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Avoid needless allocation in read-bytevector!

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This change switches the implementation strategy to basing
read-bytevector on top of read-bytevector! rather than the other way
around.
This commit is contained in:
Vasilij Schneidermann 2024-03-17 19:47:30 +01:00
parent b303bf3611
commit d0e6dc7556
1 changed files with 13 additions and 20 deletions
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33
lib/scheme/extras.scm
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@ -136,15 +136,8 @@
#u8()
(let ((in (if (pair? o) (car o) (current-input-port)))
(res (make-bytevector n)))
(let lp ((i 0))
(if (>= i n)
res
(let ((x (read-u8 in)))
(cond ((eof-object? x)
(if (zero? i) x (subbytes res 0 i)))
(else
(bytevector-u8-set! res i x)
(lp (+ i 1))))))))))
(read-bytevector! res in)
res)))
(define (read-bytevector! vec . o)
(let* ((in (if (pair? o) (car o) (current-input-port)))
@ -152,19 +145,19 @@
(start (if (pair? o) (car o) 0))
(end (if (and (pair? o) (pair? (cdr o)))
(cadr o)
(bytevector-length vec))))
(bytevector-length vec)))
(n (- end start)))
(if (>= start end)
0
(let ((res (read-bytevector (- end start) in)))
(cond
((eof-object? res)
res)
(else
(let ((len (bytevector-length res)))
(do ((i 0 (+ i 1)))
((>= i len) len)
(bytevector-u8-set! vec (+ i start) (bytevector-u8-ref res i))
))))))))
(let lp ((i 0))
(if (>= i n)
i
(let ((x (read-u8 in)))
(cond ((eof-object? x)
(if (zero? i) x i))
(else
(bytevector-u8-set! vec (+ i start) x)
(lp (+ i 1))))))))))
(define (write-bytevector vec . o)
(let* ((out (if (pair? o) (car o) (current-output-port)))