lib/ffmpeg/Filter: C+++ wrapper for several libavfilter objects

src/lib/ffmpeg/Filter.hxx

+/*
+ * Copyright 2003-2019 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.
+ */
+
+#ifndef MPD_FFMPEG_FILTER_HXX
+#define MPD_FFMPEG_FILTER_HXX
+
+#include "Error.hxx"
+
+extern "C" {
+#include <libavfilter/avfilter.h>
+}
+
+namespace Ffmpeg {
+
+class FilterInOut {
+	friend class FilterGraph;
+
+	AVFilterInOut *io = nullptr;
+
+	explicit FilterInOut(AVFilterInOut *_io) noexcept
+		:io(_io) {}
+
+public:
+	FilterInOut() = default;
+
+	FilterInOut(const char *name, AVFilterContext &context)
+		:io(avfilter_inout_alloc()) {
+		if (io == nullptr)
+			throw std::bad_alloc();
+
+		io->name = av_strdup(name);
+		io->filter_ctx = &context;
+		io->pad_idx = 0;
+		io->next = nullptr;
+	}
+
+	FilterInOut(FilterInOut &&src) noexcept
+		:io(std::exchange(src.io, nullptr)) {}
+
+	~FilterInOut() noexcept {
+		if (io != nullptr)
+			avfilter_inout_free(&io);
+	}
+
+	FilterInOut &operator=(FilterInOut &&src) noexcept {
+		using std::swap;
+		swap(io, src.io);
+		return *this;
+	}
+
+	auto *get() noexcept {
+		return io;
+	}
+};
+
+class FilterContext {
+	AVFilterContext *context = nullptr;
+
+public:
+	FilterContext() = default;
+
+	FilterContext(const AVFilter &filt,
+		      const char *name, const char *args, void *opaque,
+		      AVFilterGraph &graph_ctx) {
+		int err = avfilter_graph_create_filter(&context, &filt,
+						       name, args, opaque,
+						       &graph_ctx);
+		if (err < 0)
+			throw MakeFfmpegError(err, "avfilter_graph_create_filter() failed");
+	}
+
+	FilterContext(const AVFilter &filt,
+		      const char *name,
+		      AVFilterGraph &graph_ctx)
+		:FilterContext(filt, name, nullptr, nullptr, graph_ctx) {}
+
+	FilterContext(FilterContext &&src) noexcept
+		:context(std::exchange(src.context, nullptr)) {}
+
+	~FilterContext() noexcept {
+		if (context != nullptr)
+			avfilter_free(context);
+	}
+
+	FilterContext &operator=(FilterContext &&src) noexcept {
+		using std::swap;
+		swap(context, src.context);
+		return *this;
+	}
+
+	auto &operator*() noexcept {
+		return *context;
+	}
+
+	auto *get() noexcept {
+		return context;
+	}
+};
+
+class FilterGraph {
+	AVFilterGraph *graph = nullptr;
+
+public:
+	FilterGraph(std::nullptr_t) noexcept {}
+
+	FilterGraph():graph(avfilter_graph_alloc()) {
+		if (graph == nullptr)
+			throw std::bad_alloc();
+	}
+
+	FilterGraph(FilterGraph &&src) noexcept
+		:graph(std::exchange(src.graph, nullptr)) {}
+
+	~FilterGraph() noexcept {
+		if (graph != nullptr)
+			avfilter_graph_free(&graph);
+	}
+
+	FilterGraph &operator=(FilterGraph &&src) noexcept {
+		using std::swap;
+		swap(graph, src.graph);
+		return *this;
+	}
+
+	auto &operator*() noexcept {
+		return *graph;
+	}
+
+	auto *operator->() noexcept {
+		return graph;
+	}
+
+	std::pair<FilterInOut, FilterInOut> Parse(const char *filters,
+						  FilterInOut &&inputs,
+						  FilterInOut &&outputs) {
+		int err = avfilter_graph_parse_ptr(graph, filters,
+						   &inputs.io, &outputs.io,
+						   nullptr);
+		if (err < 0)
+			throw MakeFfmpegError(err, "avfilter_graph_parse_ptr() failed");
+
+		return std::make_pair(std::move(inputs), std::move(outputs));
+	}
+
+	std::pair<FilterInOut, FilterInOut> Parse(const char *filters) {
+		AVFilterInOut *inputs, *outputs;
+		int err = avfilter_graph_parse2(graph, filters,
+						&inputs, &outputs);
+		if (err < 0)
+			throw MakeFfmpegError(err, "avfilter_graph_parse2() failed");
+
+		return std::make_pair(FilterInOut{inputs}, FilterInOut{outputs});
+	}
+
+	void CheckAndConfigure() {
+		int err = avfilter_graph_config(graph, nullptr);
+		if (err < 0)
+			throw MakeFfmpegError(err, "avfilter_graph_config() failed");
+	}
+};
+
+}
+
+#endif