Function wasi_fd_readdir

src/wrappers.rs:1190–1264

TODO: I'm not confident this works for multiple consecutive readdir calls to the same dir Correct behavior: truncate final entry

(
    ctx: &mut VmCtx,
    v_fd: SboxFd,
    buf: SboxFd,
    buf_len: usize,
    cookie: u64,
)

// TODO: I'm not confident this works for multiple consecutive readdir calls to the same dir
// Correct behavior: truncate final entry
pub fn wasi_fd_readdir(
    ctx: &mut VmCtx,
    v_fd: SboxFd,
    buf: SboxFd,
    buf_len: usize,
    cookie: u64,
) -> RuntimeResult<u32> {
    let fd = ctx.fdmap.fd_to_native(v_fd)?;

    let mut host_buf: Vec<u8> = Vec::new();
    host_buf.reserve_exact(buf_len as usize);

    let res = trace_getdents64(ctx, fd, &mut host_buf, buf_len)?;

    // the number of entries we have read so far. If less than cookie, don't output the directory
    let mut entry_idx = 0;
    let mut in_idx = 0;
    let mut out_idx = 0;

    let mut out_buf: Vec<u8> = Vec::new();

    while in_idx < host_buf.len() && out_idx < buf_len {
        body_invariant!(ctx_safe(ctx));
        body_invariant!(trace_safe(trace, ctx));
        body_invariant!(in_idx < host_buf.len());

        let dirent = Dirent::parse(&host_buf, in_idx)?;

        // if we haven't hit the cookie entry, skip
        if entry_idx < cookie {
            in_idx += dirent.reclen as usize;
            entry_idx += 1;
            continue;
        }

        let out_next = in_idx + 24 + dirent.out_namlen;

        // If we would overflow - don't :)
        if out_next > buf_len {
            break;
        }

        // Copy in next offset verbatim
        let out_next_bytes: [u8; 8] = out_next.to_le_bytes();
        out_buf.extend_from_slice(&out_next_bytes);

        // Copy in Inode verbatim
        let d_ino_bytes: [u8; 8] = dirent.ino.to_le_bytes();
        out_buf.extend_from_slice(&d_ino_bytes);

        // Copy namlen
        let out_namlen_bytes: [u8; 4] = (dirent.out_namlen as u32).to_le_bytes();
        out_buf.extend_from_slice(&out_namlen_bytes);

        // Copy type
        let d_type = Filetype::from(dirent.typ as libc::mode_t);
        let out_type_bytes: [u8; 4] = (d_type.to_wasi() as u32).to_le_bytes();
        out_buf.extend_from_slice(&out_type_bytes);