free( mContext );
+#endif
+}
+
+PJ_CONTEXT *QgsProjContext::get()
+{
+#ifdef USE_THREAD_LOCAL
+  return sProjContext.mContext;
+#else
+  PJ_CONTEXT *pContext = nullptr;
+  if ( sProjContext.hasLocalData() )
+  {
+    pContext = sProjContext.localData()->mContext;
+  }
+  else
+  {
+    sProjContext.setLocalData( new QgsProjContext() );
+    pContext = sProjContext.localData()->mContext;
+  }
+  return pContext;
+#endif
+}

src/core/qgsprojutils.h

@@ -0,0 +1,69 @@
+/***************************************************************************
+                             qgsprojutils.h
+                             -------------------
+    begin                : March 2019
+    copyright            : (C) 2019 by Nyall Dawson
+    email                : nyall dot dawson at gmail dot com
+***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+#ifndef QGSPROJUTILS_H
+#define QGSPROJUTILS_H
+
+#include "qgis_core.h"
+#include "qgsconfig.h"
+
+#ifndef USE_THREAD_LOCAL
+#include <QThreadStorage>
+#endif
+
+#define SIP_NO_FILE
+
+#if PROJ_VERSION_MAJOR>=6
+struct projCtx_t;
+typedef struct projCtx_t PJ_CONTEXT;
+#else
+typedef void PJ_CONTEXT;
+#endif
+
+/**
+ * \class QgsProjContext
+ * \ingroup core
+ * Used to create and store a proj context object, correctly freeing the context upon destruction.
+ * \note Not available in Python bindings
+ */
+class CORE_EXPORT QgsProjContext
+{
+  public:
+
+    QgsProjContext();
+    ~QgsProjContext();
+
+    /**
+     * Returns a thread local instance of a proj context, safe for use in the current thread.
+     */
+    static PJ_CONTEXT *get();
+
+  private:
+    PJ_CONTEXT *mContext = nullptr;
+
+    /**
+     * Thread local proj context storage. A new proj context will be created
+     * for every thread.
+     */
+#ifdef USE_THREAD_LOCAL
+    static thread_local QgsProjContext sProjContext;
+#else
+    static QThreadStorage< QgsProjContext * > sProjContext;
+#endif
+};
+
+
+#endif // QGSPROJUTILS_H