Move general i/o code to stand-alone utility file.

Get rid of internal library stuff linked to the utilities.
Also rename 'count' param to 'length' clarifying handling
of the parameter internally.

lib/utils_io.h

@@ -0,0 +1,38 @@
+/*
+ * utils - miscellaneous I/O utilities for cryptsetup
+ *
+ * Copyright (C) 2004, Jana Saout <jana@saout.de>
+ * Copyright (C) 2004-2007, Clemens Fruhwirth <clemens@endorphin.org>
+ * Copyright (C) 2009-2018, Red Hat, Inc. All rights reserved.
+ * Copyright (C) 2009-2018, Milan Broz
+ *
+ * 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 _CRYPTSETUP_UTILS_IO_H
+#define _CRYPTSETUP_UTILS_IO_H
+
+ssize_t read_buffer(int fd, void *buf, size_t length);
+ssize_t write_buffer(int fd, const void *buf, size_t length);
+ssize_t write_blockwise(int fd, size_t bsize, size_t alignment,
+			void *orig_buf, size_t length);
+ssize_t read_blockwise(int fd, size_t bsize, size_t alignment,
+		       void *orig_buf, size_t length);
+ssize_t write_lseek_blockwise(int fd, size_t bsize, size_t alignment,
+			      void *buf, size_t length, off_t offset);
+ssize_t read_lseek_blockwise(int fd, size_t bsize, size_t alignment,
+			     void *buf, size_t length, off_t offset);
+
+#endif