FLAC: SEEKTABLE .last not updated (when adding a PICTURE block and then saving back)

[PandorasFox]

Reproducer

No response

Summary

• tested embedding cover.png-type art into files
• some flacs with SEEKTABLE blocks seemingly had the seektable blocks orphaned
• ffprobing the files afterwards gives the following:

[flac @ 0x5637e1740f40] invalid sync code
[flac @ 0x5637e1740f40] invalid frame header
[flac @ 0x5637e1740f40] decode_frame() failed

I'll put together a minimal repro later next week; just wanted to get this one written up for now before I forget over the weekend - my quick python struct-munging script only sees orphaned SEEKTABLE blocks following newly written PICTURE blocks.

Expected behavior

No response

Assets

No response

[Serial-ATA]

Could you try out #617?

[PandorasFox]

Yup; just tested it with the following:

Details

use lofty::config::{ParseOptions, WriteOptions};
use lofty::file::AudioFile;
use lofty::flac::FlacFile;
use lofty::ogg::OggPictureStorage;
use lofty::picture::{MimeType, Picture, PictureType};
use std::io::BufReader;
use std::path::Path;

fn main() {
    let input_flac = Path::new("/tmp/seektable-repro/Wolfgun - LIGHTS - 01 Firmament.flac");
    let cover_png = Path::new("/tmp/seektable-repro/cover.png");
    let output_flac = Path::new("/tmp/seektable-repro/output-test.flac");

    std::fs::copy(input_flac, output_flac).expect("Failed to copy input FLAC");
    let image_data = std::fs::read(cover_png).expect("Failed to read cover.png");

    let picture = Picture::unchecked(image_data)
        .pic_type(PictureType::CoverFront)
        .mime_type(MimeType::Png)
        .build();

    let file = std::fs::File::open(output_flac).expect("Failed to open output FLAC");
    let mut reader = BufReader::new(file);
    let mut flac = FlacFile::read_from(&mut reader, ParseOptions::default())
        .expect("Failed to parse FLAC");
    drop(reader);

    flac.insert_picture(picture, None)
        .expect("Failed to insert picture");

    let write_opts = WriteOptions::new().preferred_padding(0);
    flac.save_to_path(output_flac, write_opts)
        .expect("Failed to save FLAC");
}

Dropping the .preferred_padding(0) (leftover from working around #607) also 'fixes' this edge case, as it turns out, but regardless: the new pull looks good to me and fixes this.