src/StoreSwapLogData.h

   1 /*
   2  * $Id$
   3  *
   4  * SQUID Web Proxy Cache          http://www.squid-cache.org/
   5  * ----------------------------------------------------------
   6  *
   7  *  Squid is the result of efforts by numerous individuals from
   8  *  the Internet community; see the CONTRIBUTORS file for full
   9  *  details.   Many organizations have provided support for Squid's
  10  *  development; see the SPONSORS file for full details.  Squid is
  11  *  Copyrighted (C) 2001 by the Regents of the University of
  12  *  California; see the COPYRIGHT file for full details.  Squid
  13  *  incorporates software developed and/or copyrighted by other
  14  *  sources; see the CREDITS file for full details.
  15  *
  16  *  This program is free software; you can redistribute it and/or modify
  17  *  it under the terms of the GNU General Public License as published by
  18  *  the Free Software Foundation; either version 2 of the License, or
  19  *  (at your option) any later version.
  20  *
  21  *  This program is distributed in the hope that it will be useful,
  22  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  23  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  24  *  GNU General Public License for more details.
  25  *
  26  *  You should have received a copy of the GNU General Public License
  27  *  along with this program; if not, write to the Free Software
  28  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
  29  *
  30  * Copyright (c) 2003, Robert Collins <robertc@squid-cache.org>
  31  */
  32
  33 #ifndef SQUID_STORESWAPLOGDATA_H
  34 #define SQUID_STORESWAPLOGDATA_H
  35
  36 /**
  37  \defgroup FileFormatSwapStateAPI swap.state File Structure
  38  \ingroup FileSystems
  39  \section ImplementationNotes Implementation Notes
  40  \par
  41  *      When writing an object to disk, we must first write the meta data.
  42  *      This is done with a couple of functions.  First, storeSwapMetaPack()
  43  *      takes a StoreEntry as a parameter and returns a tlv linked
  44  *      list.  Second, storeSwapMetaPack() converts the tlv list
  45  *      into a character buffer that we can write.
  46  *
  47  \note  MemObject has a MemObject::swap_hdr_sz.
  48  *      This value is the size of that character buffer; the size of the
  49  *      swap file meta data.  The StoreEntry has a member
  50  *      StoreEntry::swap_file_sz that represents the size of the disk file.
  51  *      Thus, the size of the object "content" is
  52  \code    StoreEntry->swap_file_sz  - MemObject->swap_hdr_sz;    \endcode
  53  \note The swap file content includes the HTTP reply headers and the HTTP reply body (if any).
  54  *
  55  \par
  56  *      When reading a swap file, there is a similar process to extract
  57  *      the swap meta data.  First, storeSwapMetaUnpack() converts a
  58  *      character buffer into a tlv linked list.  It also tells us
  59  *      the value for MemObject->swap_hdr_sz.
  60  */
  61
  62 #include "squid-old.h"
  63
  64 /// maintains a 24-bit checksum over integer fields
  65 class SwapChecksum24 {
  66 public:
  67     SwapChecksum24() { raw[0] = raw[1] = raw[2] = 0; }
  68
  69         bool operator ==(const SwapChecksum24 &o) const {
  70         return raw[0] == o.raw[0] && raw[1] == o.raw[1] && raw[2] == o.raw[2];
  71     }
  72
  73         bool operator !=(const SwapChecksum24 &o) const {
  74         return !(*this == o);
  75     }
  76
  77     /// compute and store checksum based on three 32bit integers
  78     void set(uint32_t f1, uint32_t f2, uint32_t f3);
  79
  80     /// compute and store checksum based on int32_t and uint64_t integers
  81     void set(int32_t f1, uint64_t f2);
  82
  83     // printing for debugging
  84     std::ostream &print(std::ostream &os) const;
  85
  86 private:
  87     uint8_t raw[3]; // designed to follow "op" members, in pading space
  88 };
  89
  90 inline std::ostream &
  91 operator <<(std::ostream &os, const SwapChecksum24 &sum)
  92 {
  93     return sum.print(os);
  94 }
  95
  96 /**
  97  \ingroup FielFormatSwapStateAPI
  98  *
  99  \par
 100  * Defines the structure of a binary swap.state file entry for UFS stores.
