src/StoreMetaUnpacker.cc

   1
   2 /*
   3  * DEBUG: section 20    Storage Manager Swapfile Unpacker
   4  * AUTHOR: Robert Collins
   5  *
   6  * SQUID Web Proxy Cache          http://www.squid-cache.org/
   7  * ----------------------------------------------------------
   8  *
   9  *  Squid is the result of efforts by numerous individuals from
  10  *  the Internet community; see the CONTRIBUTORS file for full
  11  *  details.   Many organizations have provided support for Squid's
  12  *  development; see the SPONSORS file for full details.  Squid is
  13  *  Copyrighted (C) 2001 by the Regents of the University of
  14  *  California; see the COPYRIGHT file for full details.  Squid
  15  *  incorporates software developed and/or copyrighted by other
  16  *  sources; see the CREDITS file for full details.
  17  *
  18  *  This program is free software; you can redistribute it and/or modify
  19  *  it under the terms of the GNU General Public License as published by
  20  *  the Free Software Foundation; either version 2 of the License, or
  21  *  (at your option) any later version.
  22  *
  23  *  This program is distributed in the hope that it will be useful,
  24  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  25  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  26  *  GNU General Public License for more details.
  27  *
  28  *  You should have received a copy of the GNU General Public License
  29  *  along with this program; if not, write to the Free Software
  30  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
  31  *
  32  */
  33
  34 #include "squid.h"
  35 #include "defines.h"
  36 #include "Debug.h"
  37 #include "StoreMetaUnpacker.h"
  38 #include "StoreMeta.h"
  39
  40 int const StoreMetaUnpacker::MinimumBufferLength = sizeof(char) + sizeof(int);
  41
  42 /// useful for meta stored in pre-initialized (with zeros) db files
  43 bool
  44 StoreMetaUnpacker::isBufferZero()
  45 {
  46     // We could memcmp the entire buffer, but it is probably safe enough
  47     // to test a few bytes because if we do not detect a corrupted entry
  48     // it is not a big deal. Empty entries are not isBufferSane anyway.
  49     const int depth = 10;
  50     if (buflen < depth)
  51         return false; // cannot be sure enough
  52
  53     for (int i = 0; i < depth; ++i) {
  54         if (buf[i])
  55             return false;
  56     }
  57     return true;
  58 }
  59
  60 bool
  61 StoreMetaUnpacker::isBufferSane()
  62 {
  63     if (buf[0] != (char) STORE_META_OK)
  64         return false;
  65
  66     /*
  67      * sanity check on 'buflen' value.  It should be at least big
  68      * enough to hold one type and one length.
  69      */
  70     getBufferLength();
  71
  72     if (*hdr_len < MinimumBufferLength)
  73         return false;
  74
  75     if (*hdr_len > buflen)
  76         return false;
  77
  78     return true;
  79 }
  80
  81 void
  82 StoreMetaUnpacker::getBufferLength()
  83 {
  84     memcpy(hdr_len, &buf[1], sizeof(int));
  85 }
  86
  87 StoreMetaUnpacker::StoreMetaUnpacker (char const *aBuffer, ssize_t aLen, int *anInt) : buf (aBuffer), buflen(aLen), hdr_len(anInt), position(1 + sizeof(int))
  88 {
  89     assert (aBuffer != NULL);
  90 }
  91
  92 void
  93 StoreMetaUnpacker::getType()
  94 {
  95     type = buf[position];
  96     ++position;
  97 }
  98
  99 void
 100 StoreMetaUnpacker::getLength()
 101 {
 102     memcpy(&length, &buf[position], sizeof(int));
 103     position += sizeof(int);
 104 }
 105
 106 bool
 107 StoreMetaUnpacker::doOneEntry()
 108 {
 109     getType();
 110     getLength();
 111
 112     if (position + length > *hdr_len) {
 113         debugs(20, DBG_CRITICAL, "storeSwapMetaUnpack: overflow!");
 114         debugs(20, DBG_CRITICAL, "\ttype=" << type << ", length=" << length << ", *hdr_len=" << *hdr_len << ", offset=" << position);
 115         return false;
 116     }
 117
 118     StoreMeta *newNode = StoreMeta::Factory(type, length, &buf[position]);
 119
 120     if (newNode)
 121         tail = StoreMeta::Add (tail, newNode);
 122
 123     position += length;
 124
 125     return true;
 126 }
 127
 128 bool
 129 StoreMetaUnpacker::moreToProcess() const
 130 {
 131     return *hdr_len - position - MinimumBufferLength >= 0;
 132 }
 133
 134 StoreMeta *
 135 StoreMetaUnpacker::createStoreMeta ()
 136 {
 137     tlv *TLV = NULL;
 138     tail = &TLV;
 139     assert(hdr_len != NULL);
 140
 141     if (!isBufferSane())
 142         return NULL;
 143
 144     getBufferLength();
 145
 146     assert (position == 1 + sizeof(int));
 147
 148     while (moreToProcess()) {
 149         if (!doOneEntry())
 150             break;
 151     }
 152
 153     return TLV;
 154 }