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;; popen emulation, for non-stdio based ports.
;;;; Copyright (C) 1998, 1999, 2000, 2001, 2003, 2006, 2010, 2011, 2012, 2013 Free Software Foundation, Inc.
;;;;
;;;; This library is free software; you can redistribute it and/or
;;;; modify it under the terms of the GNU Lesser General Public
;;;; License as published by the Free Software Foundation; either
;;;; version 3 of the License, or (at your option) any later version.
;;;;
;;;; This library 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
;;;; Lesser General Public License for more details.
;;;;
;;;; You should have received a copy of the GNU Lesser General Public
;;;; License along with this library; if not, write to the Free Software
;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
;;;;
(define-module (ice-9 popen)
:export (port/pid-table open-pipe* open-pipe close-pipe open-input-pipe
open-output-pipe open-input-output-pipe))
(eval-when (load eval compile)
(load-extension (string-append "libguile-" (effective-version))
"scm_init_popen"))
(define (make-rw-port read-port write-port)
(make-soft-port
(vector
(lambda (c) (write-char c write-port))
(lambda (s) (display s write-port))
(lambda () (force-output write-port))
(lambda () (read-char read-port))
(lambda () (close-port read-port) (close-port write-port)))
"r+"))
;; a guardian to ensure the cleanup is done correctly when
;; an open pipe is gc'd or a close-port is used.
(define pipe-guardian (make-guardian))
;; a weak hash-table to store the process ids.
(define port/pid-table (make-weak-key-hash-table 31))
(define (open-pipe* mode command . args)
"Executes the program @var{command} with optional arguments
@var{args} (all strings) in a subprocess.
A port to the process (based on pipes) is created and returned.
@var{mode} specifies whether an input, an output or an input-output
port to the process is created: it should be the value of
@code{OPEN_READ}, @code{OPEN_WRITE} or @code{OPEN_BOTH}."
(call-with-values (lambda ()
(apply open-process mode command args))
(lambda (read-port write-port pid)
(let ((port (or (and read-port write-port
(make-rw-port read-port write-port))
read-port
write-port
(%make-void-port mode))))
(pipe-guardian port)
(hashq-set! port/pid-table port pid)
port))))
(define (open-pipe command mode)
"Executes the shell command @var{command} (a string) in a subprocess.
A port to the process (based on pipes) is created and returned.
@var{mode} specifies whether an input, an output or an input-output
port to the process is created: it should be the value of
@code{OPEN_READ}, @code{OPEN_WRITE} or @code{OPEN_BOTH}."
(open-pipe* mode "/bin/sh" "-c" command))
(define (fetch-pid port)
(let ((pid (hashq-ref port/pid-table port)))
(hashq-remove! port/pid-table port)
pid))
(define (close-process port/pid)
(close-port (car port/pid))
(cdr (waitpid (cdr port/pid))))
;; for the background cleanup handler: just clean up without reporting
;; errors. also avoids blocking the process: if the child isn't ready
;; to be collected, puts it back into the guardian's live list so it
;; can be tried again the next time the cleanup runs.
(define (close-process-quietly port/pid)
(catch 'system-error
(lambda ()
(close-port (car port/pid)))
(lambda args #f))
(catch 'system-error
(lambda ()
(let ((pid/status (waitpid (cdr port/pid) WNOHANG)))
(cond ((= (car pid/status) 0)
;; not ready for collection
(pipe-guardian (car port/pid))
(hashq-set! port/pid-table
(car port/pid) (cdr port/pid))))))
(lambda args #f)))
(define (close-pipe p)
"Closes the pipe created by @code{open-pipe}, then waits for the process
to terminate and returns its status value, @xref{Processes, waitpid}, for
information on how to interpret this value."
(let ((pid (fetch-pid p)))
(if (not pid)
(error "close-pipe: pipe not in table"))
(close-process (cons p pid))))
(define reap-pipes
(lambda ()
(let loop ((p (pipe-guardian)))
(cond (p
;; maybe removed already by close-pipe.
(let ((pid (fetch-pid p)))
(if pid
(close-process-quietly (cons p pid))))
(loop (pipe-guardian)))))))
(add-hook! after-gc-hook reap-pipes)
(define (open-input-pipe command)
"Equivalent to @code{open-pipe} with mode @code{OPEN_READ}"
(open-pipe command OPEN_READ))
(define (open-output-pipe command)
"Equivalent to @code{open-pipe} with mode @code{OPEN_WRITE}"
(open-pipe command OPEN_WRITE))
(define (open-input-output-pipe command)
"Equivalent to @code{open-pipe} with mode @code{OPEN_BOTH}"
(open-pipe command OPEN_BOTH))