From 222b277eef9d9a01cf2829a98cd761d5e0527b9e Mon Sep 17 00:00:00 2001
From: Chewing_Bever <roosensjef@gmail.com>
Date: Sat, 23 Dec 2023 14:29:33 +0100
Subject: [PATCH] feat(lsm): store iterators

---
 CHANGELOG.md                          |  1 +
 lsm/include/lsm/store.h               | 36 +++++++++++++++++
 lsm/src/_include/lsm/store_internal.h |  5 +++
 lsm/src/store/lsm_store_iter.c        | 58 +++++++++++++++++++++++++++
 4 files changed, 100 insertions(+)
 create mode 100644 lsm/src/store/lsm_store_iter.c

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 16513b9..ea1d396 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -28,6 +28,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * LSM
     * Binary tree iterators
     * Trie iterators
+    * Store iterators
 
 ## Removed
 
diff --git a/lsm/include/lsm/store.h b/lsm/include/lsm/store.h
index c680c43..1b632b9 100644
--- a/lsm/include/lsm/store.h
+++ b/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
diff --git a/lsm/src/_include/lsm/store_internal.h b/lsm/src/_include/lsm/store_internal.h
index e446a0d..e853308 100644
--- a/lsm/src/_include/lsm/store_internal.h
+++ b/lsm/src/_include/lsm/store_internal.h
@@ -34,6 +34,11 @@ typedef struct lsm_entry {
   uint64_t idx_file_offset;
 } lsm_entry;
 
+struct lsm_store_iterator {
+  lsm_trie_iterator *iter;
+  lsm_store *store;
+};
+
 /**
  * Allocate and initialize a new lsm_entry object.
  *
diff --git a/lsm/src/store/lsm_store_iter.c b/lsm/src/store/lsm_store_iter.c
new file mode 100644
index 0000000..3879d5e
--- /dev/null
+++ b/lsm/src/store/lsm_store_iter.c
@@ -0,0 +1,58 @@
+#include "lsm/store.h"
+#include "lsm/store_internal.h"
+
+lsm_error lsm_store_iter(lsm_store_iterator **out, lsm_store *store,
+                         const lsm_str *prefix) {
+  lsm_trie_iterator *trie_iter;
+  LSM_RES(lsm_trie_iter(&trie_iter, store->trie, prefix));
+
+  lsm_store_iterator *iter = calloc(1, sizeof(lsm_store_iterator));
+
+  if (iter == NULL) {
+    lsm_trie_iter_free(trie_iter);
+
+    return lsm_error_failed_alloc;
+  }
+
+  iter->iter = trie_iter;
+  iter->store = store;
+
+  *out = iter;
+
+  return lsm_error_ok;
+}
+
+lsm_error lsm_store_iter_next_read(lsm_entry_handle **out,
+                                   lsm_store_iterator *iter) {
+  lsm_entry_wrapper *wrapper = NULL;
+
+  // Traverse through the trie until a node is found with a filled data field
+  do {
+    // Exits function if iterator is done
+    LSM_RES(lsm_trie_iter_next((void **)&wrapper, iter->iter));
+
+    // TODO error handling?
+    pthread_rwlock_rdlock(&wrapper->lock);
+
+    if (wrapper->entry == NULL) {
+      pthread_rwlock_unlock(&wrapper->lock);
+
+      wrapper = NULL;
+    }
+  } while (wrapper == NULL);
+
+  lsm_entry_handle *handle;
+  LSM_RES2(lsm_entry_handle_init(&handle),
+           pthread_rwlock_unlock(&wrapper->lock));
+
+  handle->wrapper = wrapper;
+  handle->store = iter->store;
+  *out = handle;
+
+  return lsm_error_ok;
+}
+
+void lsm_store_iter_free(lsm_store_iterator *iter) {
+  lsm_trie_iter_free(iter->iter);
+  free(iter);
+}