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 // storing file sizes of indexes, which are way below 4 GB for now
  89 typedef uint32_t map_filesize_t;
  90 // each package/group/dependency gets an id
  91 typedef uint32_t map_id_t;
  92 // some files get an id, too, but in far less absolute numbers
  93 typedef uint16_t map_fileid_t;
  94 // relative pointer from cache start
  95 typedef uint32_t map_pointer_t;
  96 // same as the previous, but documented to be to a string item
  97 typedef map_pointer_t map_stringitem_t;
  98
  99 class pkgVersioningSystem;
 100 class pkgCache                                                          /*{{{*/
 101 {
 102    public:
 103    // Cache element predeclarations
 104    struct Header;
 105    struct Group;
 106    struct Package;
 107    struct PackageFile;
 108    struct Version;
 109    struct Description;
 110    struct Provides;
 111    struct Dependency;
 112    struct VerFile;
 113    struct DescFile;
 114
 115    // Iterators
 116    template<typename Str, typename Itr> class Iterator;
 117    class GrpIterator;
 118    class PkgIterator;
 119    class VerIterator;
 120    class DescIterator;
 121    class DepIterator;
 122    class PrvIterator;
 123    class PkgFileIterator;
 124    class VerFileIterator;
 125    class DescFileIterator;
 126
 127    class Namespace;
 128
 129    // These are all the constants used in the cache structures
 130
 131    // WARNING - if you change these lists you must also edit
 132    // the stringification in pkgcache.cc and also consider whether
 133    // the cache file will become incompatible.
 134    struct Dep
 135    {
 136       enum DepType {Depends=1,PreDepends=2,Suggests=3,Recommends=4,
 137          Conflicts=5,Replaces=6,Obsoletes=7,DpkgBreaks=8,Enhances=9};
 138       /** \brief available compare operators
 139
 140           The lower 4 bits are used to indicate what operator is being specified and
 141           the upper 4 bits are flags. OR indicates that the next package is
 142           or'd with the current package. */
 143       enum DepCompareOp {Or=0x10,NoOp=0,LessEq=0x1,GreaterEq=0x2,Less=0x3,
 144          Greater=0x4,Equals=0x5,NotEquals=0x6};
 145    };
 146
 147    struct State
 148    {
 149       /** \brief priority of a package version
 150
 151           Zero is used for unparsable or absent Priority fields. */
 152       enum VerPriority {Required=1,Important=2,Standard=3,Optional=4,Extra=5};
 153       enum PkgSelectedState {Unknown=0,Install=1,Hold=2,DeInstall=3,Purge=4};
 154       enum PkgInstState {Ok=0,ReInstReq=1,HoldInst=2,HoldReInstReq=3};
 155       enum PkgCurrentState {NotInstalled=0,UnPacked=1,HalfConfigured=2,
 156            HalfInstalled=4,ConfigFiles=5,Installed=6,
 157            TriggersAwaited=7,TriggersPending=8};
 158    };
 159
 160    struct Flag
 161    {
 162       enum PkgFlags {Auto=(1<<0),Essential=(1<<3),Important=(1<<4)};
 163       enum PkgFFlags {NotSource=(1<<0),NotAutomatic=(1<<1),ButAutomaticUpgrades=(1<<2)};
 164    };
 165
 166    protected:
 167
 168    // Memory mapped cache file
 169    std::string CacheFile;
 170    MMap &Map;
 171
 172    map_id_t sHash(const std::string &S) const APT_PURE;
 173    map_id_t sHash(const char *S) const APT_PURE;
 174
 175    public:
 176
 177    // Pointers to the arrays of items
 178    Header *HeaderP;
 179    Group *GrpP;
 180    Package *PkgP;
 181    VerFile *VerFileP;
 182    DescFile *DescFileP;
 183    PackageFile *PkgFileP;
 184    Version *VerP;
 185    Description *DescP;
 186    Provides *ProvideP;
 187    Dependency *DepP;
 188    char *StrP;
 189
 190    virtual bool ReMap(bool const &Errorchecks = true);
 191    inline bool Sync() {return Map.Sync();}
 192    inline MMap &GetMap() {return Map;}
 193    inline void *DataEnd() {return ((unsigned char *)Map.Data()) + Map.Size();}
 194
 195    // String hashing function (512 range)
 196    inline map_id_t Hash(const std::string &S) const {return sHash(S);}
 197    inline map_id_t Hash(const char *S) const {return sHash(S);}
 198
 199    // Useful transformation things
 200    const char *Priority(unsigned char Priority);
 201
 202    // Accessors
 203    GrpIterator FindGrp(const std::string &Name);
 204    PkgIterator FindPkg(const std::string &Name);
 205    PkgIterator FindPkg(const std::string &Name, const std::string &Arch);
 206
 207    Header &Head() {return *HeaderP;}
 208    inline GrpIterator GrpBegin();
 209    inline GrpIterator GrpEnd();
 210    inline PkgIterator PkgBegin();
 211    inline PkgIterator PkgEnd();
 212    inline PkgFileIterator FileBegin();
 213    inline PkgFileIterator FileEnd();
 214
