Make line_col faster.#229
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229: Make line_col faster. r=ptersilie a=ltratt `line_col` was previously a linear search that called another function that does a linear search. This PR changes the first linear search into a binary search (b62cab2) and removes the second linear search entirely (2d61edb). This speeds up the easy bits of `line_col` significantly, moving us from `O(4n + x)` into `O(log_n + x)` where `n` is the number of lines in the file and `x` is whatever the cost to calculate the character offset from a line containing a string of bytes. Alas, this second thing is probably impossible to speed-up given that we're dealing with UTF-8. Still, this PR does at least address the most obviously egregious inefficiencies in `line_col` and it does so while decreasing the lines of code (allowing for the fact that I've added three lines of comments)! Co-authored-by: Laurence Tratt <laurie@tratt.net>
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96f2ebc should fix the bors error and will need squashing. bors try |
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Please squash. |
This reduces the amount of work `line_col` has to do, as we can infer the same information that `span_lines_str` has to calculate from scratch.
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line_colwas previously a linear search that called another function that does a linear search. This PR changes the first linear search into a binary search (b62cab2) and removes the second linear search entirely (2d61edb).This speeds up the easy bits of
line_colsignificantly, moving us fromO(4n + x)intoO(log_n + x)wherenis the number of lines in the file andxis whatever the cost to calculate the character offset from a line containing a string of bytes. Alas, this second thing is probably impossible to speed-up given that we're dealing with UTF-8. Still, this PR does at least address the most obviously egregious inefficiencies inline_coland it does so while decreasing the lines of code (allowing for the fact that I've added three lines of comments)!