apt-pkg/pkgsystem.h

   1 // -*- mode: cpp; mode: fold -*-
   2 // Description                                                          /*{{{*/
   3 /* ######################################################################
   4
   5    System - Abstraction for running on different systems.
   6
   7    Instances of this class can be thought of as factories or meta-classes
   8    for a variety of more specialized classes. Together this class and
   9    it's specialized offspring completely define the environment and how
  10    to access resources for a specific system. There are several sub
  11    areas that are all orthogonal - each system has a unique combination of
  12    these sub areas:
  13        - Versioning. Different systems have different ideas on versions.
  14          Within a system all sub classes must follow the same versioning
  15          rules.
  16        - Local tool locking to prevent multiple tools from accessing the
  17          same database.
  18        - Candidate Version selection policy - this is probably almost always
  19          managed using a standard APT class
  20        - Actual Package installation
  21          * Indication of what kind of binary formats are supported
  22        - Selection of local 'status' indexes that make up the pkgCache.
  23
  24    It is important to note that the handling of index files is not a
  25    function of the system. Index files are handled through a separate
  26    abstraction - the only requirement is that the index files have the
  27    same idea of versioning as the target system.
  28
  29    Upon startup each supported system instantiates an instance of the
  30    pkgSystem class (using a global constructor) which will make itself
  31    available to the main APT init routine. That routine will select the
  32    proper system and make it the global default.
  33
  34    ##################################################################### */
  35                                                                         /*}}}*/
  36 #ifndef PKGLIB_PKGSYSTEM_H
  37 #define PKGLIB_PKGSYSTEM_H
  38
  39 #include <apt-pkg/pkgcache.h>
  40 #include <apt-pkg/cacheiterators.h>
  41
  42 #include <vector>
  43
  44 #ifndef APT_8_CLEANER_HEADERS
  45 #include <apt-pkg/depcache.h>
  46 #endif
  47
  48 class pkgDepCache;
  49 class pkgPackageManager;
  50 class pkgVersioningSystem;
  51 class Configuration;
  52 class pkgIndexFile;
  53
  54 class pkgSystem
  55 {
  56    public:
  57
  58    // Global list of supported systems
  59    static pkgSystem **GlobalList;
  60    static unsigned long GlobalListLen;
  61    static pkgSystem *GetSystem(const char *Label);
  62
  63    const char * const Label;
  64    pkgVersioningSystem * const VS;
  65
  66    /* Prevent other programs from touching shared data not covered by
  67       other locks (cache or state locks) */
  68    virtual bool Lock() = 0;
  69    virtual bool UnLock(bool NoErrors = false) = 0;
  70
  71    /* Various helper classes to interface with specific bits of this
  72       environment */
  73    virtual pkgPackageManager *CreatePM(pkgDepCache *Cache) const = 0;
  74
  75    /* Load environment specific configuration and perform any other setup
  76       necessary */
  77    virtual bool Initialize(Configuration &/*Cnf*/) {return true;};
  78
  79    /* Type is some kind of Globally Unique way of differentiating
  80       archive file types.. */
  81    virtual bool ArchiveSupported(const char *Type) = 0;
  82
  83    // Return a list of system index files..
  84    virtual bool AddStatusFiles(std::vector<pkgIndexFile *> &List) = 0;
  85
  86    virtual bool FindIndex(pkgCache::PkgFileIterator File,
  87                           pkgIndexFile *&Found) const = 0;
  88
  89    /* Evauluate how 'right' we are for this system based on the filesystem
  90       etc.. */
  91    virtual signed Score(Configuration const &/*Cnf*/) {
  92       return 0;
  93    };
  94
  95    //FIXME: these methods should be virtual
  96    /** does this system has support for MultiArch?
  97     *
  98     * Systems supporting only single arch (not systems which are single arch)
  99     * are considered legacy systems and support for it will likely degrade over
 100     * time.
 101     *
 102     * The default implementation returns always \b true.
 103     *
 104     * @return \b true if the system supports MultiArch, \b false if not.
 105     */
 106    bool MultiArchSupported() const;
 107    /** architectures supported by this system
 108     *
 109     * A MultiArch capable system might be configured to use
 110     * this capability.
 111     *
 112     * @return a list of all architectures (native + foreign) configured
 113     * for on this system (aka: which can be installed without force)
 114     */
 115    std::vector<std::string> ArchitecturesSupported() const;
 116
 117    pkgSystem(char const * const Label, pkgVersioningSystem * const VS);
 118    virtual ~pkgSystem();
 119    private:
 120    void * const d;
 121 };
 122
 123 // The environment we are operating in.
 124 extern pkgSystem *_system;
 125
 126 #endif