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+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2017 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 (guix build download-nar)
+ #:use-module (guix build download)
+ #:use-module (guix build utils)
+ #:use-module (guix serialization)
+ #:use-module (guix zlib)
+ #:use-module (guix progress)
+ #:use-module (web uri)
+ #:use-module (srfi srfi-11)
+ #:use-module (srfi srfi-26)
+ #:use-module (ice-9 format)
+ #:use-module (ice-9 match)
+ #:export (download-nar))
+
+;;; Commentary:
+;;;
+;;; Download a normalized archive or "nar", similar to what 'guix substitute'
+;;; does. The intent here is to use substitute servers as content-addressed
+;;; mirrors of VCS checkouts. This is mostly useful for users who have
+;;; disabled substitutes.
+;;;
+;;; Code:
+
+(define (urls-for-item item)
+ "Return the fallback nar URL for ITEM--e.g.,
+\"/gnu/store/cabbag3…-foo-1.2-checkout\"."
+ ;; Here we hard-code nar URLs without checking narinfos. That's probably OK
+ ;; though.
+ ;; TODO: Use HTTPS? The downside is the extra dependency.
+ (let ((bases '("http://mirror.hydra.gnu.org/guix"
+ "http://berlin.guixsd.org"))
+ (item (basename item)))
+ (append (map (cut string-append <> "/nar/gzip/" item) bases)
+ (map (cut string-append <> "/nar/" item) bases))))
+
+(define (restore-gzipped-nar port item size)
+ "Restore the gzipped nar read from PORT, of SIZE bytes (compressed), to
+ITEM."
+ ;; Since PORT is typically a non-file port (for instance because 'http-get'
+ ;; returns a delimited port), create a child process so we're back to a file
+ ;; port that can be passed to 'call-with-gzip-input-port'.
+ (match (pipe)
+ ((input . output)
+ (match (primitive-fork)
+ (0
+ (dynamic-wind
+ (const #t)
+ (lambda ()
+ (close-port output)
+ (close-port port)
+ (catch #t
+ (lambda ()
+ (call-with-gzip-input-port input
+ (cut restore-file <> item)))
+ (lambda (key . args)
+ (print-exception (current-error-port)
+ (stack-ref (make-stack #t) 1)
+ key args)
+ (primitive-exit 1))))
+ (lambda ()
+ (primitive-exit 0))))
+ (child
+ (close-port input)
+ (dump-port* port output
+ #:reporter (progress-reporter/file item size
+ #:abbreviation
+ store-path-abbreviation))
+ (close-port output)
+ (newline)
+ (match (waitpid child)
+ ((_ . status)
+ (unless (zero? status)
+ (error "nar decompression failed" status)))))))))
+
+(define (download-nar item)
+ "Download and extract the normalized archive for ITEM. Return #t on
+success, #f otherwise."
+ ;; Let progress reports go through.
+ (setvbuf (current-error-port) _IONBF)
+ (setvbuf (current-output-port) _IONBF)
+
+ (let loop ((urls (urls-for-item item)))
+ (match urls
+ ((url rest ...)
+ (format #t "Trying content-addressed mirror at ~a...~%"
+ (uri-host (string->uri url)))
+ (let-values (((port size)
+ (catch #t
+ (lambda ()
+ (http-fetch (string->uri url)))
+ (lambda args
+ (values #f #f)))))
+ (if (not port)
+ (loop rest)
+ (begin
+ (if size
+ (format #t "Downloading from ~a (~,2h MiB)...~%" url
+ (/ size (expt 2 20.)))
+ (format #t "Downloading from ~a...~%" url))
+ (if (string-contains url "/gzip")
+ (restore-gzipped-nar port item size)
+ (begin
+ ;; FIXME: Add progress report.
+ (restore-file port item)
+ (close-port port)))
+ #t))))
+ (()
+ #f))))