refactor(api): use an arena for nvim_buf_get_lines and buffer updates

Refactor some earlier "temporary Array" code in buffer_updates.c to use
the modern style of MAXSIZE_TEMP_ARRAY and ADD_C

6 files changed, 81 insertions, 117 deletions

diff --git a/src/nvim/api/buffer.c b/src/nvim/api/buffer.c
index 751fc1c32d..183483b329 100644
--- a/src/nvim/api/buffer.c
+++ b/src/nvim/api/buffer.c
@@ -264,6 +264,7 @@ ArrayOf(String) nvim_buf_get_lines(uint64_t channel_id,
                                    Integer start,
                                    Integer end,
                                    Boolean strict_indexing,
+                                   Arena *arena,
                                    lua_State *lstate,
                                    Error *err)
   FUNC_API_SINCE(1)
@@ -295,18 +296,10 @@ ArrayOf(String) nvim_buf_get_lines(uint64_t channel_id,
 
   size_t size = (size_t)(end - start);
 
-  init_line_array(lstate, &rv, size);
+  init_line_array(lstate, &rv, size, arena);
 
-  if (!buf_collect_lines(buf, size, (linenr_T)start, 0, (channel_id != VIML_INTERNAL_CALL), &rv,
-                         lstate, err)) {
-    goto end;
-  }
-
-end:
-  if (ERROR_SET(err)) {
-    api_free_array(rv);
-    rv.items = NULL;
-  }
+  buf_collect_lines(buf, size, (linenr_T)start, 0, (channel_id != VIML_INTERNAL_CALL), &rv,
+                    lstate, arena);
 
   return rv;
 }
@@ -763,8 +756,8 @@ early_end:
 ArrayOf(String) nvim_buf_get_text(uint64_t channel_id, Buffer buffer,
                                   Integer start_row, Integer start_col,
                                   Integer end_row, Integer end_col,
-                                  Dict(empty) *opts, lua_State *lstate,
-                                  Error *err)
+                                  Dict(empty) *opts,
+                                  Arena *arena, lua_State *lstate, Error *err)
   FUNC_API_SINCE(9)
 {
   Array rv = ARRAY_DICT_INIT;
@@ -799,44 +792,38 @@ ArrayOf(String) nvim_buf_get_text(uint64_t channel_id, Buffer buffer,
 
   size_t size = (size_t)(end_row - start_row) + 1;
 
-  init_line_array(lstate, &rv, size);
+  init_line_array(lstate, &rv, size, arena);
 
   if (start_row == end_row) {
     String line = buf_get_text(buf, start_row, start_col, end_col, err);
     if (ERROR_SET(err)) {
       goto end;
     }
-    push_linestr(lstate, &rv, line.data, line.size, 0, replace_nl);
+    push_linestr(lstate, &rv, line.data, line.size, 0, replace_nl, arena);
     return rv;
   }
 
   String str = buf_get_text(buf, start_row, start_col, MAXCOL - 1, err);
-
-  push_linestr(lstate, &rv, str.data, str.size, 0, replace_nl);
-
   if (ERROR_SET(err)) {
     goto end;
   }
 
+  push_linestr(lstate, &rv, str.data, str.size, 0, replace_nl, arena);
+
   if (size > 2) {
-    if (!buf_collect_lines(buf, size - 2, (linenr_T)start_row + 1, 1, replace_nl, &rv, lstate,
-                           err)) {
-      goto end;
-    }
+    buf_collect_lines(buf, size - 2, (linenr_T)start_row + 1, 1, replace_nl, &rv, lstate, arena);
   }
 
   str = buf_get_text(buf, end_row, 0, end_col, err);
-  push_linestr(lstate, &rv, str.data, str.size, (int)(size - 1), replace_nl);
-
   if (ERROR_SET(err)) {
     goto end;
   }
 
