input/Registry: replace the input_plugins_for_each macros with a container class

src/input/Init.cxx

@@ -73,7 +73,7 @@ input_stream_global_init(const ConfigData &config, EventLoop &event_loop)
 void
 input_stream_global_finish() noexcept
 {
-	input_plugins_for_each_enabled(plugin)
-		if (plugin->finish != nullptr)
-			plugin->finish();
+	for (const auto &plugin : GetEnabledInputPlugins())
+		if (plugin.finish != nullptr)
+			plugin.finish();
 }

src/input/Open.cxx

@@ -20,12 +20,11 @@ InputStream::Open(const char *url, Mutex &mutex)
 		return OpenLocalInputStream(path, mutex);
 	}
 
-	input_plugins_for_each_enabled(plugin) {
-		if (!plugin->SupportsUri(url))
+	for (const auto &plugin : GetEnabledInputPlugins()) {
+		if (!plugin.SupportsUri(url))
 			continue;
 
-		auto is = plugin->open(url, mutex);
-		if (is != nullptr)
+		if (auto is = plugin.open(url, mutex))
 			return input_rewind_open(std::move(is));
 	}
 

src/input/Registry.cxx

@@ -72,10 +72,11 @@ bool input_plugins_enabled[std::max(n_input_plugins, std::size_t(1))];
 bool
 HasRemoteTagScanner(const char *uri) noexcept
 {
-	input_plugins_for_each_enabled(plugin)
-		if (plugin->scan_tags != nullptr &&
-		    plugin->SupportsUri(uri))
+	for (const auto &plugin : GetEnabledInputPlugins()) {
+		if (plugin.scan_tags != nullptr &&
+		    plugin.SupportsUri(uri))
 			return true;
+	}
 
 	return false;
 }

src/input/Registry.hxx

@@ -1,8 +1,11 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 // Copyright The Music Player Daemon Project
 
-#ifndef MPD_INPUT_REGISTRY_HXX
-#define MPD_INPUT_REGISTRY_HXX
+#pragma once
+
+#include "util/DereferenceIterator.hxx"
+#include "util/FilteredContainer.hxx"
+#include "util/TerminatedArray.hxx"
 
 /**
  * NULL terminated list of all input plugins which were enabled at
@@ -12,18 +15,19 @@ extern const struct InputPlugin *const input_plugins[];
 
 extern bool input_plugins_enabled[];
 
-#define input_plugins_for_each(plugin) \
-	for (const InputPlugin *plugin, \
-		*const*input_plugin_iterator = &input_plugins[0]; \
-		(plugin = *input_plugin_iterator) != NULL; \
-		++input_plugin_iterator)
+static inline auto
+GetAllInputPlugins() noexcept
+{
+	return DereferenceContainerAdapter{TerminatedArray<const InputPlugin *const, nullptr>{input_plugins}};
+}
 
-#define input_plugins_for_each_enabled(plugin) \
-	input_plugins_for_each(plugin) \
-		if (input_plugins_enabled[input_plugin_iterator - input_plugins])
+static inline auto
+GetEnabledInputPlugins() noexcept
+{
+	const auto all = GetAllInputPlugins();
+	return FilteredContainer{all.begin(), all.end(), input_plugins_enabled};
+}
 
 [[gnu::pure]]
 bool
 HasRemoteTagScanner(const char *uri) noexcept;
-
-#endif

src/input/ScanTags.cxx

@@ -9,12 +9,11 @@
 std::unique_ptr<RemoteTagScanner>
 InputScanTags(const char *uri, RemoteTagHandler &handler)
 {
-	input_plugins_for_each_enabled(plugin) {
-		if (plugin->scan_tags == nullptr || !plugin->SupportsUri(uri))
+	for (const auto &plugin : GetEnabledInputPlugins()) {
+		if (plugin.scan_tags == nullptr || !plugin.SupportsUri(uri))
 			continue;
 
-		auto scanner = plugin->scan_tags(uri, handler);
-		if (scanner)
+		if (auto scanner = plugin.scan_tags(uri, handler))
 			return scanner;
 	}