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diff --git a/gnu/build/locale.scm b/gnu/build/locale.scm
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+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2019 Ludovic Courtès <ludo@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 build locale)
+  #:use-module (guix build utils)
+  #:use-module (srfi srfi-1)
+  #:use-module (ice-9 rdelim)
+  #:use-module (ice-9 match)
+  #:use-module (ice-9 regex)
+  #:export (build-locale
+            normalize-codeset
+            read-supported-locales))
+
+(define locale-rx
+  ;; Regexp matching a locale line in 'localedata/SUPPORTED'.
+  (make-regexp
+   "^[[:space:]]*([[:graph:]]+)/([[:graph:]]+)[[:space:]]*\\\\$"))
+
+(define (read-supported-locales port)
+  "Read the 'localedata/SUPPORTED' file from PORT.  That file is actually a
+makefile snippet, with one locale per line, and a header that can be
+discarded."
+  (let loop ((locales '()))
+    (define line
+      (read-line port))
+
+    (cond ((eof-object? line)
+           (reverse locales))
+          ((string-prefix? "#" (string-trim line)) ;comment
+           (loop locales))
+          ((string-contains line "=")            ;makefile variable assignment
+           (loop locales))
+          (else
+           (match (regexp-exec locale-rx line)
+             (#f
+              (loop locales))
+             (m
+              (loop (alist-cons (match:substring m 1)
+                                (match:substring m 2)
+                                locales))))))))
+
+(define (normalize-codeset codeset)
+  "Compute the \"normalized\" variant of CODESET."
+  ;; info "(libc) Using gettextized software", for the algorithm used to
+  ;; compute the normalized codeset.
+  (letrec-syntax ((-> (syntax-rules ()
+                        ((_ proc value)
+                         (proc value))
+                        ((_ proc rest ...)
+                         (proc (-> rest ...))))))
+    (-> (lambda (str)
+          (if (string-every char-set:digit str)
+              (string-append "iso" str)
+              str))
+        string-downcase
+        (lambda (str)
+          (string-filter char-set:letter+digit str))
+        codeset)))
+
+(define* (build-locale locale
+                       #:key
+                       (localedef "localedef")
+                       (directory ".")
+                       (codeset "UTF-8")
+                       (name (string-append locale "." codeset)))
+  "Compute locale data for LOCALE and CODESET--e.g., \"en_US\" and
+\"UTF-8\"--with LOCALEDEF, and store it in DIRECTORY under NAME."
+  (format #t "building locale '~a'...~%" name)
+  (invoke localedef "--no-archive" "--prefix" directory
+          "-i" locale "-f" codeset
+          (string-append directory "/" name)))