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 <string>
  78 #include <time.h>
  79 #include <apt-pkg/mmap.h>
  80
  81 #ifndef APT_8_CLEANER_HEADERS
  82 using std::string;
  83 #endif
  84
  85 class pkgVersioningSystem;
  86 class pkgCache                                                          /*{{{*/
  87 {
  88    public:
  89    // Cache element predeclarations
  90    struct Header;
  91    struct Group;
  92    struct Package;
  93    struct PackageFile;
  94    struct Version;
  95    struct Description;
  96    struct Provides;
  97    struct Dependency;
  98    struct StringItem;
  99    struct VerFile;
 100    struct DescFile;
 101
 102    // Iterators
 103    template<typename Str, typename Itr> class Iterator;
 104    class GrpIterator;
 105    class PkgIterator;
 106    class VerIterator;
 107    class DescIterator;
 108    class DepIterator;
 109    class PrvIterator;
 110    class PkgFileIterator;
 111    class VerFileIterator;
 112    class DescFileIterator;
 113
 114    class Namespace;
 115
 116    // These are all the constants used in the cache structures
 117
 118    // WARNING - if you change these lists you must also edit
 119    // the stringification in pkgcache.cc and also consider whether
 120    // the cache file will become incompatible.
 121    struct Dep
 122    {
 123       enum DepType {Depends=1,PreDepends=2,Suggests=3,Recommends=4,
 124          Conflicts=5,Replaces=6,Obsoletes=7,DpkgBreaks=8,Enhances=9};
 125       /** \brief available compare operators
 126
 127           The lower 4 bits are used to indicate what operator is being specified and
 128           the upper 4 bits are flags. OR indicates that the next package is
 129           or'd with the current package. */
 130       enum DepCompareOp {Or=0x10,NoOp=0,LessEq=0x1,GreaterEq=0x2,Less=0x3,
 131          Greater=0x4,Equals=0x5,NotEquals=0x6};
 132    };
 133
 134    struct State
 135    {
 136       /** \brief priority of a package version
 137
 138           Zero is used for unparsable or absent Priority fields. */
 139       enum VerPriority {Important=1,Required=2,Standard=3,Optional=4,Extra=5};
 140       enum PkgSelectedState {Unknown=0,Install=1,Hold=2,DeInstall=3,Purge=4};
 141       enum PkgInstState {Ok=0,ReInstReq=1,HoldInst=2,HoldReInstReq=3};
 142       enum PkgCurrentState {NotInstalled=0,UnPacked=1,HalfConfigured=2,
 143            HalfInstalled=4,ConfigFiles=5,Installed=6,
 144            TriggersAwaited=7,TriggersPending=8};
 145    };
 146
 147    struct Flag
 148    {
 149       enum PkgFlags {Auto=(1<<0),Essential=(1<<3),Important=(1<<4)};
 150       enum PkgFFlags {NotSource=(1<<0),NotAutomatic=(1<<1),ButAutomaticUpgrades=(1<<2)};
 151    };
 152
 153    protected:
 154
 155    // Memory mapped cache file
 156    std::string CacheFile;
 157    MMap &Map;
 158
 159    unsigned long sHash(const std::string &S) const;
 160    unsigned long sHash(const char *S) const;
 161
 162    public:
 163
 164    // Pointers to the arrays of items
 165    Header *HeaderP;
 166    Group *GrpP;
 167    Package *PkgP;
 168    VerFile *VerFileP;
 169    DescFile *DescFileP;
 170    PackageFile *PkgFileP;
 171    Version *VerP;
 172    Description *DescP;
 173    Provides *ProvideP;
 174    Dependency *DepP;
 175    StringItem *StringItemP;
 176    char *StrP;
 177
 178    virtual bool ReMap(bool const &Errorchecks = true);
 179    inline bool Sync() {return Map.Sync();}
 180    inline MMap &GetMap() {return Map;}
 181    inline void *DataEnd() {return ((unsigned char *)Map.Data()) + Map.Size();}
 182
 183    // String hashing function (512 range)
 184    inline unsigned long Hash(const std::string &S) const {return sHash(S);}
 185    inline unsigned long Hash(const char *S) const {return sHash(S);}
 186
 187    // Useful transformation things
 188    const char *Priority(unsigned char Priority);
 189
 190    // Accessors
 191    GrpIterator FindGrp(const std::string &Name);
 192    PkgIterator FindPkg(const std::string &Name);
 193    PkgIterator FindPkg(const std::string &Name, const std::string &Arch);
 194
 195    Header &Head() {return *HeaderP;}
 196    inline GrpIterator GrpBegin();
 197    inline GrpIterator GrpEnd();
 198    inline PkgIterator PkgBegin();
 199    inline PkgIterator PkgEnd();
 200    inline PkgFileIterator FileBegin();
 201    inline PkgFileIterator FileEnd();
 202
 203    inline bool MultiArchCache() const { return MultiArchEnabled; }
 204    inline char const * const NativeArch() const;
 205
 206    // Make me a function
 207    pkgVersioningSystem *VS;
 208
 209    // Converters
 210    static const char *CompTypeDeb(unsigned char Comp);
