apt-pkg/pkgcache.h

   1 // -*- mode: cpp; mode: fold -*-
   2 // Description                                                          /*{{{*/
   3 /**\file pkgcache.h
   4    \brief pkgCache - Structure definitions for the cache file
   5
   6    The goal of the cache file is two fold:
   7    Firstly to speed loading and processing of the package file array and
   8    secondly to reduce memory consumption of the package file array.
   9
  10    The implementation is aimed at an environment with many primary package
  11    files, for instance someone that has a Package file for their CD-ROM, a
  12    Package file for the latest version of the distribution on the CD-ROM and a
  13    package file for the development version. Always present is the information
  14    contained in the status file which might be considered a separate package
  15    file.
  16
  17    Please understand, this is designed as a <b>Cache file</b> it is not meant to be
  18    used on any system other than the one it was created for. It is not meant to
  19    be authoritative either, i.e. if a system crash or software failure occurs it
  20    must be perfectly acceptable for the cache file to be in an inconsistent
  21    state. Furthermore at any time the cache file may be erased without losing
  22    any information.
  23
  24    Also the structures and storage layout is optimized for use by the APT
  25    and may not be suitable for all purposes. However it should be possible
  26    to extend it with associate cache files that contain other information.
  27
  28    To keep memory use down the cache file only contains often used fields and
  29    fields that are inexpensive to store, the Package file has a full list of
  30    fields. Also the client may assume that all items are perfectly valid and
  31    need not perform checks against their correctness. Removal of information
  32    from the cache is possible, but blanks will be left in the file, and
  33    unused strings will also be present. The recommended implementation is to
  34    simply rebuild the cache each time any of the data files change. It is
  35    possible to add a new package file to the cache without any negative side
  36    effects.
  37
  38    <b>Note on Pointer access</b>
  39    Clients should always use the CacheIterators classes for access to the
  40    cache and the data in it. They also provide a simple STL-like method for
  41    traversing the links of the datastructure.
  42
  43    Every item in every structure is stored as the index to that structure.
  44    What this means is that once the files is mmaped every data access has to
  45    go through a fix up stage to get a real memory pointer. This is done
  46    by taking the index, multiplying it by the type size and then adding
  47    it to the start address of the memory block. This sounds complex, but
  48    in C it is a single array dereference. Because all items are aligned to
  49    their size and indexes are stored as multiples of the size of the structure
  50    the format is immediately portable to all possible architectures - BUT the
  51    generated files are -NOT-.
  52
  53    This scheme allows code like this to be written:
  54    <example>
  55      void *Map = mmap(...);
  56      Package *PkgList = (Package *)Map;
  57      Header *Head = (Header *)Map;
  58      char *Strings = (char *)Map;
  59      cout << (Strings + PkgList[Head->HashTable[0]]->Name) << endl;
  60    </example>
  61    Notice the lack of casting or multiplication. The net result is to return
  62    the name of the first package in the first hash bucket, without error
  63    checks.
  64
  65    The generator uses allocation pools to group similarly sized structures in
  66    large blocks to eliminate any alignment overhead. The generator also
  67    assures that no structures overlap and all indexes are unique. Although
  68    at first glance it may seem like there is the potential for two structures
  69    to exist at the same point the generator never allows this to happen.
