ruzstd 0.2.3

A decoder for the zstd compression format
Documentation 
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extern crate ruzstd;
use std::fs::File;
use std::io::Read;
use std::io::Write;

struct StateTracker {
    bytes_used: u64,
    old_percentage: i8,
}

fn main() {
    let mut file_paths: Vec<_> = std::env::args().filter(|f| !f.starts_with('-')).collect();
    let flags: Vec<_> = std::env::args().filter(|f| f.starts_with('-')).collect();
    file_paths.remove(0);

    if !flags.contains(&"-d".to_owned()) {
        eprintln!("This zstd implementation only supports decompression. Please add a \"-d\" flag");
        return;
    }

    if !flags.contains(&"-c".to_owned()) {
        eprintln!("This zstd implementation only supports output on the stdout. Please add a \"-c\" flag and pipe the output into a file");
        return;
    }

    if flags.len() != 2 {
        eprintln!(
            "No flags other than -d and -c are currently implemented. Flags used: {:?}",
            flags
        );
        return;
    }

    let mut frame_dec = ruzstd::FrameDecoder::new();

    for path in file_paths {
        let mut tracker = StateTracker {
            bytes_used: 0,
            old_percentage: -1,
        };

        eprintln!("File: {}", path);
        let mut f = File::open(path).unwrap();

        frame_dec.reset(&mut f).unwrap();

        let batch_size = 1024 * 1024 * 10;
        let mut result = vec![0; batch_size];

        while !frame_dec.is_finished() {
            frame_dec
                .decode_blocks(&mut f, ruzstd::BlockDecodingStrategy::UptoBytes(batch_size))
                .unwrap();

            if frame_dec.can_collect() > batch_size {
                let x = frame_dec.read(result.as_mut_slice()).unwrap();

                result.resize(x, 0);
                do_something(&result, &mut tracker);
                result.resize(result.capacity(), 0);

                let percentage = (tracker.bytes_used * 100) / frame_dec.content_size().unwrap();
                if percentage as i8 != tracker.old_percentage {
                    eprint!("\r");
                    eprint!("{} % done", percentage);
                    tracker.old_percentage = percentage as i8;
                }
            }
        }

        // handle the last chunk of data
        while frame_dec.can_collect() > 0 {
            let x = frame_dec.read(result.as_mut_slice()).unwrap();

            result.resize(x, 0);
            do_something(&result, &mut tracker);
            result.resize(result.capacity(), 0);
        }

        eprintln!("\nDecoded bytes: {}", tracker.bytes_used);

        match frame_dec.get_checksum_from_data() {
            Some(chksum) => {
                if frame_dec.get_calculated_checksum().unwrap() != chksum {
                    eprintln!(
                        "Checksum did not match! From data: {}, calculated while decoding: {}",
                        chksum,
                        frame_dec.get_calculated_checksum().unwrap()
                    );
                } else {
                    eprintln!("Checksums are ok!");
                }
            }
            None => eprintln!("No checksums to test"),
        }
    }
}

fn do_something(data: &[u8], s: &mut StateTracker) {
    //Do something. Like writing it to a file or to stdout...
    std::io::stdout().write_all(data).unwrap();
    s.bytes_used += data.len() as u64;
}