input/curl: add public function to construct an instance

src/input/plugins/CurlInputPlugin.cxx

@@ -468,6 +468,14 @@ CurlInputStream::Open(const char *url,
 	return std::make_unique<IcyInputStream>(std::move(c), std::move(icy));
 }
 
+InputStreamPtr
+OpenCurlInputStream(const char *uri,
+		    const std::multimap<std::string, std::string> &headers,
+		    Mutex &mutex, Cond &cond)
+{
+	return CurlInputStream::Open(uri, headers, mutex, cond);
+}
+
 static InputStreamPtr
 input_curl_open(const char *url, Mutex &mutex, Cond &cond)
 {

src/input/plugins/CurlInputPlugin.hxx

@@ -20,6 +20,26 @@
 #ifndef MPD_INPUT_CURL_HXX
 #define MPD_INPUT_CURL_HXX
 
+#include "input/Ptr.hxx"
+
+#include <string>
+#include <map>
+
+class Mutex;
+class Cond;
+
 extern const struct InputPlugin input_plugin_curl;
 
+/**
+ * Open a #CurlInputStream with custom request headers.
+ *
+ * This stream does not support Icy metadata.
+ *
+ * Throws on error.
+ */
+InputStreamPtr
+OpenCurlInputStream(const char *uri,
+		    const std::multimap<std::string, std::string> &headers,
+		    Mutex &mutex, Cond &cond);
+
 #endif