Cleanup: move utilities back out of libsquashfs

This commit removes the allocation helpers and string table functions
out of libsquashfs back into a "libutil.a". The problem of libsquashfs
exporting stuff that it shouldn't is resolved by retaining the internal
attributes and directly adding the source to libsquashfs instead of
trying to somehow link against libutil.la.

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

2 files changed, 82 insertions, 0 deletions

diff --git a/include/str_table.h b/include/str_table.h
new file mode 100644
index 0000000..61f8aa5
--- /dev/null
+++ b/include/str_table.h
@@ -0,0 +1,51 @@
+/* SPDX-License-Identifier: LGPL-3.0-or-later */
+/*
+ * str_table.h
+ *
+ * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
+ */
+#ifndef STR_TABLE_H
+#define STR_TABLE_H
+
+#include "sqfs/predef.h"
+
+typedef struct str_bucket_t {
+	struct str_bucket_t *next;
+	char *str;
+	size_t index;
+	size_t refcount;
+} str_bucket_t;
+
+/* Stores strings in a hash table and assigns an incremental, unique ID to
+   each string. Subsequent additions return the existing ID. The ID can be
+   used for (hopefully) constant time lookup of the original string. */
+typedef struct {
+	str_bucket_t **buckets;
+	size_t num_buckets;
+
+	char **strings;
+	size_t num_strings;
+	size_t max_strings;
+} str_table_t;
+
+/* `size` is the number of hash table buckets to use internally. */
+SQFS_INTERNAL int str_table_init(str_table_t *table, size_t size);
+
+SQFS_INTERNAL void str_table_cleanup(str_table_t *table);
+
+/* Resolve a string to an incremental, unique ID. */
+SQFS_INTERNAL
+int str_table_get_index(str_table_t *table, const char *str, size_t *idx);
+
+/* Resolve a unique ID to the string it represents.
+   Returns NULL if the ID is unknown, i.e. out of bounds. */
+SQFS_INTERNAL
+const char *str_table_get_string(str_table_t *table, size_t index);
+
+SQFS_INTERNAL void str_table_add_ref(str_table_t *table, size_t index);
+
+SQFS_INTERNAL void str_table_del_ref(str_table_t *table, size_t index);
+
+SQFS_INTERNAL size_t str_table_get_ref_count(str_table_t *table, size_t index);
+
+#endif /* STR_TABLE_H */
diff --git a/include/util.h b/include/util.h
new file mode 100644
index 0000000..a379c0d
--- /dev/null
+++ b/include/util.h
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: LGPL-3.0-or-later */
+/*
+ * util.h
+ *
+ * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
+ */
+#ifndef SQFS_UTIL_H
+#define SQFS_UTIL_H
+
+#include "config.h"
+#include "sqfs/predef.h"
+#include "compat.h"
+
+#include <stddef.h>
+
+/*
+  Helper for allocating data structures with flexible array members.
+
+  'base_size' is the size of the struct itself, 'item_size' the size of a
+  single array element and 'nmemb' the number of elements.
+
+  Iternally checks for arithmetic overflows when allocating the combined thing.
+ */
+SQFS_INTERNAL
+void *alloc_flex(size_t base_size, size_t item_size, size_t nmemb);
+
+/* Basically the same as calloc, but *ALWAYS* does overflow checking */
+SQFS_INTERNAL
+void *alloc_array(size_t item_size, size_t nmemb);
+
+#endif /* SQFS_UTIL_H */