current-input-port et al are srfi-39 parameters

* libguile/ports.c (scm_init_ports): Export the port fluids to Scheme,
  temporarily.

* module/ice-9/boot-9.scm (fluid->parameter): Turn `current-input-port'
  et al into srfi-39 parameters, backed by the exported fluids, then
  remove the fluids from the guile module.
  (%cond-expand-features): Add srfi-39.

* module/srfi/srfi-39.scm: Re-export features from boot-9.

* test-suite/tests/parameters.test: Add tests.

diff --git a/libguile/ports.c b/libguile/ports.c
index 677b278..a631100 100644 (file)
--- a/libguile/ports.c
+++ b/libguile/ports.c
@@ -2582,6 +2582,11 @@ scm_init_ports ()
                     (scm_from_int ((int) SCM_FAILED_CONVERSION_QUESTION_MARK)));
   scm_conversion_strategy_init = 1;
   
+  /* These bindings are used when boot-9 turns `current-input-port' et
+     al into parameters.  They are then removed from the guile module.  */
+  scm_c_define ("%current-input-port-fluid", cur_inport_fluid);
+  scm_c_define ("%current-output-port-fluid", cur_outport_fluid);
+  scm_c_define ("%current-error-port-fluid", cur_errport_fluid);
 }
 
 /*

diff --git a/module/ice-9/boot-9.scm b/module/ice-9/boot-9.scm
index d5ba67a..03dad9b 100644 (file)
--- a/module/ice-9/boot-9.scm
+++ b/module/ice-9/boot-9.scm
@@ -2914,6 +2914,36 @@ module '(ice-9 q) '(make-q q-length))}."
                body body* ...)))))))
 
 \f
+;;;
+;;; Current ports as parameters.
+;;;
+
+(let ((fluid->parameter
+       (lambda (fluid conv)
+         (make-struct <parameter> 0
+                      (case-lambda
+                        (() (fluid-ref fluid))
+                        ((x) (let ((prev (fluid-ref fluid)))
+                               (fluid-set! fluid (conv x))
+                               prev)))
+                      fluid conv))))
+  (define-syntax-rule (port-parameterize! binding fluid predicate msg)
+    (begin
+      (set! binding (fluid->parameter (module-ref (current-module) 'fluid)
+                                      (lambda (x)
+                                        (if (predicate x) x
+                                            (error msg x)))))
+      (module-remove! (current-module) 'fluid)))
+  
+  (port-parameterize! current-input-port %current-input-port-fluid
+                      input-port? "expected an input port")
+  (port-parameterize! current-output-port %current-output-port-fluid
+                      output-port? "expected an output port")
+  (port-parameterize! current-error-port %current-error-port-fluid
+                      output-port? "expected an output port"))
+
+
+\f
 ;;;
 ;;; Warnings.
 ;;;
@@ -3657,8 +3687,9 @@ module '(ice-9 q) '(make-q q-length))}."
     srfi-4   ;; homogenous numeric vectors
     srfi-6   ;; open-input-string etc, in the guile core
     srfi-13  ;; string library
-    srfi-23  ;; `error` procedure
     srfi-14  ;; character sets
+    srfi-23  ;; `error` procedure
+    srfi-39  ;; parameterize
     srfi-55  ;; require-extension
     srfi-61  ;; general cond clause
     ))

