src/StoreSwapLogData.h

   1 /*
   2  * Copyright (C) 1996-2017 The Squid Software Foundation and contributors
   3  *
   4  * Squid software is distributed under GPLv2+ license and includes
   5  * contributions from numerous individuals and organizations.
   6  * Please see the COPYING and CONTRIBUTORS files for details.
   7  */
   8
   9 #ifndef SQUID_STORESWAPLOGDATA_H
  10 #define SQUID_STORESWAPLOGDATA_H
  11
  12 /**
  13  \defgroup FileFormatSwapStateAPI swap.state File Structure
  14  \ingroup FileSystems
  15  \section ImplementationNotes Implementation Notes
  16  \par
  17  *      When writing an object to disk, we must first write the meta data.
  18  *      This is done with a couple of functions.  First, storeSwapMetaPack()
  19  *      takes a StoreEntry as a parameter and returns a tlv linked
  20  *      list.  Second, storeSwapMetaPack() converts the tlv list
  21  *      into a character buffer that we can write.
  22  *
  23  \note  MemObject has a MemObject::swap_hdr_sz.
  24  *      This value is the size of that character buffer; the size of the
  25  *      swap file meta data.  The StoreEntry has a member
  26  *      StoreEntry::swap_file_sz that represents the size of the disk file.
  27  *      Thus, the size of the object "content" is
  28  \code    StoreEntry->swap_file_sz  - MemObject->swap_hdr_sz;    \endcode
  29  \note The swap file content includes the HTTP reply headers and the HTTP reply body (if any).
  30  *
  31  \par
  32  *      When reading a swap file, there is a similar process to extract
  33  *      the swap meta data.  First, storeSwapMetaUnpack() converts a
  34  *      character buffer into a tlv linked list.  It also tells us
  35  *      the value for MemObject->swap_hdr_sz.
  36  */
  37
  38 #include "md5.h"
  39 #include "mem/forward.h"
  40 #include "store/forward.h"
  41
  42 /// maintains a 24-bit checksum over integer fields
  43 class SwapChecksum24
  44 {
  45 public:
  46     SwapChecksum24() { raw[0] = raw[1] = raw[2] = 0; }
  47
  48     bool operator ==(const SwapChecksum24 &o) const {
  49         return raw[0] == o.raw[0] && raw[1] == o.raw[1] && raw[2] == o.raw[2];
  50     }
  51
  52     bool operator !=(const SwapChecksum24 &o) const {
  53         return !(*this == o);
  54     }
  55
  56     /// compute and store checksum based on three 32bit integers
  57     void set(uint32_t f1, uint32_t f2, uint32_t f3);
  58
  59     /// compute and store checksum based on int32_t and uint64_t integers
  60     void set(int32_t f1, uint64_t f2);
  61
  62     // printing for debugging
  63     std::ostream &print(std::ostream &os) const;
  64
  65 private:
  66     uint8_t raw[3]; // designed to follow "op" members, in pading space
  67 };
  68
  69 inline std::ostream &
  70 operator <<(std::ostream &os, const SwapChecksum24 &sum)
  71 {
  72     return sum.print(os);
  73 }
  74
  75 /**
  76  \ingroup FielFormatSwapStateAPI
  77  *
  78  \par
  79  * Defines the structure of a binary swap.state file entry for UFS stores.
  80  * TODO: Move to fs/ufs
  81  *
  82  \note StoreSwapLogData entries are written in native machine byte order
  83  *     They are not necessarily portable across architectures.
  84  */
  85 class StoreSwapLogData
  86 {
  87     MEMPROXY_CLASS(StoreSwapLogData);
  88
  89 public:
  90     /// type to use for storing time-related members; must be signed
  91     typedef int64_t SwappedTime;
  92
  93     StoreSwapLogData();
  94
  95     /// consistency self-check: whether the data appears to make sense
  96     bool sane() const;
  97
  98     /// call this before storing the log entry
  99     void finalize();
 100
 101     /**
 102      * Either SWAP_LOG_ADD when an object is added to the disk storage,
 103      * or SWAP_LOG_DEL when an object is deleted.
 104      */
 105     uint8_t op;
 106
 107     /**
 108      * Fingerprint to weed out bogus/corrupted swap.state entries.
 109      */
 110     SwapChecksum24 checksum; // follows "op" because compiler will pad anyway
 111
 112     /**
 113      * The 32-bit file number which maps to a pathname.
 114      * Only the low 24-bits are relevant. The high 8-bits are
 115      * used as an index to an array of storage directories, and
 116      * are set at run time because the order of storage directories
 117      * may change over time.
 118      */
 119     sfileno swap_filen;
 120
 121     /**
 122      * A Unix time value that represents the time when
 123      * the origin server generated this response. If the response
 124      * has a valid Date: header, this timestamp corresponds
 125      * to that time. Otherwise, it is set to the Squid process time
 126      * when the response is read (as soon as the end of headers are found).
 127      */
 128     SwappedTime timestamp;
 129
 130     /**
 131      * The last time that a client requested this object.
 132      */
 133     SwappedTime lastref;
 134
 135     /**
 136      * The value of the response's Expires: header, if any.
 137      * If the response does not have an Expires: header, this
 138      * is set to -1.
 139      * If the response has an invalid (unparseable)
 140      * Expires: header, it is also set to -1.  There are some cases
 141      * where Squid sets expires to -2. This happens for the
 142      * internal "netdb" object and for FTP URL responses.
 143      */
 144     SwappedTime expires;
 145
 146     /**
 147      * The value of the response's Last-modified: header, if any.
 148      * This is set to -1 if there is no Last-modified: header,
 149      * or if it is unparseable.
 150      */
 151     SwappedTime lastmod;
 152
 153     /**
 154      * This is the number of bytes that the object occupies on
 155      * disk. It includes the Squid "swap file header".
 156      */
 157     uint64_t swap_file_sz;
 158
 159     /**
 160      * The number of times that this object has been accessed (referenced).
 161      * Since its a 16-bit quantity, it is susceptible to overflow
 162      * if a single object is accessed 65,536 times before being replaced.
 163      */
 164     uint16_t refcount;
 165
 166     /**
 167      * A copy of the StoreEntry flags field. Used as a sanity
 168      * check when rebuilding the cache at startup. Objects that
 169      * have the KEY_PRIVATE flag set are not added back to the cache.
 170      */
 171     uint16_t flags;
 172
 173     /**
 174      * The 128-bit MD5 hash for this object.
 175      */
 176     unsigned char key[SQUID_MD5_DIGEST_LENGTH];
 177 };
 178
 179 /// \ingroup FileFormatSwapStateAPI
 180 /// Swap log starts with this binary structure.
 181 class StoreSwapLogHeader
 182 {
 183 public:
 184     // sets default values for this Squid version; loaded values may differ
 185     StoreSwapLogHeader();
 186
 187     /// consistency self-check: whether the data appears to make sense
 188     bool sane() const;
 189
 190     /// number of bytes after the log header before the first log entry
 191     size_t gapSize() const;
 192
 193     uint8_t op;
 194     SwapChecksum24 checksum; // follows "op" because compiler will pad anyway
 195     int32_t version;
 196     int32_t record_size;
 197 };
 198
 199 #endif /* SQUID_STORESWAPLOGDATA_H */
 200