test/run_filter: move ReadFrames() to separate source

test/ReadFrames.cxx

@@ -0,0 +1,52 @@
+/*
+ * Copyright 2003-2021 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.
+ */
+
+#include "ReadFrames.hxx"
+#include "system/Error.hxx"
+#include "io/FileDescriptor.hxx"
+
+static size_t
+ReadOrThrow(FileDescriptor fd, void *buffer, size_t size)
+{
+	auto nbytes = fd.Read(buffer, size);
+	if (nbytes < 0)
+		throw MakeErrno("Read failed");
+
+	return nbytes;
+}
+
+std::size_t
+ReadFrames(FileDescriptor fd, void *_buffer, std::size_t size,
+	   std::size_t frame_size)
+{
+	auto buffer = (std::byte *)_buffer;
+
+	size = (size / frame_size) * frame_size;
+
+	size_t nbytes = ReadOrThrow(fd, buffer, size);
+
+	const size_t modulo = nbytes % frame_size;
+	if (modulo > 0) {
+		size_t rest = frame_size - modulo;
+		fd.FullRead(buffer + nbytes, rest);
+		nbytes += rest;
+	}
+
+	return nbytes;
+}