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
  83 #ifndef APT_8_CLEANER_HEADERS
  84 using std::string;
  85 #endif
  86
  87 class pkgVersioningSystem;
  88 class pkgCache                                                          /*{{{*/
  89 {
  90    public:
  91    // Cache element predeclarations
  92    struct Header;
  93    struct Group;
  94    struct Package;
  95    struct PackageFile;
  96    struct Version;
  97    struct Description;
  98    struct Provides;
  99    struct Dependency;
 100    struct StringItem;
 101    struct VerFile;
 102    struct DescFile;
 103
 104    // Iterators
 105    template<typename Str, typename Itr> class Iterator;
 106    class GrpIterator;
 107    class PkgIterator;
 108    class VerIterator;
 109    class DescIterator;
 110    class DepIterator;
 111    class PrvIterator;
 112    class PkgFileIterator;
 113    class VerFileIterator;
 114    class DescFileIterator;
 115
 116    class Namespace;
 117
 118    // These are all the constants used in the cache structures
 119
 120    // WARNING - if you change these lists you must also edit
 121    // the stringification in pkgcache.cc and also consider whether
 122    // the cache file will become incompatible.
 123    struct Dep
 124    {
 125       enum DepType {Depends=1,PreDepends=2,Suggests=3,Recommends=4,
 126          Conflicts=5,Replaces=6,Obsoletes=7,DpkgBreaks=8,Enhances=9};
 127       /** \brief available compare operators
 128
 129           The lower 4 bits are used to indicate what operator is being specified and
 130           the upper 4 bits are flags. OR indicates that the next package is
 131           or'd with the current package. */
 132       enum DepCompareOp {Or=0x10,NoOp=0,LessEq=0x1,GreaterEq=0x2,Less=0x3,
 133          Greater=0x4,Equals=0x5,NotEquals=0x6};
 134    };
 135
 136    struct State
 137    {
 138       /** \brief priority of a package version
 139
 140           Zero is used for unparsable or absent Priority fields. */
 141       enum VerPriority {Important=1,Required=2,Standard=3,Optional=4,Extra=5};
 142       enum PkgSelectedState {Unknown=0,Install=1,Hold=2,DeInstall=3,Purge=4};
 143       enum PkgInstState {Ok=0,ReInstReq=1,HoldInst=2,HoldReInstReq=3};
 144       enum PkgCurrentState {NotInstalled=0,UnPacked=1,HalfConfigured=2,
 145            HalfInstalled=4,ConfigFiles=5,Installed=6,
 146            TriggersAwaited=7,TriggersPending=8};
 147    };
 148
 149    struct Flag
 150    {
 151       enum PkgFlags {Auto=(1<<0),Essential=(1<<3),Important=(1<<4)};
 152       enum PkgFFlags {NotSource=(1<<0),NotAutomatic=(1<<1),ButAutomaticUpgrades=(1<<2)};
 153    };
 154
 155    protected:
 156
 157    // Memory mapped cache file
 158    std::string CacheFile;
 159    MMap &Map;
 160
 161    unsigned long sHash(const std::string &S) const APT_PURE;
 162    unsigned long sHash(const char *S) const APT_PURE;
 163
 164    public:
 165
 166    // Pointers to the arrays of items
 167    Header *HeaderP;
 168    Group *GrpP;
 169    Package *PkgP;
 170    VerFile *VerFileP;
 171    DescFile *DescFileP;
 172    PackageFile *PkgFileP;
 173    Version *VerP;
 174    Description *DescP;
 175    Provides *ProvideP;
 176    Dependency *DepP;
 177    StringItem *StringItemP;
 178    char *StrP;
 179
 180    virtual bool ReMap(bool const &Errorchecks = true);
 181    inline bool Sync() {return Map.Sync();}
 182    inline MMap &GetMap() {return Map;}
 183    inline void *DataEnd() {return ((unsigned char *)Map.Data()) + Map.Size();}
 184
 185    // String hashing function (512 range)
 186    inline unsigned long Hash(const std::string &S) const {return sHash(S);}
 187    inline unsigned long Hash(const char *S) const {return sHash(S);}
 188
 189    // Useful transformation things
 190    const char *Priority(unsigned char Priority);
 191
 192    // Accessors
 193    GrpIterator FindGrp(const std::string &Name);
 194    PkgIterator FindPkg(const std::string &Name);
 195    PkgIterator FindPkg(const std::string &Name, const std::string &Arch);
 196
 197    Header &Head() {return *HeaderP;}
 198    inline GrpIterator GrpBegin();
 199    inline GrpIterator GrpEnd();
 200    inline PkgIterator PkgBegin();
 201    inline PkgIterator PkgEnd();
 202    inline PkgFileIterator FileBegin();
 203    inline PkgFileIterator FileEnd();
 204
 205    inline bool MultiArchCache() const { return MultiArchEnabled; }
 206    inline char const * NativeArch();
 207
 208    // Make me a function
 209    pkgVersioningSystem *VS;
 210
 211    // Converters
 212    static const char *CompTypeDeb(unsigned char Comp) APT_CONST;
