Modules: Add remaining list API functions (#8439)

List functions operating on elements by index:

* RM_ListGet
* RM_ListSet
* RM_ListInsert
* RM_ListDelete

Iteration is done using a simple for loop over indices.
The index based functions use an internal iterator as an optimization.
This is explained in the docs:

```
 * Many of the list functions access elements by index. Since a list is in
 * essence a doubly-linked list, accessing elements by index is generally an
 * O(N) operation. However, if elements are accessed sequentially or with
 * indices close together, the functions are optimized to seek the index from
 * the previous index, rather than seeking from the ends of the list.
 *
 * This enables iteration to be done efficiently using a simple for loop:
 *
 *     long n = RM_ValueLength(key);
 *     for (long i = 0; i < n; i++) {
 *         RedisModuleString *elem = RedisModule_ListGet(key, i);
 *         // Do stuff...
 *     }
```

1 files changed, 21 insertions, 0 deletions

diff --git a/src/t_list.c b/src/t_list.c
index fb63c1509..80715996e 100644
--- a/src/t_list.c
+++ b/src/t_list.c
@@ -103,6 +103,13 @@ listTypeIterator *listTypeInitIterator(robj *subject, long index,
     return li;
 }
 
+/* Sets the direction of an iterator. */
+void listTypeSetIteratorDirection(listTypeIterator *li, unsigned char direction) {
+    li->direction = direction;
+    int dir = direction == LIST_HEAD ? AL_START_TAIL : AL_START_HEAD;
+    quicklistSetDirection(li->iter, dir);
+}
+
 /* Clean up the iterator. */
 void listTypeReleaseIterator(listTypeIterator *li) {
     zfree(li->iter);
@@ -159,6 +166,20 @@ void listTypeInsert(listTypeEntry *entry, robj *value, int where) {
     }
 }
 
+/* Replaces entry at the current position of the iterator. */
+void listTypeReplace(listTypeEntry *entry, robj *value) {
+    if (entry->li->encoding == OBJ_ENCODING_QUICKLIST) {
+        value = getDecodedObject(value);
+        sds str = value->ptr;
+        size_t len = sdslen(str);
+        quicklistReplaceEntry((quicklist *)entry->entry.quicklist,
+                              &entry->entry, str, len);
+        decrRefCount(value);
+    } else {
+        serverPanic("Unknown list encoding");
+    }
+}
+
 /* Compare the given object with the entry at the current position. */
 int listTypeEqual(listTypeEntry *entry, robj *o) {
     if (entry->li->encoding == OBJ_ENCODING_QUICKLIST) {