base/sched_list.hh

   1 /*
   2  * Copyright (c) 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 SCHED_LIST_HH
  30 #define SCHED_LIST_HH
  31
  32 #include <list>
  33 #include "base/misc.hh"
  34
  35 //  Any types you use this class for must be covered here...
  36 namespace {
  37     void ClearEntry(int &i) { i = 0; };
  38     void ClearEntry(unsigned &i) { i = 0; };
  39     void ClearEntry(double &i) { i = 0; };
  40     template <class T> void ClearEntry(std::list<T> &l) { l.clear(); };
  41 };
  42
  43
  44 //
  45 //  this is a special list type that allows the user to insert elements at a
  46 //  specified positive offset from the "current" element, but only allow them
  47 //  be extracted from the "current" element
  48 //
  49
  50
  51 template <class T>
  52 class SchedList
  53 {
  54     T *data_array;
  55     unsigned position;
  56     unsigned size;
  57     unsigned mask;
  58
  59   public:
  60     SchedList(unsigned size);
  61     SchedList(void);
  62
  63     void init(unsigned size);
  64
  65     T &operator[](unsigned offset);
  66
  67     void advance(void);
  68
  69     void clear(void);
  70 };
  71
  72
  73
  74 //
  75 //  Constructor
  76 //
  77 template<class T>
  78 SchedList<T>::SchedList(unsigned _size)
  79 {
  80     size = _size;
  81
  82     //  size must be a power of two
  83     if (size & (size-1)) {
  84         panic("SchedList: size must be a power of two");
  85     }
  86
  87     if (size < 2) {
  88         panic("SchedList: you don't want a list that small");
  89     }
  90
  91     //  calculate the bit mask for the modulo operation
  92     mask = size - 1;
  93
  94     data_array = new T[size];
  95
  96     if (!data_array) {
  97         panic("SchedList: could not allocate memory");
  98     }
  99
 100     clear();
 101 }
 102
 103 template<class T>
 104 SchedList<T>::SchedList(void)
 105 {
 106     data_array = 0;
 107     size = 0;
 108 }
 109
 110
 111 template<class T> void
 112 SchedList<T>::init(unsigned _size)
 113 {
 114     size = _size;
 115
 116     if (!data_array) {
 117         //  size must be a power of two
 118         if (size & (size-1)) {
 119             panic("SchedList: size must be a power of two");
 120         }
 121
 122         if (size < 2) {
 123             panic("SchedList: you don't want a list that small");
 124         }
 125
 126         //  calculate the bit mask for the modulo operation
 127         mask = size - 1;
 128
 129         data_array = new T[size];
 130
 131         if (!data_array) {
 132             panic("SchedList: could not allocate memory");
 133         }
 134
 135         clear();
 136     }
 137 }
 138
 139
 140 template<class T> void
 141 SchedList<T>::advance(void)
 142 {
 143     ClearEntry(data_array[position]);
 144
 145     //    position = (++position % size);
 146     position = ++position & mask;
 147 }
 148
 149
 150 template<class T> void
 151 SchedList<T>::clear(void)
 152 {
 153     for (unsigned i=0; i<size; ++i) {
 154         ClearEntry(data_array[i]);
 155     }
 156
 157     position = 0;
 158 }
 159
 160
 161 template<class T>  T&
 162 SchedList<T>::operator[](unsigned offset)
 163 {
 164     if (offset >= size) {
 165         panic("SchedList: can't access element beyond current pointer");
 166     }
 167
 168     //    unsigned p = (position + offset) % size;
 169     unsigned p = (position + offset) & mask;
 170
 171     return data_array[p];
 172 }
 173
 174
 175
 176 #endif