 213    static const char *CompType(unsigned char Comp) APT_CONST;
 214    static const char *DepType(unsigned char Dep);
 215
 216    pkgCache(MMap *Map,bool DoMap = true);
 217    virtual ~pkgCache() {}
 218
 219 private:
 220    bool MultiArchEnabled;
 221    PkgIterator SingleArchFindPkg(const std::string &Name);
 222 };
 223                                                                         /*}}}*/
 224 // Header structure                                                     /*{{{*/
 225 struct pkgCache::Header
 226 {
 227    /** \brief Signature information
 228
 229        This must contain the hex value 0x98FE76DC which is designed to
 230        verify that the system loading the image has the same byte order
 231        and byte size as the system saving the image */
 232    unsigned long Signature;
 233    /** These contain the version of the cache file */
 234    short MajorVersion;
 235    short MinorVersion;
 236    /** \brief indicates if the cache should be erased
 237
 238        Dirty is true if the cache file was opened for reading, the client
 239        expects to have written things to it and have not fully synced it.
 240        The file should be erased and rebuilt if it is true. */
 241    bool Dirty;
 242
 243    /** \brief Size of structure values
 244
 245        All *Sz variables contains the sizeof() that particular structure.
 246        It is used as an extra consistency check on the structure of the file.
 247
 248        If any of the size values do not exactly match what the client expects
 249        then the client should refuse the load the file. */
 250    unsigned short HeaderSz;
 251    unsigned short GroupSz;
 252    unsigned short PackageSz;
 253    unsigned short PackageFileSz;
 254    unsigned short VersionSz;
 255    unsigned short DescriptionSz;
 256    unsigned short DependencySz;
 257    unsigned short ProvidesSz;
 258    unsigned short VerFileSz;
 259    unsigned short DescFileSz;
 260
 261    /** \brief Structure counts
 262
 263        These indicate the number of each structure contained in the cache.
 264        PackageCount is especially useful for generating user state structures.
 265        See Package::Id for more info. */
 266    unsigned long GroupCount;
 267    unsigned long PackageCount;
 268    unsigned long VersionCount;
 269    unsigned long DescriptionCount;
 270    unsigned long DependsCount;
 271    unsigned long PackageFileCount;
 272    unsigned long VerFileCount;
 273    unsigned long DescFileCount;
 274    unsigned long ProvidesCount;
 275
 276    /** \brief index of the first PackageFile structure
 277
 278        The PackageFile structures are singly linked lists that represent
 279        all package files that have been merged into the cache. */
 280    map_ptrloc FileList;
 281    /** \brief index of the first StringItem structure
 282
 283        The cache contains a list of all the unique strings (StringItems).
 284        The parser reads this list into memory so it can match strings
 285        against it.*/
 286    map_ptrloc StringList;
 287    /** \brief String representing the version system used */
 288    map_ptrloc VerSysName;
 289    /** \brief Architecture(s) the cache was built against */
 290    map_ptrloc Architecture;
 291    /** \brief The maximum size of a raw entry from the original Package file */
 292    unsigned long MaxVerFileSize;
 293    /** \brief The maximum size of a raw entry from the original Translation file */
 294    unsigned long MaxDescFileSize;
 295
 296    /** \brief The Pool structures manage the allocation pools that the generator uses
 297
 298        Start indicates the first byte of the pool, Count is the number of objects
 299        remaining in the pool and ItemSize is the structure size (alignment factor)
 300        of the pool. An ItemSize of 0 indicates the pool is empty. There should be
 301        the same number of pools as there are structure types. The generator
 302        stores this information so future additions can make use of any unused pool
 303        blocks. */
 304    DynamicMMap::Pool Pools[9];
 305
 306    /** \brief hash tables providing rapid group/package name lookup
 307
 308        Each group/package name is inserted into the hash table using pkgCache::Hash(const &string)
 309        By iterating over each entry in the hash table it is possible to iterate over
 310        the entire list of packages. Hash Collisions are handled with a singly linked
 311        list of packages based at the hash item. The linked list contains only
 312        packages that match the hashing function.
