base/dbl_list.hh

   1 /*
   2  * Copyright (c) 2000-2001, 2003 The Regents of The University of Michigan
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions are
   7  * met: redistributions of source code must retain the above copyright
   8  * notice, this list of conditions and the following disclaimer;
   9  * redistributions in binary form must reproduce the above copyright
  10  * notice, this list of conditions and the following disclaimer in the
  11  * documentation and/or other materials provided with the distribution;
  12  * neither the name of the copyright holders nor the names of its
  13  * contributors may be used to endorse or promote products derived from
  14  * this software without specific prior written permission.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  17  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  18  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  19  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  20  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  21  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  22  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  26  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 #ifndef __DBL_LIST_HH__
  30 #define __DBL_LIST_HH__
  31
  32 class DblListEl {
  33     DblListEl *next;
  34     DblListEl *prev;
  35
  36     // remove this from list
  37     void remove() {
  38         prev->next = next;
  39         next->prev = prev;
  40     }
  41
  42     // insert this before old_el
  43     void insertBefore(DblListEl *old_el) {
  44         prev = old_el->prev;
  45         next = old_el;
  46         prev->next = this;
  47         next->prev = this;
  48     }
  49
  50     // insert this after old_el
  51     void insertAfter(DblListEl *old_el) {
  52         next = old_el->next;
  53         prev = old_el;
  54         next->prev = this;
  55         prev->next = this;
  56     }
  57
  58     friend class DblListBase;
  59 };
  60
  61
  62 //
  63 // doubly-linked list of DblListEl objects
  64 //
  65 class DblListBase {
  66     // dummy list head element: dummy.next is head, dummy.prev is tail
  67     DblListEl dummy;
  68
  69     // length counter
  70     unsigned length;
  71
  72     DblListEl *valid_or_null(DblListEl *el) {
  73         // make sure users never see the dummy element
  74         return (el == &dummy) ? NULL : el;
  75     }
  76
  77   public:
  78
  79     DblListEl *head() {
  80         return valid_or_null(dummy.next);
  81     }
  82
  83     DblListEl *tail() {
  84         return valid_or_null(dummy.prev);
  85     }
  86
  87     DblListEl *next(DblListEl *el) {
  88         return valid_or_null(el->next);
  89     }
  90
  91     DblListEl *prev(DblListEl *el) {
  92         return valid_or_null(el->prev);
  93     }
  94
  95     bool is_empty() {
  96         return (dummy.next == &dummy);
  97     }
  98
  99     void remove(DblListEl *el) {
 100         el->remove();
 101         --length;
 102     }
 103
 104     void insertBefore(DblListEl *new_el, DblListEl *old_el) {
 105         new_el->insertBefore(old_el);
 106         ++length;
 107     }
 108
 109     void insertAfter(DblListEl *new_el, DblListEl *old_el) {
 110         new_el->insertAfter(old_el);
 111         ++length;
 112     }
 113
 114     // append to end of list, i.e. as dummy.prev
 115     void append(DblListEl *el) {
 116         insertBefore(el, &dummy);
 117     }
 118
 119     // prepend to front of list (push), i.e. as dummy.next
 120     void prepend(DblListEl *el) {
 121         insertAfter(el, &dummy);
 122     }
 123
 124     DblListEl *pop() {
 125         DblListEl *hd = head();
 126         if (hd != NULL)
 127             remove(hd);
 128         return hd;
 129     }
 130
 131     // constructor
 132     DblListBase() {
 133         dummy.next = dummy.prev = &dummy;
 134         length = 0;
 135     }
 136 };
 137
 138
 139 //
 140 // Template class serves solely to cast args & return values
 141 // to appropriate type (T *)
 142 //
 143 template<class T> class DblList : private DblListBase {
 144
 145   public:
 146
 147     T *head() { return (T *)DblListBase::head(); }
 148     T *tail() { return (T *)DblListBase::tail(); }
 149
 150     T *next(T *el) { return (T *)DblListBase::next(el); }
 151     T *prev(T *el) { return (T *)DblListBase::prev(el); }
 152
 153     bool is_empty() { return DblListBase::is_empty(); }
 154
 155     void remove(T *el) { DblListBase::remove(el); }
 156
 157     void append(T *el) { DblListBase::append(el); }
 158     void prepend(T *el) { DblListBase::prepend(el); }
 159
 160     T *pop() { return (T *)DblListBase::pop(); }
 161
 162     DblList<T>() { }
 163 };
 164
 165 #endif // __DBL_LIST_HH__