Add runtime enumeration of supported schemas.

Fix src/ls.cxx to only print unique schemas.
Refactor src/ls.cxx to use src/input/InputPlugin functionality.

Add dynamic enumeration support to curl plugin.

src/input/InputPlugin.cxx

@@ -21,15 +21,54 @@
 #include "util/StringCompare.hxx"
 
 #include <assert.h>
+#include <algorithm>
+#include <iterator>
 
 bool
 InputPlugin::SupportsUri(const char *uri) const noexcept
 {
-	assert(prefixes != nullptr);
-
-	for (auto i = prefixes; *i != nullptr; ++i)
-		if (StringStartsWithIgnoreCase(uri, *i))
-			return true;
-
+	assert(prefixes || protocols);
+	if (prefixes != nullptr) {
+		for (auto i = prefixes; *i != nullptr; ++i)
+			if (StringStartsWithIgnoreCase(uri, *i))
+				return true;
+	} else {
+		for (auto schema : protocols()) {
+			if (StringStartsWithIgnoreCase(uri, schema.c_str())){
+				return true;
+			}
+		}
+	}
 	return false;
 }
+
+// Note: The whitelist has to be ordered alphabetically
+constexpr static const char *whitelist[] = {
+	"ftp",
+	"ftps",
+	"gopher",
+	"http",
+	"https",
+	"mmsh",
+	"mmst",
+	"rtmp",
+	"rtmpe",
+	"rtmps",
+	"rtmpt",
+	"rtmpte",
+	"rtmpts",
+	"rtp",
+	"scp",
+	"sftp",
+	"smb",
+	"srtp",
+};
+
+bool
+protocol_is_whitelisted(const char *proto) {
+	auto begin = std::begin(whitelist);
+	auto end = std::end(whitelist);
+	return std::binary_search(begin, end, proto, [](const char* a, const char* b) {
+		return strcasecmp(a,b) < 0;
+	});
+}

src/input/InputPlugin.hxx

@@ -22,6 +22,9 @@
 
 #include "Ptr.hxx"
 #include "util/Compiler.h"
+#include <assert.h>
+#include <set>
+#include <string>
 
 struct ConfigBlock;
 class Mutex;
@@ -62,6 +65,11 @@ struct InputPlugin {
 	 */
 	InputStreamPtr (*open)(const char *uri, Mutex &mutex);
 
+	/**
+	 * return a set of supported protocols
+	 */
+	std::set<std::string> (*protocols)();
+
 	/**
 	 * Prepare a #RemoteTagScanner.  The operation must be started
 	 * using RemoteTagScanner::Start().  Returns nullptr if the
@@ -76,6 +84,25 @@ struct InputPlugin {
 
 	gcc_pure
 	bool SupportsUri(const char *uri) const noexcept;
+
+	template<typename F>
+	void ForeachSupportedUri(F lambda) const noexcept {
+		assert(prefixes || protocols);
+
+		if (prefixes != nullptr) {
+			for (auto schema = prefixes; *schema != nullptr; ++schema) {
+				lambda(*schema);
+			}
+		}
+		if (protocols != nullptr) {
+			for (auto schema : protocols()) {
+				lambda(schema.c_str());
+			}
+		}
+	}
 };
 
+bool
+protocol_is_whitelisted(const char *proto);
+
 #endif

src/input/plugins/AlsaInputPlugin.cxx

@@ -486,4 +486,5 @@ const struct InputPlugin input_plugin_alsa = {
 	alsa_input_init,
 	nullptr,
 	alsa_input_open,
+	nullptr
 };

src/input/plugins/CdioParanoiaInputPlugin.cxx

@@ -357,4 +357,5 @@ const InputPlugin input_plugin_cdio_paranoia = {
 	input_cdio_init,
 	nullptr,
 	input_cdio_open,
+	nullptr
 };

src/input/plugins/CurlInputPlugin.cxx

@@ -471,16 +471,25 @@ input_curl_open(const char *url, Mutex &mutex)
 	return CurlInputStream::Open(url, {}, mutex);
 }
 
-static constexpr const char *curl_prefixes[] = {
-	"http://",
-	"https://",
-	nullptr
-};
+static std::set<std::string>
+input_curl_protocols() {
+	std::set<std::string> protocols;
+	auto version_info = curl_version_info(CURLVERSION_FIRST);
+	for (auto proto_ptr = version_info->protocols; *proto_ptr != nullptr; proto_ptr++) {
+		if (protocol_is_whitelisted(*proto_ptr)) {
+			std::string schema(*proto_ptr);
+			schema.append("://");
+			protocols.emplace(schema);
+		}
+	}
+	return protocols;
+}
 
 const struct InputPlugin input_plugin_curl = {
 	"curl",
-	curl_prefixes,
+	nullptr,
 	input_curl_init,
 	input_curl_finish,
 	input_curl_open,
+	input_curl_protocols
 };

src/input/plugins/FfmpegInputPlugin.cxx

@@ -25,8 +25,13 @@
 #include "lib/ffmpeg/Init.hxx"
 #include "lib/ffmpeg/Error.hxx"
 #include "../InputStream.hxx"
-#include "../InputPlugin.hxx"
 #include "PluginUnavailable.hxx"
+#include "util/StringAPI.hxx"
+#include "../InputPlugin.hxx"
+#include <iostream>
+#include <exception>
+#include <typeinfo>
+#include <stdexcept>
 
 class FfmpegInputStream final : public InputStream {
 	Ffmpeg::IOContext io;
@@ -71,6 +76,22 @@ input_ffmpeg_init(EventLoop &, const ConfigBlock &)
 		throw PluginUnavailable("No protocol");
 }
 
