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etc/committer: Speed up surrounding-sexp. 

The old surrounding-sexp procedure would read all S-expressions from the
beginning of the file up to the given line number and then return the last
encountered S-expression.  This is quite wasteful.  Instead we can record all
lines that begin with an S-expression and jump straight to the offset closest
to the desired line number to read the S-expression there.

* etc/committer.scm.in (lines+offsets-with-opening-parens): New procedure.
(surrounding-sexp): Use it.
master
Ricardo Wurmus 2023-09-21 16:03:50 +02:00
parent 5027bc19d8
commit 670fc6ee50
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1 changed files with 32 additions and 14 deletions
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46
etc/committer.scm.in
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@ -85,21 +85,39 @@ the expression."
(seek port start SEEK_SET) (seek port start SEEK_SET)
result)) result))
(define (surrounding-sexp port line-no) (define (lines+offsets-with-opening-parens port)
"Record all line numbers (and their offsets) where an opening parenthesis is
found in column 0. The resulting list is in reverse order."
(let loop ((acc '())
(number 0))
(let ((line (read-line port)))
(cond
((eof-object? line) acc)
((string-prefix? "(" line)
(loop (cons (cons number ;line number
(- (ftell port)
(string-length line) 1)) ;offset
acc)
(1+ number)))
(else (loop acc (1+ number)))))))
(define (surrounding-sexp port target-line-no)
"Return the top-level S-expression surrounding the change at line number "Return the top-level S-expression surrounding the change at line number
LINE-NO in PORT." TARGET-LINE-NO in PORT."
(let loop ((i (1- line-no)) (let* ((line-numbers+offsets
(last-top-level-sexp #f)) (lines+offsets-with-opening-parens port))
(if (zero? i) (closest-offset
last-top-level-sexp (or (and=> (list-index (match-lambda
(match (peek-char port) ((line-number . offset)
(#\( (< line-number target-line-no)))
(let ((sexp (read-excursion port))) line-numbers+offsets)
(read-line port) (lambda (index)
(loop (1- i) sexp))) (match (list-ref line-numbers+offsets index)
(_ ((line-number . offset) offset))))
(read-line port) (error "Could not find surrounding S-expression for line"
(loop (1- i) last-top-level-sexp)))))) target-line-no))))
(seek port closest-offset SEEK_SET)
(read port)))
;;; Whether the hunk contains a newly added package (definition), a removed ;;; Whether the hunk contains a newly added package (definition), a removed
;;; package (removal) or something else (#false). ;;; package (removal) or something else (#false).