 211    static const char *CompType(unsigned char Comp);
 212    static const char *DepType(unsigned char Dep);
 213
 214    pkgCache(MMap *Map,bool DoMap = true);
 215    virtual ~pkgCache() {}
 216
 217 private:
 218    bool MultiArchEnabled;
 219    PkgIterator SingleArchFindPkg(const std::string &Name);
 220 };
 221                                                                         /*}}}*/
 222 // Header structure                                                     /*{{{*/
 223 struct pkgCache::Header
 224 {
 225    /** \brief Signature information
 226
 227        This must contain the hex value 0x98FE76DC which is designed to
 228        verify that the system loading the image has the same byte order
 229        and byte size as the system saving the image */
 230    unsigned long Signature;
 231    /** These contain the version of the cache file */
 232    short MajorVersion;
 233    short MinorVersion;
 234    /** \brief indicates if the cache should be erased
 235
 236        Dirty is true if the cache file was opened for reading, the client
 237        expects to have written things to it and have not fully synced it.
 238        The file should be erased and rebuilt if it is true. */
 239    bool Dirty;
 240
 241    /** \brief Size of structure values
 242
 243        All *Sz variables contains the sizeof() that particular structure.
 244        It is used as an extra consistency check on the structure of the file.
 245
 246        If any of the size values do not exactly match what the client expects
 247        then the client should refuse the load the file. */
 248    unsigned short HeaderSz;
 249    unsigned short GroupSz;
 250    unsigned short PackageSz;
 251    unsigned short PackageFileSz;
 252    unsigned short VersionSz;
 253    unsigned short DescriptionSz;
 254    unsigned short DependencySz;
 255    unsigned short ProvidesSz;
 256    unsigned short VerFileSz;
 257    unsigned short DescFileSz;
 258
 259    /** \brief Structure counts
 260
 261        These indicate the number of each structure contained in the cache.
 262        PackageCount is especially useful for generating user state structures.
 263        See Package::Id for more info. */
 264    unsigned long GroupCount;
 265    unsigned long PackageCount;
 266    unsigned long VersionCount;
 267    unsigned long DescriptionCount;
 268    unsigned long DependsCount;
 269    unsigned long PackageFileCount;
 270    unsigned long VerFileCount;
 271    unsigned long DescFileCount;
 272    unsigned long ProvidesCount;
 273
 274    /** \brief index of the first PackageFile structure
 275
 276        The PackageFile structures are singly linked lists that represent
 277        all package files that have been merged into the cache. */
 278    map_ptrloc FileList;
 279    /** \brief index of the first StringItem structure
 280
 281        The cache contains a list of all the unique strings (StringItems).
 282        The parser reads this list into memory so it can match strings
 283        against it.*/
 284    map_ptrloc StringList;
 285    /** \brief String representing the version system used */
 286    map_ptrloc VerSysName;
 287    /** \brief Architecture(s) the cache was built against */
 288    map_ptrloc Architecture;
 289    /** \brief The maximum size of a raw entry from the original Package file */
 290    unsigned long MaxVerFileSize;
 291    /** \brief The maximum size of a raw entry from the original Translation file */
 292    unsigned long MaxDescFileSize;
 293
 294    /** \brief The Pool structures manage the allocation pools that the generator uses
 295
 296        Start indicates the first byte of the pool, Count is the number of objects
 297        remaining in the pool and ItemSize is the structure size (alignment factor)
 298        of the pool. An ItemSize of 0 indicates the pool is empty. There should be
 299        the same number of pools as there are structure types. The generator
 300        stores this information so future additions can make use of any unused pool
 301        blocks. */
 302    DynamicMMap::Pool Pools[9];
 303
 304    /** \brief hash tables providing rapid group/package name lookup
 305
 306        Each group/package name is inserted into the hash table using pkgCache::Hash(const &string)
 307        By iterating over each entry in the hash table it is possible to iterate over
 308        the entire list of packages. Hash Collisions are handled with a singly linked
 309        list of packages based at the hash item. The linked list contains only
 310        packages that match the hashing function.
