merge with lp:~mvo/apt/debian-sid

[apt.git] / apt-pkg / acquire.h

diff --git a/apt-pkg/acquire.h b/apt-pkg/acquire.h
index a4ea45bff3e6c6c45706c6c5df5a611fc12213d1..6c130c1b32163d9ce5bb535960fec118bb60eef0 100644 (file)
--- a/apt-pkg/acquire.h
+++ b/apt-pkg/acquire.h
@@ -1,6 +1,6 @@
 // -*- mode: cpp; mode: fold -*-
 // Description                                                         /*{{{*/
 // -*- mode: cpp; mode: fold -*-
 // Description                                                         /*{{{*/

-// $Id: acquire.h,v 1.8 1998/11/05 07:21:41 jgg Exp $
+// $Id: acquire.h,v 1.29.2.1 2003/12/24 23:09:17 mdz Exp $

 /* ######################################################################
 
    Acquire - File Acquiration
 /* ######################################################################
 
    Acquire - File Acquiration


@@ -29,18 +29,63 @@
    
    ##################################################################### */
                                                                        /*}}}*/
    
    ##################################################################### */
                                                                        /*}}}*/

+
+/** \defgroup acquire Acquire system                                   {{{
+ *
+ *  \brief The Acquire system is responsible for retrieving files from
+ *  local or remote URIs and postprocessing them (for instance,
+ *  verifying their authenticity).  The core class in this system is
+ *  pkgAcquire, which is responsible for managing the download queues
+ *  during the download.  There is at least one download queue for
+ *  each supported protocol; protocols such as http may provide one
+ *  queue per host.
+ *
+ *  Each file to download is represented by a subclass of
+ *  pkgAcquire::Item.  The files add themselves to the download
+ *  queue(s) by providing their URI information to
+ *  pkgAcquire::Item::QueueURI, which calls pkgAcquire::Enqueue.
+ *
+ *  Once the system is set up, the Run method will spawn subprocesses
+ *  to handle the enqueued URIs; the scheduler will then take items
+ *  from the queues and feed them into the handlers until the queues
+ *  are empty.
+ *
+ *  \todo Acquire supports inserting an object into several queues at
+ *  once, but it is not clear what its behavior in this case is, and
+ *  no subclass of pkgAcquire::Item seems to actually use this
+ *  capability.
+ */                                                                    /*}}}*/
+
+/** \addtogroup acquire
+ *
+ *  @{
+ *
+ *  \file acquire.h
+ */
+

 #ifndef PKGLIB_ACQUIRE_H
 #define PKGLIB_ACQUIRE_H
 
 #include <vector>
 #include <string>
 
 #ifndef PKGLIB_ACQUIRE_H
 #define PKGLIB_ACQUIRE_H
 
 #include <vector>
 #include <string>
 

-#ifdef __GNUG__
-#pragma interface "apt-pkg/acquire.h"
-#endif 
+using std::vector;
+using std::string;
+

 
 

+#include <sys/time.h>

 #include <unistd.h>
 
 #include <unistd.h>
 

+class pkgAcquireStatus;
+
+/** \brief The core download scheduler.                                        {{{
+ *
+ *  This class represents an ongoing download.  It manages the lists
+ *  of active and pending downloads and handles setting up and tearing
+ *  down download-related structures.
+ *
+ *  \todo Why all the protected data items and methods?
+ */

 class pkgAcquire
 {   
    public:
 class pkgAcquire
 {   
    public:


@@ -49,110 +94,675 @@ class pkgAcquire
    class Queue;
    class Worker;
    struct MethodConfig;
    class Queue;
    class Worker;
    struct MethodConfig;

-   friend Item;
-   friend Queue;
-   
+   struct ItemDesc;
+   friend class Item;
+   friend class Queue;
+
+   typedef vector<Item *>::iterator ItemIterator;
+   typedef vector<Item *>::const_iterator ItemCIterator;
+

    protected:
    
    protected:
    

-   // List of items to fetch
+   /** \brief A list of items to download.
+    *
+    *  This is built monotonically as items are created and only
+    *  emptied when the download shuts down.
+    */

    vector<Item *> Items;
    
    vector<Item *> Items;
    

-   // List of active queues and fetched method configuration parameters
+   /** \brief The head of the list of active queues.
+    *
+    *  \todo why a hand-managed list of queues instead of std::list or
+    *  std::set?
+    */

    Queue *Queues;
    Queue *Queues;

+
+   /** \brief The head of the list of active workers.
+    *
+    *  \todo why a hand-managed list of workers instead of std::list
+    *  or std::set?
+    */

    Worker *Workers;
    Worker *Workers;

+
+   /** \brief The head of the list of acquire method configurations.
+    *
+    *  Each protocol (http, ftp, gzip, etc) via which files can be
+    *  fetched can have a representation in this list.  The
+    *  configuration data is filled in by parsing the 100 Capabilities
+    *  string output by a method on startup (see
+    *  pkgAcqMethod::pkgAcqMethod and pkgAcquire::GetConfig).
+    *
+    *  \todo why a hand-managed config dictionary instead of std::map?
+    */

    MethodConfig *Configs;
    MethodConfig *Configs;

+
+   /** \brief The progress indicator for this download. */
+   pkgAcquireStatus *Log;
+
+   /** \brief The total size of the files which are to be fetched.
+    *
+    *  This is not necessarily the total number of bytes to download
+    *  when, e.g., download resumption and list updates via patches
+    *  are taken into account.
+    */

    unsigned long ToFetch;
    unsigned long ToFetch;