  70    (See the discussion of free space pools)
  71
  72    See \ref pkgcachegen.h for more information about generating cache structures. */
  73                                                                         /*}}}*/
  74 #ifndef PKGLIB_PKGCACHE_H
  75 #define PKGLIB_PKGCACHE_H
  76
  77 #include <apt-pkg/mmap.h>
  78 #include <apt-pkg/macros.h>
  79
  80 #include <string>
  81 #include <time.h>
  82 #include <stdint.h>
  83
  84 #ifndef APT_8_CLEANER_HEADERS
  85 using std::string;
  86 #endif
  87
  88 // size of (potentially big) files like debs or the install size of them
  89 typedef uint64_t map_filesize_t;
  90 // storing file sizes of indexes, which are way below 4 GB for now
  91 typedef uint32_t map_filesize_small_t;
  92 // each package/group/dependency gets an id
  93 typedef uint32_t map_id_t;
  94 // some files get an id, too, but in far less absolute numbers
  95 typedef uint16_t map_fileid_t;
  96 // relative pointer from cache start
  97 typedef uint32_t map_pointer_t;
  98 // same as the previous, but documented to be to a string item
  99 typedef map_pointer_t map_stringitem_t;
 100 // we have only a small amount of flags for each item
 101 typedef uint8_t map_flags_t;
 102 typedef uint8_t map_number_t;
 103
 104 class pkgVersioningSystem;
 105 class pkgCache                                                          /*{{{*/
 106 {
 107    public:
 108    // Cache element predeclarations
 109    struct Header;
 110    struct Group;
 111    struct Package;
 112    struct ReleaseFile;
 113    struct PackageFile;
 114    struct Version;
 115    struct Description;
 116    struct Provides;
 117    struct Dependency;
 118    struct DependencyData;
 119    struct StringItem;
 120    struct VerFile;
 121    struct DescFile;
 122
 123    // Iterators
 124    template<typename Str, typename Itr> class Iterator;
 125    class GrpIterator;
 126    class PkgIterator;
 127    class VerIterator;
 128    class DescIterator;
 129    class DepIterator;
 130    class PrvIterator;
 131    class RlsFileIterator;
 132    class PkgFileIterator;
 133    class VerFileIterator;
 134    class DescFileIterator;
 135
 136    class Namespace;
 137
 138    // These are all the constants used in the cache structures
 139
 140    // WARNING - if you change these lists you must also edit
 141    // the stringification in pkgcache.cc and also consider whether
 142    // the cache file will become incompatible.
 143    struct Dep
 144    {
 145       enum DepType {Depends=1,PreDepends=2,Suggests=3,Recommends=4,
 146          Conflicts=5,Replaces=6,Obsoletes=7,DpkgBreaks=8,Enhances=9};
 147       /** \brief available compare operators
 148
 149           The lower 4 bits are used to indicate what operator is being specified and
 150           the upper 4 bits are flags. OR indicates that the next package is
 151           or'd with the current package. */
 152       enum DepCompareOp {NoOp=0,LessEq=0x1,GreaterEq=0x2,Less=0x3,
 153          Greater=0x4,Equals=0x5,NotEquals=0x6,
 154          Or=0x10, /*!< or'ed with the next dependency */
 155          MultiArchImplicit=0x20, /*!< generated internally, not spelled out in the index */
 156          ArchSpecific=0x40 /*!< was decorated with an explicit architecture in index */
 157       };
 158    };
 159
 160    struct State
 161    {
 162       /** \brief priority of a package version
 163
 164           Zero is used for unparsable or absent Priority fields. */
 165       enum VerPriority {Required=1,Important=2,Standard=3,Optional=4,Extra=5};
 166       enum PkgSelectedState {Unknown=0,Install=1,Hold=2,DeInstall=3,Purge=4};
 167       enum PkgInstState {Ok=0,ReInstReq=1,HoldInst=2,HoldReInstReq=3};
 168       enum PkgCurrentState {NotInstalled=0,UnPacked=1,HalfConfigured=2,
 169            HalfInstalled=4,ConfigFiles=5,Installed=6,
 170            TriggersAwaited=7,TriggersPending=8};
 171    };
 172
 173    struct Flag
 174    {
 175       enum PkgFlags {Auto=(1<<0),Essential=(1<<3),Important=(1<<4)};
 176       enum PkgFFlags {
 177          NotSource=(1<<0), /*!< packages can't be fetched from here, e.g. dpkg/status file */
 178          LocalSource=(1<<1), /*!< local sources can't and will not be verified by hashes */
 179          NoPackages=(1<<2), /*!< the file includes no package records itself, but additions like Translations */
 180       };
 181       enum ReleaseFileFlags {
 182          NotAutomatic=(1<<0), /*!< archive has a default pin of 1 */
