refactor(typval): don't use msgpack_packer for msgpackdump()

Step towords completely eliminating msgpack_packer.

9 files changed, 146 insertions, 109 deletions

diff --git a/src/nvim/api/private/converter.c b/src/nvim/api/private/converter.c
index a78d78c057..0a4daf1dae 100644
--- a/src/nvim/api/private/converter.c
+++ b/src/nvim/api/private/converter.c
@@ -28,6 +28,7 @@ typedef struct {
 #endif
 
 #define TYPVAL_ENCODE_ALLOW_SPECIALS false
+#define TYPVAL_ENCODE_CHECK_BEFORE
 
 #define TYPVAL_ENCODE_CONV_NIL(tv) \
   kvi_push(edata->stack, NIL)
@@ -217,6 +218,7 @@ static inline void typval_encode_dict_end(EncodedData *const edata)
 #undef TYPVAL_ENCODE_CONV_LIST_START
 #undef TYPVAL_ENCODE_CONV_REAL_LIST_AFTER_START
 #undef TYPVAL_ENCODE_CONV_EMPTY_DICT
+#undef TYPVAL_ENCODE_CHECK_BEFORE
 #undef TYPVAL_ENCODE_CONV_NIL
 #undef TYPVAL_ENCODE_CONV_BOOL
 #undef TYPVAL_ENCODE_CONV_UNSIGNED_NUMBER
diff --git a/src/nvim/eval/encode.c b/src/nvim/eval/encode.c
index e216dbdaa6..eb70b0534d 100644
--- a/src/nvim/eval/encode.c
+++ b/src/nvim/eval/encode.c
@@ -13,7 +13,7 @@
 #include <string.h>
 
 #include "klib/kvec.h"
-#include "msgpack/pack.h"
+#include "nvim/api/private/helpers.h"
 #include "nvim/ascii_defs.h"
 #include "nvim/eval.h"
 #include "nvim/eval/encode.h"
@@ -28,6 +28,7 @@
 #include "nvim/mbyte.h"
 #include "nvim/memory.h"
 #include "nvim/message.h"
+#include "nvim/msgpack_rpc/packer.h"
 #include "nvim/strings.h"
 #include "nvim/types_defs.h"
 #include "nvim/vim_defs.h"  // For _()
@@ -412,6 +413,8 @@ int encode_read_from_list(ListReaderState *const state, char *const buf, const s
 #define TYPVAL_ENCODE_CONV_EMPTY_DICT(tv, dict) \
   ga_concat(gap, "{}")
 
+#define TYPVAL_ENCODE_CHECK_BEFORE
+
 #define TYPVAL_ENCODE_CONV_NIL(tv) \
   ga_concat(gap, "v:null")
 
@@ -536,6 +539,8 @@ int encode_read_from_list(ListReaderState *const state, char *const buf, const s
 #undef TYPVAL_ENCODE_ALLOW_SPECIALS
 #define TYPVAL_ENCODE_ALLOW_SPECIALS true
 
+#define TYPVAL_ENCODE_CHECK_BEFORE
+
 #undef TYPVAL_ENCODE_CONV_NIL
 #define TYPVAL_ENCODE_CONV_NIL(tv) \
   ga_concat(gap, "null")
@@ -821,6 +826,7 @@ bool encode_check_json_key(const typval_T *const tv)
 #undef TYPVAL_ENCODE_CONV_LIST_START
 #undef TYPVAL_ENCODE_CONV_REAL_LIST_AFTER_START
 #undef TYPVAL_ENCODE_CONV_EMPTY_DICT
+#undef TYPVAL_ENCODE_CHECK_BEFORE
 #undef TYPVAL_ENCODE_CONV_NIL
 #undef TYPVAL_ENCODE_CONV_BOOL
 #undef TYPVAL_ENCODE_CONV_UNSIGNED_NUMBER
@@ -913,52 +919,22 @@ char *encode_tv2json(typval_T *tv, size_t *len)
 }
 
 #define TYPVAL_ENCODE_CONV_STRING(tv, buf, len) \
-  do { \
-    if ((buf) == NULL) { \
-      msgpack_pack_bin(packer, 0); \
-    } else { \
-      const size_t len_ = (len); \
-      msgpack_pack_bin(packer, len_); \
-      msgpack_pack_bin_body(packer, buf, len_); \
-    } \
-  } while (0)
+  mpack_bin(buf, (len), packer); \
 
