1 files changed, 106 insertions, 0 deletions
diff --git a/tools/chaprecheck.py b/tools/chaprecheck.py
new file mode 100644
index 0000000..c130acf
--- /dev/null
+++ b/tools/chaprecheck.py
@@ -0,0 +1,106 @@
+"""Second pass over the feeds whose ID3 tag did not fit the first window.
+
+Reads the declared tag size from the 10-byte header, then fetches exactly that much, so the
+answer does not depend on a guessed window. Also handles ID3v2.2, whose frame headers are
+6 bytes with 3-byte ids rather than 10 with 4 -- misparsing those is what made some of them
+look truncated in the first pass.
+"""
+import sys
+import urllib.request
+import xml.etree.ElementTree as ET
+
+UA = ("Mozilla/5.0 (Linux; Android 14) AppleWebKit/537.36 (KHTML, like Gecko) "
+      "Chrome/120.0.0.0 Mobile Safari/537.36 Listen/1.0")
+
+WANTED = {
+    "Cruising the Waves Podcast", "Conversations with Tyler", "Darknet Diaries",
+    "Dan Carlin's Hardcore History", "1619", "Common Sense with Dan Carlin", "Reply All",
+    "Dan Carlin's Hardcore History: Addendum", "Flesh and Code",
+    "Talk Easy with Sam Fragoso", "This American Life", "Hooked On Wooden Boats", "Humans",
+    "Dream Chasers and Eccentrics", "Paranormal Investigations Hawaii",
+}
+
+
+def get(url, rangebytes=None, timeout=40):
+    req = urllib.request.Request(url, headers={"User-Agent": UA})
+    if rangebytes:
+        req.add_header("Range", f"bytes={rangebytes[0]}-{rangebytes[1]}")
+    with urllib.request.urlopen(req, timeout=timeout) as r:
+        return r.read()
+
+
+def enclosure_of(feed_xml):
+    root = ET.fromstring(feed_xml)
+    for item in root.iter():
+        if item.tag.split('}')[-1] not in ("item", "entry"):
+            continue
+        for child in item:
+            if child.tag.split('}')[-1] == "enclosure":
+                return child.get("url")
+    return None
+
+
+def synchsafe(b):
+    return (b[0] << 21) | (b[1] << 14) | (b[2] << 7) | b[3]
+
+
+def scan(blob, major):
+    """Walk the frame list. v2.2 uses 3-byte ids and 3-byte sizes; v2.3/2.4 use 4 and 4."""
+    pos, ids = 10, []
+    while True:
+        if major == 2:
+            if pos + 6 > len(blob):
+                break
+            fid = blob[pos:pos + 3]
+            if not fid.strip(b"\x00"):
+                break
+            size = int.from_bytes(blob[pos + 3:pos + 6], "big")
+            step = 6 + size
+        else:
+            if pos + 10 > len(blob):
+                break
+            fid = blob[pos:pos + 4]
+            if not fid.strip(b"\x00"):
+                break
+            raw = blob[pos + 4:pos + 8]
+            size = synchsafe(raw) if major == 4 else int.from_bytes(raw, "big")
+            step = 10 + size
+        if size <= 0:
+            break
+        ids.append(fid.decode("latin-1"))
+        pos += step
+    return ids
+
+
+def check(name, url):
+    feed = get(url)
+    enclosure = enclosure_of(feed)
+    if not enclosure:
+        return name, "no enclosure", []
+    head = get(enclosure, rangebytes=(0, 9))
+    if not head.startswith(b"ID3"):
+        return name, "no ID3 tag at all", []
+    major = head[3]
+    size = synchsafe(head[6:10])
+    blob = get(enclosure, rangebytes=(0, 10 + size - 1))
+    got = len(blob) >= 10 + size
+    ids = scan(blob, major)
+    verdict = "CHAP PRESENT" if "CHAP" in ids else "no CHAP"
+    detail = f"v2.{major}, tag {size / 1024:.0f}KB, {'complete' if got else 'SHORT'}, frames: {sorted(set(ids))}"
+    return name, verdict, detail
+
+
+def main(path):
+    tree = ET.parse(path)
+    feeds = [(o.get("text"), o.get("xmlUrl"))
+             for o in tree.iter("outline") if o.get("xmlUrl") and o.get("text") in WANTED]
+    for name, url in feeds:
+        try:
+            n, verdict, detail = check(name, url)
+            print(f"{verdict:<14} {n[:42]:<42} {detail}", flush=True)
+        except Exception as e:
+            print(f"{'error':<14} {name[:42]:<42} {type(e).__name__}", flush=True)
+
+
+if __name__ == "__main__":
+    main(sys.argv[1])