Add a helper utility to compare filesystem trees

The intended use case is to compare two mounted or unpacke squashfs
images, so a repacked test image can be compared against its original
or an image unpacked with unsquashfs can be compared with an image
unpacked by rdsquashfs or sqfs2tar.

Since the tool is only intended to aid development (specifically
automated testing), it is not installed by `make install`.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

1 files changed, 99 insertions, 0 deletions

diff --git a/difftool/node_compare.c b/difftool/node_compare.c
new file mode 100644
index 0000000..fae35ab
--- /dev/null
+++ b/difftool/node_compare.c
@@ -0,0 +1,99 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * node_compare.c
+ *
+ * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
+ */
+#include "difftool.h"
+
+int node_compare(tree_node_t *a, tree_node_t *b)
+{
+	char *path = node_path(a);
+	tree_node_t *ait, *bit;
+	int ret, status = 0;
+
+	if (path == NULL)
+		return -1;
+
+	if ((a->mode & S_IFMT) != (b->mode & S_IFMT)) {
+		fprintf(stdout, "%s has a different type\n", path);
+		free(path);
+		return 1;
+	}
+
+	if (!(compare_flags & COMPARE_NO_PERM)) {
+		if ((a->mode & ~S_IFMT) != (b->mode & ~S_IFMT)) {
+			fprintf(stdout, "%s has different permissions\n",
+				path);
+			status = 1;
+		}
+	}
+
+	if (!(compare_flags & COMPARE_NO_OWNER)) {
+		if (a->uid != b->uid || a->gid != b->gid) {
+			fprintf(stdout, "%s has different ownership\n", path);
+			status = 1;
+		}
+	}
+
+	switch (a->mode & S_IFMT) {
+	case S_IFSOCK:
+	case S_IFIFO:
+		break;
+	case S_IFBLK:
+	case S_IFCHR:
+		if (a->data.devno != b->data.devno) {
+			fprintf(stdout, "%s has different device number\n",
+				path);
+			status = 1;
+		}
+		break;
+	case S_IFLNK:
+		if (strcmp(a->data.slink_target, b->data.slink_target) != 0) {
+			fprintf(stdout, "%s has a different link target\n",
+				path);
+		}
+		break;
+	case S_IFDIR:
+		ret = compare_dir_entries(a, b);
+		if (ret < 0) {
+			status = -1;
+			break;
+		}
+		if (ret > 0)
+			status = 1;
+
+		free(path);
+		path = NULL;
+
+		ait = a->data.dir->children;
+		bit = b->data.dir->children;
+
+		while (ait != NULL && bit != NULL) {
+			ret = node_compare(ait, bit);
+			if (ret < 0)
+				return -1;
+			if (ret > 0)
+				status = 1;
+
+			ait = ait->next;
+			bit = bit->next;
+		}
+		break;
+	case S_IFREG:
+		ret = compare_files(a->data.file, b->data.file, path);
+		if (ret < 0) {
+			status = -1;
+		} else if (ret > 0) {
+			fprintf(stdout, "regular file %s differs\n", path);
+			status = 1;
+		}
+		break;
+	default:
+		fprintf(stdout, "%s has unknown type, ignoring\n", path);
+		break;
+	}
+
+	free(path);
+	return status;
+}