 313        In the PkgHashTable is it possible that multiple packages have the same name -
 314        these packages are stored as a sequence in the list.
 315
 316        Beware: The Hashmethod assumes that the hash table sizes are equal */
 317    map_ptrloc PkgHashTable[2*1048];
 318    map_ptrloc GrpHashTable[2*1048];
 319
 320    /** \brief Size of the complete cache file */
 321    unsigned long  CacheFileSize;
 322
 323    bool CheckSizes(Header &Against) const APT_PURE;
 324    Header();
 325 };
 326                                                                         /*}}}*/
 327 // Group structure                                                      /*{{{*/
 328 /** \brief groups architecture depending packages together
 329
 330     On or more packages with the same name form a group, so we have
 331     a simple way to access a package built for different architectures
 332     Group exists in a singly linked list of group records starting at
 333     the hash index of the name in the pkgCache::Header::GrpHashTable */
 334 struct pkgCache::Group
 335 {
 336    /** \brief Name of the group */
 337    map_ptrloc Name;             // StringItem
 338
 339    // Linked List
 340    /** \brief Link to the first package which belongs to the group */
 341    map_ptrloc FirstPackage;     // Package
 342    /** \brief Link to the last package which belongs to the group */
 343    map_ptrloc LastPackage;      // Package
 344    /** \brief Link to the next Group */
 345    map_ptrloc Next;             // Group
 346    /** \brief unique sequel ID */
 347    unsigned int ID;
 348
 349 };
 350                                                                         /*}}}*/
 351 // Package structure                                                    /*{{{*/
 352 /** \brief contains information for a single unique package
 353
 354     There can be any number of versions of a given package.
 355     Package exists in a singly linked list of package records starting at
 356     the hash index of the name in the pkgCache::Header::PkgHashTable
 357
 358     A package can be created for every architecture so package names are
 359     not unique, but it is guaranteed that packages with the same name
 360     are sequencel ordered in the list. Packages with the same name can be
 361     accessed with the Group.
 362 */
 363 struct pkgCache::Package
 364 {
 365    /** \brief Name of the package */
 366    map_ptrloc Name;              // StringItem
 367    /** \brief Architecture of the package */
 368    map_ptrloc Arch;              // StringItem
 369    /** \brief Base of a singly linked list of versions
 370
 371        Each structure represents a unique version of the package.
 372        The version structures contain links into PackageFile and the
 373        original text file as well as detailed information about the size
 374        and dependencies of the specific package. In this way multiple
 375        versions of a package can be cleanly handled by the system.
 376        Furthermore, this linked list is guaranteed to be sorted
 377        from Highest version to lowest version with no duplicate entries. */
 378    map_ptrloc VersionList;       // Version
 379    /** \brief index to the installed version */
 380    map_ptrloc CurrentVer;        // Version
 381    /** \brief indicates the deduced section
 382
 383        Should be the index to the string "Unknown" or to the section
 384        of the last parsed item. */
 385    map_ptrloc Section;           // StringItem
 386    /** \brief index of the group this package belongs to */
 387    map_ptrloc Group;             // Group the Package belongs to
 388
 389    // Linked list
 390    /** \brief Link to the next package in the same bucket */
 391    map_ptrloc NextPackage;       // Package
 392    /** \brief List of all dependencies on this package */
 393    map_ptrloc RevDepends;        // Dependency
 394    /** \brief List of all "packages" this package provide */
 395    map_ptrloc ProvidesList;      // Provides
 396
 397    // Install/Remove/Purge etc
 398    /** \brief state that the user wishes the package to be in */
 399    unsigned char SelectedState;     // What
 400    /** \brief installation state of the package
 401
 402        This should be "ok" but in case the installation failed
 403        it will be different.