 311        In the PkgHashTable is it possible that multiple packages have the same name -
 312        these packages are stored as a sequence in the list.
 313
 314        Beware: The Hashmethod assumes that the hash table sizes are equal */
 315    map_ptrloc PkgHashTable[2*1048];
 316    map_ptrloc GrpHashTable[2*1048];
 317
 318    /** \brief Size of the complete cache file */
 319    unsigned long  CacheFileSize;
 320
 321    bool CheckSizes(Header &Against) const;
 322    Header();
 323 };
 324                                                                         /*}}}*/
 325 // Group structure                                                      /*{{{*/
 326 /** \brief groups architecture depending packages together
 327
 328     On or more packages with the same name form a group, so we have
 329     a simple way to access a package built for different architectures
 330     Group exists in a singly linked list of group records starting at
 331     the hash index of the name in the pkgCache::Header::GrpHashTable */
 332 struct pkgCache::Group
 333 {
 334    /** \brief Name of the group */
 335    map_ptrloc Name;             // StringItem
 336
 337    // Linked List
 338    /** \brief Link to the first package which belongs to the group */
 339    map_ptrloc FirstPackage;     // Package
 340    /** \brief Link to the last package which belongs to the group */
 341    map_ptrloc LastPackage;      // Package
 342    /** \brief Link to the next Group */
 343    map_ptrloc Next;             // Group
 344    /** \brief unique sequel ID */
 345    unsigned int ID;
 346
 347 };
 348                                                                         /*}}}*/
 349 // Package structure                                                    /*{{{*/
 350 /** \brief contains information for a single unique package
 351
 352     There can be any number of versions of a given package.
 353     Package exists in a singly linked list of package records starting at
 354     the hash index of the name in the pkgCache::Header::PkgHashTable
 355
 356     A package can be created for every architecture so package names are
 357     not unique, but it is guaranteed that packages with the same name
 358     are sequencel ordered in the list. Packages with the same name can be
 359     accessed with the Group.
 360 */
 361 struct pkgCache::Package
 362 {
 363    /** \brief Name of the package */
 364    map_ptrloc Name;              // StringItem
 365    /** \brief Architecture of the package */
 366    map_ptrloc Arch;              // StringItem
 367    /** \brief Base of a singly linked list of versions
 368
 369        Each structure represents a unique version of the package.
 370        The version structures contain links into PackageFile and the
 371        original text file as well as detailed information about the size
 372        and dependencies of the specific package. In this way multiple
 373        versions of a package can be cleanly handled by the system.
 374        Furthermore, this linked list is guaranteed to be sorted
 375        from Highest version to lowest version with no duplicate entries. */
 376    map_ptrloc VersionList;       // Version
 377    /** \brief index to the installed version */
 378    map_ptrloc CurrentVer;        // Version
 379    /** \brief indicates the deduced section
 380
 381        Should be the index to the string "Unknown" or to the section
 382        of the last parsed item. */
 383    map_ptrloc Section;           // StringItem
 384    /** \brief index of the group this package belongs to */
 385    map_ptrloc Group;             // Group the Package belongs to
 386
 387    // Linked list
 388    /** \brief Link to the next package in the same bucket */
 389    map_ptrloc NextPackage;       // Package
 390    /** \brief List of all dependencies on this package */
 391    map_ptrloc RevDepends;        // Dependency
 392    /** \brief List of all "packages" this package provide */
 393    map_ptrloc ProvidesList;      // Provides
 394
 395    // Install/Remove/Purge etc
 396    /** \brief state that the user wishes the package to be in */
 397    unsigned char SelectedState;     // What
 398    /** \brief installation state of the package
 399
 400        This should be "ok" but in case the installation failed
 401        it will be different.