+static std::set<std::string>
+input_ffmpeg_protocols() {
+	void *opaque = nullptr;
+	const char* protocol;
+	std::set<std::string> protocols;
+	while ((protocol = avio_enum_protocols(&opaque, 0))) {
+		if (protocol_is_whitelisted(protocol)) {
+			std::string schema(protocol);
+			schema.append("://");
+			protocols.emplace(schema);
+		}
+	}
+	
+	return protocols;
+}
+
 static InputStreamPtr
 input_ffmpeg_open(const char *uri,
 		  Mutex &mutex)
@@ -111,20 +132,11 @@ FfmpegInputStream::Seek(offset_type new_offset)
 	offset = result;
 }
 
-static constexpr const char *ffmpeg_prefixes[] = {
-	"gopher://",
-	"rtp://",
-	"rtsp://",
-	"rtmp://",
-	"rtmpt://",
-	"rtmps://",
-	nullptr
-};
-
 const InputPlugin input_plugin_ffmpeg = {
 	"ffmpeg",
-	ffmpeg_prefixes,
+	nullptr,
 	input_ffmpeg_init,
 	nullptr,
 	input_ffmpeg_open,
+	input_ffmpeg_protocols
 };

src/input/plugins/MmsInputPlugin.cxx

@@ -110,4 +110,5 @@ const InputPlugin input_plugin_mms = {
 	nullptr,
 	nullptr,
 	input_mms_open,
+	nullptr
 };

src/input/plugins/NfsInputPlugin.cxx

@@ -232,4 +232,5 @@ const InputPlugin input_plugin_nfs = {
 	input_nfs_init,
 	input_nfs_finish,
 	input_nfs_open,
+	nullptr
 };

src/input/plugins/QobuzInputPlugin.cxx

@@ -219,5 +219,6 @@ const InputPlugin qobuz_input_plugin = {
 	InitQobuzInput,
 	FinishQobuzInput,
 	OpenQobuzInput,
+	nullptr,
 	ScanQobuzTags,
 };

src/input/plugins/SmbclientInputPlugin.cxx

@@ -162,4 +162,5 @@ const InputPlugin input_plugin_smbclient = {
 	input_smbclient_init,
 	nullptr,
 	input_smbclient_open,
+	nullptr
 };

src/input/plugins/TidalInputPlugin.cxx

@@ -249,5 +249,6 @@ const InputPlugin tidal_input_plugin = {
 	InitTidalInput,
 	FinishTidalInput,
 	OpenTidalInput,
+	nullptr,
 	ScanTidalTags,
 };

src/ls.cxx

@@ -22,28 +22,41 @@
 #include "input/Registry.hxx"
 #include "input/InputPlugin.hxx"
 #include "client/Response.hxx"
-#include "util/ASCII.hxx"
 #include "util/UriUtil.hxx"
 
 #include <assert.h>
 
+#include <string>
+
 void print_supported_uri_schemes_to_fp(FILE *fp)
 {
 #ifdef HAVE_UN
 	fprintf(fp, " file://");
 #endif
+	std::set<std::string> protocols;
 	input_plugins_for_each(plugin)
-		for (auto i = plugin->prefixes; *i != nullptr; ++i)
-			fprintf(fp, " %s", *i);
+		plugin->ForeachSupportedUri([&](const char* uri) {
+			protocols.emplace(uri);
+		});
+	
+	for (auto protocol : protocols) {
+		fprintf(fp, " %s", protocol.c_str());
+	}
 	fprintf(fp,"\n");
 }
 
 void
 print_supported_uri_schemes(Response &r)
 {
+	std::set<std::string> protocols;
 	input_plugins_for_each_enabled(plugin)
-		for (auto i = plugin->prefixes; *i != nullptr; ++i)
-			r.Format("handler: %s\n", *i);
+		plugin->ForeachSupportedUri([&](const char* uri) {
+			protocols.emplace(uri);
+		});
+
+	for (auto protocol : protocols) {
+		r.Format("handler: %s\n", protocol.c_str());
+	}
 }
 
 bool
@@ -52,9 +65,7 @@ uri_supported_scheme(const char *uri) noexcept
 	assert(uri_has_scheme(uri));
 
 	input_plugins_for_each_enabled(plugin)
-		for (auto i = plugin->prefixes; *i != nullptr; ++i)
-			if (StringStartsWithCaseASCII(uri, *i))
-				return true;
+		return plugin->SupportsUri(uri);
 
 	return false;
 }