[Guile] New example.

git-svn-id: https://swig.svn.sourceforge.net/svnroot/swig/trunk/SWIG@872 626c5289-ae23-0410-ae9c-e8d60b6d4f22

Examples/guile/port/Makefile

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+CC     = gcc
+SRCS   = port.c
+TARGET = port
+IFILE  = port.i
+MKDIR  = ..
+
+
+all::
+	$(MAKE) -f $(MKDIR)/Makefile		\
+		SRCS='$(SRCS)'			\
+		TARGET=$(TARGET)		\
+		IFILE=$(IFILE)			\
+		CC=$(CC)			\
+		MODULE=$(MODULE)		\
+	  sub-all
+
+clean::
+	rm -f $(TARGET) *_wrap* *~ .~* core test.out
+
+check: all

Examples/guile/port/README

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+This example illustrates the translation from Scheme file ports to
+temporary FILE streams. Read the source and run ./port -s port.scm

Examples/guile/port/port.c

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+#include <stdio.h>
+#include <errno.h>
+
+void print_int(FILE *f, int i)
+{
+  if (fprintf(f, "%d\n", i)<0)
+    perror("print_int");
+}
+
+int read_int(FILE *f)
+{
+  int i;
+  if (fscanf(f, "%d", &i)!=1) {
+    fprintf(stderr, "read_int: error reading from file\n");
+    perror("read_int");
+  }
+  return i;
+}

Examples/guile/port/port.i

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+%include guilemain.i
+
+/* Include the required FILE * typemaps */
+%include ports.i
+
+%{
+#include <stdio.h>
+%}
+
+void print_int(FILE *f, int i);
+int read_int(FILE *f);

Examples/guile/port/port.scm

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+;; Call with standard output
+(print-int (current-output-port) 314159)
+
+;; Redirection to a file. Note that the port is automatically flushed
+;; (via force-output) before calling the C function, and that the C
+;; function gets a temporary "FILE" stream, which is closed after the
+;; call. So you can simply mix Scheme and C output.
+(with-output-to-file "test.out"
+  (lambda ()
+    (display 4711)
+    (newline)
+    (print-int (current-output-port) 314159)
+    (display 815)
+    (newline)))
+
+;; Redirection to a string or soft port won't work --
+;; we can only handle file ports.
+(catch #t
+       (lambda ()
+	 (with-output-to-string
+	   (lambda ()
+	     (print-int (current-output-port) 314159))))
+       (lambda args
+	 (write args) (newline)))
+
+;; Read from a file port. Note that it is a bad idea to mix Scheme and
+;; C input because of buffering.
+(with-input-from-file "test.out"
+  (lambda ()
+    (display (read-int (current-input-port)))
+    (newline)))
+