5 files changed, 82 insertions, 1 deletions

diff --git a/include/id_table.h b/include/id_table.h
new file mode 100644
index 0000000..6d5d416
--- /dev/null
+++ b/include/id_table.h
@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#ifndef ID_TABLE_H
+#define ID_TABLE_H
+
+#include <stdint.h>
+#include <stddef.h>
+
+typedef struct {
+	uint32_t *ids;
+	size_t num_ids;
+	size_t max_ids;
+} id_table_t;
+
+int id_table_init(id_table_t *tbl);
+
+void id_table_cleanup(id_table_t *tbl);
+
+int id_table_id_to_index(id_table_t *tbl, uint32_t id, uint16_t *out);
+
+#endif /* ID_TABLE_H */
diff --git a/lib/Makemodule.am b/lib/Makemodule.am
index 86f1766..b12367d 100644
--- a/lib/Makemodule.am
+++ b/lib/Makemodule.am
@@ -8,6 +8,7 @@ libcompress_a_CPPFLAGS = $(AM_CPPFLAGS)
 
 libsquashfs_a_SOURCES = include/meta_writer.h include/squashfs.h
 libsquashfs_a_SOURCES += lib/sqfs/meta_writer.c lib/sqfs/super.c
+libsquashfs_a_SOURCES += lib/sqfs/id_table.c include/id_table.h
 
 libutil_a_SOURCES = lib/util/canonicalize_name.c lib/util/write_retry.c
 libutil_a_SOURCES += lib/util/read_retry.c include/util.h
diff --git a/lib/sqfs/id_table.c b/lib/sqfs/id_table.c
new file mode 100644
index 0000000..cd31360
--- /dev/null
+++ b/lib/sqfs/id_table.c
@@ -0,0 +1,52 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#include "id_table.h"
+
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+
+int id_table_init(id_table_t *tbl)
+{
+	memset(tbl, 0, sizeof(*tbl));
+	return 0;
+}
+
+void id_table_cleanup(id_table_t *tbl)
+{
+	free(tbl->ids);
+}
+
+int id_table_id_to_index(id_table_t *tbl, uint32_t id, uint16_t *out)
+{
+	size_t i, sz;
+	void *ptr;
+
+	for (i = 0; i < tbl->num_ids; ++i) {
+		if (tbl->ids[i] == id) {
+			*out = i;
+			return 0;
+		}
+	}
+
+	if (tbl->num_ids == 0x10000) {
+		fputs("Too many unique UIDs/GIDs (more than 64k)!\n", stderr);
+		return -1;
+	}
+
+	if (tbl->num_ids == tbl->max_ids) {
+		sz = (tbl->max_ids ? tbl->max_ids * 2 : 16);
+		ptr = realloc(tbl->ids, sizeof(tbl->ids[0]) * sz);
+
+		if (ptr == NULL) {
+			perror("growing ID table");
+			return -1;
+		}
+
+		tbl->ids = ptr;
+		tbl->max_ids = sz;
+	}
+
+	*out = tbl->num_ids;
+	tbl->ids[tbl->num_ids++] = id;
+	return 0;
+}
diff --git a/mkfs/mksquashfs.c b/mkfs/mksquashfs.c
index 7503978..3272dbc 100644
--- a/mkfs/mksquashfs.c
+++ b/mkfs/mksquashfs.c
@@ -84,10 +84,13 @@ int main(int argc, char **argv)
 		return EXIT_FAILURE;
 	}
 
+	if (id_table_init(&info.idtbl))
+		return EXIT_FAILURE;
+
 	info.outfd = open(info.opt.outfile, info.opt.outmode, 0644);
 	if (info.outfd < 0) {
 		perror(info.opt.outfile);
-		return EXIT_FAILURE;
+		goto out_idtbl;
 	}
 
 	if (sqfs_super_write(&info.super, info.outfd))
@@ -129,5 +132,7 @@ out_fstree:
 	fstree_cleanup(&info.fs);
 out_outfd:
 	close(info.outfd);
+out_idtbl:
+	id_table_cleanup(&info.idtbl);
 	return status;
 }
diff --git a/mkfs/mksquashfs.h b/mkfs/mksquashfs.h
index 2e0183e..5522268 100644
--- a/mkfs/mksquashfs.h
+++ b/mkfs/mksquashfs.h
@@ -4,6 +4,7 @@
 
 #include "squashfs.h"
 #include "compress.h"
+#include "id_table.h"
 #include "fstree.h"
 #include "config.h"
 
@@ -43,6 +44,8 @@ typedef struct {
 	file_info_t *frag_list;
 	size_t frag_offset;
 
+	id_table_t idtbl;
+
 	compressor_t *cmp;
 } sqfs_info_t;