 #define TYPVAL_ENCODE_CONV_STR_STRING(tv, buf, len) \
-  do { \
-    if ((buf) == NULL) { \
-      msgpack_pack_str(packer, 0); \
-    } else { \
-      const size_t len_ = (len); \
-      msgpack_pack_str(packer, len_); \
-      msgpack_pack_str_body(packer, buf, len_); \
-    } \
-  } while (0)
+  mpack_str(cbuf_as_string(buf, (len)), packer); \
 
 #define TYPVAL_ENCODE_CONV_EXT_STRING(tv, buf, len, type) \
-  do { \
-    if ((buf) == NULL) { \
-      msgpack_pack_ext(packer, 0, (int8_t)(type)); \
-    } else { \
-      const size_t len_ = (len); \
-      msgpack_pack_ext(packer, len_, (int8_t)(type)); \
-      msgpack_pack_ext_body(packer, buf, len_); \
-    } \
-  } while (0)
+  mpack_ext(buf, (len), (int8_t)(type), packer); \
 
 #define TYPVAL_ENCODE_CONV_BLOB(tv, blob, len) \
-  do { \
-    const size_t len_ = (size_t)(len); \
-    msgpack_pack_bin(packer, len_); \
-    if (len_ > 0) { \
-      msgpack_pack_bin_body(packer, (blob)->bv_ga.ga_data, len_); \
-    } \
-  } while (0)
+  mpack_bin((blob) ? (blob)->bv_ga.ga_data : NULL, (size_t)(len), packer); \
 
 #define TYPVAL_ENCODE_CONV_NUMBER(tv, num) \
-  msgpack_pack_int64(packer, (int64_t)(num))
+  mpack_integer(&packer->ptr, (Integer)(num))
 
 #define TYPVAL_ENCODE_CONV_FLOAT(tv, flt) \
-  msgpack_pack_double(packer, (double)(flt))
+  mpack_float8(&packer->ptr, (double)(flt))
 
 #define TYPVAL_ENCODE_CONV_FUNC_START(tv, fun) \
   return conv_error(_("E5004: Error while dumping %s, %s: " \
@@ -970,33 +946,30 @@ char *encode_tv2json(typval_T *tv, size_t *len)
 #define TYPVAL_ENCODE_CONV_FUNC_END(tv)
 
 #define TYPVAL_ENCODE_CONV_EMPTY_LIST(tv) \
-  msgpack_pack_array(packer, 0)
+  mpack_array(&packer->ptr, 0)
 
 #define TYPVAL_ENCODE_CONV_LIST_START(tv, len) \
-  msgpack_pack_array(packer, (size_t)(len))
+  mpack_array(&packer->ptr, (uint32_t)(len))
 
 #define TYPVAL_ENCODE_CONV_REAL_LIST_AFTER_START(tv, mpsv)
 
 #define TYPVAL_ENCODE_CONV_EMPTY_DICT(tv, dict) \
-  msgpack_pack_map(packer, 0)
+  mpack_map(&packer->ptr, 0)
+
+#define TYPVAL_ENCODE_CHECK_BEFORE \
+  mpack_check_buffer(packer)
 
 #define TYPVAL_ENCODE_CONV_NIL(tv) \
-  msgpack_pack_nil(packer)
+  mpack_nil(&packer->ptr)
 
 #define TYPVAL_ENCODE_CONV_BOOL(tv, num) \
-  do { \
-    if (num) { \
-      msgpack_pack_true(packer); \
-    } else { \
-      msgpack_pack_false(packer); \
-    } \
-  } while (0)
+  mpack_bool(&packer->ptr, (bool)num); \
 
 #define TYPVAL_ENCODE_CONV_UNSIGNED_NUMBER(tv, num) \
-  msgpack_pack_uint64(packer, (num))
+  mpack_uint64(&packer->ptr, (num))
 
 #define TYPVAL_ENCODE_CONV_DICT_START(tv, dict, len) \
-  msgpack_pack_map(packer, (size_t)(len))
+  mpack_map(&packer->ptr, (uint32_t)(len))
 
