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Replace SHA function by something very fast #619

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Replace SHA function by something very fast #619

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21 changes: 13 additions & 8 deletions lib/markdown2.py
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Original file line number Diff line number Diff line change
Expand Up @@ -122,12 +122,10 @@
from abc import ABC, abstractmethod
import functools
from collections.abc import Iterable
from hashlib import sha256
from random import random
from typing import Any, Callable, Dict, List, Literal, Optional, Tuple, Type, TypedDict, Union
from collections.abc import Collection
from enum import IntEnum, auto
from os import urandom

# ---- type defs
_safe_mode = Literal['replace', 'escape']
Expand All @@ -143,11 +141,18 @@
DEFAULT_TAB_WIDTH = 4


SECRET_SALT = urandom(16)
# MD5 function was previously used for this; the "md5" prefix was kept for
# backwards compatibility.
# _hash_text is used to temporarily escape (replace) characters and HTML which
# should be ignored by the processor.
#
# Afterwards, we find stuff that looks like 'key32-???' and convert it back
# to the escaped things.
def _hash_text(s: str) -> str:
return 'md5-' + sha256(SECRET_SALT + s.encode("utf-8")).hexdigest()[32:]
h = hash(s) # Not cryptographically secure, and that's fine
h = abs(h)*2 + int(h>0) # As a non-negative number
h = hex(h)[2:34] # Convert to hex.
h = '0'*(32-len(h)) + h # Pad if needed
return 'key32-' + h
HASH_REGEX = r'key32-[0-9a-f]{32}'

# Table of hash values for escaped characters:
g_escape_table = {ch: _hash_text(ch)
Expand Down Expand Up @@ -1341,7 +1346,7 @@ def _is_code_span(index, token):
except IndexError:
return False

return re.match(r'<code>md5-[A-Fa-f0-9]{32}</code>', ''.join(peek_tokens))
return re.match('<code>' + HASH_REGEX + '</code>', ''.join(peek_tokens))

def _is_comment(token):
if self.safe_mode == 'replace':
Expand Down Expand Up @@ -2491,7 +2496,7 @@ def sub_hash(self, match: re.Match) -> str:
def test(self, text):
if self.md.order < Stage.ITALIC_AND_BOLD:
return '*' in text or '_' in text
return self.hash_table and re.search(r'md5-[0-9a-z]{32}', text)
return self.hash_table and re.search(HASH_REGEX, text)


class _LinkProcessorExtraOpts(TypedDict, total=False):
Expand Down