 404    */
 405    unsigned char InstState;         // Flags
 406    /** \brief indicates if the package is installed */
 407    unsigned char CurrentState;      // State
 408
 409    /** \brief unique sequel ID
 410
 411        ID is a unique value from 0 to Header->PackageCount assigned by the generator.
 412        This allows clients to create an array of size PackageCount and use it to store
 413        state information for the package map. For instance the status file emitter uses
 414        this to track which packages have been emitted already. */
 415    unsigned int ID;
 416    /** \brief some useful indicators of the package's state */
 417    unsigned long Flags;
 418 };
 419                                                                         /*}}}*/
 420 // Package File structure                                               /*{{{*/
 421 /** \brief stores information about the files used to generate the cache
 422
 423     Package files are referenced by Version structures to be able to know
 424     after the generation still from which Packages file includes this Version
 425     as we need this information later on e.g. for pinning. */
 426 struct pkgCache::PackageFile
 427 {
 428    /** \brief physical disk file that this PackageFile represents */
 429    map_ptrloc FileName;        // StringItem
 430    /** \brief the release information
 431
 432        Please see the files document for a description of what the
 433        release information means. */
 434    map_ptrloc Archive;         // StringItem
 435    map_ptrloc Codename;        // StringItem
 436    map_ptrloc Component;       // StringItem
 437    map_ptrloc Version;         // StringItem
 438    map_ptrloc Origin;          // StringItem
 439    map_ptrloc Label;           // StringItem
 440    map_ptrloc Architecture;    // StringItem
 441    /** \brief The site the index file was fetched from */
 442    map_ptrloc Site;            // StringItem
 443    /** \brief indicates what sort of index file this is
 444
 445        @TODO enumerate at least the possible indexes */
 446    map_ptrloc IndexType;       // StringItem
 447    /** \brief Size of the file
 448
 449        Used together with the modification time as a
 450        simple check to ensure that the Packages
 451        file has not been altered since Cache generation. */
 452    unsigned long Size;
 453    /** \brief Modification time for the file */
 454    time_t mtime;
 455
 456    /** @TODO document PackageFile::Flags */
 457    unsigned long Flags;
 458
 459    // Linked list
 460    /** \brief Link to the next PackageFile in the Cache */
 461    map_ptrloc NextFile;        // PackageFile
 462    /** \brief unique sequel ID */
 463    unsigned int ID;
 464 };
 465                                                                         /*}}}*/
 466 // VerFile structure                                                    /*{{{*/
 467 /** \brief associates a version with a PackageFile
 468
 469     This allows a full description of all Versions in all files
 470     (and hence all sources) under consideration. */
 471 struct pkgCache::VerFile
 472 {
 473    /** \brief index of the package file that this version was found in */
 474    map_ptrloc File;           // PackageFile
 475    /** \brief next step in the linked list */
 476    map_ptrloc NextFile;       // PkgVerFile
 477    /** \brief position in the package file */
 478    map_ptrloc Offset;         // File offset
 479    /** @TODO document pkgCache::VerFile::Size */
 480    unsigned long Size;
 481 };
 482                                                                         /*}}}*/
 483 // DescFile structure                                                   /*{{{*/
 484 /** \brief associates a description with a Translation file */
 485 struct pkgCache::DescFile
 486 {
 487    /** \brief index of the file that this description was found in */
 488    map_ptrloc File;           // PackageFile
 489    /** \brief next step in the linked list */
 490    map_ptrloc NextFile;       // PkgVerFile
 491    /** \brief position in the file */
 492    map_ptrloc Offset;         // File offset
 493    /** @TODO document pkgCache::DescFile::Size */
 494    unsigned long Size;
 495 };
 496                                                                         /*}}}*/
 497 // Version structure                                                    /*{{{*/
 498 /** \brief information for a single version of a package
 499
 500     The version list is always sorted from highest version to lowest
 501     version by the generator. Equal version numbers are either merged
 502     or handled as separate versions based on the Hash value. */
 503 struct pkgCache::Version
 504 {
 505    /** \brief complete version string */
 506    map_ptrloc VerStr;            // StringItem
 507    /** \brief section this version is filled in */
 508    map_ptrloc Section;           // StringItem
 509
 510    /** \brief Multi-Arch capabilities of a package version */
 511    enum VerMultiArch { None = 0, /*!< is the default and doesn't trigger special behaviour */
 512                        All = (1<<0), /*!< will cause that Ver.Arch() will report "all" */
 513                        Foreign = (1<<1), /*!< can satisfy dependencies in another architecture */
 514                        Same = (1<<2), /*!< can be co-installed with itself from other architectures */
 515                        Allowed = (1<<3), /*!< other packages are allowed to depend on thispkg:any */
 516                        AllForeign = All | Foreign,
 517                        AllAllowed = All | Allowed };
 518    /** \brief stores the MultiArch capabilities of this version
 519
 520        Flags used are defined in pkgCache::Version::VerMultiArch
 521    */
 522    unsigned char MultiArch;
 523
 524    /** \brief references all the PackageFile's that this version came from
 525
 526        FileList can be used to determine what distribution(s) the Version
 527        applies to. If FileList is 0 then this is a blank version.
