[perf] tweak text file handling a bit

Author: tstack

src/logfile.cc

@@ -1067,11 +1067,13 @@ logfile::rebuild_index(std::optional<ui_clock::time_point> deadline)
                                       sbr_str.erase(line_iter->sf_begin, 22);
                                   }
                               }
-                              if (is_utf8(sbr_str).is_valid()) {
+                              const auto& sbr_meta = avail_sbr.get_metadata();
+                              if (!sbr_meta.m_valid_utf) {
+                                  return text_format_t::TF_BINARY;
+                              }
+                              if (sbr_meta.m_has_ansi) {
                                   auto new_size = erase_ansi_escapes(sbr_str);
                                   sbr_str.resize(new_size);
-                              } else {
-                                  return text_format_t::TF_BINARY;
                               }
                               return detect_text_format(sbr_str, path);
                           })

src/shared_buffer.hh

@@ -105,6 +105,8 @@ struct shared_buffer_ref {
         return (this->sb_data <= ptr && ptr < buffer_end);
     }
 
+    const file_range::metadata& get_metadata() const { return this->sb_metadata; }
+
     file_range::metadata& get_metadata() { return this->sb_metadata; }
 
     char* get_writable_data(size_t length)