 183          ButAutomaticUpgrades=(1<<1), /*!< (together with the previous) archive has a default pin of 100 */
 184       };
 185       enum ProvidesFlags {
 186          MultiArchImplicit=pkgCache::Dep::MultiArchImplicit, /*!< generated internally, not spelled out in the index */
 187          ArchSpecific=pkgCache::Dep::ArchSpecific /*!< was decorated with an explicit architecture in index */
 188       };
 189    };
 190
 191    protected:
 192
 193    // Memory mapped cache file
 194    std::string CacheFile;
 195    MMap &Map;
 196
 197    map_id_t sHash(const std::string &S) const APT_PURE;
 198    map_id_t sHash(const char *S) const APT_PURE;
 199
 200    public:
 201
 202    // Pointers to the arrays of items
 203    Header *HeaderP;
 204    Group *GrpP;
 205    Package *PkgP;
 206    VerFile *VerFileP;
 207    DescFile *DescFileP;
 208    ReleaseFile *RlsFileP;
 209    PackageFile *PkgFileP;
 210    Version *VerP;
 211    Description *DescP;
 212    Provides *ProvideP;
 213    Dependency *DepP;
 214    DependencyData *DepDataP;
 215    APT_DEPRECATED StringItem *StringItemP;
 216    char *StrP;
 217
 218    virtual bool ReMap(bool const &Errorchecks = true);
 219    inline bool Sync() {return Map.Sync();}
 220    inline MMap &GetMap() {return Map;}
 221    inline void *DataEnd() {return ((unsigned char *)Map.Data()) + Map.Size();}
 222
 223    // String hashing function (512 range)
 224    inline map_id_t Hash(const std::string &S) const {return sHash(S);}
 225    inline map_id_t Hash(const char *S) const {return sHash(S);}
 226
 227    // Useful transformation things
 228    static const char *Priority(unsigned char Priority);
 229
 230    // Accessors
 231    GrpIterator FindGrp(const std::string &Name);
 232    PkgIterator FindPkg(const std::string &Name);
 233    PkgIterator FindPkg(const std::string &Name, const std::string &Arch);
 234
 235    Header &Head() {return *HeaderP;}
 236    inline GrpIterator GrpBegin();
 237    inline GrpIterator GrpEnd();
 238    inline PkgIterator PkgBegin();
 239    inline PkgIterator PkgEnd();
 240    inline PkgFileIterator FileBegin();
 241    inline PkgFileIterator FileEnd();
 242    inline RlsFileIterator RlsFileBegin();
 243    inline RlsFileIterator RlsFileEnd();
 244
 245    inline bool MultiArchCache() const { return MultiArchEnabled; }
 246    inline char const * NativeArch();
 247
 248    // Make me a function
 249    pkgVersioningSystem *VS;
 250
 251    // Converters
 252    static const char *CompTypeDeb(unsigned char Comp) APT_CONST;
 253    static const char *CompType(unsigned char Comp) APT_CONST;
 254    static const char *DepType(unsigned char Dep);
 255
 256    pkgCache(MMap *Map,bool DoMap = true);
 257    virtual ~pkgCache();
 258
 259 private:
 260    void * const d;
 261    bool MultiArchEnabled;
 262 };
 263                                                                         /*}}}*/
 264 // Header structure                                                     /*{{{*/
 265 struct pkgCache::Header
 266 {
 267    /** \brief Signature information
 268
 269        This must contain the hex value 0x98FE76DC which is designed to
 270        verify that the system loading the image has the same byte order
 271        and byte size as the system saving the image */
 272    uint32_t Signature;
 273    /** These contain the version of the cache file */
 274    map_number_t MajorVersion;
 275    map_number_t MinorVersion;
 276    /** \brief indicates if the cache should be erased
 277
 278        Dirty is true if the cache file was opened for reading, the client
 279        expects to have written things to it and have not fully synced it.
 280        The file should be erased and rebuilt if it is true. */
 281    bool Dirty;
 282
 283    /** \brief Size of structure values
 284
 285        All *Sz variables contains the sizeof() that particular structure.
 286        It is used as an extra consistency check on the structure of the file.
 287
 288        If any of the size values do not exactly match what the client expects
 289        then the client should refuse the load the file. */
 290    uint16_t HeaderSz;
 291    map_number_t GroupSz;
 292    map_number_t PackageSz;
 293    map_number_t ReleaseFileSz;
 294    map_number_t PackageFileSz;
 295    map_number_t VersionSz;
 296    map_number_t DescriptionSz;
 297    map_number_t DependencySz;
 298    map_number_t DependencyDataSz;
 299    map_number_t ProvidesSz;
 300    map_number_t VerFileSz;
 301    map_number_t DescFileSz;