 101  * TODO: Move to fs/ufs (and remove from COSS).
 102  *
 103  \note StoreSwapLogData entries are written in native machine byte order
 104  *     They are not necessarily portable across architectures.
 105  */
 106 class StoreSwapLogData
 107 {
 108
 109 public:
 110     MEMPROXY_CLASS(StoreSwapLogData);
 111
 112     /// type to use for storing time-related members; must be signed
 113     typedef int64_t SwappedTime;
 114
 115     StoreSwapLogData();
 116
 117     /// consistency self-check: whether the data appears to make sense
 118     bool sane() const;
 119
 120     /// call this before storing the log entry
 121     void finalize();
 122
 123     /**
 124      * Either SWAP_LOG_ADD when an object is added to the disk storage,
 125      * or SWAP_LOG_DEL when an object is deleted.
 126      */
 127     uint8_t op;
 128
 129     /**
 130      * Fingerprint to weed out bogus/corrupted swap.state entries.
 131      */
 132     SwapChecksum24 checksum; // follows "op" because compiler will pad anyway
 133
 134     /**
 135      * The 32-bit file number which maps to a pathname.
 136      * Only the low 24-bits are relevant. The high 8-bits are
 137      * used as an index to an array of storage directories, and
 138      * are set at run time because the order of storage directories
 139      * may change over time.
 140      */
 141     sfileno swap_filen;
 142
 143     /**
 144      * A Unix time value that represents the time when
 145      * the origin server generated this response. If the response
 146      * has a valid Date: header, this timestamp corresponds
 147      * to that time. Otherwise, it is set to the Squid process time
 148      * when the response is read (as soon as the end of headers are found).
 149      */
 150     SwappedTime timestamp;
 151
 152     /**
 153      * The last time that a client requested this object.
 154      * Strictly speaking, this time is set whenever the StoreEntry
 155      * is locked (via storeLockObject()).
 156      */
 157     SwappedTime lastref;
 158
 159     /**
 160      * The value of the response's Expires: header, if any.
 161      * If the response does not have an Expires: header, this
 162      * is set to -1.
 163      * If the response has an invalid (unparseable)
 164      * Expires: header, it is also set to -1.  There are some cases
 165      * where Squid sets expires to -2. This happens for the
 166      * internal "netdb" object and for FTP URL responses.
 167      */
 168     SwappedTime expires;
 169
 170     /**
 171      * The value of the response's Last-modified: header, if any.
 172      * This is set to -1 if there is no Last-modified: header,
 173      * or if it is unparseable.
 174      */
 175     SwappedTime lastmod;
 176
 177     /**
 178      * This is the number of bytes that the object occupies on
 179      * disk. It includes the Squid "swap file header".
 180      */
 181     uint64_t swap_file_sz;
 182
 183     /**
 184      * The number of times that this object has been accessed (referenced).
 185      * Since its a 16-bit quantity, it is susceptible to overflow
 186      * if a single object is accessed 65,536 times before being replaced.
 187      */
 188     uint16_t refcount;
 189
 190     /**
 191      * A copy of the StoreEntry flags field. Used as a sanity
 192      * check when rebuilding the cache at startup. Objects that
 193      * have the KEY_PRIVATE flag set are not added back to the cache.
 194      */
 195     uint16_t flags;
 196
 197     /**
 198      * The 128-bit MD5 hash for this object.
 199      */
 200     unsigned char key[SQUID_MD5_DIGEST_LENGTH];
 201 };
 202
 203 MEMPROXY_CLASS_INLINE(StoreSwapLogData);
 204
 205 /// \ingroup FileFormatSwapStateAPI
 206 /// Swap log starts with this binary structure.
 207 class StoreSwapLogHeader
 208 {
 209 public:
 210     // sets default values for this Squid version; loaded values may differ
 211     StoreSwapLogHeader();
 212
 213     /// consistency self-check: whether the data appears to make sense
 214     bool sane() const;
 215
 216     /// number of bytes after the log header before the first log entry
 217     size_t gapSize() const;
 218
 219     uint8_t op;
 220     SwapChecksum24 checksum; // follows "op" because compiler will pad anyway
 221     int32_t version;
 222     int32_t record_size;
 223 };
 224
 225
 226 #endif /* SQUID_STORESWAPLOGDATA_H */