cache: add cache_set for testing

Also add documentation for the cache functions.

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>

src/cache.c

@@ -17,6 +17,17 @@ struct cache {
 	struct cache_entry *entries;
 };
 
+void cache_set(struct cache *c, const char *key, void *data) {
+	struct cache_entry *e = NULL;
+	HASH_FIND_STR(c->entries, key, e);
+	CHECK(!e);
+
+	e = ccalloc(1, struct cache_entry);
+	e->key = strdup(key);
+	e->value = data;
+	HASH_ADD_STR(c->entries, key, e);
+}
+
 void *cache_get(struct cache *c, const char *key, int *err) {
 	struct cache_entry *e;
 	HASH_FIND_STR(c->entries, key, e);

src/cache.h

@@ -4,11 +4,29 @@ struct cache;
 
 typedef void *(*cache_getter_t)(void *user_data, const char *key, int *err);
 typedef void (*cache_free_t)(void *user_data, void *data);
+
+/// Create a cache with `getter`, and a free function `f` which is used to free the cache
+/// value when they are invalidated.
+///
+/// `user_data` will be passed to `getter` and `f` when they are called.
 struct cache *new_cache(void *user_data, cache_getter_t getter, cache_free_t f);
 
+/// Fetch a value from the cache. If the value doesn't present in the cache yet, the
+/// getter will be called, and the returned value will be stored into the cache.
 void *cache_get(struct cache *, const char *key, int *err);
+
+/// Invalidate a value in the cache.
 void cache_invalidate(struct cache *, const char *key);
+
+/// Invalidate all values in the cache.
 void cache_invalidate_all(struct cache *);
 
-/// Returns the user data passed to `new_cache`
+/// Invalidate all values in the cache and free it. Returns the user data passed to
+/// `new_cache`
 void *cache_free(struct cache *);
+
+/// Insert a key-value pair into the cache. Only used for internal testing. Takes
+/// ownership of `data`
+///
+/// If `key` already exists in the cache, this function will abort the program.
+void cache_set(struct cache *c, const char *key, void *data);