Implement list slicing functions.

* include/mailutils/list.h (mu_list_slice_dup,mu_list_slice)
(mu_list_slice2_dup,mu_list_slice2): New protos.
* libmailutils/list/slice.c: New file.
* libmailutils/list/slice2.c: New file.
* libmailutils/list/Makefile.am: Add slice.c and slice2.c
* libmailutils/tests/list.at: Add slicing tests.
* libmailutils/tests/listop.c: New command: "slice"

@@ -177,7 +177,45 @@ int mu_list_intersect_dup (mu_list_t *_pdest,
 			   void *_dup_data);
   
   /* Same as mu_list_intersect_dup with _dup_item = NULL */
-int mu_list_intersect (mu_list_t *, mu_list_t, mu_list_t);  
+int mu_list_intersect (mu_list_t *, mu_list_t, mu_list_t);
+
+  /* ************************************************* */
+  /* List slicing                                      */
+  /* ************************************************* */
+  /* Create a new list from elements of _list located between
+     indices in _posv.  Return the result in _pdest.  
+     The resulting list will contain elements between _posv[0] and
+     _posv[1], _posv[2] and _posv[3], ..., _posv[_posc-2]
+     and _posv[_posc-1], inclusive.  If _posc is an odd number, an extra
+     element with the value [count-1] (where count is the number of
+     elements in _list) is implied.
+
+     The elements in _posv are sorted in ascending order prior to use. 
+     
+     See mu_list_intersect_dup for a description of _dup_item and
+     _dup_data */
+int mu_list_slice_dup (mu_list_t *_pdest, mu_list_t _list,
+		       size_t *_posv, size_t _posc,
+		       int (*_dup_item) (void **, void *, void *),
+		       void *_dup_data);
+  /* Same as mu_list_slice_dup invoked with _dup_item=NULL */
+int mu_list_slice (mu_list_t *_pdest, mu_list_t _list,
+		   size_t *_posv, size_t _posc);
+  
+  /* Two functions for the most common case: */
+  /* Create a slice containing elements between indices _from and
+     _to in the _list.
+
+     See mu_list_intersect_dup for a description of _dup_item and
+     _dup_data */
+int mu_list_slice2_dup (mu_list_t *_pdest, mu_list_t _list,
+			size_t _from, size_t _to,
+			int (*_dup_item) (void **, void *, void *),
+			void *_dup_data);
+  /* Same as mu_list_slice2_dup with _dup_item=NULL */
+int mu_list_slice2 (mu_list_t *_pdest, mu_list_t _list,
+                    size_t _from, size_t _to);
+  
 
   /* ************************************************* */
   /* List mapper functions                             */

@@ -39,7 +39,9 @@ liblist_la_SOURCES = \
  remove.c\
  replace.c\
  setcomp.c\
- setdestr.c
+ setdestr.c\
+ slice.c\
+ slice2.c
 
 INCLUDES = @MU_LIB_COMMON_INCLUDES@ -I/libmailutils
 

+/* GNU Mailutils -- a suite of utilities for electronic mail
+   Copyright (C) 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, see 
+   <http://www.gnu.org/licenses/>. */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+#include <stdlib.h>
+#include <mailutils/list.h>
+#include <mailutils/sys/list.h>
+
+struct slice_info
+{
+  size_t cur;
+  size_t *posv;
+  size_t posc;
+  size_t idx;
+  int (*dup_item) (void **, void *, void *);
+  void *dup_data;
+  int err;
+};
+
+static int
+_slice_mapper (void **itmv, size_t itmc, void *call_data)
+{
+  struct slice_info *si = call_data;
+  size_t cur = si->cur++;
+
+  while (1)
+    {
+      if (cur < si->posv[si->idx])
+	return MU_LIST_MAP_SKIP;
+      if (si->idx + 1 < si->posc && cur > si->posv[si->idx + 1])
+	{
+	  si->idx += 2;
+	  if (si->idx >= si->posc)
+	    return MU_LIST_MAP_STOP|MU_LIST_MAP_SKIP;
+	}
+      else
+	break;
+    }
+  
+  if (si->dup_item && itmv[0])
+    {
+      void *p;
+      int rc = si->dup_item (&p, itmv[0], si->dup_data);
+      if (rc)
+	{
+	  si->err = rc;
+	  return MU_LIST_MAP_STOP|MU_LIST_MAP_SKIP;
+	}
+      itmv[0] = p;
+    }
+  return MU_LIST_MAP_OK;
+}
+
+static int
+poscmp (const void *a, const void *b)
+{
+  size_t posa = *(size_t*)a;
+  size_t posb = *(size_t*)b;
+
+  if (posa < posb)
+    return -1;
+  else if (posa > posb)
+    return 1;
+  return 0;
+}
+
+int
+mu_list_slice_dup (mu_list_t *pdest, mu_list_t list, size_t *posv, size_t posc,
+		   int (*dup_item) (void **, void *, void *),
+		   void *dup_data)
+{
+  int rc;
+  struct slice_info si;
+  mu_list_t dest;
+  
+  si.cur = 0;
+  si.idx = 0;
+  si.posv = posv;
+  si.posc = posc;
+  si.dup_item = dup_item;
+  si.dup_data = dup_data;
+  si.err = 0;
+
+  qsort (posv, posc, sizeof (posv[0]), poscmp);
+  
+  rc = mu_list_map (list, _slice_mapper, &si, 1, &dest);
+
+  if (rc == 0)
+    {
+      if (si.err)
+	{
+	  mu_list_destroy (&dest);
+	  rc = si.err;
+	}
+      else
+	{
+	  if (dup_item)
+	    mu_list_set_destroy_item (dest, list->destroy_item);
+	  *pdest = dest;
+	}
+    }
+  return rc;
+}
+
+int
+mu_list_slice (mu_list_t *pdest, mu_list_t list, size_t *posv, size_t posc)
+{
+  return mu_list_slice_dup (pdest, list, posv, posc, NULL, NULL);
+}