 402    */
 403    unsigned char InstState;         // Flags
 404    /** \brief indicates if the package is installed */
 405    unsigned char CurrentState;      // State
 406
 407    /** \brief unique sequel ID
 408
 409        ID is a unique value from 0 to Header->PackageCount assigned by the generator.
 410        This allows clients to create an array of size PackageCount and use it to store
 411        state information for the package map. For instance the status file emitter uses
 412        this to track which packages have been emitted already. */
 413    unsigned int ID;
 414    /** \brief some useful indicators of the package's state */
 415    unsigned long Flags;
 416 };
 417                                                                         /*}}}*/
 418 // Package File structure                                               /*{{{*/
 419 /** \brief stores information about the files used to generate the cache
 420
 421     Package files are referenced by Version structures to be able to know
 422     after the generation still from which Packages file includes this Version
 423     as we need this information later on e.g. for pinning. */
 424 struct pkgCache::PackageFile
 425 {
 426    /** \brief physical disk file that this PackageFile represents */
 427    map_ptrloc FileName;        // StringItem
 428    /** \brief the release information
 429
 430        Please see the files document for a description of what the
 431        release information means. */
 432    map_ptrloc Archive;         // StringItem
 433    map_ptrloc Codename;        // StringItem
 434    map_ptrloc Component;       // StringItem
 435    map_ptrloc Version;         // StringItem
 436    map_ptrloc Origin;          // StringItem
 437    map_ptrloc Label;           // StringItem
 438    map_ptrloc Architecture;    // StringItem
 439    /** \brief The site the index file was fetched from */
 440    map_ptrloc Site;            // StringItem
 441    /** \brief indicates what sort of index file this is
 442
 443        @TODO enumerate at least the possible indexes */
 444    map_ptrloc IndexType;       // StringItem
 445    /** \brief Size of the file
 446
 447        Used together with the modification time as a
 448        simple check to ensure that the Packages
 449        file has not been altered since Cache generation. */
 450    unsigned long Size;
 451    /** \brief Modification time for the file */
 452    time_t mtime;
 453
 454    /** @TODO document PackageFile::Flags */
 455    unsigned long Flags;
 456
 457    // Linked list
 458    /** \brief Link to the next PackageFile in the Cache */
 459    map_ptrloc NextFile;        // PackageFile
 460    /** \brief unique sequel ID */
 461    unsigned int ID;
 462 };
 463                                                                         /*}}}*/
 464 // VerFile structure                                                    /*{{{*/
 465 /** \brief associates a version with a PackageFile
 466
 467     This allows a full description of all Versions in all files
 468     (and hence all sources) under consideration. */
 469 struct pkgCache::VerFile
 470 {
 471    /** \brief index of the package file that this version was found in */
 472    map_ptrloc File;           // PackageFile
 473    /** \brief next step in the linked list */
 474    map_ptrloc NextFile;       // PkgVerFile
 475    /** \brief position in the package file */
 476    map_ptrloc Offset;         // File offset
 477    /** @TODO document pkgCache::VerFile::Size */
 478    unsigned long Size;
 479 };
 480                                                                         /*}}}*/
 481 // DescFile structure                                                   /*{{{*/
 482 /** \brief associates a description with a Translation file */
 483 struct pkgCache::DescFile
 484 {
 485    /** \brief index of the file that this description was found in */
 486    map_ptrloc File;           // PackageFile
 487    /** \brief next step in the linked list */
 488    map_ptrloc NextFile;       // PkgVerFile
 489    /** \brief position in the file */
 490    map_ptrloc Offset;         // File offset
 491    /** @TODO document pkgCache::DescFile::Size */
 492    unsigned long Size;
 493 };
 494                                                                         /*}}}*/
 495 // Version structure                                                    /*{{{*/
 496 /** \brief information for a single version of a package
 497
 498     The version list is always sorted from highest version to lowest
 499     version by the generator. Equal version numbers are either merged
 500     or handled as separate versions based on the Hash value. */
 501 struct pkgCache::Version
 502 {
 503    /** \brief complete version string */
 504    map_ptrloc VerStr;            // StringItem
 505    /** \brief section this version is filled in */
 506    map_ptrloc Section;           // StringItem
 507
 508    /** \brief Multi-Arch capabilities of a package version */
 509    enum VerMultiArch { None = 0, /*!< is the default and doesn't trigger special behaviour */
 510                        All = (1<<0), /*!< will cause that Ver.Arch() will report "all" */
 511                        Foreign = (1<<1), /*!< can satisfy dependencies in another architecture */
 512                        Same = (1<<2), /*!< can be co-installed with itself from other architectures */
 513                        Allowed = (1<<3), /*!< other packages are allowed to depend on thispkg:any */
 514                        AllForeign = All | Foreign,
 515                        AllAllowed = All | Allowed };
 516    /** \brief stores the MultiArch capabilities of this version
 517
 518        Flags used are defined in pkgCache::Version::VerMultiArch
 519    */
 520    unsigned char MultiArch;
 521
 522    /** \brief references all the PackageFile's that this version came from
 523
 524        FileList can be used to determine what distribution(s) the Version
 525        applies to. If FileList is 0 then this is a blank version.