diff --git a/module/srfi/srfi-39.scm b/module/srfi/srfi-39.scm
dissimilarity index 63%
index d1c46d0..0d54063 100644 (file)
--- a/module/srfi/srfi-39.scm
+++ b/module/srfi/srfi-39.scm
@@ -1,138 +1,53 @@
-;;; srfi-39.scm --- Parameter objects
-
-;;     Copyright (C) 2004, 2005, 2006, 2008, 2011 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
-
-;;; Author: Jose Antonio Ortega Ruiz <jao@gnu.org>
-;;; Date: 2004-05-05
-
-;;; Commentary:
-
-;; This is an implementation of SRFI-39 (Parameter objects).
-;;
-;; The implementation is based on Guile's fluid objects, and is, therefore,
-;; thread-safe (parameters are thread-local).
-;;
-;; In addition to the forms defined in SRFI-39 (`make-parameter',
-;; `parameterize'), a new procedure `with-parameters*' is provided.
-;; This procedures is analogous to `with-fluids*' but taking as first
-;; argument a list of parameter objects instead of a list of fluids.
-;;
-
-;;; Code:
-
-(define-module (srfi srfi-39)
-  #:use-module (srfi srfi-16)
-
-  #:export (make-parameter)
-  #:export-syntax (parameterize)
-
-  ;; helper procedure not in srfi-39.
-  #:export (with-parameters*)
-  #:replace (current-input-port current-output-port current-error-port))
-
-;; Make 'srfi-39 available as a feature identifiere to `cond-expand'.
-;;
-(cond-expand-provide (current-module) '(srfi-39))
-
-(define make-parameter
-  (case-lambda
-    ((val) (make-parameter/helper val (lambda (x) x)))
-    ((val conv) (make-parameter/helper val conv))))
-
-(define get-fluid-tag (lambda () 'get-fluid)) ;; arbitrary unique (as per eq?) value
-(define get-conv-tag (lambda () 'get-conv)) ;; arbitrary unique (as per eq?) value
-
-(define (make-parameter/helper val conv)
-  (let ((fluid (make-fluid (conv val))))
-    (case-lambda
-      (()
-       (fluid-ref fluid))
-      ((new-value)
-       (cond
-        ((eq? new-value get-fluid-tag) fluid)
-        ((eq? new-value get-conv-tag) conv)
-        (else (fluid-set! fluid (conv new-value))))))))
-
-(define-syntax-rule (parameterize ((?param ?value) ...) ?body ...)
-  (with-parameters* (list ?param ...)
-                    (list ?value ...)
-                    (lambda () ?body ...)))
-
-(define current-input-port
-  (case-lambda
-    (()
-     ((@ (guile) current-input-port)))
-    ((new-value)
-     (set-current-input-port new-value))))
-
-(define current-output-port
-  (case-lambda
-    (()
-     ((@ (guile) current-output-port)))
-    ((new-value)
-     (set-current-output-port new-value))))
-
-(define current-error-port
-  (case-lambda
-    (()
-     ((@ (guile) current-error-port)))
-    ((new-value)
-     (set-current-error-port new-value))))
-
-(define port-list
-  (list current-input-port current-output-port current-error-port))
-
-;; There are no fluids behind current-input-port etc, so those parameter
-;; objects are picked out of the list and handled separately with a
-;; dynamic-wind to swap their values to and from a location (the "value"
-;; variable in the swapper procedure "let").
-;;
-;; current-input-port etc are already per-dynamic-root, so this arrangement
-;; works the same as a fluid.  Perhaps they could become fluids for ease of
-;; implementation here.
-;;
-;; Notice the use of a param local variable for the swapper procedure.  It
-;; ensures any application changes to the PARAMS list won't affect the
-;; winding.
-;;
-(define (with-parameters* params values thunk)
-  (let more ((params params)
-            (values values)
-            (fluids '())     ;; fluids from each of PARAMS
-            (convs  '())     ;; VALUES with conversion proc applied
-            (swapper noop))  ;; wind/unwind procedure for ports handling
-    (if (null? params)
-       (if (eq? noop swapper)
-           (with-fluids* fluids convs thunk)
-           (dynamic-wind
-               swapper
-               (lambda ()
-                 (with-fluids* fluids convs thunk))
-               swapper))
-       (if (memq (car params) port-list)
-           (more (cdr params) (cdr values)
-                 fluids convs
-                 (let ((param (car params))
-                       (value (car values))
-                       (prev-swapper swapper))
-                   (lambda ()
-                     (set! value (param value))
-                     (prev-swapper))))
-           (more (cdr params) (cdr values)
-                 (cons ((car params) get-fluid-tag) fluids)
-                 (cons (((car params) get-conv-tag) (car values)) convs)
-                 swapper)))))
+;;; srfi-39.scm --- Parameter objects
+
+;;     Copyright (C) 2004, 2005, 2006, 2008, 2011 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
+
+;;; Author: Jose Antonio Ortega Ruiz <jao@gnu.org>
+;;; Date: 2004-05-05
+
+;;; Commentary:
+
+;; This is an implementation of SRFI-39 (Parameter objects).
+;;
+;; The implementation is based on Guile's fluid objects, and is, therefore,
+;; thread-safe (parameters are thread-local).
+;;
+;; In addition to the forms defined in SRFI-39 (`make-parameter',
+;; `parameterize'), a new procedure `with-parameters*' is provided.
+;; This procedures is analogous to `with-fluids*' but taking as first
+;; argument a list of parameter objects instead of a list of fluids.
+;;
+
+;;; Code:
+
+(define-module (srfi srfi-39)
+  ;; helper procedure not in srfi-39.
+  #:export (with-parameters*)
+  #:re-export (make-parameter
+               parameterize
+               current-input-port current-output-port current-error-port))
+
+(define (with-parameters* params values thunk)
+  (let more ((params params)
+            (values values)
+            (fluids '())     ;; fluids from each of PARAMS
+            (convs  '()))    ;; VALUES with conversion proc applied
+    (if (null? params)
+       (with-fluids* fluids convs thunk)
+        (more (cdr params) (cdr values)
+              (cons (parameter-fluid (car params)) fluids)
+              (cons ((parameter-converter (car params)) (car values)) convs)))))

