1 files changed, 124 insertions, 0 deletions
diff --git a/difftool/super.c b/difftool/super.c
new file mode 100644
index 0000000..7bda728
--- /dev/null
+++ b/difftool/super.c
@@ -0,0 +1,124 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * super.c
+ *
+ * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
+ */
+#include "difftool.h"
+
+static const struct {
+	uint16_t mask;
+	const char *name;
+} sqfs_flags[] = {
+	{ SQFS_FLAG_UNCOMPRESSED_INODES, "uncompressed inodes" },
+	{ SQFS_FLAG_UNCOMPRESSED_DATA, "uncompressed data" },
+	{ SQFS_FLAG_UNCOMPRESSED_FRAGMENTS, "uncompressed fragments" },
+	{ SQFS_FLAG_NO_FRAGMENTS, "no fragments" },
+	{ SQFS_FLAG_ALWAYS_FRAGMENTS, "always fragments" },
+	{ SQFS_FLAG_DUPLICATES, "duplicates" },
+	{ SQFS_FLAG_EXPORTABLE, "exportable" },
+	{ SQFS_FLAG_UNCOMPRESSED_XATTRS, "uncompressed xattrs" },
+	{ SQFS_FLAG_NO_XATTRS, "no xattrs" },
+	{ SQFS_FLAG_COMPRESSOR_OPTIONS, "compressor options" },
+	{ SQFS_FLAG_UNCOMPRESSED_IDS, "uncompressed ids" },
+};
+
+static void print_value_difference(const char *name, uint64_t a, uint64_t b)
+{
+	uint64_t diff;
+	char c;
+
+	if (a != b) {
+		if (a < b) {
+			c = '+';
+			diff = b - a;
+		} else {
+			c = '-';
+			diff = a - b;
+		}
+		fprintf(stdout, "%s: %c%lu\n", name, c, diff);
+	}
+}
+
+static void print_offset_diff(const char *name, uint64_t a, uint64_t b)
+{
+	if (a != b)
+		fprintf(stdout, "Location of %s differs\n", name);
+}
+
+static void print_flag_diff(uint16_t a, uint16_t b)
+{
+	uint16_t diff = a ^ b, mask;
+	size_t i;
+	char c;
+
+	if (diff == 0)
+		return;
+
+	fputs("flags:\n", stdout);
+
+	for (i = 0; i < sizeof(sqfs_flags) / sizeof(sqfs_flags[0]); ++i) {
+		if (diff & sqfs_flags[i].mask) {
+			c = a & sqfs_flags[i].mask ? '<' : '>';
+
+			fprintf(stdout, "\t%c%s\n", c, sqfs_flags[i].name);
+		}
+
+		a &= ~sqfs_flags[i].mask;
+		b &= ~sqfs_flags[i].mask;
+		diff &= ~sqfs_flags[i].mask;
+	}
+
+	for (i = 0, mask = 0x01; i < 16; ++i, mask <<= 1) {
+		if (diff & mask) {
+			fprintf(stdout, "\t%c additional unknown\n",
+				a & mask ? '<' : '>');
+		}
+	}
+}
+
+int compare_super_blocks(const sqfs_super_t *a, const sqfs_super_t *b)
+{
+	if (memcmp(a, b, sizeof(*a)) == 0)
+		return 0;
+
+	fputs("======== super blocks are different ========\n", stdout);
+
+	/* TODO: if a new magic number or squashfs version is introduced,
+	   compare them. */
+
+	print_value_difference("inode count", a->inode_count, b->inode_count);
+	print_value_difference("modification time", a->modification_time,
+			       b->modification_time);
+	print_value_difference("block size", a->block_size, b->block_size);
+	print_value_difference("block log", a->block_log, b->block_log);
+	print_value_difference("fragment table entries",
+			       a->fragment_entry_count,
+			       b->fragment_entry_count);
+	print_value_difference("ID table entries", a->id_count, b->id_count);
+
+	if (a->compression_id != b->compression_id) {
+		fprintf(stdout, "compressor: %s vs %s\n",
+			compressor_name_from_id(a->compression_id),
+			compressor_name_from_id(b->compression_id));
+	}
+
+	print_flag_diff(a->flags, b->flags);
+
+	print_value_difference("total bytes used", a->bytes_used,
+			       b->bytes_used);
+
+	print_offset_diff("root inode", a->root_inode_ref, b->root_inode_ref);
+	print_offset_diff("ID table", a->id_table_start, b->id_table_start);
+	print_offset_diff("xattr ID table", a->xattr_id_table_start,
+			  b->xattr_id_table_start);
+	print_offset_diff("inode table", a->inode_table_start,
+			  b->inode_table_start);
+	print_offset_diff("directory table", a->directory_table_start,
+			  b->directory_table_start);
+	print_offset_diff("fragment table", a->fragment_table_start,
+			  b->fragment_table_start);
+	print_offset_diff("export table", a->export_table_start,
+			  b->export_table_start);
+	return 1;
+}