 215    inline bool MultiArchCache() const { return MultiArchEnabled; }
 216    inline char const * NativeArch();
 217
 218    // Make me a function
 219    pkgVersioningSystem *VS;
 220
 221    // Converters
 222    static const char *CompTypeDeb(unsigned char Comp) APT_CONST;
 223    static const char *CompType(unsigned char Comp) APT_CONST;
 224    static const char *DepType(unsigned char Dep);
 225
 226    pkgCache(MMap *Map,bool DoMap = true);
 227    virtual ~pkgCache() {}
 228
 229 private:
 230    bool MultiArchEnabled;
 231    APT_HIDDEN PkgIterator SingleArchFindPkg(const std::string &Name);
 232 };
 233                                                                         /*}}}*/
 234 // Header structure                                                     /*{{{*/
 235 struct pkgCache::Header
 236 {
 237    /** \brief Signature information
 238
 239        This must contain the hex value 0x98FE76DC which is designed to
 240        verify that the system loading the image has the same byte order
 241        and byte size as the system saving the image */
 242    unsigned long Signature;
 243    /** These contain the version of the cache file */
 244    short MajorVersion;
 245    short MinorVersion;
 246    /** \brief indicates if the cache should be erased
 247
 248        Dirty is true if the cache file was opened for reading, the client
 249        expects to have written things to it and have not fully synced it.
 250        The file should be erased and rebuilt if it is true. */
 251    bool Dirty;
 252
 253    /** \brief Size of structure values
 254
 255        All *Sz variables contains the sizeof() that particular structure.
 256        It is used as an extra consistency check on the structure of the file.
 257
 258        If any of the size values do not exactly match what the client expects
 259        then the client should refuse the load the file. */
 260    unsigned short HeaderSz;
 261    unsigned short GroupSz;
 262    unsigned short PackageSz;
 263    unsigned short PackageFileSz;
 264    unsigned short VersionSz;
 265    unsigned short DescriptionSz;
 266    unsigned short DependencySz;
 267    unsigned short ProvidesSz;
 268    unsigned short VerFileSz;
 269    unsigned short DescFileSz;
 270
 271    /** \brief Structure counts
 272
 273        These indicate the number of each structure contained in the cache.
 274        PackageCount is especially useful for generating user state structures.
 275        See Package::Id for more info. */
 276    map_id_t GroupCount;
 277    map_id_t PackageCount;
 278    map_id_t VersionCount;
 279    map_id_t DescriptionCount;
 280    map_id_t DependsCount;
 281    map_fileid_t PackageFileCount;
 282    map_fileid_t VerFileCount;
 283    map_fileid_t DescFileCount;
 284    map_id_t ProvidesCount;
 285
 286    /** \brief index of the first PackageFile structure
 287
 288        The PackageFile structures are singly linked lists that represent
 289        all package files that have been merged into the cache. */
 290    map_pointer_t FileList;
 291    /** \brief String representing the version system used */
 292    map_pointer_t VerSysName;
 293    /** \brief native architecture the cache was built against */
 294    map_pointer_t Architecture;
 295    /** \brief all architectures the cache was built against */
 296    map_pointer_t Architectures;
 297    /** \brief The maximum size of a raw entry from the original Package file */
 298    map_filesize_t MaxVerFileSize;
 299    /** \brief The maximum size of a raw entry from the original Translation file */
 300    map_filesize_t MaxDescFileSize;
 301
 302    /** \brief The Pool structures manage the allocation pools that the generator uses
 303
 304        Start indicates the first byte of the pool, Count is the number of objects
 305        remaining in the pool and ItemSize is the structure size (alignment factor)
 306        of the pool. An ItemSize of 0 indicates the pool is empty. There should be
 307        the same number of pools as there are structure types. The generator
 308        stores this information so future additions can make use of any unused pool
 309        blocks. */
 310    DynamicMMap::Pool Pools[9];
 311
 312    /** \brief hash tables providing rapid group/package name lookup
 313
 314        Each group/package name is inserted into a hash table using pkgCache::Hash(const &string)
 315        By iterating over each entry in the hash table it is possible to iterate over
 316        the entire list of packages. Hash Collisions are handled with a singly linked
 317        list of packages based at the hash item. The linked list contains only
 318        packages that match the hashing function.