+/* GNU Mailutils -- a suite of utilities for electronic mail
+   Copyright (C) 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, see 
+   <http://www.gnu.org/licenses/>. */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+#include <stdlib.h>
+#include <mailutils/list.h>
+#include <mailutils/sys/list.h>
+
+int
+mu_list_slice2_dup (mu_list_t *pdest, mu_list_t list,
+		    size_t from, size_t to,
+		    int (*dup_item) (void **, void *, void *),
+		    void *dup_data)
+{
+  size_t arr[2] = { from, to };
+  return mu_list_slice_dup (pdest, list, arr, 2, dup_item, dup_data);
+}
+
+int
+mu_list_slice2 (mu_list_t *pdest, mu_list_t list, size_t from, size_t to)
+{
+  return mu_list_slice2_dup (pdest, list, from, to, NULL, NULL);
+}
+
+
+  

@@ -323,7 +323,60 @@ to
 ])
 
 m4_popdef([MU_TEST_KEYWORDS])
+
+# ------------------------------------------------------------
+# Slices
+# ------------------------------------------------------------
+
+m4_define([MU_TEST_GROUP],[Slice])
+m4_pushdef([MU_TEST_KEYWORDS],MU_TEST_KEYWORDS[ slice])
+
+TESTLIST([one limit],[],
+[add null en to tre fire
+slice 3
+],
+[# items: 2
+tre
+fire
+])
+
+TESTLIST([two limits],[],
+[add null en to tre fire fem seks syv atte ni ti
+slice 4 7
+],
+[# items: 4
+fire
+fem
+seks
+syv
+])
 
+TESTLIST([four limits],[],
+[add null en to tre fire fem seks syv atte ni ti
+slice 4 6 9 10
+],
+[# items: 5
+fire
+fem
+seks
+ni
+ti
+])
+
+TESTLIST([four limits unsorted],[],
+[add null en to tre fire fem seks syv atte ni ti
+slice 10 6 9 4 
+],
+[# items: 5
+fire
+fem
+seks
+ni
+ti
+])
+
+m4_popdef([MU_TEST_KEYWORDS])
+
 dnl ------------------------------------------------------------
 dnl Cleanup
 m4_popdef([TESTLIST])

@@ -619,6 +619,71 @@ map (mu_list_t *plist, int argc, char **argv)
   return 0;
 }
 
+static int
+dup_string (void **res, void *itm, void *closure)
+{
+  *res = strdup (itm);
+  return *res ? 0 : ENOMEM;
+}
+
+int
+slice (mu_list_t *plist, int argc, char **argv)
+{
+  mu_list_t list = *plist;
+  mu_list_t result;
+  int rc, i;
+  int replace = 0;
+  size_t *buf;
+  
+  argc--;
+  argv++;
+  
+  if (argc > 0 && strcmp (argv[0], "-replace") == 0)
+    {
+      replace = 1;
+      argc--;
+      argv++;
+    }
+  
+  if (argc < 1)
+    {
+      fprintf (stderr, "slice [-replace] num [num...]\n");
+      return 0;
+    }
+
+  buf = calloc (argc, sizeof (buf[0]));
+  if (!buf)
+    abort ();
+  for (i = 0; i < argc; i++)
+    buf[i] = atoi (argv[i]);
+
+  rc = mu_list_slice_dup (&result, list, buf, argc,
+			  dup_string, NULL);
+  if (rc)
+    {
+      mu_error ("slice failed: %s", mu_strerror (rc));
+      return 0;
+    }
+  if (replace)
+    {
+      size_t count[2];
+      mu_list_count (list, &count[0]);
+      mu_list_count (result, &count[1]);
+      
+      printf ("%lu in, %lu out\n", (unsigned long) count[0],
+	      (unsigned long) count[1]);
+      mu_list_destroy (&list);
+      *plist = result;
+      return 1;
+    }
+  else
+    {
+      print (result);
+      mu_list_destroy (&result);
+    }
+  return 0;  
+}
+
 void
 help ()
 {
@@ -637,8 +702,9 @@ help ()
   printf ("ictl repl item\n");
   printf ("ictl ins item [item*]\n");
   printf ("ictl dir [backwards|forwards]\n");
-  printf ("map NAME [ARGS]\n");
+  printf ("map [-replace] NAME [ARGS]\n");
   printf ("print\n");
+  printf ("slice [-replace] num [num...]\n");
   printf ("quit\n");
   printf ("iter num\n");
   printf ("help\n");
@@ -717,6 +783,14 @@ shell (mu_list_t list)
 		for (i = 0; i < NITR; i++)
 		  mu_iterator_destroy (&itr[i]);
 	    }
+	  else if (strcmp (ws.ws_wordv[0], "slice") == 0)
+	    {
+	      int i;
+	      
+	      if (slice (&list, ws.ws_wordc, ws.ws_wordv))
+		for (i = 0; i < NITR; i++)
+		  mu_iterator_destroy (&itr[i]);
+	    }
 	  else if (strcmp (ws.ws_wordv[0], "quit") == 0)
 	    return;
 	  else if (strcmp (ws.ws_wordv[0], "iter") == 0)