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;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2012, 2013, 2014, 2016 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2014 Mark H Weaver <mhw@netris.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 union)
#:use-module (ice-9 match)
#:use-module (ice-9 format)
#:use-module (srfi srfi-1)
#:use-module (srfi srfi-26)
#:use-module (rnrs bytevectors)
#:use-module (rnrs io ports)
#:export (union-build))
;;; Commentary:
;;;
;;; Build a directory that is the union of a set of directories, using
;;; symbolic links.
;;;
;;; Code:
(define (files-in-directory dirname)
(let ((dir (opendir dirname)))
(let loop ((files '()))
(match (readdir dir)
((or "." "..")
(loop files))
((? eof-object?)
(closedir dir)
(sort files string<?))
(file
(loop (cons file files)))))))
(define (file-is-directory? file)
(eq? 'directory (stat:type (stat file))))
(define (file=? file1 file2)
"Return #t if FILE1 and FILE2 are regular files and their contents are
identical, #f otherwise."
(let ((st1 (stat file1))
(st2 (stat file2)))
;; When deduplication is enabled, identical files share the same inode.
(or (= (stat:ino st1) (stat:ino st2))
(and (eq? (stat:type st1) 'regular)
(eq? (stat:type st2) 'regular)
(= (stat:size st1) (stat:size st2))
(call-with-input-file file1
(lambda (port1)
(call-with-input-file file2
(lambda (port2)
(define len 8192)
(define buf1 (make-bytevector len))
(define buf2 (make-bytevector len))
(let loop ()
(let ((n1 (get-bytevector-n! port1 buf1 0 len))
(n2 (get-bytevector-n! port2 buf2 0 len)))
(and (equal? n1 n2)
(or (eof-object? n1)
(loop)))))))))))))
(define* (union-build output inputs
#:key (log-port (current-error-port)))
"Build in the OUTPUT directory a symlink tree that is the union of all
the INPUTS."
(define (symlink* input output)
(format log-port "`~a' ~~> `~a'~%" input output)
(symlink input output))
(define (resolve-collisions output dirs files)
(cond ((null? dirs)
;; The inputs are all files.
(format (current-error-port)
"warning: collision encountered: ~{~a ~}~%"
files)
(let ((file (first files)))
;; TODO: Implement smarter strategies.
(format (current-error-port)
"warning: arbitrarily choosing ~a~%"
file)
(symlink* file output)))
(else
;; The inputs are a mixture of files and directories
(error "union-build: collision between file and directories"
`((files ,files) (dirs ,dirs))))))
(define (union output inputs)
(match inputs
((input)
;; There's only one input, so just make a link.
(symlink* input output))
(_
(call-with-values (lambda () (partition file-is-directory? inputs))
(match-lambda*
((dirs ())
;; All inputs are directories.
(union-of-directories output dirs))
((() (file (? (cut file=? <> file)) ...))
;; There are no directories, and all files have the same contents,
;; so there's no conflict.
(symlink* file output))
((dirs files)
(resolve-collisions output dirs files)))))))
(define (union-of-directories output dirs)
;; Create a new directory where we will merge the input directories.
(mkdir output)
;; Build a hash table mapping each file to a list of input
;; directories containing that file.
(let ((table (make-hash-table)))
(define (add-to-table! file dir)
(hash-set! table file (cons dir (hash-ref table file '()))))
;; Populate the table.
(for-each (lambda (dir)
(for-each (cut add-to-table! <> dir)
(files-in-directory dir)))
dirs)
;; Now iterate over the table and recursively
;; perform a union for each entry.
(hash-for-each (lambda (file dirs-with-file)
(union (string-append output "/" file)
(map (cut string-append <> "/" file)
(reverse dirs-with-file))))
table)))
(setvbuf (current-output-port) _IOLBF)
(setvbuf (current-error-port) _IOLBF)
(when (file-port? log-port)
(setvbuf log-port _IOLBF))
(union-of-directories output (delete-duplicates inputs)))
;;; union.scm ends here
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