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-rw-r--r--lib/util/Makemodule.am1
-rw-r--r--lib/util/file_cmp.c41
2 files changed, 42 insertions, 0 deletions
diff --git a/lib/util/Makemodule.am b/lib/util/Makemodule.am
index b65ebda..830a338 100644
--- a/lib/util/Makemodule.am
+++ b/lib/util/Makemodule.am
@@ -13,6 +13,7 @@ libutil_a_SOURCES += lib/util/mkdir_p.c
libutil_a_SOURCES += lib/util/canonicalize_name.c
libutil_a_SOURCES += lib/util/filename_sane.c
libutil_a_SOURCES += lib/util/source_date_epoch.c
+libutil_a_SOURCES += lib/util/file_cmp.c
libutil_a_CFLAGS = $(AM_CFLAGS)
libutil_a_CPPFLAGS = $(AM_CPPFLAGS)
diff --git a/lib/util/file_cmp.c b/lib/util/file_cmp.c
new file mode 100644
index 0000000..2aa0cc2
--- /dev/null
+++ b/lib/util/file_cmp.c
@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: LGPL-3.0-or-later */
+/*
+ * file_cmp.c
+ *
+ * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
+ */
+#include "config.h"
+
+#include "util/util.h"
+#include "sqfs/io.h"
+
+#include <string.h>
+
+int check_file_range_equal(sqfs_file_t *file, void *scratch, size_t scratch_sz,
+ sqfs_u64 loc_a, sqfs_u64 loc_b, sqfs_u64 size)
+{
+ sqfs_u8 *ptr_a = scratch, *ptr_b = ptr_a + scratch_sz / 2;
+ int ret;
+
+ while (size > 0) {
+ size_t diff = scratch_sz / 2;
+ diff = (sqfs_u64)diff > size ? size : diff;
+
+ ret = file->read_at(file, loc_a, ptr_a, diff);
+ if (ret != 0)
+ return ret;
+
+ ret = file->read_at(file, loc_b, ptr_b, diff);
+ if (ret != 0)
+ return ret;
+
+ if (memcmp(ptr_a, ptr_b, diff) != 0)
+ return 1;
+
+ size -= diff;
+ loc_a += diff;
+ loc_b += diff;
+ }
+
+ return 0;
+}