z230

26 Analyze one.py

@@ -0,0 +1,93 @@
+import binascii
+
+RAW_FILE = r"u:\PycharmProjects\NewsGroups\downloads\raw\part_001.raw"
+
+# --------------------------------------------------
+# yEnc decoder (offline, minimal, correct)
+# --------------------------------------------------
+def yenc_decode(lines: list[bytes]) -> bytes:
+    out = bytearray()
+
+    for line in lines:
+        # undo NNTP dot-stuffing
+        if line.startswith(b".."):
+            line = line[1:]
+        elif line.startswith(b"."):
+            line = line[1:]
+
+        i = 0
+        while i < len(line):
+            c = line[i]
+            if c == ord("="):
+                i += 1
+                c = (line[i] - 64) & 0xFF
+            out.append((c - 42) & 0xFF)
+            i += 1
+
+    return bytes(out)
+
+# --------------------------------------------------
+# 1. read RAW file
+# --------------------------------------------------
+with open(RAW_FILE, "rb") as f:
+    raw_lines = f.read().splitlines()
+
+print(f"📄 RAW lines: {len(raw_lines)}")
+
+# --------------------------------------------------
+# 2. split parts
+# --------------------------------------------------
+ybegin = None
+ypart = None
+yend = None
+data_lines = []
+
+for line in raw_lines:
+    if line.startswith(b"=ybegin"):
+        ybegin = line.decode(errors="replace")
+        continue
+
+    if line.startswith(b"=ypart"):
+        ypart = line.decode(errors="replace")
+        continue
+
+    if line.startswith(b"=yend"):
+        yend = line.decode(errors="replace")
+        continue
+
+    data_lines.append(line)
+
+print("🧾 ybegin:", ybegin)
+print("🧾 ypart :", ypart)
+print("🧾 yend  :", yend)
+print(f"📦 DATA lines: {len(data_lines)}")
+
+# --------------------------------------------------
+# 3. decode yEnc DATA
+# --------------------------------------------------
+decoded = yenc_decode(data_lines)
+
+print(f"📦 Decoded bytes: {len(decoded)}")
+
+# --------------------------------------------------
+# 4. extract pcrc32
+# --------------------------------------------------
+pcrc = None
+if "pcrc32=" in yend:
+    pcrc = yend.split("pcrc32=")[1].strip()
+
+if not pcrc:
+    raise RuntimeError("No pcrc32 found")
+
+# --------------------------------------------------
+# 5. compute CRC32
+# --------------------------------------------------
+crc_calc = f"{binascii.crc32(decoded) & 0xffffffff:08x}"
+
+print(f"🔎 CRC expected: {pcrc}")
+print(f"🔎 CRC computed: {crc_calc}")
+
+if crc_calc == pcrc:
+    print("✅ CRC MATCH — PART IS PERFECT")
+else:
+    print("❌ CRC MISMATCH — DATA IS BROKEN")