 528        The structure should also have a 0 in all other fields excluding
 529        pkgCache::Version::VerStr and Possibly pkgCache::Version::NextVer. */
 530    map_ptrloc FileList;          // VerFile
 531    /** \brief next (lower or equal) version in the linked list */
 532    map_ptrloc NextVer;           // Version
 533    /** \brief next description in the linked list */
 534    map_ptrloc DescriptionList;   // Description
 535    /** \brief base of the dependency list */
 536    map_ptrloc DependsList;       // Dependency
 537    /** \brief links to the owning package
 538
 539        This allows reverse dependencies to determine the package */
 540    map_ptrloc ParentPkg;         // Package
 541    /** \brief list of pkgCache::Provides */
 542    map_ptrloc ProvidesList;      // Provides
 543
 544    /** \brief archive size for this version
 545
 546        For Debian this is the size of the .deb file. */
 547    unsigned long long Size;      // These are the .deb size
 548    /** \brief uncompressed size for this version */
 549    unsigned long long InstalledSize;
 550    /** \brief characteristic value representing this version
 551
 552        No two packages in existence should have the same VerStr
 553        and Hash with different contents. */
 554    unsigned short Hash;
 555    /** \brief unique sequel ID */
 556    unsigned int ID;
 557    /** \brief parsed priority value */
 558    unsigned char Priority;
 559 };
 560                                                                         /*}}}*/
 561 // Description structure                                                /*{{{*/
 562 /** \brief datamember of a linked list of available description for a version */
 563 struct pkgCache::Description
 564 {
 565    /** \brief Language code of this description (translation)
 566
 567        If the value has a 0 length then this is read using the Package
 568        file else the Translation-CODE file is used. */
 569    map_ptrloc language_code;     // StringItem
 570    /** \brief MD5sum of the original description
 571
 572        Used to map Translations of a description to a version
 573        and to check that the Translation is up-to-date. */
 574    map_ptrloc md5sum;            // StringItem
 575
 576    /** @TODO document pkgCache::Description::FileList */
 577    map_ptrloc FileList;          // DescFile
 578    /** \brief next translation for this description */
 579    map_ptrloc NextDesc;          // Description
 580    /** \brief the text is a description of this package */
 581    map_ptrloc ParentPkg;         // Package
 582
 583    /** \brief unique sequel ID */
 584    unsigned int ID;
 585 };
 586                                                                         /*}}}*/
 587 // Dependency structure                                                 /*{{{*/
 588 /** \brief information for a single dependency record
 589
 590     The records are split up like this to ease processing by the client.
 591     The base of the linked list is pkgCache::Version::DependsList.
 592     All forms of dependencies are recorded here including Depends,
 593     Recommends, Suggests, Enhances, Conflicts, Replaces and Breaks. */
 594 struct pkgCache::Dependency
 595 {
 596    /** \brief string of the version the dependency is applied against */
 597    map_ptrloc Version;         // StringItem
 598    /** \brief index of the package this depends applies to
 599
 600        The generator will - if the package does not already exist -
 601        create a blank (no version records) package. */
 602    map_ptrloc Package;         // Package
 603    /** \brief next dependency of this version */
 604    map_ptrloc NextDepends;     // Dependency
 605    /** \brief next reverse dependency of this package */
 606    map_ptrloc NextRevDepends;  // Dependency
 607    /** \brief version of the package which has the reverse depends */
 608    map_ptrloc ParentVer;       // Version
 609
 610    /** \brief unique sequel ID */
 611    map_ptrloc ID;
 612    /** \brief Dependency type - Depends, Recommends, Conflicts, etc */
 613    unsigned char Type;
 614    /** \brief comparison operator specified on the depends line
 615
 616        If the high bit is set then it is a logical OR with the previous record. */
 617    unsigned char CompareOp;
 618 };
 619                                                                         /*}}}*/
 620 // Provides structure                                                   /*{{{*/
 621 /** \brief handles virtual packages
 622
 623     When a Provides: line is encountered a new provides record is added
 624     associating the package with a virtual package name.
