csv-txt-excel-parallel-toolkit 0.4.7

A parallel and fast command line toolkit for small and large (>10G) CSV, TXT, and EXCEL files, with a unified api.
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use crate::utils::cli_result::CliResult;
use std::fs::File;
use std::io::{BufRead, BufReader};
use std::path::Path;

pub fn run(path: &Path) -> CliResult {
    // read 20000 lines to estimate bytes per line
    let file = File::open(path)?;
    let filesize = file.metadata()?.len() as f64;

    let mut total_bytes = 0;
    let mut n = 0;
    for l in BufReader::new(file).lines().skip(1) {
        total_bytes += l.unwrap().len() + 1;
        n += 1;
        if n > 20000 {
            break;
        }
    }

    // estimate line count
    let mut estimate_n = filesize / ((total_bytes as f64) / (n as f64));

    // default to have a header
    if estimate_n > 1.0 {
        estimate_n -= 1.0;
    }

    println!("{}", estimate_n as usize);

    Ok(())
}