[Bug]: Cannot load some Classic models with I/O error: failed to fill whole buffer

[t4cmyk]

Prerequisites

• I have searched existing issues to ensure this isn't a duplicate
• I am using the latest version or main branch

Bug Description

Most models work fine with the library but for some I get this error:

Failed to parse M2 'world\generic\passivedoodads\lights\generaltorch01.m2': I/O error: failed to fill whole buffer
Failed to parse M2 'world\azeroth\westfall\passivedoodads\lamppost\westfalllamppost02.m2': I/O error: failed to fill whole buffer
Failed to parse M2 'world\generic\passivedoodads\lights\candle02.m2': I/O error: failed to fill whole buffer

with this code:

    let m2_format = parse_m2(&mut Cursor::new(&m2_bytes))
        .inspect_err(|e| warn!("Failed to parse M2 '{}': {e}", m2_path))
        .ok()?;

While debugging the issue if found out that the problem seem related to the particle emitters.

Expected Behavior

The model files should load correctly.

Steps to Reproduce

See my code example above. I read the files through the wow_mpq::patch_chain::PatchChain but it also fails if I read the models from the filesystem directly.

Version

0.6.4

Rust Toolchain

rustc 1.94.1 (e408947bf 2026-03-25)

Operating System

Linux

Cargo Output

Backtrace

Additional Context

No response

[t4cmyk]

I just double-checked with the latest git version the bug is still reproducible with the Torch.m2 model and load_model example.

[warcraft-rs]$ cargo run --example load_model -- Torch.m2 
   Compiling built v0.7.7
   Compiling rav1e v0.7.1
   Compiling ravif v0.11.20
   Compiling image v0.25.6
   Compiling wow-blp v0.6.4 (/media/storage/Projects/warcraft-rs/file-formats/graphics/wow-blp)
   Compiling wow-m2 v0.6.4 (/media/storage/Projects/warcraft-rs/file-formats/graphics/wow-m2)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 11.84s
warning: the following packages contain code that will be rejected by a future version of Rust: num-bigint-dig v0.8.4
note: to see what the problems were, use the option `--future-incompat-report`, or run `cargo report future-incompatibilities --id 1`
     Running `target/debug/examples/load_model Torch.m2`
Loading model from: Torch.m2
Error: Io(Error { kind: UnexpectedEof, message: "failed to fill whole buffer" })

[t4cmyk]

I'm also pretty sure its caused by the particle emitters. When I remove this line the file works.

        // Parse particle emitters
        // let particle_emitters = read_array(reader, &header.particle_emitters.convert(), |r| {
        //     M2ParticleEmitter::parse(r, header.version)
        // })?;
        let particle_emitters = Vec::new();

[t4cmyk]

This might or might not be related to this issue but from the same version there is also a problem for reading lights and texture_animations. At least I couldn't load Interface\Glues\Models\UI_MainMenu\UI_MainMenu.m2 unless I removed those parts as well. M2Model::parse