src/filemap.cc

   1
   2 /*
   3  * $Id: filemap.cc,v 1.36 2000/10/13 08:45:07 wessels Exp $
   4  *
   5  * DEBUG: section 8     Swap File Bitmap
   6  * AUTHOR: Harvest Derived
   7  *
   8  * SQUID Internet Object Cache  http://squid.nlanr.net/Squid/
   9  * ----------------------------------------------------------
  10  *
  11  *  Squid is the result of efforts by numerous individuals from the
  12  *  Internet community.  Development is led by Duane Wessels of the
  13  *  National Laboratory for Applied Network Research and funded by the
  14  *  National Science Foundation.  Squid is Copyrighted (C) 1998 by
  15  *  the Regents of the University of California.  Please see the
  16  *  COPYRIGHT file for full details.  Squid incorporates software
  17  *  developed and/or copyrighted by other sources.  Please see the
  18  *  CREDITS file for full details.
  19  *
  20  *  This program is free software; you can redistribute it and/or modify
  21  *  it under the terms of the GNU General Public License as published by
  22  *  the Free Software Foundation; either version 2 of the License, or
  23  *  (at your option) any later version.
  24  *
  25  *  This program is distributed in the hope that it will be useful,
  26  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  27  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  28  *  GNU General Public License for more details.
  29  *
  30  *  You should have received a copy of the GNU General Public License
  31  *  along with this program; if not, write to the Free Software
  32  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
  33  *
  34  */
  35
  36 #include "squid.h"
  37
  38 /* Number of bits in a long */
  39 #if SIZEOF_LONG == 8
  40 #define LONG_BIT_SHIFT 6
  41 #define BITS_IN_A_LONG 0x40
  42 #define LONG_BIT_MASK  0x3F
  43 #define ALL_ONES (unsigned long) 0xFFFFFFFFFFFFFFFF
  44 #elif SIZEOF_LONG == 4
  45 #define LONG_BIT_SHIFT 5
  46 #define BITS_IN_A_LONG 0x20
  47 #define LONG_BIT_MASK  0x1F
  48 #define ALL_ONES (unsigned long) 0xFFFFFFFF
  49 #else
  50 #define LONG_BIT_SHIFT 5
  51 #define BITS_IN_A_LONG 0x20
  52 #define LONG_BIT_MASK  0x1F
  53 #define ALL_ONES (unsigned long) 0xFFFFFFFF
  54 #endif
  55
  56 #define FM_INITIAL_NUMBER (1<<14)
  57
  58 fileMap *
  59 file_map_create(void)
  60 {
  61     fileMap *fm = xcalloc(1, sizeof(fileMap));
  62     fm->max_n_files = FM_INITIAL_NUMBER;
  63     fm->nwords = fm->max_n_files >> LONG_BIT_SHIFT;
  64     debug(8, 3) ("file_map_create: creating space for %d files\n", fm->max_n_files);
  65     debug(8, 5) ("--> %d words of %d bytes each\n",
  66         fm->nwords, sizeof(*fm->file_map));
  67     fm->file_map = xcalloc(fm->nwords, sizeof(*fm->file_map));
  68     /* XXX account fm->file_map */
  69     return fm;
  70 }
  71
  72 static void
  73 file_map_grow(fileMap * fm)
  74 {
  75     int old_sz = fm->nwords * sizeof(*fm->file_map);
  76     void *old_map = fm->file_map;
  77     fm->max_n_files <<= 1;
  78     assert(fm->max_n_files <= (1 << 30));
  79     fm->nwords = fm->max_n_files >> LONG_BIT_SHIFT;
  80     debug(8, 3) ("file_map_grow: creating space for %d files\n", fm->max_n_files);
  81     fm->file_map = xcalloc(fm->nwords, sizeof(*fm->file_map));
  82     debug(8, 3) ("copying %d old bytes\n", old_sz);
  83     xmemcpy(fm->file_map, old_map, old_sz);
  84     xfree(old_map);
  85     /* XXX account fm->file_map */
  86 }
  87
  88 int
  89 file_map_bit_set(fileMap * fm, int file_number)
  90 {
  91     unsigned long bitmask = (1L << (file_number & LONG_BIT_MASK));
  92     while (file_number >= fm->max_n_files)
  93         file_map_grow(fm);
  94     fm->file_map[file_number >> LONG_BIT_SHIFT] |= bitmask;
  95     fm->n_files_in_map++;
  96     return file_number;
  97 }
  98
  99 /*
 100  * WARNING: file_map_bit_reset does not perform array bounds
 101  * checking!  It assumes that 'file_number' is valid, and that the
 102  * bit is already set.  The caller must verify both of those
 103  * conditions by calling file_map_bit_test() first.
 104  */
 105 void
 106 file_map_bit_reset(fileMap * fm, int file_number)
 107 {
 108     unsigned long bitmask = (1L << (file_number & LONG_BIT_MASK));
 109     fm->file_map[file_number >> LONG_BIT_SHIFT] &= ~bitmask;
 110     fm->n_files_in_map--;
 111 }
 112
 113 int
 114 file_map_bit_test(fileMap * fm, int file_number)
 115 {
 116     unsigned long bitmask = (1L << (file_number & LONG_BIT_MASK));
 117     if (file_number >= fm->max_n_files)
 118         return 0;
 119     /* be sure the return value is an int, not a u_long */
 120     return (fm->file_map[file_number >> LONG_BIT_SHIFT] & bitmask ? 1 : 0);
 121 }
 122
 123 int
 124 file_map_allocate(fileMap * fm, int suggestion)
 125 {
 126     int word;
 127     int bit;
 128     int count;
 129     if (suggestion >= fm->max_n_files)
 130         suggestion = 0;
 131     if (!file_map_bit_test(fm, suggestion))
 132         return suggestion;
 133     word = suggestion >> LONG_BIT_SHIFT;
 134     for (count = 0; count < fm->nwords; count++) {
 135         if (fm->file_map[word] != ALL_ONES)
 136             break;
 137         word = (word + 1) % fm->nwords;
 138     }
 139     for (bit = 0; bit < BITS_IN_A_LONG; bit++) {
 140         suggestion = ((unsigned long) word << LONG_BIT_SHIFT) | bit;
 141         if (!file_map_bit_test(fm, suggestion)) {
 142             return suggestion;
 143         }
 144     }
 145     debug(8, 3) ("growing from file_map_allocate\n");
 146     file_map_grow(fm);
 147     return file_map_allocate(fm, fm->max_n_files >> 1);
 148 }
 149
 150 void
 151 filemapFreeMemory(fileMap * fm)
 152 {
 153     safe_free(fm->file_map);
 154     safe_free(fm);
 155 }
 156
 157 #ifdef TEST
 158
 159 #define TEST_SIZE 1<<16
 160 main(argc, argv)
 161 {
 162     int i;
 163
 164     fm = file_map_create(TEST_SIZE);
 165
 166     for (i = 0; i < TEST_SIZE; ++i) {
 167         file_map_bit_set(i);
 168         assert(file_map_bit_test(i));
 169         file_map_bit_reset(i);
 170     }
 171 }
 172 #endif