Add (guix download) and (guix build download).

* guix/download.scm, guix/build/download.scm: New files.
* Makefile.am (MODULES): Add them.
* tests/builders.scm ("url-fetch"): New test.
* distro/packages/bootstrap.scm (bootstrap-origin): Support
  `url-fetch'.
* guix/snix.scm (snix-derivation->guix-package): Use `url-fetch' instead
  of `http-fetch'.

Makefile.am

@@ -26,6 +26,7 @@ MODULES =					\
   guix/base32.scm				\
   guix/utils.scm				\
   guix/derivations.scm				\
+  guix/download.scm				\
   guix/build-system.scm				\
   guix/build-system/gnu.scm			\
   guix/build-system/trivial.scm			\
@@ -34,6 +35,7 @@ MODULES =					\
   guix/http.scm					\
   guix/store.scm				\
   guix/ui.scm					\
+  guix/build/download.scm			\
   guix/build/gnu-build-system.scm		\
   guix/build/ftp.scm				\
   guix/build/http.scm				\

distro/packages/bootstrap.scm

@@ -21,6 +21,7 @@
   #:use-module (guix packages)
   #:use-module (guix ftp)
   #:use-module (guix http)
+  #:use-module (guix download)
   #:use-module (guix build-system)
   #:use-module (guix build-system gnu)
   #:use-module (guix build-system trivial)
@@ -70,6 +71,8 @@
                      (boot http-fetch))
                     ((eq? orig-method ftp-fetch)
                      (boot ftp-fetch))
+                    ((eq? orig-method url-fetch)
+                     (boot url-fetch))
                     (else orig-method))))))
 
 (define (package-from-tarball name* source* program-to-test description*)

guix/build/download.scm

@@ -0,0 +1,157 @@
+;;; Guix --- Nix package management from Guile.         -*- coding: utf-8 -*-
+;;; Copyright (C) 2012 Ludovic Courtès <ludo@gnu.org>
+;;;
+;;; This file is part of Guix.
+;;;
+;;; 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.
+;;;
+;;; 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 Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (guix build download)
+  #:use-module (web uri)
+  #:use-module (web client)
+  #:use-module (web response)
+  #:use-module (guix ftp-client)
+  #:use-module (guix build utils)
+  #:use-module (rnrs io ports)
+  #:use-module (srfi srfi-11)
+  #:use-module (ice-9 match)
+  #:export (url-fetch))
+
+;;; Commentary:
+;;;
+;;; Fetch data such as tarballs over HTTP or FTP (builder-side code).
+;;;
+;;; Code:
+
+(define (ftp-fetch uri file)
+  "Fetch data from URI and write it to FILE.  Return FILE on success."
+  (let* ((conn (ftp-open (uri-host uri)))
+         (in   (ftp-retr conn (basename (uri-path uri))
+                         (dirname (uri-path uri)))))
+    (call-with-output-file file
+      (lambda (out)
+        ;; TODO: Show a progress bar.
+        (dump-port in out)))
+
+    (ftp-close conn))
+  file)
+
+(define (open-connection-for-uri uri)
+  "Return an open input/output port for a connection to URI.
+
+This is the same as Guile's `open-socket-for-uri', except that we always
+use a numeric port argument, to avoid the need to go through libc's NSS,
+which is not available during bootstrap."
+  (define addresses
+    (let ((port (or (uri-port uri)
+                    (case (uri-scheme uri)
+                      ((http) 80)           ; /etc/services, not for me!
+                      (else
+                       (error "unsupported URI scheme" uri))))))
+      (getaddrinfo (uri-host uri)
+                   (number->string port)
+                   AI_NUMERICSERV)))
+
+  (let loop ((addresses addresses))
+    (let* ((ai (car addresses))
+           (s  (with-fluids ((%default-port-encoding #f))
+                 (socket (addrinfo:fam ai) (addrinfo:socktype ai)
+                         (addrinfo:protocol ai)))))
+      (catch 'system-error
+        (lambda ()
+          (connect s (addrinfo:addr ai))
+
+          ;; Buffer input and output on this port.
+          (setvbuf s _IOFBF)
+          ;; Enlarge the receive buffer.
+          (setsockopt s SOL_SOCKET SO_RCVBUF (* 12 1024))
+          s)
+        (lambda args
+          ;; Connection failed, so try one of the other addresses.
+          (close s)
+          (if (null? addresses)
+              (apply throw args)
+              (loop (cdr addresses))))))))
+
+;; XXX: This is an awful hack to make sure the (set-port-encoding! p
+;; "ISO-8859-1") call in `read-response' passes, even during bootstrap
+;; where iconv is not available.
+(module-define! (resolve-module '(web response))
+                'set-port-encoding!
+                (lambda (p e) #f))
+
+(define (http-fetch uri file)
+  "Fetch data from URI and write it to FILE.  Return FILE on success."
+
+  ;; FIXME: Use a variant of `http-get' that returns a port instead of
+  ;; loading everything in memory.
+  (let*-values (((connection)
+                 (open-connection-for-uri uri))
+                ((resp bv)
+                 (http-get uri #:port connection #:decode-body? #f))
+                ((code)
+                 (response-code resp)))
+    (if (= 200 code)
+        (begin
+          (call-with-output-file file
+            (lambda (p)
+              (put-bytevector p bv)))
+          file)
+        (error "download failed" (uri->string uri)
+               code (response-reason-phrase resp)))))
+
+
+(define-syntax-rule (false-if-exception* body ...)
+  "Like `false-if-exception', but print the exception on the error port."
+  (catch #t
+    (lambda ()
+      body ...)
+    (lambda (key . args)
+      #f)
+    (lambda (key . args)
+      (print-exception (current-error-port) #f key args))))
+
+(define (url-fetch url file)
+  "Fetch FILE from URL; URL may be either a single string, or a list of
+string denoting alternate URLs for FILE.  Return #f on failure, and FILE
+on success."
+  (define uri
+    (match url
+      ((_ ...) (map string->uri url))
+      (_       (list (string->uri url)))))
+
+  (define (fetch uri file)
+    (format #t "starting download of `~a' from `~a'...~%"
+            file (uri->string uri))
+    (case (uri-scheme uri)
+      ((http)  (false-if-exception* (http-fetch uri file)))
+      ((ftp)   (false-if-exception* (ftp-fetch uri file)))
+      (else
+       (format #t "skipping URI with unsupported scheme: ~s~%"
+               uri)
+       #f)))
+
+  (setvbuf (current-output-port) _IOLBF)
+  (setvbuf (current-error-port) _IOLBF)
+
+  (let try ((uri uri))
+    (match uri
+      ((uri tail ...)
+       (or (fetch uri file)
+           (try tail)))
+      (()
+       (format (current-error-port) "failed to download ~s from ~s~%"
+               file url)
+       #f))))
+
+;;; download.scm ends here

