guix/guix/utils.scm

;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2012, 2013, 2014 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2013 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 utils)
  #:use-module (guix config)
  #:use-module (srfi srfi-1)
  #:use-module (srfi srfi-9)
  #:use-module (srfi srfi-26)
  #:use-module (srfi srfi-39)
  #:use-module (srfi srfi-60)
  #:use-module (rnrs bytevectors)
  #:use-module ((rnrs io ports) #:select (put-bytevector))
  #:use-module ((guix build utils) #:select (dump-port))
  #:use-module (ice-9 vlist)
  #:use-module (ice-9 format)
  #:autoload   (ice-9 popen)  (open-pipe*)
  #:autoload   (ice-9 rdelim) (read-line)
  #:use-module (ice-9 regex)
  #:use-module (ice-9 match)
  #:use-module (ice-9 format)
  #:use-module (system foreign)
  #:export (bytevector->base16-string
            base16-string->bytevector

            %nixpkgs-directory
            nixpkgs-derivation
            nixpkgs-derivation*

            compile-time-value
            fcntl-flock
            memoize
            default-keyword-arguments
            substitute-keyword-arguments

            <location>
            location
            location?
            location-file
            location-line
            location-column
            source-properties->location

            gnu-triplet->nix-system
            %current-system
            %current-target-system
            version-compare
            version>?
            guile-version>?
            package-name->name+version
            string-tokenize*
            string-replace-substring
            file-extension
            file-sans-extension
            call-with-temporary-output-file
            with-atomic-file-output
            fold2
            filtered-port))


;;;
;;; Compile-time computations.
;;;

(define-syntax compile-time-value
  (syntax-rules ()
    "Evaluate the given expression at compile time.  The expression must
evaluate to a simple datum."
    ((_ exp)
     (let-syntax ((v (lambda (s)
                       (let ((val exp))
                         (syntax-case s ()
                           (_ #`'#,(datum->syntax s val)))))))
       v))))


;;;
;;; Base 16.
;;;

(define (bytevector->base16-string bv)
  "Return the hexadecimal representation of BV's contents."
  (define len
    (bytevector-length bv))

  (let-syntax ((base16-chars (lambda (s)
                               (syntax-case s ()
                                 (_
                                  (let ((v (list->vector
                                            (unfold (cut > <> 255)
                                                    (lambda (n)
                                                      (format #f "~2,'0x" n))
                                                    1+
                                                    0))))
                                    v))))))
    (define chars base16-chars)
    (let loop ((i 0)
               (r '()))
      (if (= i len)
          (string-concatenate-reverse r)
          (loop (+ 1 i)
                (cons (vector-ref chars (bytevector-u8-ref bv i)) r))))))

(define base16-string->bytevector
  (let ((chars->value (fold (lambda (i r)
                              (vhash-consv (string-ref (number->string i 16)
                                                       0)
                                           i r))
                            vlist-null
                            (iota 16))))
    (lambda (s)
      "Return the bytevector whose hexadecimal representation is string S."
      (define bv
        (make-bytevector (quotient (string-length s) 2) 0))

      (string-fold (lambda (chr i)
                     (let ((j (quotient i 2))
                           (v (and=> (vhash-assv chr chars->value) cdr)))
                       (if v
                           (if (zero? (logand i 1))
                               (bytevector-u8-set! bv j
                                                   (arithmetic-shift v 4))
                               (let ((w (bytevector-u8-ref bv j)))
                                 (bytevector-u8-set! bv j (logior v w))))
                           (error "invalid hexadecimal character" chr)))
                     (+ i 1))
                   0
                   s)
      bv)))



;;;
;;; Filtering & pipes.
;;;

(define (filtered-port command input)
  "Return an input port where data drained from INPUT is filtered through
COMMAND (a list).  In addition, return a list of PIDs that the caller must
wait.  When INPUT is a file port, it must be unbuffered; otherwise, any
buffered data is lost."
  (let loop ((input input)
             (pids  '()))
    (if (file-port? input)
        (match (pipe)
          ((in . out)
           (match (primitive-fork)
             (0
              (dynamic-wind
                (const #f)
                (lambda ()
                  (close-port in)
                  (close-port (current-input-port))
                  (dup2 (fileno input) 0)
                  (close-port (current-output-port))
                  (dup2 (fileno out) 1)
                  (catch 'system-error
                    (lambda ()
                      (apply execl (car command) command))
                    (lambda args
                      (format (current-error-port)
                              "filtered-port: failed to execute '~{~a ~}': ~a~%"
                              command (strerror (system-error-errno args))))))
                (lambda ()
                  (primitive-_exit 1))))
             (child
              (close-port out)
              (values in (cons child pids))))))

