perf(api): avoid spurious allocations when converting small objects

Converter functions use a heap-allocated stack to handle complex
nested objects. However, these are often called with simple,
primitive values like integers or bools wrapped in an Object.
Avoid the memory allocation in this case using kvec_withinit_t

1 files changed, 12 insertions, 10 deletions

diff --git a/src/nvim/msgpack_rpc/helpers.c b/src/nvim/msgpack_rpc/helpers.c
index a4a36e5ebf..35f126eab1 100644
--- a/src/nvim/msgpack_rpc/helpers.c
+++ b/src/nvim/msgpack_rpc/helpers.c
@@ -86,8 +86,9 @@ bool msgpack_rpc_to_object(const msgpack_object *const obj, Object *const arg)
   FUNC_ATTR_NONNULL_ALL
 {
   bool ret = true;
-  kvec_t(MPToAPIObjectStackItem) stack = KV_INITIAL_VALUE;
-  kv_push(stack, ((MPToAPIObjectStackItem) {
+  kvec_withinit_t(MPToAPIObjectStackItem, 2) stack = KV_INITIAL_VALUE;
+  kvi_init(stack);
+  kvi_push(stack, ((MPToAPIObjectStackItem) {
     .mobj = obj,
     .aobj = arg,
     .container = false,
@@ -155,7 +156,7 @@ bool msgpack_rpc_to_object(const msgpack_object *const obj, Object *const arg)
             const size_t idx = cur.idx;
             cur.idx++;
             kv_last(stack) = cur;
-            kv_push(stack, ((MPToAPIObjectStackItem) {
+            kvi_push(stack, ((MPToAPIObjectStackItem) {
               .mobj = &cur.mobj->via.array.ptr[idx],
               .aobj = &cur.aobj->data.array.items[idx],
               .container = false,
@@ -209,7 +210,7 @@ bool msgpack_rpc_to_object(const msgpack_object *const obj, Object *const arg)
               }
             }
             if (ret) {
-              kv_push(stack, ((MPToAPIObjectStackItem) {
+              kvi_push(stack, ((MPToAPIObjectStackItem) {
                 .mobj = &cur.mobj->via.map.ptr[idx].val,
                 .aobj = &cur.aobj->data.dictionary.items[idx].value,
                 .container = false,
@@ -265,7 +266,7 @@ bool msgpack_rpc_to_object(const msgpack_object *const obj, Object *const arg)
       (void)kv_pop(stack);
     }
   }
-  kv_destroy(stack);
+  kvi_destroy(stack);
   return ret;
 }
 
@@ -375,8 +376,9 @@ typedef struct {
 void msgpack_rpc_from_object(const Object result, msgpack_packer *const res)
   FUNC_ATTR_NONNULL_ARG(2)
 {
-  kvec_t(APIToMPObjectStackItem) stack = KV_INITIAL_VALUE;
-  kv_push(stack, ((APIToMPObjectStackItem) { &result, false, 0 }));
+  kvec_withinit_t(APIToMPObjectStackItem, 2) stack = KV_INITIAL_VALUE;
+  kvi_init(stack);
+  kvi_push(stack, ((APIToMPObjectStackItem) { &result, false, 0 }));
   while (kv_size(stack)) {
     APIToMPObjectStackItem cur = kv_last(stack);
     STATIC_ASSERT(kObjectTypeWindow == kObjectTypeBuffer + 1
@@ -428,7 +430,7 @@ void msgpack_rpc_from_object(const Object result, msgpack_packer *const res)
             const size_t idx = cur.idx;
             cur.idx++;
             kv_last(stack) = cur;
-            kv_push(stack, ((APIToMPObjectStackItem) {
+            kvi_push(stack, ((APIToMPObjectStackItem) {
               .aobj = &cur.aobj->data.array.items[idx],
               .container = false,
             }));
@@ -451,7 +453,7 @@ void msgpack_rpc_from_object(const Object result, msgpack_packer *const res)
             kv_last(stack) = cur;
             msgpack_rpc_from_string(cur.aobj->data.dictionary.items[idx].key,
                                     res);
-            kv_push(stack, ((APIToMPObjectStackItem) {
+            kvi_push(stack, ((APIToMPObjectStackItem) {
               .aobj = &cur.aobj->data.dictionary.items[idx].value,
               .container = false,
             }));
@@ -468,7 +470,7 @@ void msgpack_rpc_from_object(const Object result, msgpack_packer *const res)
       (void)kv_pop(stack);
     }
   }
-  kv_destroy(stack);
+  kvi_destroy(stack);
 }
 
 void msgpack_rpc_from_array(Array result, msgpack_packer *res)