 #define TYPVAL_ENCODE_CONV_REAL_DICT_AFTER_START(tv, dict, mpsv)
 
@@ -1021,7 +994,7 @@ char *encode_tv2json(typval_T *tv, size_t *len)
 
 #define TYPVAL_ENCODE_SCOPE
 #define TYPVAL_ENCODE_NAME msgpack
-#define TYPVAL_ENCODE_FIRST_ARG_TYPE msgpack_packer *const
+#define TYPVAL_ENCODE_FIRST_ARG_TYPE PackerBuffer *const
 #define TYPVAL_ENCODE_FIRST_ARG_NAME packer
 #include "nvim/eval/typval_encode.c.h"
 #undef TYPVAL_ENCODE_SCOPE
@@ -1043,6 +1016,7 @@ char *encode_tv2json(typval_T *tv, size_t *len)
 #undef TYPVAL_ENCODE_CONV_LIST_START
 #undef TYPVAL_ENCODE_CONV_REAL_LIST_AFTER_START
 #undef TYPVAL_ENCODE_CONV_EMPTY_DICT
+#undef TYPVAL_ENCODE_CHECK_BEFORE
 #undef TYPVAL_ENCODE_CONV_NIL
 #undef TYPVAL_ENCODE_CONV_BOOL
 #undef TYPVAL_ENCODE_CONV_UNSIGNED_NUMBER
diff --git a/src/nvim/eval/encode.h b/src/nvim/eval/encode.h
index 6d1c0b61c5..efccfcb5a6 100644
--- a/src/nvim/eval/encode.h
+++ b/src/nvim/eval/encode.h
@@ -5,6 +5,7 @@
 
 #include "nvim/eval/typval_defs.h"
 #include "nvim/garray_defs.h"
+#include "nvim/msgpack_rpc/packer_defs.h"
 
 /// Convert Vimscript value to msgpack string
 ///
@@ -13,7 +14,7 @@
 /// @param[in]  objname  Object name, used for error message.
 ///
 /// @return OK in case of success, FAIL otherwise.
-int encode_vim_to_msgpack(msgpack_packer *packer, typval_T *tv, const char *objname);
+int encode_vim_to_msgpack(PackerBuffer *packer, typval_T *tv, const char *objname);
 
 /// Convert Vimscript value to :echo output
 ///
diff --git a/src/nvim/eval/funcs.c b/src/nvim/eval/funcs.c
index 666d46cdad..9cb504c074 100644
--- a/src/nvim/eval/funcs.c
+++ b/src/nvim/eval/funcs.c
@@ -94,6 +94,7 @@
 #include "nvim/move.h"
 #include "nvim/msgpack_rpc/channel.h"
 #include "nvim/msgpack_rpc/channel_defs.h"
+#include "nvim/msgpack_rpc/packer.h"
 #include "nvim/msgpack_rpc/server.h"
 #include "nvim/normal.h"
 #include "nvim/normal_defs.h"
@@ -5501,15 +5502,7 @@ static void f_msgpackdump(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
     return;
   }
   list_T *const list = argvars[0].vval.v_list;
-  msgpack_packer *packer;
-  if (argvars[1].v_type != VAR_UNKNOWN
-      && strequal(tv_get_string(&argvars[1]), "B")) {
-    tv_blob_alloc_ret(rettv);
-    packer = msgpack_packer_new(rettv->vval.v_blob, &encode_blob_write);
-  } else {
-    packer = msgpack_packer_new(tv_list_alloc_ret(rettv, kListLenMayKnow),
-                                &encode_list_write);
-  }
+  PackerBuffer packer = packer_string_buffer();
   const char *const msg = _("msgpackdump() argument, index %i");
   // Assume that translation will not take more then 4 times more space
   char msgbuf[sizeof("msgpackdump() argument, index ") * 4 + NUMBUFLEN];
@@ -5517,11 +5510,20 @@ static void f_msgpackdump(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   TV_LIST_ITER(list, li, {
     vim_snprintf(msgbuf, sizeof(msgbuf), msg, idx);
     idx++;
-    if (encode_vim_to_msgpack(packer, TV_LIST_ITEM_TV(li), msgbuf) == FAIL) {
+    if (encode_vim_to_msgpack(&packer, TV_LIST_ITEM_TV(li), msgbuf) == FAIL) {
       break;
     }
   });
-  msgpack_packer_free(packer);
+  String data = packer_take_string(&packer);
+  if (argvars[1].v_type != VAR_UNKNOWN && strequal(tv_get_string(&argvars[1]), "B")) {
+    blob_T *b = tv_blob_alloc_ret(rettv);
+    b->bv_ga.ga_data = data.data;
+    b->bv_ga.ga_len = (int)data.size;
+    b->bv_ga.ga_maxlen = (int)(packer.endptr - packer.startptr);
+  } else {
+    encode_list_write(tv_list_alloc_ret(rettv, kListLenMayKnow), data.data, data.size);
+    api_free_string(data);
+  }
 }
 
