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serialization: 'read-byte-string' makes a single read(2) call.

On "guix build libreoffice -nd", this reduces the number of read(2)
system calls from 10,434 to 8092.

* guix/serialization.scm (sub-bytevector): New procedure.
(read-byte-string): Make a single 'get-bytevector-n*' call and use
'sub-bytevector'.
gn-latest-20200428
Ludovic Courtès 2 years ago
parent
commit
01e5d63c87
No known key found for this signature in database GPG Key ID: 90B11993D9AEBB5
1 changed files with 15 additions and 4 deletions
  1. +15
    -4
      guix/serialization.scm

+ 15
- 4
guix/serialization.scm View File

@ -27,6 +27,7 @@
#:use-module ((ice-9 rdelim) #:prefix rdelim:)
#:use-module (ice-9 match)
#:use-module (ice-9 ftw)
#:use-module (system foreign)
#:export (write-int read-int
write-long-long read-long-long
write-padding
@ -80,6 +81,17 @@
(port port)))))
bv))
(define (sub-bytevector bv len)
"Return a bytevector that aliases the first LEN bytes of BV."
(define max (bytevector-length bv))
(cond ((= len max) bv)
((< len max)
;; Yes, this is safe because the result of each conversion procedure
;; has its life cycle synchronized with that of its argument.
(pointer->bytevector (bytevector->pointer bv) len))
(else
(error "sub-bytevector called to get a super bytevector"))))
(define (write-int n p)
(let ((b (make-bytevector 8 0)))
(bytevector-u32-set! b 0 n (endianness little))
@ -119,10 +131,9 @@
(define (read-byte-string p)
(let* ((len (read-int p))
(m (modulo len 8))
(bv (get-bytevector-n* p len)))
(or (zero? m)
(get-bytevector-n* p (- 8 m)))
bv))
(pad (if (zero? m) 0 (- 8 m)))
(bv (get-bytevector-n* p (+ len pad))))
(sub-bytevector bv len)))
(define (read-string p)
(utf8->string (read-byte-string p)))


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