* oldfmt.c: New file: Used by application writers to adapt to

new-style error format strings.

doc/oldfmt.c

@@ -0,0 +1,219 @@
+/*	Copyright (C) 2000 Free Software Foundation, Inc.
+ * 
+ * This program 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 2, or (at your option)
+ * any later version.
+ * 
+ * This program 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 this software; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
+ * Boston, MA 02111-1307 USA
+ *
+ * As a special exception, the Free Software Foundation gives permission
+ * for additional uses of the text contained in its release of GUILE.
+ *
+ * The exception is that, if you link the GUILE library with other files
+ * to produce an executable, this does not by itself cause the
+ * resulting executable to be covered by the GNU General Public License.
+ * Your use of that executable is in no way restricted on account of
+ * linking the GUILE library code into it.
+ *
+ * This exception does not however invalidate any other reasons why
+ * the executable file might be covered by the GNU General Public License.
+ *
+ * This exception applies only to the code released by the
+ * Free Software Foundation under the name GUILE.  If you copy
+ * code from other Free Software Foundation releases into a copy of
+ * GUILE, as the General Public License permits, the exception does
+ * not apply to the code that you add in this way.  To avoid misleading
+ * anyone as to the status of such modified files, you must delete
+ * this exception notice from them.
+ *
+ * If you write modifications of your own for GUILE, it is your choice
+ * whether to permit this exception to apply to your modifications.
+ * If you do not wish that, delete this exception notice.
+ */
+
+
+
+/* From NEWS:
+ * 
+ * * New primitive: `simple-format', affects `scm-error', scm_display_error, & scm_error message strings
+ * 
+ * (ice-9 boot) makes `format' an alias for `simple-format' until possibly
+ * extended by the more sophisticated version in (ice-9 format)
+ * 
+ * (simple-format port message . args)
+ * Write MESSAGE to DESTINATION, defaulting to `current-output-port'.
+ * MESSAGE can contain ~A (was %s) and ~S (was %S) escapes.  When printed,
+ * the escapes are replaced with corresponding members of ARGS:
+ * ~A formats using `display' and ~S formats using `write'.
+ * If DESTINATION is #t, then use the `current-output-port',
+ * if DESTINATION is #f, then return a string containing the formatted text.
+ * Does not add a trailing newline."
+ * 
+ * The two C procedures: scm_display_error and scm_error, as well as the
+ * primitive `scm-error', now use scm_format to do their work.  This means
+ * that the message strings of all code must be updated to use ~A where %s
+ * was used before, and ~S where %S was used before.
+ * 
+ * During the period when there still are a lot of old Guiles out there,
+ * you might want to support both old and new versions of Guile.
+ * 
+ * There are basically two methods to achieve this.  Both methods use
+ * autoconf.  Put
+ * 
+ *   AC_CHECK_FUNCS(scm_simple_format)
+ * 
+ * in your configure.in.
+ * 
+ * Method 1: Use the string concatenation features of ANSI C's
+ *           preprocessor.
+ * 
+ * In C:
+ * 
+ * #ifdef HAVE_SCM_SIMPLE_FORMAT
+ * #define FMT_S "~S"
+ * #else
+ * #define FMT_S "%S"
+ * #endif
+ * 
+ * Then represent each of your error messages using a preprocessor macro:
+ * 
+ * #define E_SPIDER_ERROR "There's a spider in your " ## FMT_S ## "!!!"
+ * 
+ * In Scheme:
+ * 
+ * (define fmt-s (if (defined? 'simple-format) "~S" "%S"))
+ * (define make-message string-append)
+ * 
+ * (define e-spider-error
+ *         (make-message "There's a spider in your " fmt-s "!!!"))
+ * 
+ * Method 2: Use the oldfmt function found in doc/oldfmt.c.
+ * 
+ * In C:
+ * 
+ * scm_misc_error ("picnic", scm_c_oldfmt0 ("There's a spider in your ~S!!!"),
+ *                 ...);
+ * 
+ * In Scheme:
+ * 
+ * (scm-error 'misc-error "picnic" (oldfmt "There's a spider in your ~S!!!")
+ *            ...)
+ * 
+ */
+
+/* 
+ * Take a format string FROM adhering to the new standard format (~A and ~S
+ * as placeholders) of length N and return a string which is adapted
+ * to the format used by the Guile interpreter which you are running.
+ *
+ * On successive calls with similar strings but different storage, the
+ * same string with same storage is returned.  This is necessary since
+ * the existence of a garbage collector in the system may cause the same
+ * format string to be represented with different storage at different
+ * calls.
+ */
+
+char *
+scm_c_oldfmt (char *from, int n)
+{
+#ifdef HAVE_SCM_SIMPLE_FORMAT
+  return from;
+#else
+  static struct { int n; char *from; char *to; } *strings;
+  static int size = 0;
+  static int n_strings = 0;
+  char *to;
+  int i;
+  
+  for (i = 0; i < n_strings; ++i)
+    if (n == strings[i].n && strncmp (from, strings[i].from, n) == 0)
+      return strings[i].to;
+  
+  if (n_strings == size)
+    {
+      if (size == 0)
+	{
+	  size = 10;
+	  strings = scm_must_malloc (size * sizeof (*strings), s_oldfmt);
+	}
+      else
+	{
+	  int oldsize = size;
+	  size = 3 * oldsize / 2;
+	  strings = scm_must_realloc (strings,
+				      oldsize * sizeof (*strings),
+				      size * sizeof (*strings),
+				      s_oldfmt);
+	}
+    }
+
+  strings[n_strings].n = n;
+  strings[n_strings].from = strncpy (scm_must_malloc (n, s_oldfmt), from, n);
+  to = strings[n_strings].to = scm_must_malloc (n + 1, s_oldfmt);
+  n_strings++;
+
+  for (i = 0; i < n; ++i)
+    {
+      if (from[i] == '~' && ++i < n)
+	{
+	  if (from[i] == 'A')
+	    {
+	      to[i - 1] = '%';
+	      to[i] = 's';
+	    }
+	  else if (from[i] == 'S')
+	    {
+	      to[i - 1] = '%';
+	      to[i] = 'S';
+	    }
+	  else
+	    {
+	      to[i - 1] = '~';
+	      to[i] = from[i];
+	    }
+	  continue;
+	}
+      to[i] = from[i];
+    }
+  to[i] = '\0';
+  
+  return to;
+#endif
+}
+
+char *
+scm_c_oldfmt0 (char *s)
+{
+#ifdef HAVE_SCM_SIMPLE_FORMAT
+  return s;
+#else
+  return scm_c_oldfmt (s, strlen (s));
+#endif
+}
+
+SCM_PROC (s_oldfmt, "oldfmt", 1, 0, 0, scm_oldfmt);
+
+SCM
+scm_oldfmt (SCM s)
+{
+#ifdef HAVE_SCM_SIMPLE_FORMAT
+  return s;
+#else
+  int n;
+  SCM_ASSERT (SCM_NIMP (s) && SCM_STRINGP (s), s, 1, s_oldfmt);
+  n = SCM_LENGTH (s);
+  return scm_return_first (scm_makfromstr (scm_c_oldfmt (SCM_ROCHARS (s), n),
+					   n,
+					   0),
+			   s);
+#endif
+}