You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: fst_values_mapper.rs
    path of file: ./repos/greptimedb/src/index/src/inverted_index/search
    
    the code of the file until where you have to start completion: // Copyright 2023 Greptime Team
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicabl
    
    pub async fn map_values(&mut self, values: &[u64]) -> Result<BitVec> {
        let mut bitmap = BitVec::new();

        for value in values {
            // relative_offset (higher 32 bits), size (lower 32 bits)
            let [relative_offset, size] = bytemuck::cast::<u64, [u32; 2]>(*value);

            let bm = self
                .reader
                .bitmap(self.metadata, relative_offset, size)
                .await?;

            // Ensure the longest BitVec is the left operand to prevent truncation during OR.
            if bm.len() > bitmap.len() {
                bitmap = bm | bitmap
            } else {
                bitmap |= bm
            }
        }

        Ok(bitmap)
    }