 302
 303    /** \brief Structure counts
 304
 305        These indicate the number of each structure contained in the cache.
 306        PackageCount is especially useful for generating user state structures.
 307        See Package::Id for more info. */
 308    map_id_t GroupCount;
 309    map_id_t PackageCount;
 310    map_id_t VersionCount;
 311    map_id_t DescriptionCount;
 312    map_id_t DependsCount;
 313    map_id_t DependsDataCount;
 314    map_fileid_t ReleaseFileCount;
 315    map_fileid_t PackageFileCount;
 316    map_fileid_t VerFileCount;
 317    map_fileid_t DescFileCount;
 318    map_id_t ProvidesCount;
 319
 320    /** \brief index of the first PackageFile structure
 321
 322        The PackageFile structures are singly linked lists that represent
 323        all package files that have been merged into the cache. */
 324    map_pointer_t FileList;
 325    /** \brief index of the first ReleaseFile structure */
 326    map_pointer_t RlsFileList;
 327
 328    /** \brief String representing the version system used */
 329    map_pointer_t VerSysName;
 330    /** \brief native architecture the cache was built against */
 331    map_pointer_t Architecture;
 332    /** \brief all architectures the cache was built against */
 333    map_pointer_t Architectures;
 334    /** \brief The maximum size of a raw entry from the original Package file */
 335    map_filesize_t MaxVerFileSize;
 336    /** \brief The maximum size of a raw entry from the original Translation file */
 337    map_filesize_t MaxDescFileSize;
 338
 339    /** \brief The Pool structures manage the allocation pools that the generator uses
 340
 341        Start indicates the first byte of the pool, Count is the number of objects
 342        remaining in the pool and ItemSize is the structure size (alignment factor)
 343        of the pool. An ItemSize of 0 indicates the pool is empty. There should be
 344        the same number of pools as there are structure types. The generator
 345        stores this information so future additions can make use of any unused pool
 346        blocks. */
 347    DynamicMMap::Pool Pools[12];
 348
 349    /** \brief hash tables providing rapid group/package name lookup
 350
 351        Each group/package name is inserted into a hash table using pkgCache::Hash(const &string)
 352        By iterating over each entry in the hash table it is possible to iterate over
 353        the entire list of packages. Hash Collisions are handled with a singly linked
 354        list of packages based at the hash item. The linked list contains only
 355        packages that match the hashing function.
 356        In the PkgHashTable is it possible that multiple packages have the same name -
 357        these packages are stored as a sequence in the list.
 358        The size of both tables is the same. */
 359    uint32_t HashTableSize;
 360    uint32_t GetHashTableSize() const { return HashTableSize; }
 361    void SetHashTableSize(unsigned int const sz) { HashTableSize = sz; }
 362    map_pointer_t GetArchitectures() const { return Architectures; }
 363    void SetArchitectures(map_pointer_t const idx) { Architectures = idx; }
 364    map_pointer_t * PkgHashTableP() const { return (map_pointer_t*) (this + 1); }
 365    map_pointer_t * GrpHashTableP() const { return PkgHashTableP() + GetHashTableSize(); }
 366
 367    /** \brief Size of the complete cache file */
 368    map_filesize_small_t CacheFileSize;
 369
 370    bool CheckSizes(Header &Against) const APT_PURE;
 371    Header();
 372 };
 373                                                                         /*}}}*/
 374 // Group structure                                                      /*{{{*/
 375 /** \brief groups architecture depending packages together
 376
 377     On or more packages with the same name form a group, so we have
 378     a simple way to access a package built for different architectures
 379     Group exists in a singly linked list of group records starting at
 380     the hash index of the name in the pkgCache::Header::GrpHashTable */
 381 struct pkgCache::Group
 382 {
 383    /** \brief Name of the group */
 384    map_stringitem_t Name;
 385
 386    // Linked List
 387    /** \brief Link to the first package which belongs to the group */
 388    map_pointer_t FirstPackage;  // Package
 389    /** \brief Link to the last package which belongs to the group */
 390    map_pointer_t LastPackage;   // Package
 391    /** \brief Link to the next Group */
 392    map_pointer_t Next;          // Group
 393    /** \brief unique sequel ID */
 394    map_id_t ID;
 395
 396 };
 397                                                                         /*}}}*/
 398 // Package structure                                                    /*{{{*/
 399 /** \brief contains information for a single unique package
 400
 401     There can be any number of versions of a given package.
 402     Package exists in a singly linked list of package records starting at
 403     the hash index of the name in the pkgCache::Header::PkgHashTable
 404
 405     A package can be created for every architecture so package names are
 406     not unique, but it is guaranteed that packages with the same name
 407     are sequencel ordered in the list. Packages with the same name can be
 408     accessed with the Group.