+  push_linestr(lstate, &rv, str.data, str.size, (int)(size - 1), replace_nl, arena);
+
 end:
   if (ERROR_SET(err)) {
-    api_free_array(rv);
-    rv.size = 0;
-    rv.items = NULL;
+    return (Array)ARRAY_DICT_INIT;
   }
 
   return rv;
@@ -1394,13 +1381,12 @@ static void fix_cursor_cols(win_T *win, linenr_T start_row, colnr_T start_col, l
 /// @param lstate  Lua state. When NULL the Array is initialized instead.
 /// @param a       Array to initialize
 /// @param size    Size of array
-static inline void init_line_array(lua_State *lstate, Array *a, size_t size)
+static inline void init_line_array(lua_State *lstate, Array *a, size_t size, Arena *arena)
 {
   if (lstate) {
     lua_createtable(lstate, (int)size, 0);
   } else {
-    a->size = size;
-    a->items = xcalloc(a->size, sizeof(Object));
+    *a = arena_array(arena, size);
   }
 }
 
@@ -1413,14 +1399,15 @@ static inline void init_line_array(lua_State *lstate, Array *a, size_t size)
 /// @param a           Array to push onto when not using Lua
 /// @param s           String to push
 /// @param len         Size of string
-/// @param idx         0-based index to place s
+/// @param idx         0-based index to place s (only used for Lua)
 /// @param replace_nl  Replace newlines ('\n') with null ('\0')
 static void push_linestr(lua_State *lstate, Array *a, const char *s, size_t len, int idx,
-                         bool replace_nl)
+                         bool replace_nl, Arena *arena)
 {
   if (lstate) {
     // Vim represents NULs as NLs
     if (s && replace_nl && strchr(s, '\n')) {
+      // TODO(bfredl): could manage scratch space in the arena, for the NUL case
       char *tmp = xmemdupz(s, len);
       strchrsub(tmp, '\n', '\0');
       lua_pushlstring(lstate, tmp, len);
@@ -1431,15 +1418,15 @@ static void push_linestr(lua_State *lstate, Array *a, const char *s, size_t len,
     lua_rawseti(lstate, -2, idx + 1);
   } else {
     String str = STRING_INIT;
-    if (s) {
-      str = cbuf_to_string(s, len);
+    if (len > 0) {
+      str = arena_string(arena, cbuf_as_string((char *)s, len));
       if (replace_nl) {
         // Vim represents NULs as NLs, but this may confuse clients.
         strchrsub(str.data, '\n', '\0');
       }
     }
 
-    a->items[idx] = STRING_OBJ(str);
+    ADD_C(*a, STRING_OBJ(str));
   }
 }
 
@@ -1450,27 +1437,17 @@ static void push_linestr(lua_State *lstate, Array *a, const char *s, size_t len,
 /// @param n Number of lines to collect
 /// @param replace_nl Replace newlines ("\n") with NUL
 /// @param start Line number to start from
-/// @param start_idx First index to push to
+/// @param start_idx First index to push to (only used for Lua)
 /// @param[out] l If not NULL, Lines are copied here
 /// @param[out] lstate If not NULL, Lines are pushed into a table onto the stack
 /// @param err[out] Error, if any
 /// @return true unless `err` was set
-bool buf_collect_lines(buf_T *buf, size_t n, linenr_T start, int start_idx, bool replace_nl,
-                       Array *l, lua_State *lstate, Error *err)
+void buf_collect_lines(buf_T *buf, size_t n, linenr_T start, int start_idx, bool replace_nl,
+                       Array *l, lua_State *lstate, Arena *arena)
 {
   for (size_t i = 0; i < n; i++) {
     linenr_T lnum = start + (linenr_T)i;
-
-    if (lnum >= MAXLNUM) {
-      if (err != NULL) {
-        api_set_error(err, kErrorTypeValidation, "Line index is too high");
-      }
-      return false;
-    }
-
     char *bufstr = ml_get_buf(buf, lnum);
-    push_linestr(lstate, l, bufstr, strlen(bufstr), start_idx + (int)i, replace_nl);
+    push_linestr(lstate, l, bufstr, strlen(bufstr), start_idx + (int)i, replace_nl, arena);
   }
-
-  return true;
 }
diff --git a/src/nvim/api/deprecated.c b/src/nvim/api/deprecated.c
index 27f0589e53..dccaeb6922 100644
--- a/src/nvim/api/deprecated.c
+++ b/src/nvim/api/deprecated.c
@@ -245,20 +245,18 @@ void buffer_insert(Buffer buffer, Integer lnum, ArrayOf(String) lines, Error *er
 /// @param index    Line index
 /// @param[out] err Error details, if any
 /// @return Line string
-String buffer_get_line(Buffer buffer, Integer index, Error *err)
+String buffer_get_line(Buffer buffer, Integer index, Arena *arena, Error *err)
   FUNC_API_DEPRECATED_SINCE(1)
 {
   String rv = { .size = 0 };
 
