refactor: use ml_get_buf_len() in API code (#27825)

src/nvim/lua/executor.c

@@ -1767,7 +1767,7 @@ void ex_luado(exarg_T *const eap)
     lua_pushvalue(lstate, -1);
     const char *const old_line = ml_get_buf(curbuf, l);
     // Get length of old_line here as calling Lua code may free it.
-    const size_t old_line_len = strlen(old_line);
+    const colnr_T old_line_len = ml_get_buf_len(curbuf, l);
     lua_pushstring(lstate, old_line);
     lua_pushnumber(lstate, (lua_Number)l);
     if (nlua_pcall(lstate, 2, 1)) {
@@ -1791,7 +1791,7 @@ void ex_luado(exarg_T *const eap)
         }
       }
       ml_replace(l, new_line_transformed, false);
-      inserted_bytes(l, 0, (int)old_line_len, (int)new_line_len);
+      inserted_bytes(l, 0, old_line_len, (int)new_line_len);
     }
     lua_pop(lstate, 1);
   }

src/nvim/lua/stdlib.c

@@ -107,15 +107,15 @@ static int regex_match_line(lua_State *lstate)
   }
 
   char *line = ml_get_buf(buf, rownr + 1);
-  size_t len = strlen(line);
+  colnr_T len = ml_get_buf_len(buf, rownr + 1);
 
-  if (start < 0 || (size_t)start > len) {
+  if (start < 0 || start > len) {
     return luaL_error(lstate, "invalid start");
   }
 
   char save = NUL;
   if (end >= 0) {
-    if ((size_t)end > len || end < start) {
+    if (end > len || end < start) {
       return luaL_error(lstate, "invalid end");
     }
     save = line[end];

src/nvim/lua/treesitter.c

@@ -371,7 +371,7 @@ static const char *input_cb(void *payload, uint32_t byte_index, TSPoint position
     return "";
   }
   char *line = ml_get_buf(bp, (linenr_T)position.row + 1);
-  size_t len = strlen(line);
+  size_t len = (size_t)ml_get_buf_len(bp, (linenr_T)position.row + 1);
   if (position.column > len) {
     *bytes_read = 0;
     return "";