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Optimize max_line_len #1109

Merged
merged 1 commit into from Nov 14, 2021
Merged

Optimize max_line_len #1109

merged 1 commit into from Nov 14, 2021

Commits on Nov 14, 2021

  1. Optimize max_line_len 

    The old max_line_len code fell into a surprising slowdown where repeatedly inserting chars in the middle of a string falls into O(n^2) behavior. Surprising because V8 already implements advanced data structures for string slicing and joining (`SlicedString` and `ConsString`). It seems like this should be easily handled by the two.

Anyways, we avoid this by slowing building a committed string (which is unlikely to be changed). Whenever we insert, we commit the left hand side, and can avoid slicing it in the future.

In testing a 5mb file (done by repeating a program several times), I dropped the simple parse+output case from 5min to 5sec.
    @jridgewell
    jridgewell committed Nov 14, 2021
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