 static int msgpackparse_convert_item(const msgpack_object data, const msgpack_unpack_return result,
diff --git a/src/nvim/eval/typval.c b/src/nvim/eval/typval.c
index 13b31ab30f..f9eb5c33c0 100644
--- a/src/nvim/eval/typval.c
+++ b/src/nvim/eval/typval.c
@@ -3064,8 +3064,7 @@ void f_blob2list(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 /// list2blob() function
 void f_list2blob(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 {
-  tv_blob_alloc_ret(rettv);
-  blob_T *const blob = rettv->vval.v_blob;
+  blob_T *blob = tv_blob_alloc_ret(rettv);
 
   if (tv_check_for_list_arg(argvars, 0) == FAIL) {
     return;
@@ -3252,11 +3251,12 @@ void tv_dict_remove(typval_T *argvars, typval_T *rettv, const char *arg_errmsg)
 /// Also sets reference count.
 ///
 /// @param[out]  ret_tv  Structure where blob is saved.
-void tv_blob_alloc_ret(typval_T *const ret_tv)
+blob_T *tv_blob_alloc_ret(typval_T *const ret_tv)
   FUNC_ATTR_NONNULL_ALL
 {
   blob_T *const b = tv_blob_alloc();
   tv_blob_set_ret(ret_tv, b);
+  return b;
 }
 
 /// Copy a blob typval to a different typval.
@@ -3284,6 +3284,7 @@ void tv_blob_copy(blob_T *const from, typval_T *const to)
 
 //{{{3 Clear
 #define TYPVAL_ENCODE_ALLOW_SPECIALS false
+#define TYPVAL_ENCODE_CHECK_BEFORE
 
 #define TYPVAL_ENCODE_CONV_NIL(tv) \
   do { \
@@ -3500,6 +3501,7 @@ static inline void _nothing_conv_dict_end(typval_T *const tv, dict_T **const dic
 #undef TYPVAL_ENCODE_FIRST_ARG_NAME
 
 #undef TYPVAL_ENCODE_ALLOW_SPECIALS
+#undef TYPVAL_ENCODE_CHECK_BEFORE
 #undef TYPVAL_ENCODE_CONV_NIL
 #undef TYPVAL_ENCODE_CONV_BOOL
 #undef TYPVAL_ENCODE_CONV_NUMBER
diff --git a/src/nvim/eval/typval_encode.c.h b/src/nvim/eval/typval_encode.c.h
index c0cd0ce557..afee6dab18 100644
--- a/src/nvim/eval/typval_encode.c.h
+++ b/src/nvim/eval/typval_encode.c.h
@@ -6,6 +6,11 @@
 /// something else. For these macros to work the following macros must be
 /// defined:
 
+/// @def TYPVAL_ENCODE_CHECK_BEFORE
+/// @brief Macro used before any specific CONV function
+///
+/// can be used for a common check, like flushing a buffer if necessary
+
 /// @def TYPVAL_ENCODE_CONV_NIL
 /// @brief Macros used to convert NIL value
 ///
@@ -323,6 +328,7 @@ static int TYPVAL_ENCODE_CONVERT_ONE_VALUE(
                                            TYPVAL_ENCODE_FIRST_ARG_TYPE TYPVAL_ENCODE_FIRST_ARG_NAME, MPConvStack *const mpstack,
                                            MPConvStackVal *const cur_mpsv, typval_T *const tv, const int copyID, const char *const objname)
 {
+  TYPVAL_ENCODE_CHECK_BEFORE;
   switch (tv->v_type) {
   case VAR_STRING:
     TYPVAL_ENCODE_CONV_STRING(tv, tv->vval.v_string, tv_strlen(tv));
@@ -420,6 +426,7 @@ static int TYPVAL_ENCODE_CONVERT_ONE_VALUE(
           break;
         }
       }
+      TYPVAL_ENCODE_CHECK_BEFORE;
       if (i == ARRAY_SIZE(eval_msgpack_type_lists)) {
         goto _convert_one_value_regular_dict;
       }
diff --git a/src/nvim/lua/converter.c b/src/nvim/lua/converter.c
index 38ccb03cfc..1b1794e244 100644
--- a/src/nvim/lua/converter.c
+++ b/src/nvim/lua/converter.c
@@ -425,6 +425,8 @@ static bool typval_conv_special = false;
 
