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Speed up processing junk before or after first or last boundary #178

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defnull wants to merge 2 commits into from
+11 −4
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Speed up processing junk before or after first or last boundary #178

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6ed5a49
fix: Reduce overhead while parsing junk
defnull Oct 28, 2024
89eb2ae
change: Fail if there is too much junk
defnull Oct 28, 2024
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15 changes: 11 additions & 4 deletions python_multipart/multipart.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1102,10 +1102,17 @@ def data_callback(name: CallbackName, end_i: int, remaining: bool = False) -> No
c = data[i]

if state == MultipartState.START:
# Stop parsing if there is no boundary within the first chunk
if i == 16:
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@Kludex Kludex Oct 28, 2024

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Why 16?

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@defnull defnull Oct 28, 2024

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Yea, I'm not happy about that either. Two line breaks should be allowed, that's not that uncommon. More are uncommon, but who knows? It's just an arbitrary number between 2 and "too much to waste time on it". Maybe ignore the second commit for now and just remove the log lines?

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@defnull defnull Oct 28, 2024 •
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The comment is lying, I was first checking for i == length-1 but that broke tests. This needs more work I guess.

msg = "Too much junk in front of first boundary (%d)" % (i,)
self.logger.warning(msg)
e = MultipartParseError(msg)
e.offset = i
raise e

# Skip leading newlines
if c == CR or c == LF:
i += 1
self.logger.debug("Skipping leading CR/LF at %d", i)
continue

# index is used as in index into our boundary. Set to 0.
Expand Down Expand Up @@ -1398,9 +1405,9 @@ def data_callback(name: CallbackName, end_i: int, remaining: bool = False) -> No
i -= 1

elif state == MultipartState.END:
# Do nothing and just consume a byte in the end state.
if c not in (CR, LF):
self.logger.warning("Consuming a byte '0x%x' in the end state", c) # pragma: no cover
# Skip junk after the last boundary
i = length
break

else: # pragma: no cover (error case)
# We got into a strange state somehow! Just stop processing.
Expand Down