gems: move reusable code to include/gems

This patch makes various utilities that were originally developed for
the backdrop application publicly available.

repos/gems/src/lib/file/file.cc

@@ -0,0 +1,55 @@
+/*
+ * \brief  Utility for loading a file
+ * \author Norman Feske
+ * \date   2014-08-14
+ */
+
+/*
+ * Copyright (C) 2014 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU General Public License version 2.
+ */
+
+/* Genode includes */
+#include <base/printf.h>
+
+/* gems includes */
+#include <gems/file.h>
+
+/* libc includes */
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+
+
+static Genode::size_t file_size(char const *name)
+{
+	struct stat s;
+	s.st_size = 0;
+	stat(name, &s);
+	return s.st_size;
+}
+
+
+File::File(char const *name, Genode::Allocator &alloc)
+:
+	_alloc(alloc),
+	_file_size(file_size(name)),
+	_data(alloc.alloc(_file_size))
+{
+	int const fd = open(name, O_RDONLY);
+	if (read(fd, _data, _file_size) < 0) {
+		PERR("reading from file \"%s\" failed (error %d)", name, errno);
+		throw Reading_failed();
+	}
+	close(fd);
+}
+
+
+File::~File()
+{
+	_alloc.free(_data, _file_size);
+}