guix/download.scm

@@ -0,0 +1,73 @@
+;;; Guix --- Nix package management from Guile.         -*- coding: utf-8 -*-
+;;; Copyright (C) 2012 Ludovic Courtès <ludo@gnu.org>
+;;;
+;;; This file is part of Guix.
+;;;
+;;; 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.
+;;;
+;;; 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 Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (guix download)
+  #:use-module (ice-9 match)
+  #:use-module (guix derivations)
+  #:use-module (guix packages)
+  #:use-module ((guix store) #:select (derivation-path?))
+  #:use-module (guix utils)
+  #:export (url-fetch))
+
+;;; Commentary:
+;;;
+;;; Produce fixed-output derivations with data fetched over HTTP or FTP.
+;;;
+;;; Code:
+
+(define* (url-fetch store url hash-algo hash
+                    #:optional name
+                    #:key (system (%current-system)) guile)
+  "Return the path of a fixed-output derivation in STORE that fetches
+URL (a string, or a list of strings denoting alternate URLs), which is
+expected to have hash HASH of type HASH-ALGO (a symbol).  By default,
+the file name is the base name of URL; optionally, NAME can specify a
+different file name."
+  (define builder
+    `(begin
+       (use-modules (guix build download))
+       (url-fetch ',url %output)))
+
+  (define guile-for-build
+    (match guile
+      ((? package?)
+       (package-derivation store guile system))
+      ((and (? string?) (? derivation-path?))
+       guile)
+      (#f                                         ; the default
+       (let* ((distro (resolve-interface '(distro packages base)))
+              (guile  (module-ref distro 'guile-final)))
+         (package-derivation store guile system)))))
+
+  (define file-name
+    (match url
+      ((head _ ...)
+       (basename head))
+      (_
+       (basename url))))
+
+  (build-expression->derivation store (or name file-name) system
+                                builder '()
+                                #:hash-algo hash-algo
+                                #:hash hash
+                                #:modules '((guix build download)
+                                            (guix build utils)
+                                            (guix ftp-client))
+                                #:guile-for-build guile-for-build))
+
+;;; download.scm ends here

guix/snix.scm

@@ -400,7 +400,7 @@ location of DERIVATION."
              (name ,name)
              (version ,version)
              (source (origin
-                      (method http-fetch)
+                      (method url-fetch)
                       (uri ,(pretty-uri (car urls) version))
                       (sha256
                        (base32

tests/builders.scm

@@ -19,6 +19,7 @@
 
 (define-module (test-builders)
   #:use-module (guix http)
+  #:use-module (guix download)
   #:use-module (guix build-system)
   #:use-module (guix build-system gnu)
   #:use-module (guix store)
@@ -63,6 +64,17 @@
          (file-exists? out-path)
          (valid-path? %store out-path))))
 
+(test-assert "url-fetch"
+  (let* ((url      '("http://ftp.gnu.org/gnu/hello/hello-2.8.tar.gz"
+                     "ftp://ftp.gnu.org/gnu/hello/hello-2.8.tar.gz"))
+         (hash     (nix-base32-string->bytevector
+                    "0wqd8sjmxfskrflaxywc7gqw7sfawrfvdxd9skxawzfgyy0pzdz6"))
+         (drv-path (url-fetch %store url 'sha256 hash))
+         (out-path (derivation-path->output-path drv-path)))
+    (and (build-derivations %store (list drv-path))
+         (file-exists? out-path)
+         (valid-path? %store out-path))))
+
 (test-assert "gnu-build-system"
   (and (build-system? gnu-build-system)
        (eq? gnu-build (build-system-builder gnu-build-system))))