 319        In the PkgHashTable is it possible that multiple packages have the same name -
 320        these packages are stored as a sequence in the list.
 321        The size of both tables is the same. */
 322    unsigned int HashTableSize;
 323    map_pointer_t * PkgHashTable() const { return (map_pointer_t*) (this + 1); }
 324    map_pointer_t * GrpHashTable() const { return PkgHashTable() + HashTableSize; }
 325
 326    /** \brief Size of the complete cache file */
 327    unsigned long long CacheFileSize;
 328
 329    bool CheckSizes(Header &Against) const APT_PURE;
 330    Header();
 331 };
 332                                                                         /*}}}*/
 333 // Group structure                                                      /*{{{*/
 334 /** \brief groups architecture depending packages together
 335
 336     On or more packages with the same name form a group, so we have
 337     a simple way to access a package built for different architectures
 338     Group exists in a singly linked list of group records starting at
 339     the hash index of the name in the pkgCache::Header::GrpHashTable */
 340 struct pkgCache::Group
 341 {
 342    /** \brief Name of the group */
 343    map_stringitem_t Name;
 344
 345    // Linked List
 346    /** \brief Link to the first package which belongs to the group */
 347    map_pointer_t FirstPackage;  // Package
 348    /** \brief Link to the last package which belongs to the group */
 349    map_pointer_t LastPackage;   // Package
 350    /** \brief Link to the next Group */
 351    map_pointer_t Next;          // Group
 352    /** \brief unique sequel ID */
 353    map_id_t ID;
 354
 355 };
 356                                                                         /*}}}*/
 357 // Package structure                                                    /*{{{*/
 358 /** \brief contains information for a single unique package
 359
 360     There can be any number of versions of a given package.
 361     Package exists in a singly linked list of package records starting at
 362     the hash index of the name in the pkgCache::Header::PkgHashTable
 363
 364     A package can be created for every architecture so package names are
 365     not unique, but it is guaranteed that packages with the same name
 366     are sequencel ordered in the list. Packages with the same name can be
 367     accessed with the Group.
 368 */
 369 struct pkgCache::Package
 370 {
 371    /** \brief Name of the package
 372     * Note that the access method Name() will remain. It is just this data member
 373     * deprecated as this information is already stored and available via the
 374     * associated Group – so it is wasting precious binary cache space */
 375    APT_DEPRECATED map_stringitem_t Name;
 376    /** \brief Architecture of the package */
 377    map_stringitem_t Arch;
 378    /** \brief Base of a singly linked list of versions
 379
 380        Each structure represents a unique version of the package.
 381        The version structures contain links into PackageFile and the
 382        original text file as well as detailed information about the size
 383        and dependencies of the specific package. In this way multiple
 384        versions of a package can be cleanly handled by the system.
 385        Furthermore, this linked list is guaranteed to be sorted
 386        from Highest version to lowest version with no duplicate entries. */
 387    map_pointer_t VersionList;       // Version
 388    /** \brief index to the installed version */
 389    map_pointer_t CurrentVer;        // Version
 390    /** \brief index of the group this package belongs to */
 391    map_pointer_t Group;             // Group the Package belongs to
 392
 393    // Linked list
 394    /** \brief Link to the next package in the same bucket */
 395    map_pointer_t Next;       // Package
 396    /** \brief List of all dependencies on this package */
 397    map_pointer_t RevDepends;        // Dependency
 398    /** \brief List of all "packages" this package provide */
 399    map_pointer_t ProvidesList;      // Provides
 400
 401    // Install/Remove/Purge etc
 402    /** \brief state that the user wishes the package to be in */
 403    unsigned char SelectedState;     // What
 404    /** \brief installation state of the package
 405
 406        This should be "ok" but in case the installation failed
 407        it will be different.
