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⚡ Bolt: Optimize yEnc decoding performance #16

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⚡ Bolt: Optimize yEnc decoding performance #16

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36 changes: 25 additions & 11 deletions verify_nzb.py
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Original file line number Diff line number Diff line change
Expand Up @@ -115,19 +115,33 @@ def _parse_yenc_attrs(line: bytes) -> dict[str, str]:
return attrs


_YENC_TABLE = bytes((i - 42) % 256 for i in range(256))

def _decode_yenc_lines(lines: Iterable[bytes]) -> bytes:
joined = b"".join(lines)
if not joined:
return b""
parts = joined.split(b"=")
Comment on lines +121 to +124
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@chatgpt-codex-connector chatgpt-codex-connector Bot May 24, 2026

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P1 Badge Reject escapes that cross yEnc line boundaries

Parse escapes per source line instead of on b"".join(lines): the new split-based logic allows a line ending with = to consume the first byte of the next line, so malformed input no longer triggers dangling yEnc escape. This changes validation semantics and can produce false positives in validate_yenc_body when CRC is absent (e.g., =ybegin size=1, data lines b"=" + b"k", =yend size=1 now returns ok=True instead of rejecting the malformed body).

Useful? React with 👍 / 👎.

if len(parts) == 1:
return joined.translate(_YENC_TABLE)

decoded = bytearray()
for line in lines:
index = 0
while index < len(line):
byte = line[index]
if byte == 61:
index += 1
if index >= len(line):
raise ValueError("dangling yEnc escape")
byte = (line[index] - 64) % 256
decoded.append((byte - 42) % 256)
index += 1
decoded.extend(parts[0].translate(_YENC_TABLE))

iterator = iter(parts[1:])
for part in iterator:
if not part:
decoded.append(211) # (61 - 106) % 256
try:
next_part = next(iterator)
decoded.extend(next_part.translate(_YENC_TABLE))
except StopIteration:
raise ValueError("dangling yEnc escape")
else:
decoded.append((part[0] - 106) % 256)
if len(part) > 1:
decoded.extend(part[1:].translate(_YENC_TABLE))

Comment on lines +131 to +144
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@coderabbitai coderabbitai Bot May 24, 2026

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⚠️ Potential issue | 🟡 Minor | ⚡ Quick win

Use explicit exception chaining with from None.

When converting StopIteration to ValueError, use from None to indicate this is an intentional transformation rather than an error during exception handling. This improves debugging clarity and satisfies B904.

Proposed fix 
             except StopIteration:
-                raise ValueError("dangling yEnc escape")
+                raise ValueError("dangling yEnc escape") from None
📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change
iterator = iter(parts[1:])
for part in iterator:
if not part:
decoded.append(211) # (61 - 106) % 256
try:
next_part = next(iterator)
decoded.extend(next_part.translate(_YENC_TABLE))
except StopIteration:
raise ValueError("dangling yEnc escape")
else:
decoded.append((part[0] - 106) % 256)
if len(part) > 1:
decoded.extend(part[1:].translate(_YENC_TABLE))
iterator = iter(parts[1:])
for part in iterator:
if not part:
decoded.append(211) # (61 - 106) % 256
try:
next_part = next(iterator)
decoded.extend(next_part.translate(_YENC_TABLE))
except StopIteration:
raise ValueError("dangling yEnc escape") from None
else:
decoded.append((part[0] - 106) % 256)
if len(part) > 1:
decoded.extend(part[1:].translate(_YENC_TABLE))
🧰 Tools
🪛 Ruff (0.15.13)

[warning] 139-139: Within an except clause, raise exceptions with raise ... from err or raise ... from None to distinguish them from errors in exception handling

(B904)

🤖 Prompt for AI Agents 
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@verify_nzb.py` around lines 131 - 144, In the yEnc decoding loop where you
catch StopIteration (inside the for loop iterating over iterator =
iter(parts[1:])), re-raise the ValueError("dangling yEnc escape") using explicit
exception chaining suppression by writing "raise ValueError('dangling yEnc
escape') from None" so the StopIteration is intentionally masked; update the
except StopIteration block accordingly around the next_part = next(iterator)
handling.

return bytes(decoded)


Expand Down