mes/guile/guix/shell-utils.scm

;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2013 Andreas Enge <andreas@enge.fr>
;;; Copyright © 2013 Nikita Karetnikov <nikita@karetnikov.org>
;;; Copyright © 2015 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 shell-utils)
  #:use-module (ice-9 match)
  #:use-module (ice-9 rdelim)
  #:use-module (ice-9 regex)
  #:use-module (srfi srfi-1)
  #:use-module (rnrs bytevectors)
  #:use-module (rnrs io ports)
  #:export (dump-port
            mkdir-p
            with-directory-excursion
            substitute
            substitute*))

;;;
;;; Directories.
;;;

(define (mkdir-p dir)
  "Create directory DIR and all its ancestors."
  (define absolute?
    (string-prefix? "/" dir))

  (define not-slash
    (char-set-complement (char-set #\/)))

  (let loop ((components (string-tokenize dir not-slash))
             (root       (if absolute?
                             ""
                             ".")))
    (match components
      ((head tail ...)
       (let ((path (string-append root "/" head)))
         (catch 'system-error
           (lambda ()
             (mkdir path)
             (loop tail path))
           (lambda args
             (if (= EEXIST (system-error-errno args))
                 (loop tail path)
                 (apply throw args))))))
      (() #t))))

(define-syntax-rule (with-directory-excursion dir body ...)
  "Run BODY with DIR as the process's current directory."
  (let ((init (getcwd)))
   (dynamic-wind
     (lambda ()
       (chdir dir))
     (lambda ()
       body ...)
     (lambda ()
       (chdir init)))))

(define* (dump-port in out
                    #:key (buffer-size 16384)
                    (progress (lambda (t k) (k))))
  "Read as much data as possible from IN and write it to OUT, using chunks of
BUFFER-SIZE bytes.  Call PROGRESS at the beginning and after each successful
transfer of BUFFER-SIZE bytes or less, passing it the total number of bytes
transferred and the continuation of the transfer as a thunk."
  (define buffer
    (make-bytevector buffer-size))

  (define (loop total bytes)
    (or (eof-object? bytes)
        (let ((total (+ total bytes)))
          (put-bytevector out buffer 0 bytes)
          (progress total
                    (lambda ()
                      (loop total
                            (get-bytevector-n! in buffer 0 buffer-size)))))))

  ;; Make sure PROGRESS is called when we start so that it can measure
  ;; throughput.
  (progress 0
            (lambda ()
              (loop 0 (get-bytevector-n! in buffer 0 buffer-size)))))


;;;
;;; Text substitution (aka. sed).
;;;

(define (with-atomic-file-replacement file proc)
  "Call PROC with two arguments: an input port for FILE, and an output
port for the file that is going to replace FILE.  Upon success, FILE is
atomically replaced by what has been written to the output port, and
PROC's result is returned."
  (let* ((template (string-append file ".XXXXXX"))
         (out      (mkstemp! template))
         (mode     (stat:mode (stat file))))
    (with-throw-handler #t
      (lambda ()
        (call-with-input-file file
          (lambda (in)
            (let ((result (proc in out)))
              (close out)
              (chmod template mode)
              (rename-file template file)
              result))))
      (lambda (key . args)
        (false-if-exception (delete-file template))))))

(define (substitute file pattern+procs)
  "PATTERN+PROCS is a list of regexp/two-argument-procedure pairs.  For each
line of FILE, and for each PATTERN that it matches, call the corresponding
PROC as (PROC LINE MATCHES); PROC must return the line that will be written as
a substitution of the original line.  Be careful about using '$' to match the
end of a line; by itself it won't match the terminating newline of a line."
  (let ((rx+proc  (map (match-lambda
                        (((? regexp? pattern) . proc)
                         (cons pattern proc))
                        ((pattern . proc)
                         (cons (make-regexp pattern regexp/extended)
                               proc)))
                       pattern+procs)))
    (with-atomic-file-replacement file
      (lambda (in out)
        (let loop ((line (read-line in 'concat)))
          (if (eof-object? line)
              #t
              (let ((line (fold (lambda (r+p line)
                                  (match r+p
                                    ((regexp . proc)
                                     (match (list-matches regexp line)
                                       ((and m+ (_ _ ...))
                                        (proc line m+))
                                       (_ line)))))
                                line
                                rx+proc)))
                (display line out)
                (loop (read-line in 'concat)))))))))


(define-syntax let-matches
  ;; Helper macro for `substitute*'.
  (syntax-rules (_)
    ((let-matches index match (_ vars ...) body ...)
     (let-matches (+ 1 index) match (vars ...)
                  body ...))
    ((let-matches index match (var vars ...) body ...)
     (let ((var (match:substring match index)))
       (let-matches (+ 1 index) match (vars ...)
                    body ...)))
    ((let-matches index match () body ...)
     (begin body ...))))

(define-syntax substitute*
  (syntax-rules ()
    "Substitute REGEXP in FILE by the string returned by BODY.  BODY is
evaluated with each MATCH-VAR bound to the corresponding positional regexp
sub-expression.  For example:

  (substitute* file
     ((\"hello\")
      \"good morning\\n\")
     ((\"foo([a-z]+)bar(.*)$\" all letters end)
      (string-append \"baz\" letter end)))

Here, anytime a line of FILE contains \"hello\", it is replaced by \"good
morning\".  Anytime a line of FILE matches the second regexp, ALL is bound to
the complete match, LETTERS is bound to the first sub-expression, and END is
bound to the last one.

When one of the MATCH-VAR is `_', no variable is bound to the corresponding
match substring.

Alternatively, FILE may be a list of file names, in which case they are
all subject to the substitutions.

Be careful about using '$' to match the end of a line; by itself it won't
match the terminating newline of a line."
    ((substitute* file ((regexp match-var ...) body ...) ...)
     (let ()
       (define (substitute-one-file file-name)
         (substitute
          file-name
          (list (cons regexp
                      (lambda (l m+)
                        ;; Iterate over matches M+ and return the
                        ;; modified line based on L.
                        (let loop ((m* m+)  ; matches
                                   (o  0)   ; offset in L
                                   (r  '())) ; result
                          (match m*
                            (()
                             (let ((r (cons (substring l o) r)))
                               (string-concatenate-reverse r)))
                            ((m . rest)
                             (let-matches 0 m (match-var ...)
                               (loop rest
                                     (match:end m)
                                     (cons*
                                      (begin body ...)
                                      (substring l o (match:start m))
                                      r))))))))
                ...)))

       (match file
         ((files (... ...))
          (for-each substitute-one-file files))
         ((? string? f)
          (substitute-one-file f)))))))