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lzlib: Define 'dictionary-size+match-length-limit'.

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* guix/lzlib.scm (%compression-levels): Splice the rest of each element.
(dictionary-size+match-length-limit): New procedure.
(make-lzip-output-port, make-lzip-input-port/compressed): Use it.
* tests/lzlib.scm ("Bytevector of size relative to Lzip internal buffers (2 * dictionary)"):
Use 'dictionary-size+match-length-limit' instead of 'assoc-ref'.
This commit is contained in:
Ludovic Courtès 2020-01-16 21:42:27 +01:00
parent 584e46b1e0
commit 3597c0396b
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GPG Key ID: 090B11993D9AEBB5
2 changed files with 27 additions and 18 deletions
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42
guix/lzlib.scm
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@ -1,6 +1,6 @@
;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2019 Pierre Neidhardt <mail@ambrevar.xyz>
;;; Copyright © 2019 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2019, 2020 Ludovic Courtès <ludo@gnu.org>
;;;
;;; This file is part of GNU Guix.
;;;
@ -32,7 +32,8 @@
call-with-lzip-input-port
call-with-lzip-output-port
%default-member-length-limit
%default-compression-level))
%default-compression-level
dictionary-size+match-length-limit))
;;; Commentary:
;;;
@ -569,20 +570,27 @@ the number of uncompressed bytes written, a non-negative integer."
;; Alist of (levels (dictionary-size match-length-limit)). 0 is the fastest.
;; See bbexample.c in lzlib's source.
(define %compression-levels
`((0 (65535 16))
(1 (,(bitwise-arithmetic-shift-left 1 20) 5))
(2 (,(bitwise-arithmetic-shift-left 3 19) 6))
(3 (,(bitwise-arithmetic-shift-left 1 21) 8))
(4 (,(bitwise-arithmetic-shift-left 3 20) 12))
(5 (,(bitwise-arithmetic-shift-left 1 22) 20))
(6 (,(bitwise-arithmetic-shift-left 1 23) 36))
(7 (,(bitwise-arithmetic-shift-left 1 24) 68))
(8 (,(bitwise-arithmetic-shift-left 3 23) 132))
(9 (,(bitwise-arithmetic-shift-left 1 25) 273))))
`((0 65535 16)
(1 ,(bitwise-arithmetic-shift-left 1 20) 5)
(2 ,(bitwise-arithmetic-shift-left 3 19) 6)
(3 ,(bitwise-arithmetic-shift-left 1 21) 8)
(4 ,(bitwise-arithmetic-shift-left 3 20) 12)
(5 ,(bitwise-arithmetic-shift-left 1 22) 20)
(6 ,(bitwise-arithmetic-shift-left 1 23) 36)
(7 ,(bitwise-arithmetic-shift-left 1 24) 68)
(8 ,(bitwise-arithmetic-shift-left 3 23) 132)
(9 ,(bitwise-arithmetic-shift-left 1 25) 273)))
(define %default-compression-level
6)
(define (dictionary-size+match-length-limit level)
"Return two values: the dictionary size for LEVEL, and its match-length
limit. LEVEL must be a compression level, an integer between 0 and 9."
(match (assv-ref %compression-levels level)
((dictionary-size match-length-limit)
(values dictionary-size match-length-limit))))
(define* (make-lzip-input-port port)
"Return an input port that decompresses data read from PORT, a file port.
PORT is automatically closed when the resulting port is closed."
@ -602,8 +610,9 @@ PORT is automatically closed when the resulting port is closed."
"Return an output port that compresses data at the given LEVEL, using PORT,
a file port, as its sink. PORT is automatically closed when the resulting
port is closed."
(define encoder (apply lz-compress-open
(car (assoc-ref %compression-levels level))))
(define encoder
(call-with-values (lambda () (dictionary-size+match-length-limit level))
lz-compress-open))
(define (write! bv start count)
(lzwrite encoder bv port start count))
@ -626,8 +635,9 @@ port is closed."
(level %default-compression-level))
"Return an input port that compresses data read from PORT, with the given LEVEL.
PORT is automatically closed when the resulting port is closed."
(define encoder (apply lz-compress-open
(car (assoc-ref %compression-levels level))))
(define encoder
(call-with-values (lambda () (dictionary-size+match-length-limit level))
lz-compress-open))
(define input-buffer (make-bytevector 8192))
(define input-len 0)

3
tests/lzlib.scm
View File

@ -87,8 +87,7 @@
(test-assert* "Bytevector of size relative to Lzip internal buffers (2 * dictionary)"
(compress-and-decompress
(random-bytevector
(* 2 (car (car (assoc-ref (@@ (guix lzlib) %compression-levels)
(@@ (guix lzlib) %default-compression-level))))))))
(* 2 (dictionary-size+match-length-limit %default-compression-level)))))
(test-assert* "Bytevector of size relative to Lzip internal buffers (64KiB)"
(compress-and-decompress (random-bytevector (* 64 1024))))