 409 */
 410 struct pkgCache::Package
 411 {
 412    /** \brief Name of the package
 413     * Note that the access method Name() will remain. It is just this data member
 414     * deprecated as this information is already stored and available via the
 415     * associated Group – so it is wasting precious binary cache space */
 416    APT_DEPRECATED map_stringitem_t Name;
 417    /** \brief Architecture of the package */
 418    map_stringitem_t Arch;
 419    /** \brief Base of a singly linked list of versions
 420
 421        Each structure represents a unique version of the package.
 422        The version structures contain links into PackageFile and the
 423        original text file as well as detailed information about the size
 424        and dependencies of the specific package. In this way multiple
 425        versions of a package can be cleanly handled by the system.
 426        Furthermore, this linked list is guaranteed to be sorted
 427        from Highest version to lowest version with no duplicate entries. */
 428    map_pointer_t VersionList;       // Version
 429    /** \brief index to the installed version */
 430    map_pointer_t CurrentVer;        // Version
 431    /** \brief index of the group this package belongs to */
 432    map_pointer_t Group;             // Group the Package belongs to
 433
 434    // Linked list
 435    /** \brief Link to the next package in the same bucket */
 436    map_pointer_t NextPackage;       // Package
 437    /** \brief List of all dependencies on this package */
 438    map_pointer_t RevDepends;        // Dependency
 439    /** \brief List of all "packages" this package provide */
 440    map_pointer_t ProvidesList;      // Provides
 441
 442    // Install/Remove/Purge etc
 443    /** \brief state that the user wishes the package to be in */
 444    map_number_t SelectedState;     // What
 445    /** \brief installation state of the package
 446
 447        This should be "ok" but in case the installation failed
 448        it will be different.
 449    */
 450    map_number_t InstState;         // Flags
 451    /** \brief indicates if the package is installed */
 452    map_number_t CurrentState;      // State
 453
 454    /** \brief unique sequel ID
 455
 456        ID is a unique value from 0 to Header->PackageCount assigned by the generator.
 457        This allows clients to create an array of size PackageCount and use it to store
 458        state information for the package map. For instance the status file emitter uses
 459        this to track which packages have been emitted already. */
 460    map_id_t ID;
 461    /** \brief some useful indicators of the package's state */
 462    map_flags_t Flags;
 463 };
 464                                                                         /*}}}*/
 465 // Release File structure                                               /*{{{*/
 466 /** \brief stores information about the release files used to generate the cache
 467
 468     PackageFiles reference ReleaseFiles as we need to keep record of which
 469     version belongs to which release e.g. for pinning. */
 470 struct pkgCache::ReleaseFile
 471 {
 472    /** \brief physical disk file that this ReleaseFile represents */
 473    map_stringitem_t FileName;
 474    /** \brief the release information
 475
 476        Please see the files document for a description of what the
 477        release information means. */
 478    map_stringitem_t Archive;
 479    map_stringitem_t Codename;
 480    map_stringitem_t Version;
 481    map_stringitem_t Origin;
 482    map_stringitem_t Label;
 483    /** \brief The site the index file was fetched from */
 484    map_stringitem_t Site;
 485
 486    /** \brief Size of the file
 487
 488        Used together with the modification time as a
 489        simple check to ensure that the Packages
 490        file has not been altered since Cache generation. */
 491    map_filesize_t Size;
 492    /** \brief Modification time for the file */
 493    time_t mtime;
 494
 495    /** @TODO document PackageFile::Flags */
 496    map_flags_t Flags;
 497
 498    // Linked list
 499    /** \brief Link to the next ReleaseFile in the Cache */
 500    map_pointer_t NextFile;
 501    /** \brief unique sequel ID */
 502    map_fileid_t ID;
 503 };
 504                                                                         /*}}}*/
 505 // Package File structure                                               /*{{{*/
 506 /** \brief stores information about the files used to generate the cache
 507
 508     Package files are referenced by Version structures to be able to know
 509     after the generation still from which Packages file includes this Version
 510     as we need this information later on e.g. for pinning. */
 511 struct pkgCache::PackageFile
 512 {
