Redirect Follower — HTTP 301/302 Chain + Hop Guard (sigil-apps a17790d)

redirect_follow.sg is the T14 sprint — following an HTTP redirect chain (301→302→200) with a 5-hop guard. Each hop builds a synthetic HTTP response in resp_buf @0x440000, parses the status code and Location header via byte scan, and updates the current URL in scratch. Final status, hop count, and resolved URL stored at redir_buf @0x480000. REDIRECT-PASS 7/7. 13784 B arm-el0.

Redirect chain model

301/302 chain follower with 5-hop guard

redirect_follow(initial_url, max_hops) follows a redirect chain starting at initial_url. Each iteration proceeds in four steps:

1. Build response

Construct a synthetic HTTP response for the current URL in resp_buf @0x440000.

2. Parse status

Scan for two consecutive spaces after HTTP/1.1 ; extract the 3-digit decimal status code.

3. Follow redirect

If status is 301 or 302, scan for the Location: header; extract the URL value (from after Location: to the next CR); update current URL in scratch. Increment hop_count.

4. Terminate on 200

If status is 200, write final status + hop_count + resolved URL to redir_buf @0x480000 and return.

Hop guard: if hop_count >= max_hops (default 5), abort and write final status = 0 (timeout/loop) to redir_buf @0x480000.

redirect_follow(initial_url, max_hops=5)
  loop:
    build synthetic HTTP response → resp_buf @0x440000
    parse status code (scan after "HTTP/1.1 ")
    if status == 301 or 302:
      scan for "Location: " → extract URL to CR
      update current_url in scratch
      hop_count++
      if hop_count >= max_hops: write status=0 → redir_buf; return
      continue
    if status == 200:
      write { status=200, hop_count, resolved_url } → redir_buf @0x480000
      return

Test: 301→302→200 chain, 7 checks PASS:

Check	Expected	Result
initial status	301	PASS
hop1 Location correct	intermediate URL	PASS
hop2 status	302	PASS
hop2 Location correct	final URL	PASS
final status	200	PASS
hop_count	2	PASS
final URL correct	resolved destination	PASS

REDIRECT-PASS 7/7.