Get class path from java class file

playground.rs

fn main() -> anyhow::Result<()> {
    println!("{}", get_name(include_bytes!("../Class.class"))?);
    Ok(())
}

fn get_name(cf: &[u8]) -> anyhow::Result<String> {
    use anyhow::Context;
    use classfile_parser::constant_info::ConstantInfo::{Class, Utf8};
    use classfile_parser::constant_info::ClassConstant;

    let cf = match classfile_parser::class_parser(&cf) {
        Ok((_, cf)) => cf,
        Err(e) => anyhow::bail!("Invalid class file: {}", e)
    };
    let ci = cf
        .const_pool
        .get(cf.this_class as usize - 1)
        .context(format!("this_class index {} out of bounds", cf.this_class))?;
    let name_index = match ci {
        Class(ClassConstant { name_index, .. }) => *name_index,
        _ => anyhow::bail!(
            "Expected a NameAndTypeConstant for this_class, found {:?}",
            ci
        )
    };
    let ci = cf.const_pool.get(name_index as usize - 1).context(format!(
        "name_index for this_class {} out of bounds",
        name_index
    ))?;
    let s = match ci {
        Utf8(s) => &s.utf8_string,
        _ => anyhow::bail!(
            "Expected a Utf8 constant for this_class' name, found {:?}",
            ci
        )
    };
    Ok(s.to_owned())
}