 513    /** \brief physical disk file that this PackageFile represents */
 514    map_stringitem_t FileName;
 515    /** \brief the release information */
 516    map_pointer_t Release;
 517
 518    map_stringitem_t Component;
 519    map_stringitem_t Architecture;
 520
 521    /** \brief indicates what sort of index file this is
 522
 523        @TODO enumerate at least the possible indexes */
 524    map_stringitem_t IndexType;
 525    /** \brief Size of the file
 526
 527        Used together with the modification time as a
 528        simple check to ensure that the Packages
 529        file has not been altered since Cache generation. */
 530    map_filesize_t Size;
 531    /** \brief Modification time for the file */
 532    time_t mtime;
 533
 534    /** @TODO document PackageFile::Flags */
 535    map_flags_t Flags;
 536
 537    // Linked list
 538    /** \brief Link to the next PackageFile in the Cache */
 539    map_pointer_t NextFile;        // PackageFile
 540    /** \brief unique sequel ID */
 541    map_fileid_t ID;
 542 };
 543                                                                         /*}}}*/
 544 // VerFile structure                                                    /*{{{*/
 545 /** \brief associates a version with a PackageFile
 546
 547     This allows a full description of all Versions in all files
 548     (and hence all sources) under consideration. */
 549 struct pkgCache::VerFile
 550 {
 551    /** \brief index of the package file that this version was found in */
 552    map_pointer_t File;           // PackageFile
 553    /** \brief next step in the linked list */
 554    map_pointer_t NextFile;       // PkgVerFile
 555    /** \brief position in the package file */
 556    map_filesize_t Offset;         // File offset
 557    /** @TODO document pkgCache::VerFile::Size */
 558    map_filesize_t Size;
 559 };
 560                                                                         /*}}}*/
 561 // DescFile structure                                                   /*{{{*/
 562 /** \brief associates a description with a Translation file */
 563 struct pkgCache::DescFile
 564 {
 565    /** \brief index of the file that this description was found in */
 566    map_pointer_t File;           // PackageFile
 567    /** \brief next step in the linked list */
 568    map_pointer_t NextFile;       // PkgVerFile
 569    /** \brief position in the file */
 570    map_filesize_t Offset;         // File offset
 571    /** @TODO document pkgCache::DescFile::Size */
 572    map_filesize_t Size;
 573 };
 574                                                                         /*}}}*/
 575 // Version structure                                                    /*{{{*/
 576 /** \brief information for a single version of a package
 577
 578     The version list is always sorted from highest version to lowest
 579     version by the generator. Equal version numbers are either merged
 580     or handled as separate versions based on the Hash value. */
 581 struct pkgCache::Version
 582 {
 583    /** \brief complete version string */
 584    map_stringitem_t VerStr;
 585    /** \brief section this version is filled in */
 586    map_stringitem_t Section;
 587    /** \brief source package name this version comes from
 588       Always contains the name, even if it is the same as the binary name */
 589    map_stringitem_t SourcePkgName;
 590    /** \brief source version this version comes from
 591       Always contains the version string, even if it is the same as the binary version */
 592    map_stringitem_t SourceVerStr;
 593
 594    /** \brief Multi-Arch capabilities of a package version */
 595    enum VerMultiArch { No = 0, /*!< is the default and doesn't trigger special behaviour */
 596                        All = (1<<0), /*!< will cause that Ver.Arch() will report "all" */
 597                        Foreign = (1<<1), /*!< can satisfy dependencies in another architecture */
 598                        Same = (1<<2), /*!< can be co-installed with itself from other architectures */
 599                        Allowed = (1<<3), /*!< other packages are allowed to depend on thispkg:any */
 600                        AllForeign = All | Foreign,
 601                        AllAllowed = All | Allowed };
 602
 603    /** \brief deprecated variant of No */
 604    static const APT_DEPRECATED VerMultiArch None = No;
 605
 606    /** \brief stores the MultiArch capabilities of this version
 607
 608        Flags used are defined in pkgCache::Version::VerMultiArch
 609    */
 610    map_number_t MultiArch;
 611
 612    /** \brief references all the PackageFile's that this version came from
 613
 614        FileList can be used to determine what distribution(s) the Version
 615        applies to. If FileList is 0 then this is a blank version.
