cam: Add BufferWriter helper

Add a simpler helper to allow the cam application to write raw captured
frames to disk.

Signed-off-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

src/cam/buffer_writer.cpp

@@ -0,0 +1,63 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * buffer_writer.cpp - Buffer writer
+ */
+
+#include <fcntl.h>
+#include <iomanip>
+#include <iostream>
+#include <sstream>
+#include <string.h>
+#include <unistd.h>
+
+#include "buffer_writer.h"
+
+BufferWriter::BufferWriter(const std::string &pattern)
+	: pattern_(pattern)
+{
+}
+
+int BufferWriter::write(libcamera::Buffer *buffer)
+{
+	std::string filename;
+	size_t pos;
+	int fd, ret = 0;
+
+	filename = pattern_;
+	pos = filename.find_first_of('#');
+	if (pos != std::string::npos) {
+		std::stringstream ss;
+		ss << std::setw(6) << std::setfill('0') << buffer->sequence();
+		filename.replace(pos, 1, ss.str());
+	}
+
+	fd = open(filename.c_str(), O_CREAT | O_WRONLY |
+		  (pos == std::string::npos ? O_APPEND : O_TRUNC),
+		  S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH);
+	if (fd == -1)
+		return -errno;
+
+	for (libcamera::Plane &plane : buffer->planes()) {
+		void *data = plane.mem();
+		unsigned int length = plane.length();
+
+		ret = ::write(fd, data, length);
+		if (ret < 0) {
+			ret = -errno;
+			std::cerr << "write error: " << strerror(-ret)
+				  << std::endl;
+			break;
+		} else if (ret != (int)length) {
+			std::cerr << "write error: only " << ret
+				  << " bytes written instead of "
+				  << length << std::endl;
+			break;
+		}
+	}
+
+	close(fd);
+
+	return ret;
+}

src/cam/buffer_writer.h

@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * buffer_writer.h - Buffer writer
+ */
+#ifndef __LIBCAMERA_BUFFER_WRITER_H__
+#define __LIBCAMERA_BUFFER_WRITER_H__
+
+#include <string>
+
+#include <libcamera/buffer.h>
+
+class BufferWriter
+{
+public:
+	BufferWriter(const std::string &pattern = "frame-#.bin");
+
+	int write(libcamera::Buffer *buffer);
+
+private:
+	std::string pattern_;
+};
+
+#endif /* __LIBCAMERA_BUFFER_WRITER_H__ */

src/cam/meson.build

@@ -1,4 +1,5 @@
 cam_sources = files([
+    'buffer_writer.cpp',
     'event_loop.cpp',
     'main.cpp',
     'options.cpp',