👌 IMPROVE: Backticks performance

Adds a cache `StateInline->backticks` which remembers
positions for every possible backtick closer.

The algorithm is similar to the one described here: mity/md4c@685b714

Implements: markdown-it/markdown-it@1e8aff0 and markdown-it/markdown-it@fece91e

Author: chrisjsewell

markdown_it/rules_inline/backticks.py

@@ -19,25 +19,37 @@ def backtick(state: StateInline, silent: bool) -> bool:
     pos += 1
     maximum = state.posMax
 
-    # /* ` */
-    while pos < maximum and (state.srcCharCode[pos] == 0x60):
+    # scan marker length
+    while pos < maximum and (state.srcCharCode[pos] == 0x60):  # /* ` */
         pos += 1
 
     marker = state.src[start:pos]
+    openerLength = len(marker)
+
+    if state.backticksScanned and state.backticks.get(openerLength, 0) <= start:
+        if not silent:
+            state.pending += marker
+        state.pos += openerLength
+        return True
 
     matchStart = matchEnd = pos
 
+    # Nothing found in the cache, scan until the end of the line (or until marker is found)
     while True:
         try:
             matchStart = state.src.index("`", matchEnd)
         except ValueError:
             break
         matchEnd = matchStart + 1
-        # /* ` */
-        while matchEnd < maximum and (state.srcCharCode[matchEnd] == 0x60):
+
+        # scan marker length
+        while matchEnd < maximum and (state.srcCharCode[matchEnd] == 0x60):  # /* ` */
             matchEnd += 1
 
-        if matchEnd - matchStart == len(marker):
+        closerLength = matchEnd - matchStart
+
+        if closerLength == openerLength:
+            # Found matching closer length.
             if not silent:
                 token = state.push("code_inline", "code", 0)
                 token.markup = marker
@@ -51,7 +63,13 @@ def backtick(state: StateInline, silent: bool) -> bool:
             state.pos = matchEnd
             return True
 
+        # Some different length found, put it in cache as upper limit of where closer can be found
+        state.backticks[closerLength] = matchStart
+
+    # Scanned through the end, didn't find anything
+    state.backticksScanned = True
+
     if not silent:
         state.pending += marker
-    state.pos += len(marker)
+    state.pos += openerLength
     return True

markdown_it/rules_inline/state_inline.py

@@ -72,6 +72,10 @@ def __init__(
         # Stack of delimiter lists for upper level tags
         self._prev_delimiters: List[List[Delimiter]] = []
 
+        # backticklength => last seen position
+        self.backticks: Dict[int, int] = {}
+        self.backticksScanned = False
+
     def __repr__(self):
         return (
             f"{self.__class__.__name__}"

tests/test_port/fixtures/commonmark_extras.md

@@ -330,6 +330,14 @@ Coverage. Unpaired nested backtick (silent mode)
 .
 
 
+Coverage. Should continue scanning after closing "```" despite cache
+.
+```aaa``bbb``ccc```ddd``eee``
+.
+<p><code>aaa``bbb``ccc</code>ddd<code>eee</code></p>
+.
+
+
 Coverage. Entities.
 .
 *&*