 616        The structure should also have a 0 in all other fields excluding
 617        pkgCache::Version::VerStr and Possibly pkgCache::Version::NextVer. */
 618    map_pointer_t FileList;          // VerFile
 619    /** \brief next (lower or equal) version in the linked list */
 620    map_pointer_t NextVer;           // Version
 621    /** \brief next description in the linked list */
 622    map_pointer_t DescriptionList;   // Description
 623    /** \brief base of the dependency list */
 624    map_pointer_t DependsList;       // Dependency
 625    /** \brief links to the owning package
 626
 627        This allows reverse dependencies to determine the package */
 628    map_pointer_t ParentPkg;         // Package
 629    /** \brief list of pkgCache::Provides */
 630    map_pointer_t ProvidesList;      // Provides
 631
 632    /** \brief archive size for this version
 633
 634        For Debian this is the size of the .deb file. */
 635    map_filesize_t Size; // These are the .deb size
 636    /** \brief uncompressed size for this version */
 637    map_filesize_t InstalledSize;
 638    /** \brief characteristic value representing this version
 639
 640        No two packages in existence should have the same VerStr
 641        and Hash with different contents. */
 642    unsigned short Hash;
 643    /** \brief unique sequel ID */
 644    map_id_t ID;
 645    /** \brief parsed priority value */
 646    map_number_t Priority;
 647 };
 648                                                                         /*}}}*/
 649 // Description structure                                                /*{{{*/
 650 /** \brief datamember of a linked list of available description for a version */
 651 struct pkgCache::Description
 652 {
 653    /** \brief Language code of this description (translation)
 654
 655        If the value has a 0 length then this is read using the Package
 656        file else the Translation-CODE file is used. */
 657    map_stringitem_t language_code;
 658    /** \brief MD5sum of the original description
 659
 660        Used to map Translations of a description to a version
 661        and to check that the Translation is up-to-date. */
 662    map_stringitem_t md5sum;
 663
 664    /** @TODO document pkgCache::Description::FileList */
 665    map_pointer_t FileList;          // DescFile
 666    /** \brief next translation for this description */
 667    map_pointer_t NextDesc;          // Description
 668    /** \brief the text is a description of this package */
 669    map_pointer_t ParentPkg;         // Package
 670
 671    /** \brief unique sequel ID */
 672    map_id_t ID;
 673 };
 674                                                                         /*}}}*/
 675 // Dependency structure                                                 /*{{{*/
 676 /** \brief information for a single dependency record
 677
 678     The records are split up like this to ease processing by the client.
 679     The base of the linked list is pkgCache::Version::DependsList.
 680     All forms of dependencies are recorded here including Depends,
 681     Recommends, Suggests, Enhances, Conflicts, Replaces and Breaks. */
 682 struct pkgCache::DependencyData
 683 {
 684    /** \brief string of the version the dependency is applied against */
 685    map_stringitem_t Version;
 686    /** \brief index of the package this depends applies to
 687
 688        The generator will - if the package does not already exist -
 689        create a blank (no version records) package. */
 690    map_pointer_t Package;         // Package
 691
 692    /** \brief Dependency type - Depends, Recommends, Conflicts, etc */
 693    map_number_t Type;
 694    /** \brief comparison operator specified on the depends line
 695
 696        If the high bit is set then it is a logical OR with the previous record. */
 697    map_flags_t CompareOp;
 698
 699    map_pointer_t NextData;
 700 };
 701 struct pkgCache::Dependency
 702 {
 703    map_pointer_t DependencyData;  // DependencyData
 704    /** \brief version of the package which has the depends */
 705    map_pointer_t ParentVer;       // Version
 706    /** \brief next reverse dependency of this package */
 707    map_pointer_t NextRevDepends;  // Dependency
 708    /** \brief next dependency of this version */
 709    map_pointer_t NextDepends;     // Dependency
 710
 711    /** \brief unique sequel ID */
 712    map_id_t ID;
 713 };
 714                                                                         /*}}}*/
 715 // Provides structure                                                   /*{{{*/
 716 /** \brief handles virtual packages
 717
 718     When a Provides: line is encountered a new provides record is added
 719     associating the package with a virtual package name.