 #define TYPVAL_ENCODE_ALLOW_SPECIALS true
 
+#define TYPVAL_ENCODE_CHECK_BEFORE
+
 #define TYPVAL_ENCODE_CONV_NIL(tv) \
   do { \
     if (typval_conv_special) { \
@@ -574,6 +576,7 @@ static bool typval_conv_special = false;
 #undef TYPVAL_ENCODE_CONV_LIST_START
 #undef TYPVAL_ENCODE_CONV_REAL_LIST_AFTER_START
 #undef TYPVAL_ENCODE_CONV_EMPTY_DICT
+#undef TYPVAL_ENCODE_CHECK_BEFORE
 #undef TYPVAL_ENCODE_CONV_NIL
 #undef TYPVAL_ENCODE_CONV_BOOL
 #undef TYPVAL_ENCODE_CONV_UNSIGNED_NUMBER
diff --git a/src/nvim/msgpack_rpc/packer.c b/src/nvim/msgpack_rpc/packer.c
index 58318b88b0..279cbb3925 100644
--- a/src/nvim/msgpack_rpc/packer.c
+++ b/src/nvim/msgpack_rpc/packer.c
@@ -8,7 +8,7 @@
 # include "msgpack_rpc/packer.c.generated.h"
 #endif
 
-static void check_buffer(PackerBuffer *packer)
+void mpack_check_buffer(PackerBuffer *packer)
 {
   if (mpack_remaining(packer) < MPACK_ITEM_SIZE) {
     packer->packer_flush(packer);
@@ -87,7 +87,25 @@ void mpack_str(String str, PackerBuffer *packer)
   mpack_raw(str.data, len, packer);
 }
 
-void mpack_raw(char *data, size_t len, PackerBuffer *packer)
+void mpack_bin(const char *data, size_t len, PackerBuffer *packer)
+{
+  if (len < 0xff) {
+    mpack_w(&packer->ptr, 0xc4);
+    mpack_w(&packer->ptr, len);
+  } else if (len < 0xffff) {
+    mpack_w(&packer->ptr, 0xc5);
+    mpack_w2(&packer->ptr, (uint32_t)len);
+  } else if (len < 0xffffffff) {
+    mpack_w(&packer->ptr, 0xc6);
+    mpack_w4(&packer->ptr, (uint32_t)len);
+  } else {
+    abort();
+  }
+
+  mpack_raw(data, len, packer);
+}
+
+void mpack_raw(const char *data, size_t len, PackerBuffer *packer)
 {
   size_t pos = 0;
   while (pos < len) {
@@ -103,6 +121,27 @@ void mpack_raw(char *data, size_t len, PackerBuffer *packer)
   }
 }
 
+void mpack_ext(char *buf, size_t len, int8_t type, PackerBuffer *packer)
+{
+  if (len == 1) {
+    mpack_w(&packer->ptr, 0xd4);
+  } else if (len == 2) {
+    mpack_w(&packer->ptr, 0xd5);
+  } else if (len <= 0xff) {
+    mpack_w(&packer->ptr, 0xc7);
+  } else if (len < 0xffff) {
+    mpack_w(&packer->ptr, 0xc8);
+    mpack_w2(&packer->ptr, (uint32_t)len);
+  } else if (len < 0xffffffff) {
+    mpack_w(&packer->ptr, 0xc9);
+    mpack_w4(&packer->ptr, (uint32_t)len);
+  } else {
+    abort();
+  }
+  mpack_w(&packer->ptr, type);
+  mpack_raw(buf, len, packer);
+}
+
 void mpack_handle(ObjectType type, handle_T handle, PackerBuffer *packer)
 {
   char exttype = (char)(type - EXT_OBJECT_TYPE_SHIFT);
@@ -156,7 +195,7 @@ void mpack_object_inner(Object *current, Object *container, size_t container_idx
   kvi_init(stack);
 
