1 files changed, 111 insertions, 0 deletions
diff --git a/src/third_party/wiredtiger/src/support/update_vector.c b/src/third_party/wiredtiger/src/support/update_vector.c
new file mode 100644
index 00000000000..ef57b28f7f4
--- /dev/null
+++ b/src/third_party/wiredtiger/src/support/update_vector.c
@@ -0,0 +1,111 @@
+/*-
+ * Copyright (c) 2014-present MongoDB, Inc.
+ * Copyright (c) 2008-2014 WiredTiger, Inc.
+ *	All rights reserved.
+ *
+ * See the file LICENSE for redistribution information.
+ */
+
+#include "wt_internal.h"
+
+/*
+ * __wt_update_vector_init --
+ *     Initialize a update vector.
+ */
+void
+__wt_update_vector_init(WT_SESSION_IMPL *session, WT_UPDATE_VECTOR *updates)
+{
+    WT_CLEAR(*updates);
+    updates->session = session;
+    updates->listp = updates->list;
+}
+
+/*
+ * __wt_update_vector_push --
+ *     Push a update pointer to a update vector. If we exceed the allowed stack space in the vector,
+ *     we'll be doing malloc here.
+ */
+int
+__wt_update_vector_push(WT_UPDATE_VECTOR *updates, WT_UPDATE *upd)
+{
+    WT_DECL_RET;
+    bool migrate_from_stack;
+
+    migrate_from_stack = false;
+
+    if (updates->size >= WT_UPDATE_VECTOR_STACK_SIZE) {
+        if (updates->allocated_bytes == 0 && updates->size == WT_UPDATE_VECTOR_STACK_SIZE) {
+            migrate_from_stack = true;
+            updates->listp = NULL;
+        }
+        WT_ERR(__wt_realloc_def(
+          updates->session, &updates->allocated_bytes, updates->size + 1, &updates->listp));
+        if (migrate_from_stack)
+            memcpy(updates->listp, updates->list, sizeof(updates->list));
+    }
+    updates->listp[updates->size++] = upd;
+    return (0);
+
+err:
+    /*
+     * This only happens when we're migrating from the stack to the heap but failed to allocate. In
+     * that case, point back to the stack allocated memory and set the allocation to zero to
+     * indicate that we don't have heap memory to free.
+     *
+     * If we're already on the heap, we have nothing to do. The realloc call above won't touch the
+     * list pointer unless allocation is successful and we won't have incremented the size yet.
+     */
+    if (updates->listp == NULL) {
+        WT_ASSERT(updates->session, updates->size == WT_UPDATE_VECTOR_STACK_SIZE);
+        updates->listp = updates->list;
+        updates->allocated_bytes = 0;
+    }
+    return (ret);
+}
+
+/*
+ * __wt_update_vector_pop --
+ *     Pop an update pointer off a update vector.
+ */
+void
+__wt_update_vector_pop(WT_UPDATE_VECTOR *updates, WT_UPDATE **updp)
+{
+    WT_ASSERT(updates->session, updates->size > 0);
+
+    *updp = updates->listp[--updates->size];
+}
+
+/*
+ * __wt_update_vector_peek --
+ *     Peek an update pointer off a update vector.
+ */
+void
+__wt_update_vector_peek(WT_UPDATE_VECTOR *updates, WT_UPDATE **updp)
+{
+    WT_ASSERT(updates->session, updates->size > 0);
+
+    *updp = updates->listp[updates->size - 1];
+}
+
+/*
+ * __wt_update_vector_clear --
+ *     Clear a update vector.
+ */
+void
+__wt_update_vector_clear(WT_UPDATE_VECTOR *updates)
+{
+    updates->size = 0;
+}
+
+/*
+ * __wt_update_vector_free --
+ *     Free any resources associated with a update vector. If we exceeded the allowed stack space on
+ *     the vector and had to fallback to dynamic allocations, we'll be doing a free here.
+ */
+void
+__wt_update_vector_free(WT_UPDATE_VECTOR *updates)
+{
+    if (updates->allocated_bytes != 0)
+        __wt_free(updates->session, updates->listp);
+    __wt_update_vector_init(updates->session, updates);
+}