 720     The provides structures are linked off the package structures.
 721     This simplifies the analysis of dependencies and other aspects A provides
 722     refers to a specific version of a specific package, not all versions need to
 723     provide that provides.*/
 724 struct pkgCache::Provides
 725 {
 726    /** \brief index of the package providing this */
 727    map_pointer_t ParentPkg;        // Package
 728    /** \brief index of the version this provide line applies to */
 729    map_pointer_t Version;          // Version
 730    /** \brief version in the provides line (if any)
 731
 732        This version allows dependencies to depend on specific versions of a
 733        Provides, as well as allowing Provides to override existing packages. */
 734    map_stringitem_t ProvideVersion;
 735    map_flags_t Flags;
 736    /** \brief next provides (based of package) */
 737    map_pointer_t NextProvides;     // Provides
 738    /** \brief next provides (based of version) */
 739    map_pointer_t NextPkgProv;      // Provides
 740 };
 741                                                                         /*}}}*/
 742 // UNUSED StringItem structure                                          /*{{{*/
 743 struct APT_DEPRECATED  pkgCache::StringItem
 744 {
 745    /** \brief string this refers to */
 746    map_ptrloc String;        // StringItem
 747    /** \brief Next link in the chain */
 748    map_ptrloc NextItem;      // StringItem
 749 };
 750                                                                         /*}}}*/
 751
 752 inline char const * pkgCache::NativeArch()
 753         { return StrP + HeaderP->Architecture; }
 754
 755 #include <apt-pkg/cacheiterators.h>
 756
 757 inline pkgCache::GrpIterator pkgCache::GrpBegin()
 758        {return GrpIterator(*this);}
 759 inline pkgCache::GrpIterator pkgCache::GrpEnd()
 760        {return GrpIterator(*this,GrpP);}
 761 inline pkgCache::PkgIterator pkgCache::PkgBegin()
 762        {return PkgIterator(*this);}
 763 inline pkgCache::PkgIterator pkgCache::PkgEnd()
 764        {return PkgIterator(*this,PkgP);}
 765 inline pkgCache::PkgFileIterator pkgCache::FileBegin()
 766        {return PkgFileIterator(*this,PkgFileP + HeaderP->FileList);}
 767 inline pkgCache::PkgFileIterator pkgCache::FileEnd()
 768        {return PkgFileIterator(*this,PkgFileP);}
 769 inline pkgCache::RlsFileIterator pkgCache::RlsFileBegin()
 770        {return RlsFileIterator(*this,RlsFileP + HeaderP->RlsFileList);}
 771 inline pkgCache::RlsFileIterator pkgCache::RlsFileEnd()
 772        {return RlsFileIterator(*this,RlsFileP);}
 773
 774
 775 // Oh I wish for Real Name Space Support
 776 class pkgCache::Namespace                                               /*{{{*/
 777 {
 778    public:
 779    typedef pkgCache::GrpIterator GrpIterator;
 780    typedef pkgCache::PkgIterator PkgIterator;
 781    typedef pkgCache::VerIterator VerIterator;
 782    typedef pkgCache::DescIterator DescIterator;
 783    typedef pkgCache::DepIterator DepIterator;
 784    typedef pkgCache::PrvIterator PrvIterator;
 785    typedef pkgCache::RlsFileIterator RlsFileIterator;
 786    typedef pkgCache::PkgFileIterator PkgFileIterator;
 787    typedef pkgCache::VerFileIterator VerFileIterator;
 788    typedef pkgCache::Version Version;
 789    typedef pkgCache::Description Description;
 790    typedef pkgCache::Package Package;
 791    typedef pkgCache::Header Header;
 792    typedef pkgCache::Dep Dep;
 793    typedef pkgCache::Flag Flag;
 794 };
 795                                                                         /*}}}*/
 796 #endif