   while (true) {
-    check_buffer(packer);
+    mpack_check_buffer(packer);
     switch (current->type) {
     case kObjectTypeLuaRef:
       // TODO(bfredl): could also be an error. Though kObjectTypeLuaRef
@@ -231,7 +270,7 @@ void mpack_object_inner(Object *current, Object *container, size_t container_idx
     } else {
       Dictionary dict = container->data.dictionary;
       KeyValuePair *it = &dict.items[container_idx++];
-      check_buffer(packer);
+      mpack_check_buffer(packer);
       mpack_str(it->key, packer);
       current = &it->value;
       if (container_idx >= dict.size) {
@@ -241,3 +280,32 @@ void mpack_object_inner(Object *current, Object *container, size_t container_idx
   }
   kvi_destroy(stack);
 }
+
+PackerBuffer packer_string_buffer(void)
+{
+  const size_t initial_size = 64;  // must be larger than SHADA_MPACK_FREE_SPACE
+  char *alloc = xmalloc(initial_size);
+  return (PackerBuffer) {
+    .startptr = alloc,
+    .ptr = alloc,
+    .endptr = alloc + initial_size,
+    .packer_flush = flush_string_buffer,
+  };
+}
+
+static void flush_string_buffer(PackerBuffer *buffer)
+{
+  size_t current_capacity = (size_t)(buffer->endptr - buffer->startptr);
+  size_t new_capacity = 2 * current_capacity;
+  size_t len = (size_t)(buffer->ptr - buffer->startptr);
+
+  buffer->startptr = xrealloc(buffer->startptr, new_capacity);
+  buffer->ptr = buffer->startptr + len;
+  buffer->endptr = buffer->startptr + new_capacity;
+}
+
+/// can only be used with a PackerBuffer from `packer_string_buffer`
+String packer_take_string(PackerBuffer *buffer)
+{
+  return (String){ .data = buffer->startptr, .size = (size_t)(buffer->ptr - buffer->startptr) };
+}
diff --git a/src/nvim/shada.c b/src/nvim/shada.c
index 5736ea0f09..34e1590458 100644
--- a/src/nvim/shada.c
+++ b/src/nvim/shada.c
@@ -1354,6 +1354,12 @@ static char *shada_filename(const char *file)
 
 #define SHADA_MPACK_FREE_SPACE (4 * MPACK_ITEM_SIZE)
 
