storage/Plugin: add "prefixes"

src/storage/Registry.cxx

@@ -58,13 +58,25 @@ GetStoragePluginByName(const char *name) noexcept
 	return nullptr;
 }
 
+const StoragePlugin *
+GetStoragePluginByUri(const char *uri) noexcept
+{
+	for (auto i = storage_plugins; *i != nullptr; ++i) {
+		const StoragePlugin &plugin = **i;
+		if (plugin.SupportsUri(uri))
+			return *i;
+	}
+
+	return nullptr;
+}
+
 std::unique_ptr<Storage>
 CreateStorageURI(EventLoop &event_loop, const char *uri)
 {
 	for (auto i = storage_plugins; *i != nullptr; ++i) {
 		const StoragePlugin &plugin = **i;
 
-		if (plugin.create_uri == nullptr)
+		if (plugin.create_uri == nullptr || !plugin.SupportsUri(uri))
 			continue;
 
 		auto storage = plugin.create_uri(event_loop, uri);

src/storage/Registry.hxx

@@ -38,6 +38,10 @@ gcc_nonnull_all gcc_pure
 const StoragePlugin *
 GetStoragePluginByName(const char *name) noexcept;
 
+gcc_nonnull_all gcc_pure
+const StoragePlugin *
+GetStoragePluginByUri(const char *uri) noexcept;
+
 gcc_nonnull_all
 std::unique_ptr<Storage>
 CreateStorageURI(EventLoop &event_loop, const char *uri);

src/storage/StoragePlugin.cxx

@@ -0,0 +1,34 @@
+/*
+ * Copyright 2003-2021 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "StoragePlugin.hxx"
+#include "util/StringCompare.hxx"
+
+bool
+StoragePlugin::SupportsUri(const char *uri) const noexcept
+{
+	if (prefixes == nullptr)
+		return false;
+
+	for (auto i = prefixes; *i != nullptr; ++i)
+		if (StringStartsWithIgnoreCase(uri, *i))
+			return true;
+
+	return false;
+}

src/storage/StoragePlugin.hxx

@@ -28,11 +28,20 @@ class EventLoop;
 struct StoragePlugin {
 	const char *name;
 
+	/**
+	 * A nullptr-terminated list of URI prefixes handled by this
+	 * plugin.  This is usually a string in the form "scheme://".
+	 */
+	const char *const*prefixes;
+
 	/**
 	 * Throws #std::runtime_error on error.
 	 */
 	std::unique_ptr<Storage> (*create_uri)(EventLoop &event_loop,
 					       const char *uri);
+
+	[[gnu::pure]]
+	bool SupportsUri(const char *uri) const noexcept;
 };
 
 #endif

src/storage/meson.build

@@ -1,6 +1,7 @@
 storage_api = static_library(
   'storage_api',
   'StorageInterface.cxx',
+  'StoragePlugin.cxx',
   include_directories: inc,
 )
 

src/storage/plugins/CurlStorage.cxx

@@ -570,14 +570,15 @@ CurlStorage::OpenDirectory(std::string_view uri_utf8)
 static std::unique_ptr<Storage>
 CreateCurlStorageURI(EventLoop &event_loop, const char *uri)
 {
-	if (!StringStartsWithCaseASCII(uri, "http://") &&
-	    !StringStartsWithCaseASCII(uri, "https://"))
-		return nullptr;
-
 	return std::make_unique<CurlStorage>(event_loop, uri);
 }
 
+static constexpr const char *curl_prefixes[] = {
+	"http://", "https://", nullptr
+};
+
 const StoragePlugin curl_storage_plugin = {
 	"curl",
+	curl_prefixes,
 	CreateCurlStorageURI,
 };

src/storage/plugins/LocalStorage.cxx

@@ -173,4 +173,5 @@ CreateLocalStorage(Path base_fs)
 constexpr StoragePlugin local_storage_plugin = {
 	"local",
 	nullptr,
+	nullptr,
 };

src/storage/plugins/NfsStorage.cxx

@@ -425,7 +425,10 @@ CreateNfsStorageURI(EventLoop &event_loop, const char *base)
 					    server.c_str(), mount);
 }
 
+static constexpr const char *nfs_prefixes[] = { "nfs://", nullptr };
+
 const StoragePlugin nfs_storage_plugin = {
 	"nfs",
+	nfs_prefixes,
 	CreateNfsStorageURI,
 };

src/storage/plugins/UdisksStorage.cxx

@@ -377,7 +377,10 @@ CreateUdisksStorageURI(EventLoop &event_loop, const char *base_uri)
 					       std::move(inside_path));
 }
 
+static constexpr const char *udisks_prefixes[] = { "udisks://", nullptr };
+
 const StoragePlugin udisks_storage_plugin = {
 	"udisks",
+	udisks_prefixes,
 	CreateUdisksStorageURI,
 };