1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
|
;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2012, 2013 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 union)
#:use-module (ice-9 ftw)
#: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 (tree-union
delete-duplicate-leaves
union-build))
;;; Commentary:
;;;
;;; Build a directory that is the union of a set of directories, using
;;; symbolic links.
;;;
;;; Code:
(define (tree-union trees)
"Return a tree that is the union of the trees listed in TREES. Each
tree has the form (PARENT LEAVES ...) or just LEAF, where each leaf is
itself a tree. "
(let loop ((trees trees))
(match trees
(() ; nothing left
'())
(_
(let ((dirs (filter pair? trees))
(leaves (remove pair? trees)))
`(,@leaves
,@(fold (lambda (dir result)
(cons `(,dir
,@(loop
(concatenate
(filter-map (match-lambda
((head children ...)
(and (equal? head dir)
children)))
dirs))))
result))
'()
(delete-duplicates (map car dirs)))))))))
(define* (delete-duplicate-leaves tree
#:optional
(leaf=? equal?)
(delete-duplicates (match-lambda
((head _ ...) head))))
"Delete duplicate leaves from TREE. Two leaves are considered equal
when LEAF=? applied to them returns #t. Each collision (list of leaves
that are LEAF=?) is passed to DELETE-DUPLICATES, which must return a
single leaf."
(let loop ((tree tree))
(match tree
((dir children ...)
(let ((dirs (filter pair? children))
(leaves (remove pair? children)))
(define collisions
(fold (lambda (leaf result)
(define same?
(cut leaf=? leaf <>))
(if (any (cut find same? <>) result)
result
(match (filter same? leaves)
((_)
result)
((collision ...)
(cons collision result)))))
'()
leaves))
(define non-collisions
(filter (lambda (leaf)
(match (filter (cut leaf=? leaf <>) leaves)
((_) #t)
((_ _ ..1) #f)))
leaves))
`(,dir
,@non-collisions
,@(map delete-duplicates collisions)
,@(map loop dirs))))
(leaf leaf))))
(define (file=? file1 file2)
"Return #t if the contents of FILE1 and FILE2 are identical, #f otherwise."
(and (= (stat:size (stat file1)) (stat:size (stat file2)))
(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 directories
#:key (log-port (current-error-port)))
"Build in the OUTPUT directory a symlink tree that is the union of all
the DIRECTORIES."
(define (file-tree dir)
;; Return the contents of DIR as a tree.
(define (others-have-it? subdir)
;; Return #t if other elements of DIRECTORIES have SUBDIR.
(let ((subdir (substring subdir (string-length dir))))
(any (lambda (other)
(and (not (string=? other dir))
(file-exists? (string-append other "/" subdir))))
directories)))
(match (file-system-fold (lambda (subdir stat result) ; enter?
;; No need to traverse DIR since there's
;; nothing to union it with. Thus, we avoid
;; creating a gazillon symlinks (think
;; share/emacs/24.3, share/texmf, etc.)
(or (string=? subdir dir)
(others-have-it? subdir)))
(lambda (file stat result) ; leaf
(match result
(((siblings ...) rest ...)
`((,file ,@siblings) ,@rest))))
(lambda (dir stat result) ; down
`(() ,@result))
(lambda (dir stat result) ; up
(match result
(((leaves ...) (siblings ...) rest ...)
`(((,(basename dir) ,@leaves) ,@siblings)
,@rest))))
(lambda (dir stat result) ; skip
;; DIR is not available elsewhere, so treat it
;; as a leaf.
(match result
(((siblings ...) rest ...)
`((,dir ,@siblings) ,@rest))))
(lambda (file stat errno result)
(format (current-error-port) "union-build: ~a: ~a~%"
file (strerror errno)))
'(())
dir)
(((tree)) tree)
(() #f)))
(define tree-leaves
;; Return the leaves of the given tree.
(match-lambda
(((? string?) leaves ...)
leaves)))
(define (leaf=? a b)
(equal? (basename a) (basename b)))
(define (resolve-collision leaves)
;; LEAVES all have the same basename, so choose one of them.
(match (delete-duplicates leaves string=?)
((one-and-the-same)
;; LEAVES all actually point to the same file, so nothing to worry
;; about.
one-and-the-same)
((and lst (head rest ...))
;; A real collision, unless those files are all identical.
(unless (every (cut file=? head <>) rest)
(format (current-error-port) "warning: collision encountered: ~{~a ~}~%"
lst)
;; TODO: Implement smarter strategies.
(format (current-error-port) "warning: arbitrarily choosing ~a~%"
head))
head)))
(setvbuf (current-output-port) _IOLBF)
(setvbuf (current-error-port) _IOLBF)
(when (file-port? log-port)
(setvbuf log-port _IOLBF))
(mkdir output)
(let loop ((tree (delete-duplicate-leaves
(cons "."
(tree-union
(append-map (compose tree-leaves file-tree)
(delete-duplicates directories))))
leaf=?
resolve-collision))
(dir '()))
(match tree
((? string?)
;; A leaf: create a symlink.
(let* ((dir (string-join dir "/"))
(target (string-append output "/" dir "/" (basename tree))))
(format log-port "`~a' ~~> `~a'~%" tree target)
(symlink tree target)))
(((? string? subdir) leaves ...)
;; A sub-directory: create it in OUTPUT, and iterate over LEAVES.
(unless (string=? subdir ".")
(let ((dir (string-join dir "/")))
(mkdir (string-append output "/" dir "/" subdir))))
(for-each (cute loop <> `(,@dir ,subdir))
leaves))
((leaves ...)
;; A series of leaves: iterate over them.
(for-each (cut loop <> dir) leaves)))))
;;; union.scm ends here
|