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+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2022 Mathieu Othacehe <othacehe@gnu.org>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (gnu compression)
+  #:use-module (guix gexp)
+  #:use-module (guix ui)
+  #:use-module ((gnu packages compression) #:hide (zip))
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-9)
+  #:use-module (ice-9 match)
+  #:export (compressor
+            compressor?
+            compressor-name
+            compressor-extension
+            compressor-command
+            %compressors
+            lookup-compressor))
+
+;; Type of a compression tool.
+(define-record-type <compressor>
+  (compressor name extension command)
+  compressor?
+  (name       compressor-name)      ;string (e.g., "gzip")
+  (extension  compressor-extension) ;string (e.g., ".lz")
+  (command    compressor-command))  ;gexp (e.g., #~(list "/gnu/store/…/gzip"
+                                    ;                    "-9n" ))
+
+(define %compressors
+  ;; Available compression tools.
+  (list (compressor "gzip"  ".gz"
+                    #~(list #+(file-append gzip "/bin/gzip") "-9n"))
+        (compressor "lzip"  ".lz"
+                    #~(list #+(file-append lzip "/bin/lzip") "-9"))
+        (compressor "xz"    ".xz"
+                    #~(append (list #+(file-append xz "/bin/xz")
+                                    "-e")
+                              (%xz-parallel-args)))
+        (compressor "bzip2" ".bz2"
+                    #~(list #+(file-append bzip2 "/bin/bzip2") "-9"))
+        (compressor "zstd" ".zst"
+                    ;; The default level 3 compresses better than gzip in a
+                    ;; fraction of the time, while the highest level 19
+                    ;; (de)compresses more slowly and worse than xz.
+                    #~(list #+(file-append zstd "/bin/zstd") "-3"))
+        (compressor "none" "" #f)))
+
+(define (lookup-compressor name)
+  "Return the compressor object called NAME.  Error out if it could not be
+found."
+  (or (find (match-lambda
+              (($ <compressor> name*)
+               (string=? name* name)))
+            %compressors)
+      (leave (G_ "~a: compressor not found~%") name)))