05/15: gexp: Micro-optimize sexp serialization.

[guix-commits]

civodul pushed a commit to branch wip-build-systems-gexp
in repository guix.

commit 0ffe892e215b2db7800fa0ca7829ad241dd51ce7
Author: Ludovic Courtès <ludo@gnu.org>
AuthorDate: Sat Mar 28 21:44:01 2015 +0100

    gexp: Micro-optimize sexp serialization.
    
    * guix/gexp.scm (sexp->string): New procedure.
    (gexp->derivation): Use it instead of 'object->string'.
---
 guix/gexp.scm | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/guix/gexp.scm b/guix/gexp.scm
index 620a86e..8e7e64b 100644
--- a/guix/gexp.scm
+++ b/guix/gexp.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2014, 2015, 2016, 2017, 2018, 2019, 2020 Ludovic Courtès 
<ludo@gnu.org>
+;;; Copyright © 2014, 2015, 2016, 2017, 2018, 2019, 2020, 2021 Ludovic Courtès 
<ludo@gnu.org>
 ;;; Copyright © 2018 Clément Lassieur <clement@lassieur.org>
 ;;; Copyright © 2018 Jan Nieuwenhuizen <janneke@gnu.org>
 ;;; Copyright © 2019, 2020 Mathieu Othacehe <m.othacehe@gmail.com>
@@ -943,6 +943,15 @@ second element is the derivation to compile them."
            modules
            system extensions guile deprecation-warnings module-path))
 
+(define (sexp->string sexp)
+  "Like 'object->string', but deterministic and slightly faster."
+  ;; Explicitly use UTF-8 for determinism, and also because UTF-8 output is
+  ;; faster.
+  (with-fluids ((%default-port-encoding "UTF-8"))
+    (call-with-output-string
+     (lambda (port)
+       (write sexp port)))))
+
 (define* (lower-gexp exp
                      #:key
                      (module-path %load-path)
@@ -1161,7 +1170,7 @@ The other arguments are as for 'derivation'."
                                        (return #f)))
                        (guile -> (lowered-gexp-guile lowered))
                        (builder  (text-file script-name
-                                            (object->string
+                                            (sexp->string
                                              (lowered-gexp-sexp lowered)))))
     (mbegin %store-monad
       (set-grafting graft?)                       ;restore the initial setting