diff --git a/test-suite/tests/parameters.test b/test-suite/tests/parameters.test
index 9d0a092..78b57c6 100644 (file)
--- a/test-suite/tests/parameters.test
+++ b/test-suite/tests/parameters.test
@@ -67,3 +67,64 @@
                   (lambda ()
                     (parameterize ((inside? #t))
                       (raise 'some-exception)))))))))
+
+(let ()
+  (define (test-ports param new-port new-port-2)
+    (let ((old-port (param)))
+
+      (pass-if "new value"
+       (parameterize ((param new-port))
+         (eq? (param) new-port)))
+
+      (pass-if "set value"
+       (parameterize ((param old-port))
+         (param new-port)
+         (eq? (param) new-port)))
+
+      (pass-if "old restored"
+       (parameterize ((param new-port))
+         #f)
+       (eq? (param) old-port))
+
+      (pass-if "throw exit"
+       (catch 'bail
+         (lambda ()
+           (parameterize ((param new-port))
+             (throw 'bail)))
+         (lambda args #f))
+       (eq? (param) old-port))
+
+      (pass-if "call/cc re-enter"
+       (let ((cont  #f)
+             (count 0)
+             (port  #f)
+             (good  #t))
+         (parameterize ((param new-port))
+           (call/cc (lambda (k) (set! cont k)))
+           (set! count (1+ count))
+           (set! port (param))
+           (if (= 1 count) (param new-port-2)))
+         (set! good (and good (eq? (param) old-port)))
+         (case count
+           ((1)
+            (set! good (and good (eq? port new-port)))
+            ;; re-entering should give new-port-2 left there last time
+            (cont))
+           ((2)
+            (set! good (and good (eq? port new-port-2)))))
+         good))
+
+      (pass-if "original unchanged"
+       (eq? (param) old-port))))
+
+  (with-test-prefix "current-input-port"
+    (test-ports current-input-port
+               (open-input-string "xyz") (open-input-string "xyz")))
+
+  (with-test-prefix "current-output-port"
+    (test-ports current-output-port
+               (open-output-string) (open-output-string)))
+
+  (with-test-prefix "current-error-port"
+    (test-ports current-error-port
+               (open-output-string) (open-output-string))))