 408    */
 409    unsigned char InstState;         // Flags
 410    /** \brief indicates if the package is installed */
 411    unsigned char CurrentState;      // State
 412
 413    /** \brief unique sequel ID
 414
 415        ID is a unique value from 0 to Header->PackageCount assigned by the generator.
 416        This allows clients to create an array of size PackageCount and use it to store
 417        state information for the package map. For instance the status file emitter uses
 418        this to track which packages have been emitted already. */
 419    map_id_t ID;
 420    /** \brief some useful indicators of the package's state */
 421    unsigned long Flags;
 422 };
 423                                                                         /*}}}*/
 424 // Package File structure                                               /*{{{*/
 425 /** \brief stores information about the files used to generate the cache
 426
 427     Package files are referenced by Version structures to be able to know
 428     after the generation still from which Packages file includes this Version
 429     as we need this information later on e.g. for pinning. */
 430 struct pkgCache::PackageFile
 431 {
 432    /** \brief physical disk file that this PackageFile represents */
 433    map_stringitem_t FileName;
 434    /** \brief the release information
 435
 436        Please see the files document for a description of what the
 437        release information means. */
 438    map_stringitem_t Archive;
 439    map_stringitem_t Codename;
 440    map_stringitem_t Component;
 441    map_stringitem_t Version;
 442    map_stringitem_t Origin;
 443    map_stringitem_t Label;
 444    map_stringitem_t Architecture;
 445    /** \brief The site the index file was fetched from */
 446    map_stringitem_t Site;
 447    /** \brief indicates what sort of index file this is
 448
 449        @TODO enumerate at least the possible indexes */
 450    map_stringitem_t IndexType;
 451    /** \brief Size of the file
 452
 453        Used together with the modification time as a
 454        simple check to ensure that the Packages
 455        file has not been altered since Cache generation. */
 456    map_filesize_t Size;
 457    /** \brief Modification time for the file */
 458    time_t mtime;
 459
 460    /** @TODO document PackageFile::Flags */
 461    unsigned long Flags;
 462
 463    // Linked list
 464    /** \brief Link to the next PackageFile in the Cache */
 465    map_pointer_t NextFile;        // PackageFile
 466    /** \brief unique sequel ID */
 467    map_fileid_t ID;
 468 };
 469                                                                         /*}}}*/
 470 // VerFile structure                                                    /*{{{*/
 471 /** \brief associates a version with a PackageFile
 472
 473     This allows a full description of all Versions in all files
 474     (and hence all sources) under consideration. */
 475 struct pkgCache::VerFile
 476 {
 477    /** \brief index of the package file that this version was found in */
 478    map_pointer_t File;           // PackageFile
 479    /** \brief next step in the linked list */
 480    map_pointer_t NextFile;       // PkgVerFile
 481    /** \brief position in the package file */
 482    map_filesize_t Offset;         // File offset
 483    /** @TODO document pkgCache::VerFile::Size */
 484    map_filesize_t Size;
 485 };
 486                                                                         /*}}}*/
 487 // DescFile structure                                                   /*{{{*/
 488 /** \brief associates a description with a Translation file */
 489 struct pkgCache::DescFile
 490 {
 491    /** \brief index of the file that this description was found in */
 492    map_pointer_t File;           // PackageFile
 493    /** \brief next step in the linked list */
 494    map_pointer_t NextFile;       // PkgVerFile
 495    /** \brief position in the file */
 496    map_filesize_t Offset;         // File offset
 497    /** @TODO document pkgCache::DescFile::Size */
 498    map_filesize_t Size;
 499 };
 500                                                                         /*}}}*/
 501 // Version structure                                                    /*{{{*/
 502 /** \brief information for a single version of a package
 503
 504     The version list is always sorted from highest version to lowest
 505     version by the generator. Equal version numbers are either merged
 506     or handled as separate versions based on the Hash value. */
