feat(lsm): store iterators

lsm/include/lsm/store.h

@@ -228,4 +228,40 @@ lsm_error lsm_entry_data_read(uint64_t *out, char *buf,
  */
 uint64_t lsm_entry_data_len(lsm_entry_handle *handle);
 
+/**
+ * Represents an in-flight iterator over an LSM store.
+ */
+typedef struct lsm_store_iterator lsm_store_iterator;
+
+/**
+ * Initialize an iterator to iterate over all entries with keys starting
+ * with the given prefix.
+ *
+ * @param out pointer to store iterator pointer in
+ * @param trie trie to iterate
+ * @param prefix prefix of the keys; a zero-length string means iterating over
+ *  the entire trie; NULL is interpreted as a zero-length string
+ */
+lsm_error lsm_store_iter(lsm_store_iterator **out, lsm_store *store,
+                         const lsm_str *prefix);
+
+/**
+ * Advance the iterator, returning a read handle to the next entry. The caller
+ * is responsible for closing this handle.
+ */
+lsm_error lsm_store_iter_next_read(lsm_entry_handle **out,
+                                   lsm_store_iterator *iter);
+
+/**
+ * Advance the iterator, returning a write handle to the next entry. The caller
+ * is responsible for closing this handle.
+ */
+/* lsm_error lsm_store_iter_next_write(lsm_entry_handle **out,
+ * lsm_store_iterator *iter); */
+
+/**
+ * Free the given iterator.
+ */
+void lsm_store_iter_free(lsm_store_iterator *iter);
+
 #endif