        ;; INPUT is not a file port, so fork just for the sake of tunneling it
        ;; through a file port.
        (match (pipe)
          ((in . out)
           (match (primitive-fork)
             (0
              (dynamic-wind
                (const #t)
                (lambda ()
                  (close-port in)
                  (dump-port input out))
                (lambda ()
                  (false-if-exception (close out))
                  (primitive-_exit 0))))
             (child
              (close-port out)
              (loop in (cons child pids)))))))))


;;;
;;; Nixpkgs.
;;;

(define %nixpkgs-directory
  (make-parameter
   ;; Capture the build-time value of $NIXPKGS.
   (or %nixpkgs
       (and=> (getenv "NIXPKGS")
              (lambda (val)
                ;; Bail out when passed an empty string, otherwise
                ;; `nix-instantiate' will sit there and attempt to read
                ;; from its standard input.
                (if (string=? val "")
                    #f
                    val))))))

(define* (nixpkgs-derivation attribute #:optional (system (%current-system)))
  "Return the derivation path of ATTRIBUTE in Nixpkgs."
  (let* ((p (open-pipe* OPEN_READ (or (getenv "NIX_INSTANTIATE")
                                      %nix-instantiate)
                        "-A" attribute (%nixpkgs-directory)
                        "--argstr" "system" system))
         (l (read-line p))
         (s (close-pipe p)))
    (and (zero? (status:exit-val s))
         (not (eof-object? l))
         l)))

(define-syntax-rule (nixpkgs-derivation* attribute)
  "Evaluate the given Nixpkgs derivation at compile-time."
  (compile-time-value (nixpkgs-derivation attribute)))


;;;
;;; Advisory file locking.
;;;

(define %struct-flock
  ;; 'struct flock' from <fcntl.h>.
  (list short                                     ; l_type
        short                                     ; l_whence
        size_t                                    ; l_start
        size_t                                    ; l_len
        int))                                     ; l_pid

(define F_SETLKW
  ;; On Linux-based systems, this is usually 7, but not always
  ;; (exceptions include SPARC.)  On GNU/Hurd, it's 9.
  (compile-time-value
   (cond ((string-contains %host-type "sparc") 9) ; sparc-*-linux-gnu
         ((string-contains %host-type "linux") 7) ; *-linux-gnu
         (else 9))))                              ; *-gnu*

(define F_SETLK
  ;; Likewise: GNU/Hurd and SPARC use 8, while the others typically use 6.
  (compile-time-value
   (cond ((string-contains %host-type "sparc") 8) ; sparc-*-linux-gnu
         ((string-contains %host-type "linux") 6) ; *-linux-gnu
         (else 8))))                              ; *-gnu*

(define F_xxLCK
  ;; The F_RDLCK, F_WRLCK, and F_UNLCK constants.
  (compile-time-value
   (cond ((string-contains %host-type "sparc") #(1 2 3))    ; sparc-*-linux-gnu
         ((string-contains %host-type "hppa")  #(1 2 3))    ; hppa-*-linux-gnu
         ((string-contains %host-type "linux") #(0 1 2))    ; *-linux-gnu
         (else                                 #(1 2 3))))) ; *-gnu*

(define %libc-errno-pointer
  ;; Glibc's 'errno' pointer.
  (let ((errno-loc (dynamic-func "__errno_location" (dynamic-link))))
    (and errno-loc
         (let ((proc (pointer->procedure '* errno-loc '())))
           (proc)))))

(define (errno)
  "Return the current errno."
  ;; XXX: We assume that nothing changes 'errno' while we're doing all this.
  ;; In particular, that means that no async must be running here.
  (if %libc-errno-pointer
      (let ((bv (pointer->bytevector %libc-errno-pointer (sizeof int))))
        (bytevector-sint-ref bv 0 (native-endianness) (sizeof int)))
      0))

(define fcntl-flock
  (let* ((ptr  (dynamic-func "fcntl" (dynamic-link)))
         (proc (pointer->procedure int ptr `(,int ,int *))))
    (lambda* (fd-or-port operation #:key (wait? #t))
      "Perform locking OPERATION on the file beneath FD-OR-PORT.  OPERATION
must be a symbol, one of 'read-lock, 'write-lock, or 'unlock.  When WAIT? is
true, block until the lock is acquired; otherwise, thrown an 'flock-error'
exception if it's already taken."
      (define (operation->int op)
        (case op
          ((read-lock)  (vector-ref F_xxLCK 0))
          ((write-lock) (vector-ref F_xxLCK 1))
          ((unlock)     (vector-ref F_xxLCK 2))
          (else         (error "invalid fcntl-flock operation" op))))

