lib.rs

struct NoMemEntryStore<TSource: Read + Seek> {

    /// information about the archive as a whole
    archive: Archive,

    /// the input source of the archive
    source: TSource,
}

impl<TSource: Read + Seek> IndexStrategy for NoMemEntryStore<TSource> {

    fn find_exact(&self, name: &str) -> Result<Option<&Entry>, EntryParseError> {
        let archive = &self.archive;
        let mut source = &self.source;
        let opts = &opts_for_archive(
            &archive.archive_version, &archive.archive_type
        );

        source.seek(SeekFrom::Start(archive.archive_start as u64))?;

        for _i in 1 ..= archive.archive_size {
            let entry = Entry::load_from(&mut source, opts)?; // E0277 source doesn't implement Read

            if entry.0 == name {
                return Ok(Some(&entry.1));
            }
        }

        return Ok(None);
    }
}

// ...

impl Entry {
    pub fn load_from(
        source: &mut impl Read,
        archive_opts: &ArchiveOpts,
    ) -> Result<(String, Entry), EntryParseError> {
        let name = {
            let mut buffer = vec![0; archive_opts.name_size];
            source.read_exact(&mut buffer)?;
            cstring_from_bytes(&buffer)?.to_str()?.to_owned()
        };

        let offset = decode_u32(&mut source)?;
        let length = decode_u32(&mut source)?;
        let unknown = decode_u32(&mut source)?;

        return Ok((name, Entry { offset, length, unknown, }));
    }
}

out.txt

PS C:\Code\lod> cargo check
    Checking mysteriouspants-lod v0.1.0 (C:\Code\lod\lod)
error[E0277]: the trait bound `&TSource: std::io::Read` is not satisfied
   --> lod\src\lib.rs:200:42
    |
200 |             let entry = Entry::load_from(&mut source, opts)?;
    |                                          -^^^^^^^^^^
    |                                          |
    |                                          the trait `std::io::Read` is not implemented for `&TSource`
    |                                          help: consider removing 1 leading `&`-references
...
363 |     pub fn load_from(
    |            ---------
364 |         source: &mut impl Read,
    |                           ---- required by this bound in `Entry::load_from`