 625     The provides structures are linked off the package structures.
 626     This simplifies the analysis of dependencies and other aspects A provides
 627     refers to a specific version of a specific package, not all versions need to
 628     provide that provides.*/
 629 struct pkgCache::Provides
 630 {
 631    /** \brief index of the package providing this */
 632    map_ptrloc ParentPkg;        // Package
 633    /** \brief index of the version this provide line applies to */
 634    map_ptrloc Version;          // Version
 635    /** \brief version in the provides line (if any)
 636
 637        This version allows dependencies to depend on specific versions of a
 638        Provides, as well as allowing Provides to override existing packages.
 639        This is experimental. Note that Debian doesn't allow versioned provides */
 640    map_ptrloc ProvideVersion;   // StringItem
 641    /** \brief next provides (based of package) */
 642    map_ptrloc NextProvides;     // Provides
 643    /** \brief next provides (based of version) */
 644    map_ptrloc NextPkgProv;      // Provides
 645 };
 646                                                                         /*}}}*/
 647 // StringItem structure                                                 /*{{{*/
 648 /** \brief used for generating single instances of strings
 649
 650     Some things like Section Name are are useful to have as unique tags.
 651     It is part of a linked list based at pkgCache::Header::StringList
 652
 653     All strings are simply inlined any place in the file that is natural
 654     for the writer. The client should make no assumptions about the positioning
 655     of strings. All StringItems should be null-terminated. */
 656 struct pkgCache::StringItem
 657 {
 658    /** \brief string this refers to */
 659    map_ptrloc String;        // StringItem
 660    /** \brief Next link in the chain */
 661    map_ptrloc NextItem;      // StringItem
 662 };
 663                                                                         /*}}}*/
 664
 665
 666 inline char const * pkgCache::NativeArch()
 667         { return StrP + HeaderP->Architecture; }
 668
 669 #include <apt-pkg/cacheiterators.h>
 670
 671 inline pkgCache::GrpIterator pkgCache::GrpBegin()
 672        {return GrpIterator(*this);}
 673 inline pkgCache::GrpIterator pkgCache::GrpEnd()
 674        {return GrpIterator(*this,GrpP);}
 675 inline pkgCache::PkgIterator pkgCache::PkgBegin()
 676        {return PkgIterator(*this);}
 677 inline pkgCache::PkgIterator pkgCache::PkgEnd()
 678        {return PkgIterator(*this,PkgP);}
 679 inline pkgCache::PkgFileIterator pkgCache::FileBegin()
 680        {return PkgFileIterator(*this,PkgFileP + HeaderP->FileList);}
 681 inline pkgCache::PkgFileIterator pkgCache::FileEnd()
 682        {return PkgFileIterator(*this,PkgFileP);}
 683
 684 // Oh I wish for Real Name Space Support
 685 class pkgCache::Namespace                                               /*{{{*/
 686 {
 687    public:
 688    typedef pkgCache::GrpIterator GrpIterator;
 689    typedef pkgCache::PkgIterator PkgIterator;
 690    typedef pkgCache::VerIterator VerIterator;
 691    typedef pkgCache::DescIterator DescIterator;
 692    typedef pkgCache::DepIterator DepIterator;
 693    typedef pkgCache::PrvIterator PrvIterator;
 694    typedef pkgCache::PkgFileIterator PkgFileIterator;
 695    typedef pkgCache::VerFileIterator VerFileIterator;
 696    typedef pkgCache::Version Version;
 697    typedef pkgCache::Description Description;
 698    typedef pkgCache::Package Package;
 699    typedef pkgCache::Header Header;
 700    typedef pkgCache::Dep Dep;
 701    typedef pkgCache::Flag Flag;
 702 };
 703                                                                         /*}}}*/
 704 #endif