base/sched_list.hh

   1 /*
   2  * Copyright (c) 2002-2005 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/intmath.hh"
  34 #include "base/misc.hh"
  35
  36
  37 //  Any types you use this class for must be covered here...
  38 namespace {
  39     void ClearEntry(int &i) { i = 0; };
  40     void ClearEntry(unsigned &i) { i = 0; };
  41     void ClearEntry(double &i) { i = 0; };
  42     template <class T> void ClearEntry(std::list<T> &l) { l.clear(); };
  43 };
  44
  45
  46 //
  47 //  this is a special list type that allows the user to insert elements at a
  48 //  specified positive offset from the "current" element, but only allow them
  49 //  be extracted from the "current" element
  50 //
  51
  52
  53 template <class T>
  54 class SchedList
  55 {
  56     T *data_array;
  57     unsigned position;
  58     unsigned size;
  59     unsigned mask;
  60
  61   public:
  62     SchedList(unsigned size);
  63     SchedList(void);
  64
  65     void init(unsigned size);
  66
  67     T &operator[](unsigned offset);
  68
  69     void advance(void);
  70
  71     void clear(void);
  72 };
  73
  74
  75
  76 //
  77 //  Constructor
  78 //
  79 template<class T>
  80 SchedList<T>::SchedList(unsigned _size)
  81 {
  82     size = _size;
  83
  84     //  size must be a power of two
  85     if (!isPowerOf2(size)) {
  86         panic("SchedList: size must be a power of two");
  87     }
  88
  89     if (size < 2) {
  90         panic("SchedList: you don't want a list that small");
  91     }
  92
  93     //  calculate the bit mask for the modulo operation
  94     mask = size - 1;
  95
  96     data_array = new T[size];
  97
  98     if (!data_array) {
  99         panic("SchedList: could not allocate memory");
 100     }
 101
 102     clear();
 103 }
 104
 105 template<class T>
 106 SchedList<T>::SchedList(void)
 107 {
 108     data_array = 0;
 109     size = 0;
 110 }
 111
 112
 113 template<class T> void
 114 SchedList<T>::init(unsigned _size)
 115 {
 116     size = _size;
 117
 118     if (!data_array) {
 119         //  size must be a power of two
 120         if (size & (size-1)) {
 121             panic("SchedList: size must be a power of two");
 122         }
 123
 124         if (size < 2) {
 125             panic("SchedList: you don't want a list that small");
 126         }
 127
 128         //  calculate the bit mask for the modulo operation
 129         mask = size - 1;
 130
 131         data_array = new T[size];
 132
 133         if (!data_array) {
 134             panic("SchedList: could not allocate memory");
 135         }
 136
 137         clear();
 138     }
 139 }
 140
 141
 142 template<class T> void
 143 SchedList<T>::advance(void)
 144 {
 145     ClearEntry(data_array[position]);
 146
 147     //    position = (++position % size);
 148     position = ++position & mask;
 149 }
 150
 151
 152 template<class T> void
 153 SchedList<T>::clear(void)
 154 {
 155     for (unsigned i=0; i<size; ++i) {
 156         ClearEntry(data_array[i]);
 157     }
 158
 159     position = 0;
 160 }
 161
 162
 163 template<class T>  T&
 164 SchedList<T>::operator[](unsigned offset)
 165 {
 166     if (offset >= size) {
 167         panic("SchedList: can't access element beyond current pointer");
 168     }
 169
 170     //    unsigned p = (position + offset) % size;
 171     unsigned p = (position + offset) & mask;
 172
 173     return data_array[p];
 174 }
 175
 176
 177
 178 #endif