;;; GNU Guix --- Functional package management for GNU ;;; Copyright © 2012, 2013, 2014 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))) (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