From 0f0e06c6b893c11631b9da7a837f30c55eaaa31f Mon Sep 17 00:00:00 2001
From: Mathis Logemann <mathisloge@gmail.com>
Date: Mon, 14 Feb 2022 10:14:59 +0100
Subject: [PATCH] [datasource] add plugin_registered function

---
 include/mapnik/datasource_cache.hpp |  5 +++--
 src/datasource_cache.cpp            | 26 ++++++++++++++++++++++++--
 2 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/include/mapnik/datasource_cache.hpp b/include/mapnik/datasource_cache.hpp
index 8504b05c2..4e321c9ad 100644
--- a/include/mapnik/datasource_cache.hpp
+++ b/include/mapnik/datasource_cache.hpp
@@ -47,7 +47,8 @@ class MAPNIK_DECL datasource_cache : public singleton<datasource_cache, CreateSt
     friend class CreateStatic<datasource_cache>;
 
   public:
-    std::vector<std::string> plugin_names();
+    bool plugin_registered(const std::string& plugin_name) const;
+    std::vector<std::string> plugin_names() const;
     std::string plugin_directories();
     bool register_datasources(std::string const& path, bool recurse = false);
     bool register_datasource(std::string const& path);
@@ -62,7 +63,7 @@ class MAPNIK_DECL datasource_cache : public singleton<datasource_cache, CreateSt
     // but the instance also needs its own mutex to protect the
     // plugins_ and plugin_directories_ members which are potentially
     // modified recusrively by register_datasources(path, true);
-    std::recursive_mutex instance_mutex_;
+    mutable std::recursive_mutex instance_mutex_;
 };
 
 extern template class MAPNIK_DECL singleton<datasource_cache, CreateStatic>;
diff --git a/src/datasource_cache.cpp b/src/datasource_cache.cpp
index 28ae3a12d..bcb5d49da 100644
--- a/src/datasource_cache.cpp
+++ b/src/datasource_cache.cpp
@@ -113,7 +113,7 @@ datasource_ptr datasource_cache::create(parameters const& params)
 #ifdef __GNUC__
     __extension__
 #endif
-    datasource_plugin* create_datasource = reinterpret_cast<datasource_plugin*>(itr->second->get_symbol("plugin"));
+      datasource_plugin* create_datasource = reinterpret_cast<datasource_plugin*>(itr->second->get_symbol("plugin"));
 
     if (!create_datasource)
     {
@@ -131,7 +131,29 @@ std::string datasource_cache::plugin_directories()
     return boost::algorithm::join(plugin_directories_, ", ");
 }
 
-std::vector<std::string> datasource_cache::plugin_names()
+bool datasource_cache::plugin_registered(const std::string& plugin_name) const
+{
+#ifdef MAPNIK_STATIC_PLUGINS
+    const auto static_names = get_static_datasource_names();
+    const auto static_it = std::find(static_names.begin(), static_names.end(), plugin_name);
+    if (static_it != static_names.end())
+        return true;
+#endif
+
+#ifdef MAPNIK_THREADSAFE
+    std::lock_guard<std::recursive_mutex> lock(instance_mutex_);
+#endif
+
+    std::map<std::string, std::shared_ptr<PluginInfo>>::const_iterator itr;
+    for (itr = plugins_.begin(); itr != plugins_.end(); ++itr)
+    {
+        if (itr->second->name() == plugin_name)
+            return true;
+    }
+    return false;
+}
+
+std::vector<std::string> datasource_cache::plugin_names() const
 {
     std::vector<std::string> names;