code: @Override
      void _parseMappings(String aStr, String aSourceRoot) {
          this.__generatedMappings = new ArrayList<>();
          this.__originalMappings = new ArrayList<>();
          for (int i = 0; i < this._sections.size(); i++) {
              ParsedSection section = this._sections.get(i);
              List<ParsedMapping> sectionMappings = section.consumer._generatedMappings();
              for (int j = 0; j < sectionMappings.size(); j++) {
                  ParsedMapping mapping = sectionMappings.get(j);
  
                  String source = section.consumer._sources.at(mapping.source);
                  if (section.consumer.sourceRoot != null) {
                      source = Util.join(section.consumer.sourceRoot, source);
                  }
                  this._sources.add(source);
                  Integer source_ = this._sources.indexOf(source);
  
                  String name = section.consumer._names.at(mapping.name);
                  this._names.add(name);
                  Integer name_ = this._names.indexOf(name);
  
                  // The mappings coming from the consumer for the section have
                  // generated positions relative to the start of the section, so we
                  // need to offset them to be relative to the start of the concatenated
                  // generated file.
                  ParsedMapping adjustedMapping = new ParsedMapping(mapping.generatedLine + (section.generatedOffset.generatedLine - 1),
                          mapping.generatedColumn + ((section.generatedOffset.generatedLine == mapping.generatedLine)
                                  ? section.generatedOffset.generatedColumn - 1 : 0),
                          mapping.originalLine, mapping.originalColumn, source_, name_);
  
                  this.__generatedMappings.add(adjustedMapping);
                  if (adjustedMapping.originalLine != null) {
                      this.__originalMappings.add(adjustedMapping);
                  }
              }
          }
  
          Collections.sort(this.__generatedMappings, Util::compareByGeneratedPositionsDeflated);
          Collections.sort(this.__originalMappings, Util::compareByOriginalPositions);
      }
docs: Parse the mappings in a string in to a data structure which we can easily query (the ordered arrays in the `this.__generatedMappings` and
  `this.__originalMappings` properties).