 507 struct pkgCache::Version
 508 {
 509    /** \brief complete version string */
 510    map_stringitem_t VerStr;
 511    /** \brief section this version is filled in */
 512    map_stringitem_t Section;
 513    /** \brief source package name this version comes from
 514       Always contains the name, even if it is the same as the binary name */
 515    map_stringitem_t SourcePkgName;
 516    /** \brief source version this version comes from
 517       Always contains the version string, even if it is the same as the binary version */
 518    map_stringitem_t SourceVerStr;
 519
 520    /** \brief Multi-Arch capabilities of a package version */
 521    enum VerMultiArch { None = 0, /*!< is the default and doesn't trigger special behaviour */
 522                        All = (1<<0), /*!< will cause that Ver.Arch() will report "all" */
 523                        Foreign = (1<<1), /*!< can satisfy dependencies in another architecture */
 524                        Same = (1<<2), /*!< can be co-installed with itself from other architectures */
 525                        Allowed = (1<<3), /*!< other packages are allowed to depend on thispkg:any */
 526                        AllForeign = All | Foreign,
 527                        AllAllowed = All | Allowed };
 528    /** \brief stores the MultiArch capabilities of this version
 529
 530        Flags used are defined in pkgCache::Version::VerMultiArch
 531    */
 532    unsigned char MultiArch;
 533
 534    /** \brief references all the PackageFile's that this version came from
 535
 536        FileList can be used to determine what distribution(s) the Version
 537        applies to. If FileList is 0 then this is a blank version.
 538        The structure should also have a 0 in all other fields excluding
 539        pkgCache::Version::VerStr and Possibly pkgCache::Version::NextVer. */
 540    map_pointer_t FileList;          // VerFile
 541    /** \brief next (lower or equal) version in the linked list */
 542    map_pointer_t NextVer;           // Version
 543    /** \brief next description in the linked list */
 544    map_pointer_t DescriptionList;   // Description
 545    /** \brief base of the dependency list */
 546    map_pointer_t DependsList;       // Dependency
 547    /** \brief links to the owning package
 548
 549        This allows reverse dependencies to determine the package */
 550    map_pointer_t ParentPkg;         // Package
 551    /** \brief list of pkgCache::Provides */
 552    map_pointer_t ProvidesList;      // Provides
 553
 554    /** \brief archive size for this version
 555
 556        For Debian this is the size of the .deb file. */
 557    uint64_t Size; // These are the .deb size
 558    /** \brief uncompressed size for this version */
 559    uint64_t InstalledSize;
 560    /** \brief characteristic value representing this version
 561
 562        No two packages in existence should have the same VerStr
 563        and Hash with different contents. */
 564    unsigned short Hash;
 565    /** \brief unique sequel ID */
 566    map_id_t ID;
 567    /** \brief parsed priority value */
 568    unsigned char Priority;
 569 };
 570                                                                         /*}}}*/
 571 // Description structure                                                /*{{{*/
 572 /** \brief datamember of a linked list of available description for a version */
 573 struct pkgCache::Description
 574 {
 575    /** \brief Language code of this description (translation)
 576
 577        If the value has a 0 length then this is read using the Package
 578        file else the Translation-CODE file is used. */
 579    map_stringitem_t language_code;
 580    /** \brief MD5sum of the original description
 581
 582        Used to map Translations of a description to a version
 583        and to check that the Translation is up-to-date. */
 584    map_stringitem_t md5sum;
 585
 586    /** @TODO document pkgCache::Description::FileList */
 587    map_pointer_t FileList;          // DescFile
 588    /** \brief next translation for this description */
 589    map_pointer_t NextDesc;          // Description
 590    /** \brief the text is a description of this package */
 591    map_pointer_t ParentPkg;         // Package
 592
 593    /** \brief unique sequel ID */
 594    map_id_t ID;
 595 };
 596                                                                         /*}}}*/
 597 // Dependency structure                                                 /*{{{*/