   index = convert_index(index);
-  Array slice = nvim_buf_get_lines(0, buffer, index, index + 1, true, NULL, err);
+  Array slice = nvim_buf_get_lines(0, buffer, index, index + 1, true, arena, NULL, err);
 
   if (!ERROR_SET(err) && slice.size) {
     rv = slice.items[0].data.string;
   }
 
-  xfree(slice.items);
-
   return rv;
 }
 
@@ -319,12 +317,13 @@ ArrayOf(String) buffer_get_line_slice(Buffer buffer,
                                       Integer end,
                                       Boolean include_start,
                                       Boolean include_end,
+                                      Arena *arena,
                                       Error *err)
   FUNC_API_DEPRECATED_SINCE(1)
 {
   start = convert_index(start) + !include_start;
   end = convert_index(end) + include_end;
-  return nvim_buf_get_lines(0, buffer, start, end, false, NULL, err);
+  return nvim_buf_get_lines(0, buffer, start, end, false, arena, NULL, err);
 }
 
 /// Replaces a line range on the buffer
diff --git a/src/nvim/api/vim.c b/src/nvim/api/vim.c
index a47694a0cf..78c2561bbd 100644
--- a/src/nvim/api/vim.c
+++ b/src/nvim/api/vim.c
@@ -656,10 +656,10 @@ void nvim_set_current_dir(String dir, Error *err)
 ///
 /// @param[out] err Error details, if any
 /// @return Current line string
-String nvim_get_current_line(Error *err)
+String nvim_get_current_line(Arena *arena, Error *err)
   FUNC_API_SINCE(1)
 {
-  return buffer_get_line(curbuf->handle, curwin->w_cursor.lnum - 1, err);
+  return buffer_get_line(curbuf->handle, curwin->w_cursor.lnum - 1, arena, err);
 }
 
 /// Sets the current line.
diff --git a/src/nvim/buffer_updates.c b/src/nvim/buffer_updates.c
index a91a890d0e..1a02ac78d7 100644
--- a/src/nvim/buffer_updates.c
+++ b/src/nvim/buffer_updates.c
@@ -55,36 +55,33 @@ bool buf_updates_register(buf_T *buf, uint64_t channel_id, BufUpdateCallbacks cb
   kv_push(buf->update_channels, channel_id);
 
   if (send_buffer) {
-    Array args = ARRAY_DICT_INIT;
-    args.size = 6;
-    args.items = xcalloc(args.size, sizeof(Object));
+    MAXSIZE_TEMP_ARRAY(args, 6);
 
     // the first argument is always the buffer handle
-    args.items[0] = BUFFER_OBJ(buf->handle);
-    args.items[1] = INTEGER_OBJ(buf_get_changedtick(buf));
+    ADD_C(args, BUFFER_OBJ(buf->handle));
+    ADD_C(args, INTEGER_OBJ(buf_get_changedtick(buf)));
     // the first line that changed (zero-indexed)
-    args.items[2] = INTEGER_OBJ(0);
+    ADD_C(args, INTEGER_OBJ(0));
     // the last line that was changed
-    args.items[3] = INTEGER_OBJ(-1);
-    Array linedata = ARRAY_DICT_INIT;
+    ADD_C(args, INTEGER_OBJ(-1));
 
     // collect buffer contents
 
     STATIC_ASSERT(SIZE_MAX >= MAXLNUM, "size_t smaller than MAXLNUM");
     size_t line_count = (size_t)buf->b_ml.ml_line_count;
 
-    if (line_count >= 1) {
-      linedata.size = line_count;
-      linedata.items = xcalloc(line_count, sizeof(Object));
-
-      buf_collect_lines(buf, line_count, 1, 0, true, &linedata, NULL, NULL);
+    Array linedata = ARRAY_DICT_INIT;
+    Arena arena = ARENA_EMPTY;
+    if (line_count > 0) {
+      linedata = arena_array(&arena, line_count);
+      buf_collect_lines(buf, line_count, 1, 0, true, &linedata, NULL, &arena);
     }
 