 526        The structure should also have a 0 in all other fields excluding
 527        pkgCache::Version::VerStr and Possibly pkgCache::Version::NextVer. */
 528    map_ptrloc FileList;          // VerFile
 529    /** \brief next (lower or equal) version in the linked list */
 530    map_ptrloc NextVer;           // Version
 531    /** \brief next description in the linked list */
 532    map_ptrloc DescriptionList;   // Description
 533    /** \brief base of the dependency list */
 534    map_ptrloc DependsList;       // Dependency
 535    /** \brief links to the owning package
 536
 537        This allows reverse dependencies to determine the package */
 538    map_ptrloc ParentPkg;         // Package
 539    /** \brief list of pkgCache::Provides */
 540    map_ptrloc ProvidesList;      // Provides
 541
 542    /** \brief archive size for this version
 543
 544        For Debian this is the size of the .deb file. */
 545    unsigned long long Size;      // These are the .deb size
 546    /** \brief uncompressed size for this version */
 547    unsigned long long InstalledSize;
 548    /** \brief characteristic value representing this version
 549
 550        No two packages in existence should have the same VerStr
 551        and Hash with different contents. */
 552    unsigned short Hash;
 553    /** \brief unique sequel ID */
 554    unsigned int ID;
 555    /** \brief parsed priority value */
 556    unsigned char Priority;
 557 };
 558                                                                         /*}}}*/
 559 // Description structure                                                /*{{{*/
 560 /** \brief datamember of a linked list of available description for a version */
 561 struct pkgCache::Description
 562 {
 563    /** \brief Language code of this description (translation)
 564
 565        If the value has a 0 length then this is read using the Package
 566        file else the Translation-CODE file is used. */
 567    map_ptrloc language_code;     // StringItem
 568    /** \brief MD5sum of the original description
 569
 570        Used to map Translations of a description to a version
 571        and to check that the Translation is up-to-date. */
 572    map_ptrloc md5sum;            // StringItem
 573
 574    /** @TODO document pkgCache::Description::FileList */
 575    map_ptrloc FileList;          // DescFile
 576    /** \brief next translation for this description */
 577    map_ptrloc NextDesc;          // Description
 578    /** \brief the text is a description of this package */
 579    map_ptrloc ParentPkg;         // Package
 580
 581    /** \brief unique sequel ID */
 582    unsigned int ID;
 583 };
 584                                                                         /*}}}*/
 585 // Dependency structure                                                 /*{{{*/
 586 /** \brief information for a single dependency record
 587
 588     The records are split up like this to ease processing by the client.
 589     The base of the linked list is pkgCache::Version::DependsList.
 590     All forms of dependencies are recorded here including Depends,
 591     Recommends, Suggests, Enhances, Conflicts, Replaces and Breaks. */
 592 struct pkgCache::Dependency
 593 {
 594    /** \brief string of the version the dependency is applied against */
 595    map_ptrloc Version;         // StringItem
 596    /** \brief index of the package this depends applies to
 597
 598        The generator will - if the package does not already exist -
 599        create a blank (no version records) package. */
 600    map_ptrloc Package;         // Package
 601    /** \brief next dependency of this version */
 602    map_ptrloc NextDepends;     // Dependency
 603    /** \brief next reverse dependency of this package */
 604    map_ptrloc NextRevDepends;  // Dependency
 605    /** \brief version of the package which has the reverse depends */
 606    map_ptrloc ParentVer;       // Version
 607
 608    /** \brief unique sequel ID */
 609    map_ptrloc ID;
 610    /** \brief Dependency type - Depends, Recommends, Conflicts, etc */
 611    unsigned char Type;
 612    /** \brief comparison operator specified on the depends line
 613
 614        If the high bit is set then it is a logical OR with the previous record. */
 615    unsigned char CompareOp;
 616 };
 617                                                                         /*}}}*/
 618 // Provides structure                                                   /*{{{*/
 619 /** \brief handles virtual packages
 620
 621     When a Provides: line is encountered a new provides record is added
 622     associating the package with a virtual package name.
