Add a data-invariant linear-search map structure

I'm going to use this for looking op keys server-side for ntor.

1 files changed, 14 insertions, 0 deletions

diff --git a/src/common/di_ops.h b/src/common/di_ops.h
index 8f0bb698f..a86f56c96 100644
--- a/src/common/di_ops.h
+++ b/src/common/di_ops.h
@@ -27,5 +27,19 @@ int tor_memeq(const void *a, const void *b, size_t sz);
 #define fast_memeq(a,b,c)  (0==memcmp((a),(b),(c)))
 #define fast_memneq(a,b,c) (0!=memcmp((a),(b),(c)))
 
+/** A type for a map from DIGEST256_LEN-byte blobs to void*, such that
+ * data lookups take an amount of time proportional only to the size
+ * of the map, and not to the position or presence of the item in the map.
+ *
+ * Not efficient for large maps! */
+typedef struct di_digest256_map_t di_digest256_map_t;
+typedef void (*dimap_free_fn)(void *);
+
+void dimap_free(di_digest256_map_t *map, dimap_free_fn free_fn);
+void dimap_add_entry(di_digest256_map_t **map,
+                     const uint8_t *key, void *val);
+void *dimap_search(const di_digest256_map_t *map, const uint8_t *key,
+                   void *dflt_val);
+
 #endif