build: Require GNU libgcrypt.

* guix/utils.scm (sha256): Remove Coreutils- and libchop-based
  implementations.
* README: Update accordingly.

* m4/guix.m4: New file.
* configure.ac: Use `GUIX_ASSERT_LIBGCRYPT_USABLE'.  Set and substitute
  `LIBGCRYPT_PREFIX'.
* Makefile.am (AM_DISTCHECK_CONFIGURE_FLAGS): Pass
  `--with-libgcrypt-prefix=$(LIBGCRYPT_PREFIX)'.

5 files changed, 52 insertions, 51 deletions

diff --git a/Makefile.am b/Makefile.am
index b06f575e6c..24fc22e2d3 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -172,4 +172,5 @@ EXTRA_DIST += doc/fdl-1.3.texi
 
 ACLOCAL_AMFLAGS = -I m4
 AM_DISTCHECK_CONFIGURE_FLAGS =			\
+  --with-libgcrypt-prefix="$(LIBGCRYPT_PREFIX)"	\
   --with-nix-prefix="$(NIX_PREFIX)"
diff --git a/README b/README
index 5be253bd49..02c1f34e2e 100644
--- a/README
+++ b/README
@@ -17,7 +17,7 @@ Guix currently depends on the following packages:
 
   - [[http://gnu.org/software/guile/][GNU Guile 2.0.x]]
   - [[http://nixos.org/nix/][Nix]]
-  - [[http://gnupg.org/][GNU libgcrypt]], or [[http://nongnu.org/libchop/][libchop]]
+  - [[http://gnupg.org/][GNU libgcrypt]]
 
 Optionally, packages from Nixpkgs may be transparently reused from Guix.
 For this to work, you need to have a checkout of the Nixpkgs repository;
diff --git a/configure.ac b/configure.ac
index 6d3d1482b4..cd07a54a3d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -65,9 +65,11 @@ AC_ARG_WITH([libgcrypt-prefix],
   [case "$withval" in
     yes|no)
       LIBGCRYPT="libgcrypt"
+      LIBGCRYPT_PREFIX="no"
       ;;
     *)
       LIBGCRYPT="$withval/lib/libgcrypt"
+      LIBGCRYPT_PREFIX="$withval"
       ;;
    esac],
   [LIBGCRYPT="libgcrypt"])
@@ -76,6 +78,10 @@ dnl Library name suitable for `dynamic-link'.
 AC_MSG_CHECKING([for libgcrypt shared library name])
 AC_MSG_RESULT([$LIBGCRYPT])
 AC_SUBST([LIBGCRYPT])
+AC_SUBST([LIBGCRYPT_PREFIX])
+
+GUIX_ASSERT_LIBGCRYPT_USABLE
+
 
 AC_CONFIG_FILES([Makefile
                  po/Makefile.in
diff --git a/guix/utils.scm b/guix/utils.scm
index 10b0c15fad..345ed374cd 100644
--- a/guix/utils.scm
+++ b/guix/utils.scm
@@ -394,58 +394,17 @@ starting from the right of S."
 ;;;
 
 (define sha256
-  (cond
-   ((compile-time-value
-     (false-if-exception (dynamic-link %libgcrypt)))
-    ;; Using libgcrypt.
-    (let ((hash   (pointer->procedure void
-                                      (dynamic-func "gcry_md_hash_buffer"
-                                                    (dynamic-link %libgcrypt))
-                                      `(,int * * ,size_t)))
-          (sha256 8))                           ; GCRY_MD_SHA256, as of 1.5.0
-      (lambda (bv)
-        "Return the SHA256 of BV as a bytevector."
-        (let ((digest (make-bytevector (/ 256 8))))
-          (hash sha256 (bytevector->pointer digest)
-                (bytevector->pointer bv) (bytevector-length bv))
-          digest))))
-
-   ((compile-time-value
-     (false-if-exception (resolve-interface '(chop hash))))
-    ;; Using libchop.
-    (let ((bytevector-hash    (@ (chop hash) bytevector-hash))
-          (hash-method/sha256 (@ (chop hash) hash-method/sha256)))
-      (lambda (bv)
-        "Return the SHA256 of BV as a bytevector."
-        (bytevector-hash hash-method/sha256 bv))))
-
-   (else
-    ;; Slow, poor programmer's implementation that uses Coreutils.
+  (let ((hash   (pointer->procedure void
+                                    (dynamic-func "gcry_md_hash_buffer"
+                                                  (dynamic-link %libgcrypt))
+                                    `(,int * * ,size_t)))
+        (sha256 8))                        ; GCRY_MD_SHA256, as of 1.5.0
     (lambda (bv)
       "Return the SHA256 of BV as a bytevector."
-      (let ((in  (pipe))
-            (out (pipe))
-            (pid (primitive-fork)))
-        (if (= 0 pid)
-            (begin                                 ; child
-              (close (cdr in))
-              (close (car out))
-              (close 0)
-              (close 1)
-              (dup2 (fileno (car in)) 0)
-              (dup2 (fileno (cdr out)) 1)
-              (execlp "sha256sum" "sha256sum"))
-            (begin                                 ; parent
-              (close (car in))
-              (close (cdr out))
-              (put-bytevector (cdr in) bv)
-              (close (cdr in))                     ; EOF
-              (let ((line (car (string-tokenize (read-line (car out))))))
-                (close (car out))
-                (and (and=> (status:exit-val (cdr (waitpid pid)))
-                            zero?)
-                     (base16-string->bytevector line))))))))))
-
+      (let ((digest (make-bytevector (/ 256 8))))
+        (hash sha256 (bytevector->pointer digest)
+              (bytevector->pointer bv) (bytevector-length bv))
+        digest))))
 
 
 ;;;
diff --git a/m4/guix.m4 b/m4/guix.m4
new file mode 100644
index 0000000000..29f928f653
--- /dev/null
+++ b/m4/guix.m4
@@ -0,0 +1,35 @@
+dnl Guix --- Nix package management from Guile.         -*- coding: utf-8 -*-
+dnl Copyright (C) 2012 Ludovic Courtès <ludo@gnu.org>
+dnl
+dnl This file is part of Guix.
+dnl
+dnl Guix is free software; you can redistribute it and/or modify it
+dnl under the terms of the GNU General Public License as published by
+dnl the Free Software Foundation; either version 3 of the License, or (at
+dnl your option) any later version.
+dnl
+dnl Guix is distributed in the hope that it will be useful, but
+dnl WITHOUT ANY WARRANTY; without even the implied warranty of
+dnl MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+dnl GNU General Public License for more details.
+dnl
+dnl You should have received a copy of the GNU General Public License
+dnl along with Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+dnl GUIX_ASSERT_LIBGCRYPT_USABLE
+dnl
+dnl Assert that GNU libgcrypt is usable from Guile.
+AC_DEFUN([GUIX_ASSERT_LIBGCRYPT_USABLE],
+  [AC_CACHE_CHECK([whether $LIBGCRYPT can be dynamically loaded],
+    [guix_cv_libgcrypt_usable_p],
+    [GUILE_CHECK([retval],
+      [(dynamic-func \"gcry_md_hash_buffer\" (dynamic-link \"$LIBGCRYPT\"))])
+     if test "$retval" = 0; then
+       guix_cv_libgcrypt_usable_p="yes"
+     else
+       guix_cv_libgcrypt_usable_p="no"
+     fi])
+
+   if test "x$guix_cv_libgcrypt_usable_p" != "xyes"; then
+     AC_MSG_ERROR([GNU libgcrypt does not appear to be usable; see `--with-libgcrypt-prefix' and `README'.])
+   fi])