 623     The provides structures are linked off the package structures.
 624     This simplifies the analysis of dependencies and other aspects A provides
 625     refers to a specific version of a specific package, not all versions need to
 626     provide that provides.*/
 627 struct pkgCache::Provides
 628 {
 629    /** \brief index of the package providing this */
 630    map_ptrloc ParentPkg;        // Package
 631    /** \brief index of the version this provide line applies to */
 632    map_ptrloc Version;          // Version
 633    /** \brief version in the provides line (if any)
 634
 635        This version allows dependencies to depend on specific versions of a
 636        Provides, as well as allowing Provides to override existing packages.
 637        This is experimental. Note that Debian doesn't allow versioned provides */
 638    map_ptrloc ProvideVersion;   // StringItem
 639    /** \brief next provides (based of package) */
 640    map_ptrloc NextProvides;     // Provides
 641    /** \brief next provides (based of version) */
 642    map_ptrloc NextPkgProv;      // Provides
 643 };
 644                                                                         /*}}}*/
 645 // StringItem structure                                                 /*{{{*/
 646 /** \brief used for generating single instances of strings
 647
 648     Some things like Section Name are are useful to have as unique tags.
 649     It is part of a linked list based at pkgCache::Header::StringList
 650
 651     All strings are simply inlined any place in the file that is natural
 652     for the writer. The client should make no assumptions about the positioning
 653     of strings. All StringItems should be null-terminated. */
 654 struct pkgCache::StringItem
 655 {
 656    /** \brief string this refers to */
 657    map_ptrloc String;        // StringItem
 658    /** \brief Next link in the chain */
 659    map_ptrloc NextItem;      // StringItem
 660 };
 661                                                                         /*}}}*/
 662
 663
 664 inline char const * const pkgCache::NativeArch() const
 665         { return StrP + HeaderP->Architecture; }
 666
 667 #include <apt-pkg/cacheiterators.h>
 668
 669 inline pkgCache::GrpIterator pkgCache::GrpBegin()
 670        {return GrpIterator(*this);}
 671 inline pkgCache::GrpIterator pkgCache::GrpEnd()
 672        {return GrpIterator(*this,GrpP);}
 673 inline pkgCache::PkgIterator pkgCache::PkgBegin()
 674        {return PkgIterator(*this);}
 675 inline pkgCache::PkgIterator pkgCache::PkgEnd()
 676        {return PkgIterator(*this,PkgP);}
 677 inline pkgCache::PkgFileIterator pkgCache::FileBegin()
 678        {return PkgFileIterator(*this,PkgFileP + HeaderP->FileList);}
 679 inline pkgCache::PkgFileIterator pkgCache::FileEnd()
 680        {return PkgFileIterator(*this,PkgFileP);}
 681
 682 // Oh I wish for Real Name Space Support
 683 class pkgCache::Namespace                                               /*{{{*/
 684 {
 685    public:
 686    typedef pkgCache::GrpIterator GrpIterator;
 687    typedef pkgCache::PkgIterator PkgIterator;
 688    typedef pkgCache::VerIterator VerIterator;
 689    typedef pkgCache::DescIterator DescIterator;
 690    typedef pkgCache::DepIterator DepIterator;
 691    typedef pkgCache::PrvIterator PrvIterator;
 692    typedef pkgCache::PkgFileIterator PkgFileIterator;
 693    typedef pkgCache::VerFileIterator VerFileIterator;
 694    typedef pkgCache::Version Version;
 695    typedef pkgCache::Description Description;
 696    typedef pkgCache::Package Package;
 697    typedef pkgCache::Header Header;
 698    typedef pkgCache::Dep Dep;
 699    typedef pkgCache::Flag Flag;
 700 };
 701                                                                         /*}}}*/
 702 #endif