+static int mpack_raw_wrapper(void *cookie, const char *data, size_t len)
+{
+  mpack_raw(data, len, (PackerBuffer *)cookie);
+  return 0;
+}
+
 /// Write single ShaDa entry
 ///
 /// @param[in]  packer     Packer used to write entry.
@@ -1367,14 +1373,13 @@ static ShaDaWriteResult shada_pack_entry(PackerBuffer *const packer, ShadaEntry
   FUNC_ATTR_NONNULL_ALL
 {
   ShaDaWriteResult ret = kSDWriteFailed;
-  msgpack_sbuffer sbuf;
-  msgpack_sbuffer_init(&sbuf);
-  msgpack_packer *spacker = msgpack_packer_new(&sbuf, &msgpack_sbuffer_write);
+  PackerBuffer sbuf = packer_string_buffer();
+  msgpack_packer *spacker = msgpack_packer_new(&sbuf, &mpack_raw_wrapper);
 #define DUMP_ADDITIONAL_ELEMENTS(src, what) \
   do { \
     if ((src) != NULL) { \
       TV_LIST_ITER((src), li, { \
-        if (encode_vim_to_msgpack(spacker, TV_LIST_ITEM_TV(li), \
+        if (encode_vim_to_msgpack(&sbuf, TV_LIST_ITEM_TV(li), \
                                   _("additional elements of ShaDa " what)) \
             == FAIL) { \
           goto shada_pack_entry_error; \
@@ -1394,7 +1399,7 @@ static ShaDaWriteResult shada_pack_entry(PackerBuffer *const packer, ShadaEntry
           const size_t key_len = strlen(hi->hi_key); \
           msgpack_pack_str(spacker, key_len); \
           msgpack_pack_str_body(spacker, hi->hi_key, key_len); \
-          if (encode_vim_to_msgpack(spacker, &di->di_tv, \
+          if (encode_vim_to_msgpack(&sbuf, &di->di_tv, \
                                     _("additional data of ShaDa " what)) \
               == FAIL) { \
             goto shada_pack_entry_error; \
@@ -1460,7 +1465,7 @@ static ShaDaWriteResult shada_pack_entry(PackerBuffer *const packer, ShadaEntry
     char vardesc[256] = "variable g:";
     memcpy(&vardesc[sizeof("variable g:") - 1], varname.data,
            varname.size + 1);
-    if (encode_vim_to_msgpack(spacker, &entry.data.global_var.value, vardesc)
+    if (encode_vim_to_msgpack(&sbuf, &entry.data.global_var.value, vardesc)
         == FAIL) {
       ret = kSDWriteIgnError;
       semsg(_(WERR "Failed to write variable %s"),
@@ -1645,7 +1650,8 @@ static ShaDaWriteResult shada_pack_entry(PackerBuffer *const packer, ShadaEntry
   }
 #undef CHECK_DEFAULT
 #undef ONE_IF_NOT_DEFAULT
-  if (!max_kbyte || sbuf.size <= max_kbyte * 1024) {
+  String packed = packer_take_string(&sbuf);
+  if (!max_kbyte || packed.size <= max_kbyte * 1024) {
     if (mpack_remaining(packer) < SHADA_MPACK_FREE_SPACE) {
       packer->packer_flush(packer);
     }
@@ -1656,9 +1662,9 @@ static ShaDaWriteResult shada_pack_entry(PackerBuffer *const packer, ShadaEntry
       mpack_uint64(&packer->ptr, (uint64_t)entry.type);
     }
     mpack_uint64(&packer->ptr, (uint64_t)entry.timestamp);
-    if (sbuf.size > 0) {
-      mpack_uint64(&packer->ptr, (uint64_t)sbuf.size);
-      mpack_raw(sbuf.data, sbuf.size, packer);
+    if (packed.size > 0) {
+      mpack_uint64(&packer->ptr, (uint64_t)packed.size);
+      mpack_raw(packed.data, packed.size, packer);
     }
 
     if (packer->anyint != 0) {  // error code
@@ -1668,7 +1674,7 @@ static ShaDaWriteResult shada_pack_entry(PackerBuffer *const packer, ShadaEntry
   ret = kSDWriteSuccessful;
 shada_pack_entry_error:
   msgpack_packer_free(spacker);
-  msgpack_sbuffer_destroy(&sbuf);
+  xfree(sbuf.startptr);
   return ret;
 }
 
@@ -3960,34 +3966,6 @@ static inline size_t shada_init_jumps(PossiblyFreedShadaEntry *jumps,
   return jumps_size;
 }
 
-static PackerBuffer packer_string_buffer(void)
-{
-  const size_t initial_size = 64;  // must be larger than SHADA_MPACK_FREE_SPACE
-  char *alloc = xmalloc(initial_size);
-  return (PackerBuffer) {
-    .startptr = alloc,
-    .ptr = alloc,
-    .endptr = alloc + initial_size,
-    .packer_flush = flush_string_buffer,
-  };
-}
-
-static void flush_string_buffer(PackerBuffer *buffer)
-{
-  size_t current_capacity = (size_t)(buffer->endptr - buffer->startptr);
-  size_t new_capacity = 2 * current_capacity;
-  size_t len = (size_t)(buffer->ptr - buffer->startptr);
-
-  buffer->startptr = xrealloc(buffer->startptr, new_capacity);
-  buffer->ptr = buffer->startptr + len;
-  buffer->endptr = buffer->startptr + new_capacity;
-}
-
-static String packer_take_string(PackerBuffer *buffer)
-{
-  return (String){ .data = buffer->startptr, .size = (size_t)(buffer->ptr - buffer->startptr) };
-}
-
 /// Write registers ShaDa entries in given msgpack_sbuffer.
 ///
 /// @param[in]  sbuf  target msgpack_sbuffer to write to.