 598 /** \brief information for a single dependency record
 599
 600     The records are split up like this to ease processing by the client.
 601     The base of the linked list is pkgCache::Version::DependsList.
 602     All forms of dependencies are recorded here including Depends,
 603     Recommends, Suggests, Enhances, Conflicts, Replaces and Breaks. */
 604 struct pkgCache::Dependency
 605 {
 606    /** \brief string of the version the dependency is applied against */
 607    map_stringitem_t Version;
 608    /** \brief index of the package this depends applies to
 609
 610        The generator will - if the package does not already exist -
 611        create a blank (no version records) package. */
 612    map_pointer_t Package;         // Package
 613    /** \brief next dependency of this version */
 614    map_pointer_t NextDepends;     // Dependency
 615    /** \brief next reverse dependency of this package */
 616    map_pointer_t NextRevDepends;  // Dependency
 617    /** \brief version of the package which has the reverse depends */
 618    map_pointer_t ParentVer;       // Version
 619
 620    /** \brief unique sequel ID */
 621    map_id_t ID;
 622    /** \brief Dependency type - Depends, Recommends, Conflicts, etc */
 623    unsigned char Type;
 624    /** \brief comparison operator specified on the depends line
 625
 626        If the high bit is set then it is a logical OR with the previous record. */
 627    unsigned char CompareOp;
 628 };
 629                                                                         /*}}}*/
 630 // Provides structure                                                   /*{{{*/
 631 /** \brief handles virtual packages
 632
 633     When a Provides: line is encountered a new provides record is added
 634     associating the package with a virtual package name.
 635     The provides structures are linked off the package structures.
 636     This simplifies the analysis of dependencies and other aspects A provides
 637     refers to a specific version of a specific package, not all versions need to
 638     provide that provides.*/
 639 struct pkgCache::Provides
 640 {
 641    /** \brief index of the package providing this */
 642    map_pointer_t ParentPkg;        // Package
 643    /** \brief index of the version this provide line applies to */
 644    map_pointer_t Version;          // Version
 645    /** \brief version in the provides line (if any)
 646
 647        This version allows dependencies to depend on specific versions of a
 648        Provides, as well as allowing Provides to override existing packages.
 649        This is experimental. Note that Debian doesn't allow versioned provides */
 650    map_stringitem_t ProvideVersion;
 651    /** \brief next provides (based of package) */
 652    map_pointer_t NextProvides;     // Provides
 653    /** \brief next provides (based of version) */
 654    map_pointer_t NextPkgProv;      // Provides
 655 };
 656                                                                         /*}}}*/
 657
 658 inline char const * pkgCache::NativeArch()
 659         { return StrP + HeaderP->Architecture; }
 660
 661 #include <apt-pkg/cacheiterators.h>
 662
 663 inline pkgCache::GrpIterator pkgCache::GrpBegin()
 664        {return GrpIterator(*this);}
 665 inline pkgCache::GrpIterator pkgCache::GrpEnd()
 666        {return GrpIterator(*this,GrpP);}
 667 inline pkgCache::PkgIterator pkgCache::PkgBegin()
 668        {return PkgIterator(*this);}
 669 inline pkgCache::PkgIterator pkgCache::PkgEnd()
 670        {return PkgIterator(*this,PkgP);}
 671 inline pkgCache::PkgFileIterator pkgCache::FileBegin()
 672        {return PkgFileIterator(*this,PkgFileP + HeaderP->FileList);}
 673 inline pkgCache::PkgFileIterator pkgCache::FileEnd()
 674        {return PkgFileIterator(*this,PkgFileP);}
 675
 676 // Oh I wish for Real Name Space Support
 677 class pkgCache::Namespace                                               /*{{{*/
 678 {
 679    public:
 680    typedef pkgCache::GrpIterator GrpIterator;
 681    typedef pkgCache::PkgIterator PkgIterator;
 682    typedef pkgCache::VerIterator VerIterator;
 683    typedef pkgCache::DescIterator DescIterator;
 684    typedef pkgCache::DepIterator DepIterator;
 685    typedef pkgCache::PrvIterator PrvIterator;
 686    typedef pkgCache::PkgFileIterator PkgFileIterator;
 687    typedef pkgCache::VerFileIterator VerFileIterator;
 688    typedef pkgCache::Version Version;
 689    typedef pkgCache::Description Description;
 690    typedef pkgCache::Package Package;
 691    typedef pkgCache::Header Header;
 692    typedef pkgCache::Dep Dep;
 693    typedef pkgCache::Flag Flag;
 694 };
 695                                                                         /*}}}*/
 696 #endif