      (define fd
        (if (port? fd-or-port)
            (fileno fd-or-port)
            fd-or-port))

      ;; XXX: 'fcntl' is a vararg function, but here we happily use the
      ;; standard ABI; crossing fingers.
      (let ((err (proc fd
                       (if wait?
                           F_SETLKW               ; lock & wait
                           F_SETLK)               ; non-blocking attempt
                       (make-c-struct %struct-flock
                                      (list (operation->int operation)
                                            SEEK_SET
                                            0 0   ; whole file
                                            0)))))
        (or (zero? err)

            ;; Presumably we got EAGAIN or so.
            (throw 'flock-error (errno)))))))


;;;
;;; Miscellaneous.
;;;

(define (memoize proc)
  "Return a memoizing version of PROC."
  (let ((cache (make-hash-table)))
    (lambda args
      (let ((results (hash-ref cache args)))
        (if results
            (apply values results)
            (let ((results (call-with-values (lambda ()
                                               (apply proc args))
                             list)))
              (hash-set! cache args results)
              (apply values results)))))))

(define (default-keyword-arguments args defaults)
  "Return ARGS augmented with any keyword/value from DEFAULTS for
keywords not already present in ARGS."
  (let loop ((defaults defaults)
             (args     args))
    (match defaults
      ((kw value rest ...)
       (loop rest
             (if (assoc-ref kw args)
                 args
                 (cons* kw value args))))
      (()
       args))))

(define-syntax substitute-keyword-arguments
  (syntax-rules ()
    "Return a new list of arguments where the value for keyword arg KW is
replaced by EXP.  EXP is evaluated in a context where VAR is boud to the
previous value of the keyword argument."
    ((_ original-args ((kw var) exp) ...)
     (let loop ((args    original-args)
                (before '()))
       (match args
         ((kw var rest (... ...))
          (loop rest (cons* exp kw before)))
         ...
         ((x rest (... ...))
          (loop rest (cons x before)))
         (()
          (reverse before)))))))

(define (gnu-triplet->nix-system triplet)
  "Return the Nix system type corresponding to TRIPLET, a GNU triplet as
returned by `config.guess'."
  (let ((triplet (cond ((string-match "^i[345]86-(.*)$" triplet)
                        =>
                        (lambda (m)
                          (string-append "i686-" (match:substring m 1))))
                       (else triplet))))
    (cond ((string-match "^([^-]+)-([^-]+-)?linux-gnu.*" triplet)
           =>
           (lambda (m)
             ;; Nix omits `-gnu' for GNU/Linux.
             (string-append (match:substring m 1) "-linux")))
          ((string-match "^([^-]+)-([^-]+-)?([[:alpha:]]+)([0-9]+\\.?)*$" triplet)
           =>
           (lambda (m)
             ;; Nix strip the version number from names such as `gnu0.3',
             ;; `darwin10.2.0', etc., and always strips the vendor part.
             (string-append (match:substring m 1) "-"
                            (match:substring m 3))))
          (else triplet))))

(define %current-system
  ;; System type as expected by Nix, usually ARCHITECTURE-KERNEL.
  ;; By default, this is equal to (gnu-triplet->nix-system %host-type).
  (make-parameter %system))

(define %current-target-system
  ;; Either #f or a GNU triplet representing the target system we are
  ;; cross-building to.
  (make-parameter #f))

(define version-compare
  (let ((strverscmp
         (let ((sym (or (dynamic-func "strverscmp" (dynamic-link))
                        (error "could not find `strverscmp' (from GNU libc)"))))
           (pointer->procedure int sym (list '* '*)))))
    (lambda (a b)
      "Return '> when A denotes a newer version than B,
'< when A denotes a older version than B,
or '= when they denote equal versions."
      (let ((result (strverscmp (string->pointer a) (string->pointer b))))
        (cond ((positive? result) '>)
              ((negative? result) '<)
              (else '=))))))

(define (version>? a b)
  "Return #t when A denotes a newer version than B."
  (eq? '> (version-compare a b)))

(define (guile-version>? str)
  "Return #t if the running Guile version is greater than STR."
  ;; Note: Using (version>? (version) "2.0.5") or similar doesn't work,
  ;; because the result of (version) can have a prefix, like "2.0.5-deb1".
  (version>? (string-append (major-version) "."
                            (minor-version) "."
                            (micro-version))
             str))

(define (package-name->name+version name)
  "Given NAME, a package name like \"foo-0.9.1b\", return two values:
\"foo\" and \"0.9.1b\".  When the version part is unavailable, NAME and
#f are returned.  The first hyphen followed by a digit is considered to
introduce the version part."
  ;; See also `DrvName' in Nix.

