lib/yajl/Callbacks: OO wrapper for yajl_callbacks

Makefile.am

@@ -244,6 +244,7 @@ CURL_SOURCES = \
 
 YAJL_SOURCES = \
 	src/lib/yajl/ParseInputStream.cxx src/lib/yajl/ParseInputStream.hxx \
+	src/lib/yajl/Callbacks.hxx \
 	src/lib/yajl/Handle.hxx
 
 UPNP_SOURCES = \

src/lib/yajl/Callbacks.hxx

+/*
+ * Copyright (C) 2018 Max Kellermann <max.kellermann@gmail.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef YAJL_CALLBACKS_HXX
+#define YAJL_CALLBACKS_HXX
+
+#include "util/Cast.hxx"
+#include "util/StringView.hxx"
+
+#include <yajl/yajl_parse.h>
+
+namespace Yajl {
+
+/**
+ * Helper template which allows implementing callbacks as regular
+ * methods.  The "ctx" parameter is casted to the enclosing class.
+ */
+template<class T>
+struct CallbacksWrapper {
+	static T &Cast(void *ctx) {
+		return *(T *)ctx;
+	}
+
+	static int Integer(void *ctx, long long integerVal) noexcept {
+		return Cast(ctx).Integer(integerVal);
+	}
+
+	static int String(void *ctx, const unsigned char *stringVal,
+			  size_t stringLen) noexcept {
+		return Cast(ctx).String(StringView((const char *)stringVal,
+						   stringLen));
+	}
+
+	static int StartMap(void *ctx) noexcept {
+		return Cast(ctx).StartMap();
+	}
+
+	static int MapKey(void *ctx, const unsigned char *key,
+			  size_t stringLen) noexcept {
+		return Cast(ctx).MapKey(StringView((const char *)key,
+						   stringLen));
+	}
+
+	static int EndMap(void *ctx) noexcept {
+		return Cast(ctx).EndMap();
+	}
+};
+
+} // namespace Yajl
+
+#endif

src/playlist/plugins/SoundCloudPlaylistPlugin.cxx

@@ -22,6 +22,7 @@
 #include "../PlaylistPlugin.hxx"
 #include "../MemorySongEnumerator.hxx"
 #include "lib/yajl/Handle.hxx"
+#include "lib/yajl/Callbacks.hxx"
 #include "lib/yajl/ParseInputStream.hxx"
 #include "config/Block.hxx"
 #include "input/InputStream.hxx"
@@ -109,111 +110,106 @@ struct SoundCloudJsonData {
 	int got_url = 0; /* nesting level of last stream_url */
 
 	std::forward_list<DetachedSong> songs;
+
+	bool Integer(long long value) noexcept;
+	bool String(StringView value) noexcept;
+	bool StartMap() noexcept;
+	bool MapKey(StringView value) noexcept;
+	bool EndMap() noexcept;
 };
 
-static int
-handle_integer(void *ctx, long long intval)
+inline bool
+SoundCloudJsonData::Integer(long long intval) noexcept
 {
-	auto *data = (SoundCloudJsonData *) ctx;
-
-	switch (data->key) {
+	switch (key) {
 	case SoundCloudJsonData::Key::DURATION:
-		data->duration = intval;
+		duration = intval;
 		break;
 	default:
 		break;
 	}
 
-	return 1;
+	return true;
 }
 
-static int
-handle_string(void *ctx, const unsigned char *stringval, size_t stringlen)
+inline bool
+SoundCloudJsonData::String(StringView value) noexcept
 {
-	auto *data = (SoundCloudJsonData *) ctx;
-	const char *s = (const char *) stringval;
-
-	switch (data->key) {
+	switch (key) {
 	case SoundCloudJsonData::Key::TITLE:
-		data->title.assign(s, stringlen);
+		title.assign(value.data, value.size);
 		break;
 
 	case SoundCloudJsonData::Key::STREAM_URL:
-		data->stream_url.assign(s, stringlen);
-		data->got_url = 1;
+		stream_url.assign(value.data, value.size);
+		got_url = 1;
 		break;
 
 	default:
 		break;
 	}
 
-	return 1;
+	return true;
 }
 
-static int
-handle_mapkey(void *ctx, const unsigned char *stringval, size_t stringlen)
+inline bool
+SoundCloudJsonData::MapKey(StringView value) noexcept
 {
-	auto *data = (SoundCloudJsonData *) ctx;
-
 	const auto *i = key_str;
-	while (*i != nullptr &&
-	       !StringStartsWith(*i, {(const char *)stringval, stringlen}))
+	while (*i != nullptr && !StringStartsWith(*i, value))
 		++i;
 
-	data->key = SoundCloudJsonData::Key(i - key_str);
-	return 1;
+	key = SoundCloudJsonData::Key(i - key_str);
+	return true;
 }
 
-static int
-handle_start_map(void *ctx)
+inline bool
+SoundCloudJsonData::StartMap() noexcept
 {
-	auto *data = (SoundCloudJsonData *) ctx;
-
-	if (data->got_url > 0)
-		data->got_url++;
+	if (got_url > 0)
+		got_url++;
 
-	return 1;
+	return true;
 }
 
-static int
-handle_end_map(void *ctx)
+inline bool
+SoundCloudJsonData::EndMap() noexcept
 {
-	auto *data = (SoundCloudJsonData *) ctx;
-
-	if (data->got_url > 1) {
-		data->got_url--;
+	if (got_url > 1) {
+		got_url--;
 		return 1;
 	}
 
-	if (data->got_url == 0)
+	if (got_url == 0)
 		return 1;
 
 	/* got_url == 1, track finished, make it into a song */
-	data->got_url = 0;
+	got_url = 0;
 
-	const std::string u = data->stream_url + "?client_id=" +
+	const std::string u = stream_url + "?client_id=" +
 		soundcloud_config.apikey;
 
 	TagBuilder tag;
-	tag.SetDuration(SignedSongTime::FromMS(data->duration));
-	if (!data->title.empty())
-		tag.AddItem(TAG_NAME, data->title.c_str());
+	tag.SetDuration(SignedSongTime::FromMS(duration));
+	if (!title.empty())
+		tag.AddItem(TAG_NAME, title.c_str());
 
-	data->songs.emplace_front(u.c_str(), tag.Commit());
+	songs.emplace_front(u.c_str(), tag.Commit());
 
-	return 1;
+	return true;
 }
 
+using Wrapper = Yajl::CallbacksWrapper<SoundCloudJsonData>;
 static constexpr yajl_callbacks parse_callbacks = {
 	nullptr,
 	nullptr,
-	handle_integer,
+	Wrapper::Integer,
 	nullptr,
 	nullptr,
-	handle_string,
-	handle_start_map,
-	handle_mapkey,
-	handle_end_map,
+	Wrapper::String,
+	Wrapper::StartMap,
+	Wrapper::MapKey,
+	Wrapper::EndMap,
 	nullptr,
 	nullptr,
 };