-    args.items[4] = ARRAY_OBJ(linedata);
-    args.items[5] = BOOLEAN_OBJ(false);
+    ADD_C(args, ARRAY_OBJ(linedata));
+    ADD_C(args, BOOLEAN_OBJ(false));
 
     rpc_send_event(channel_id, "nvim_buf_lines_event", args);
-    api_free_array(args);  // TODO(bfredl): no
+    arena_mem_free(arena_finish(&arena));
   } else {
     buf_updates_changedtick_single(buf, channel_id);
   }
@@ -176,13 +173,10 @@ void buf_updates_unload(buf_T *buf, bool can_reload)
     }
 
     if (thecb != LUA_NOREF) {
-      Array args = ARRAY_DICT_INIT;
-      Object items[1];
-      args.size = 1;
-      args.items = items;
+      MAXSIZE_TEMP_ARRAY(args, 1);
 
       // the first argument is always the buffer handle
-      args.items[0] = BUFFER_OBJ(buf->handle);
+      ADD_C(args, BUFFER_OBJ(buf->handle));
 
       TEXTLOCK_WRAP({
         nlua_call_ref(thecb, keep ? "reload" : "detach", args, false, NULL);
@@ -219,45 +213,43 @@ void buf_updates_send_changes(buf_T *buf, linenr_T firstline, int64_t num_added,
   // if one the channels doesn't work, put its ID here so we can remove it later
   uint64_t badchannelid = 0;
 
+  Arena arena = ARENA_EMPTY;
+  Array linedata = ARRAY_DICT_INIT;
+  if (num_added > 0 && kv_size(buf->update_channels)) {
+    STATIC_ASSERT(SIZE_MAX >= MAXLNUM, "size_t smaller than MAXLNUM");
+    linedata = arena_array(&arena, (size_t)num_added);
+    buf_collect_lines(buf, (size_t)num_added, firstline, 0, true, &linedata,
+                      NULL, &arena);
+  }
+
   // notify each of the active channels
   for (size_t i = 0; i < kv_size(buf->update_channels); i++) {
     uint64_t channelid = kv_A(buf->update_channels, i);
 
     // send through the changes now channel contents now
-    Array args = ARRAY_DICT_INIT;
-    args.size = 6;
-    args.items = xcalloc(args.size, sizeof(Object));
+    MAXSIZE_TEMP_ARRAY(args, 6);
 
     // the first argument is always the buffer handle
-    args.items[0] = BUFFER_OBJ(buf->handle);
+    ADD_C(args, BUFFER_OBJ(buf->handle));
 
     // next argument is b:changedtick
-    args.items[1] = send_tick ? INTEGER_OBJ(buf_get_changedtick(buf)) : NIL;
+    ADD_C(args, send_tick ? INTEGER_OBJ(buf_get_changedtick(buf)) : NIL);
 
     // the first line that changed (zero-indexed)
-    args.items[2] = INTEGER_OBJ(firstline - 1);
+    ADD_C(args, INTEGER_OBJ(firstline - 1));
 
     // the last line that was changed
-    args.items[3] = INTEGER_OBJ(firstline - 1 + num_removed);
+    ADD_C(args, INTEGER_OBJ(firstline - 1 + num_removed));
 
     // linedata of lines being swapped in
-    Array linedata = ARRAY_DICT_INIT;
-    if (num_added > 0) {
-      STATIC_ASSERT(SIZE_MAX >= MAXLNUM, "size_t smaller than MAXLNUM");
-      linedata.size = (size_t)num_added;
-      linedata.items = xcalloc((size_t)num_added, sizeof(Object));
-      buf_collect_lines(buf, (size_t)num_added, firstline, 0, true, &linedata,
-                        NULL, NULL);
-    }
-    args.items[4] = ARRAY_OBJ(linedata);
-    args.items[5] = BOOLEAN_OBJ(false);
+    ADD_C(args, ARRAY_OBJ(linedata));
+    ADD_C(args, BOOLEAN_OBJ(false));
     if (!rpc_send_event(channelid, "nvim_buf_lines_event", args)) {
       // We can't unregister the channel while we're iterating over the
       // update_channels array, so we remember its ID to unregister it at
       // the end.
       badchannelid = channelid;
     }
-    api_free_array(args);  // TODO(bfredl): no
   }
 
   // We can only ever remove one dead channel at a time. This is OK because the
@@ -268,38 +260,37 @@ void buf_updates_send_changes(buf_T *buf, linenr_T firstline, int64_t num_added,
     buf_updates_unregister(buf, badchannelid);
   }
 