  (define number?
    (cut char-set-contains? char-set:digit <>))

  (let loop ((chars   (string->list name))
             (prefix '()))
    (match chars
      (()
       (values name #f))
      ((#\- (? number? n) rest ...)
       (values (list->string (reverse prefix))
               (list->string (cons n rest))))
      ((head tail ...)
       (loop tail (cons head prefix))))))

(define (file-extension file)
  "Return the extension of FILE or #f if there is none."
  (let ((dot (string-rindex file #\.)))
    (and dot (substring file (+ 1 dot) (string-length file)))))

(define (file-sans-extension file)
  "Return the substring of FILE without its extension, if any."
  (let ((dot (string-rindex file #\.)))
    (if dot
        (substring file 0 dot)
        file)))

(define (string-tokenize* string separator)
  "Return the list of substrings of STRING separated by SEPARATOR.  This is
like `string-tokenize', but SEPARATOR is a string."
  (define (index string what)
    (let loop ((string string)
               (offset 0))
      (cond ((string-null? string)
             #f)
            ((string-prefix? what string)
             offset)
            (else
             (loop (string-drop string 1) (+ 1 offset))))))

  (define len
    (string-length separator))

  (let loop ((string string)
             (result  '()))
    (cond ((index string separator)
           =>
           (lambda (offset)
             (loop (string-drop string (+ offset len))
                   (cons (substring string 0 offset)
                         result))))
          (else
           (reverse (cons string result))))))

(define* (string-replace-substring str substr replacement
                                   #:optional
                                   (start 0)
                                   (end (string-length str)))
  "Replace all occurrences of SUBSTR in the START--END range of STR by
REPLACEMENT."
  (match (string-length substr)
    (0
     (error "string-replace-substring: empty substring"))
    (substr-length
     (let loop ((start  start)
                (pieces (list (substring str 0 start))))
       (match (string-contains str substr start end)
         (#f
          (string-concatenate-reverse
           (cons (substring str start) pieces)))
         (index
          (loop (+ index substr-length)
                (cons* replacement
                       (substring str start index)
                       pieces))))))))

(define (call-with-temporary-output-file proc)
  "Call PROC with a name of a temporary file and open output port to that
file; close the file and delete it when leaving the dynamic extent of this
call."
  (let* ((template (string-copy "guix-file.XXXXXX"))
         (out      (mkstemp! template)))
    (dynamic-wind
      (lambda ()
        #t)
      (lambda ()
        (proc template out))
      (lambda ()
        (false-if-exception (close out))
        (false-if-exception (delete-file template))))))

(define (with-atomic-file-output file proc)
  "Call PROC with 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)))
    (with-throw-handler #t
      (lambda ()
        (let ((result (proc out)))
          (close out)
          (rename-file template file)
          result))
      (lambda (key . args)
        (false-if-exception (delete-file template))))))

(define fold2
  (case-lambda
    ((proc seed1 seed2 lst)
     "Like `fold', but with a single list and two seeds."
     (let loop ((result1 seed1)
                (result2 seed2)
                (lst     lst))
       (if (null? lst)
           (values result1 result2)
           (call-with-values
               (lambda () (proc (car lst) result1 result2))
             (lambda (result1 result2)
               (loop result1 result2 (cdr lst)))))))
    ((proc seed1 seed2 lst1 lst2)
     "Like `fold', but with a two lists and two seeds."
     (let loop ((result1 seed1)
                (result2 seed2)
                (lst1    lst1)
                (lst2    lst2))
       (if (or (null? lst1) (null? lst2))
           (values result1 result2)
           (call-with-values
               (lambda () (proc (car lst1) (car lst2) result1 result2))
             (lambda (result1 result2)
               (fold2 proc result1 result2 (cdr lst1) (cdr lst2)))))))))


;;;
;;; Source location.
;;;

;; A source location.
(define-record-type <location>
  (make-location file line column)
  location?
  (file          location-file)                   ; file name
  (line          location-line)                   ; 1-indexed line
  (column        location-column))                ; 0-indexed column

(define location
  (memoize
   (lambda (file line column)
     "Return the <location> object for the given FILE, LINE, and COLUMN."
     (and line column file
          (make-location file line column)))))

(define (source-properties->location loc)
  "Return a location object based on the info in LOC, an alist as returned
by Guile's `source-properties', `frame-source', `current-source-location',
etc."
  (let ((file (assq-ref loc 'filename))
        (line (assq-ref loc 'line))
        (col  (assq-ref loc 'column)))
    ;; In accordance with the GCS, start line and column numbers at 1.  Note
    ;; that unlike LINE and `port-column', COL is actually 1-indexed here...
    (location file (and line (+ line 1)) col)))