2 files changed, 42 insertions, 1 deletions
diff --git a/lib/Makemodule.am b/lib/Makemodule.am
index ddc78f6..a676291 100644
--- a/lib/Makemodule.am
+++ b/lib/Makemodule.am
@@ -30,7 +30,7 @@ libutil_a_SOURCES = lib/util/canonicalize_name.c lib/util/write_retry.c
 libutil_a_SOURCES += lib/util/read_retry.c include/util.h
 libutil_a_SOURCES += lib/util/print_version.c lib/util/mkdir_p.c
 libutil_a_SOURCES += lib/util/str_table.c include/str_table.h
-libutil_a_SOURCES += lib/util/dirstack.c
+libutil_a_SOURCES += lib/util/dirstack.c lib/util/padd_file.c
 
 if WITH_GZIP
 libcompress_a_SOURCES += lib/comp/gzip.c
diff --git a/lib/util/padd_file.c b/lib/util/padd_file.c
new file mode 100644
index 0000000..8598b8b
--- /dev/null
+++ b/lib/util/padd_file.c
@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#include "util.h"
+
+#include <stdlib.h>
+#include <stdio.h>
+
+int padd_file(int outfd, uint64_t size, size_t blocksize)
+{
+	size_t padd_sz = size % blocksize;
+	int status = -1;
+	uint8_t *buffer;
+	ssize_t ret;
+
+	if (padd_sz == 0)
+		return 0;
+
+	padd_sz = blocksize - padd_sz;
+
+	buffer = calloc(1, padd_sz);
+	if (buffer == NULL)
+		goto fail_errno;
+
+	ret = write_retry(outfd, buffer, padd_sz);
+
+	if (ret < 0)
+		goto fail_errno;
+
+	if ((size_t)ret < padd_sz)
+		goto fail_trunc;
+
+	status = 0;
+out:
+	free(buffer);
+	return status;
+fail_trunc:
+	fputs("padding output to block size: truncated write\n", stderr);
+	goto out;
+fail_errno:
+	perror("padding output file to block size");
+	goto out;
+}