-  // notify each of the active channels
+  // callbacks don't use linedata
+  arena_mem_free(arena_finish(&arena));
+
+  // notify each of the active callbacks
   size_t j = 0;
   for (size_t i = 0; i < kv_size(buf->update_callbacks); i++) {
     BufUpdateCallbacks cb = kv_A(buf->update_callbacks, i);
     bool keep = true;
     if (cb.on_lines != LUA_NOREF && (cb.preview || !cmdpreview)) {
-      Array args = ARRAY_DICT_INIT;
-      Object items[8];
-      args.size = 6;  // may be increased to 8 below
-      args.items = items;
+      MAXSIZE_TEMP_ARRAY(args, 8);  // 6 or 8 used
 
       // the first argument is always the buffer handle
-      args.items[0] = BUFFER_OBJ(buf->handle);
+      ADD_C(args, BUFFER_OBJ(buf->handle));
 
       // next argument is b:changedtick
-      args.items[1] = send_tick ? INTEGER_OBJ(buf_get_changedtick(buf)) : NIL;
+      ADD_C(args, send_tick ? INTEGER_OBJ(buf_get_changedtick(buf)) : NIL);
 
       // the first line that changed (zero-indexed)
-      args.items[2] = INTEGER_OBJ(firstline - 1);
+      ADD_C(args, INTEGER_OBJ(firstline - 1));
 
       // the last line that was changed
-      args.items[3] = INTEGER_OBJ(firstline - 1 + num_removed);
+      ADD_C(args, INTEGER_OBJ(firstline - 1 + num_removed));
 
       // the last line in the updated range
-      args.items[4] = INTEGER_OBJ(firstline - 1 + num_added);
+      ADD_C(args, INTEGER_OBJ(firstline - 1 + num_added));
 
       // byte count of previous contents
-      args.items[5] = INTEGER_OBJ((Integer)deleted_bytes);
+      ADD_C(args, INTEGER_OBJ((Integer)deleted_bytes));
       if (cb.utf_sizes) {
-        args.size = 8;
-        args.items[6] = INTEGER_OBJ((Integer)deleted_codepoints);
-        args.items[7] = INTEGER_OBJ((Integer)deleted_codeunits);
+        ADD_C(args, INTEGER_OBJ((Integer)deleted_codepoints));
+        ADD_C(args, INTEGER_OBJ((Integer)deleted_codeunits));
       }
 
       Object res;
diff --git a/src/nvim/generators/gen_api_dispatch.lua b/src/nvim/generators/gen_api_dispatch.lua
index da3010878d..04fe43b712 100644
--- a/src/nvim/generators/gen_api_dispatch.lua
+++ b/src/nvim/generators/gen_api_dispatch.lua
@@ -55,15 +55,15 @@ local function add_function(fn)
       -- for specifying errors
       fn.parameters[#fn.parameters] = nil
     end
+    if #fn.parameters ~= 0 and fn.parameters[#fn.parameters][1] == 'lstate' then
+      fn.has_lua_imp = true
+      fn.parameters[#fn.parameters] = nil
+    end
     if #fn.parameters ~= 0 and fn.parameters[#fn.parameters][1] == 'arena' then
       -- return value is allocated in an arena
       fn.arena_return = true
       fn.parameters[#fn.parameters] = nil
     end
-    if #fn.parameters ~= 0 and fn.parameters[#fn.parameters][1] == 'lstate' then
-      fn.has_lua_imp = true
-      fn.parameters[#fn.parameters] = nil
-    end
   end
 end
 
diff --git a/src/nvim/highlight_group.c b/src/nvim/highlight_group.c
index a1ce206a2b..75c23c5bc4 100644
--- a/src/nvim/highlight_group.c
+++ b/src/nvim/highlight_group.c
@@ -1672,10 +1672,7 @@ Dictionary ns_get_hl_defs(NS ns_id, Dict(get_highlight) *opts, Arena *arena, Err
   return rv;
 
 cleanup:
-  api_free_integer(id);
-  api_free_boolean(link);
-  Dictionary empty = ARRAY_DICT_INIT;
-  return empty;
+  return (Dictionary)ARRAY_DICT_INIT;
 }
 
 /// Outputs a highlight when doing ":hi MyHighlight"