Re: Accessing multiple values from C

[Julian Graham <joolean@gmail.com>]

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Howdy,


>> Not yet.  You interested in adding scm_c_value_ref (SCM, size_t) to the
>> API, and documentation to api-control.texi?  If you do it soon, it
>> will make it into 2.0.4.
>
> Sure.  Gimme a day or so and I'll have something for review.

Find attached a patch.  Let me know if I missed anything.


Regards,
Julian

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From 8d1bf16a607c6e8a0913ef982df88286dd887d51 Mon Sep 17 00:00:00 2001
From: Julian Graham <julian@navigator.(none)>
Date: Wed, 11 Jan 2012 22:08:51 -0500
Subject: [PATCH] Add `scm_c_value_ref' to allow access to multiple returned
 values from C.

* libguile/values.c, libguile/values.h (scm_c_value_ref): New function.
* doc/ref/api-control.texi (Multiple Values): Add documentation for
  `scm_c_value_ref'.
* test-suite/standalone/test-scm-values.c: New file.
* test-suite/standalone/Makefile.am: Ensure that test-scm-values.c gets
  built and executed as part of `make check'.
---
 doc/ref/api-control.texi                |    5 +++
 libguile/values.c                       |    7 ++++
 libguile/values.h                       |    1 +
 test-suite/standalone/Makefile.am       |    7 ++++
 test-suite/standalone/test-scm-values.c |   60 +++++++++++++++++++++++++++++++
 5 files changed, 80 insertions(+), 0 deletions(-)
 create mode 100644 test-suite/standalone/test-scm-values.c

diff --git a/doc/ref/api-control.texi b/doc/ref/api-control.texi
index c1502b0..4077bd9 100644
--- a/doc/ref/api-control.texi
+++ b/doc/ref/api-control.texi
@@ -785,6 +785,11 @@ the current implementation that object shares structure with
 @var{args}, so @var{args} should not be modified subsequently.
 @end deffn
 
+@deffn {C Function} scm_c_value_ref (values, idx)
+Returns the value at the position specified by @var{idx} in the
+multiple-values object @var{values}.
+@end deffn
+
 @rnindex call-with-values
 @deffn {Scheme Procedure} call-with-values producer consumer
 Calls its @var{producer} argument with no values and a
diff --git a/libguile/values.c b/libguile/values.c
index ab77731..3a213fa 100644
--- a/libguile/values.c
+++ b/libguile/values.c
@@ -67,6 +67,13 @@ print_values (SCM obj, SCM pwps)
   return SCM_UNSPECIFIED;
 }
 
+SCM
+scm_c_value_ref (SCM obj, size_t idx)
+{
+  SCM values = scm_struct_ref (obj, SCM_INUM0);
+  return scm_list_ref (values, SCM_I_MAKINUM (idx));
+}
+
 SCM_DEFINE (scm_values, "values", 0, 0, 1,
 	    (SCM args),
 	    "Delivers all of its arguments to its continuation.  Except for\n"
diff --git a/libguile/values.h b/libguile/values.h
index 65ad8a1..5f79855 100644
--- a/libguile/values.h
+++ b/libguile/values.h
@@ -33,6 +33,7 @@ SCM_API SCM scm_values_vtable;
 SCM_INTERNAL void scm_i_extract_values_2 (SCM obj, SCM *p1, SCM *p2);
 
 SCM_API SCM scm_values (SCM args);
+SCM_API SCM scm_c_value_ref (SCM values, size_t idx);
 SCM_INTERNAL void scm_init_values (void);
 
 #endif  /* SCM_VALUES_H */
diff --git a/test-suite/standalone/Makefile.am b/test-suite/standalone/Makefile.am
index 08d249c..7b96785 100644
--- a/test-suite/standalone/Makefile.am
+++ b/test-suite/standalone/Makefile.am
@@ -189,6 +189,13 @@ test_scm_to_latin1_string_LDADD = $(LIBGUILE_LDADD)
 check_PROGRAMS += test-scm-to-latin1-string
 TESTS += test-scm-to-latin1-string
 
+# test-values
+test_scm_values_SOURCES = test-scm-values.c
+test_scm_values_CFLAGS = ${test_cflags}
+test_scm_values_LDADD = $(LIBGUILE_LDADD)
+check_PROGRAMS += test-scm-values
+TESTS += test-scm-values
+
 if HAVE_SHARED_LIBRARIES
 
 # test-extensions
diff --git a/test-suite/standalone/test-scm-values.c b/test-suite/standalone/test-scm-values.c
new file mode 100644
index 0000000..25acd2e
--- /dev/null
+++ b/test-suite/standalone/test-scm-values.c
@@ -0,0 +1,60 @@
+/* Copyright (C) 2012 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
+ */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include <assert.h>
+#include <libguile.h>
+#include <stdlib.h>
+#include <string.h>
+
+static void
+test_scm_c_value_ref ()
+{
+  SCM values = scm_values (scm_list_3 (scm_from_locale_string ("foo"),
+				       scm_from_locale_string ("bar"),
+				       scm_from_locale_string ("baz")));
+
+  
+  char *foo = scm_to_locale_string (scm_c_value_ref (values, 0));
+  char *bar = scm_to_locale_string (scm_c_value_ref (values, 1));
+  char *baz = scm_to_locale_string (scm_c_value_ref (values, 2));
+
+  assert (strcmp (foo, "foo") == 0);
+  assert (strcmp (bar, "bar") == 0);
+  assert (strcmp (baz, "baz") == 0);
+
+  free (foo);
+  free (bar);
+  free (baz);
+}
+
+static void
+tests (void *data, int argc, char **argv)
+{
+  test_scm_c_value_ref ();
+}
+
+int
+main (int argc, char *argv[])
+{
+  scm_boot_guile (argc, argv, tests, NULL);
+  return 0;
+}
-- 
1.7.5.4