-   
-   // Configurable parameters for the schedular
-   enum {QueueHost,QueueAccess} QueueMode;
+
+   // Configurable parameters for the scheduler
+
+   /** \brief Represents the queuing strategy for remote URIs. */
+   enum QueueStrategy {
+     /** \brief Generate one queue for each protocol/host combination; downloads from 
+      *  multiple hosts can proceed in parallel.
+      */
+     QueueHost,
+     /** \brief Generate a single queue for each protocol; serialize
+      *  downloads from multiple hosts.
+      */
+     QueueAccess} QueueMode;
+
+   /** \brief If \b true, debugging information will be dumped to std::clog. */

    bool Debug;
    bool Debug;

+   /** \brief If \b true, a download is currently in progress. */

    bool Running;
    bool Running;

-   
+
+   /** \brief Add the given item to the list of items. */

    void Add(Item *Item);
    void Add(Item *Item);

+
+   /** \brief Remove the given item from the list of items. */

    void Remove(Item *Item);
    void Remove(Item *Item);

+
+   /** \brief Add the given worker to the list of workers. */

    void Add(Worker *Work);
    void Add(Worker *Work);

+
+   /** \brief Remove the given worker from the list of workers. */

    void Remove(Worker *Work);
    
    void Remove(Worker *Work);
    

-   void Enqueue(Item *Item,string URI,string Description);
+   /** \brief Insert the given fetch request into the appropriate queue.
+    *
+    *  \param Item The URI to download and the item to download it
+    *  for.  Copied by value into the queue; no reference to Item is
+    *  retained.
+    */
+   void Enqueue(ItemDesc &Item);
+
+   /** \brief Remove all fetch requests for this item from all queues. */

    void Dequeue(Item *Item);
    void Dequeue(Item *Item);

-   string QueueName(string URI);

 
 

-   // FDSET managers for derived classes
-   void SetFds(int &Fd,fd_set *RSet,fd_set *WSet);
-   void RunFds(fd_set *RSet,fd_set *WSet);   
+   /** \brief Determine the fetch method and queue of a URI.
+    *
+    *  \param URI The URI to fetch.
+    *
+    *  \param[out] Config A location in which to place the method via
+    *  which the URI is to be fetched.
+    *
+    *  \return the string-name of the queue in which a fetch request
+    *  for the given URI should be placed.
+    */
+   string QueueName(string URI,MethodConfig const *&Config);
+
+   /** \brief Build up the set of file descriptors upon which select() should
+    *  block.
+    *
+    *  The default implementation inserts the file descriptors
+    *  corresponding to active downloads.
+    *
+    *  \param[out] Fd The largest file descriptor in the generated sets.
+    *
+    *  \param[out] RSet The set of file descriptors that should be
+    *  watched for input.
+    *
+    *  \param[out] WSet The set of file descriptors that should be
+    *  watched for output.
+    */
+   virtual void SetFds(int &Fd,fd_set *RSet,fd_set *WSet);

 
 

-   // A queue calls this when it dequeues an item
+   /** Handle input from and output to file descriptors which select()
+    *  has determined are ready.  The default implementation
+    *  dispatches to all active downloads.
+    *
+    *  \param RSet The set of file descriptors that are ready for
+    *  input.
+    *
+    *  \param WSet The set of file descriptors that are ready for
+    *  output.
+    */
+   virtual void RunFds(fd_set *RSet,fd_set *WSet);   
+
+   /** \brief Check for idle queues with ready-to-fetch items.
+    *
+    *  Called by pkgAcquire::Queue::Done each time an item is dequeued
+    *  but remains on some queues; i.e., another queue should start
+    *  fetching it.
+    */

    void Bump();
    
    public:
 
    void Bump();
    
    public:
 

+   /** \brief Retrieve information about a fetch method by name.
+    *
+    *  \param Access The name of the method to look up.
+    *
+    *  \return the method whose name is Access, or \b NULL if no such method exists.
+    */

    MethodConfig *GetConfig(string Access);
    MethodConfig *GetConfig(string Access);

-   bool Run();
+
+   /** \brief Provides information on how a download terminated. */
+   enum RunResult {
+     /** \brief All files were fetched successfully. */
+     Continue,
+
+     /** \brief Some files failed to download. */
+     Failed,
+
+     /** \brief The download was cancelled by the user (i.e., #Log's
+      *  pkgAcquireStatus::Pulse() method returned \b false).
+      */
+     Cancelled};
+
+   /** \brief Download all the items that have been Add()ed to this
+    *  download process.
+    *
+    *  This method will block until the download completes, invoking
+    *  methods on #Log to report on the progress of the download.
+    *
+    *  \param PulseInterval The method pkgAcquireStatus::Pulse will be
+    *  invoked on #Log at intervals of PulseInterval milliseconds.
+    *
+    *  \return the result of the download.
+    */
+   RunResult Run(int PulseInterval=500000);
+
+   /** \brief Remove all items from this download process, terminate
+    *  all download workers, and empty all queues.
+    */
+   void Shutdown();
+   
+   /** \brief Get the first #Worker object.
+    *
+    *  \return the first active worker in this download process.
+    */
+   inline Worker *WorkersBegin() {return Workers;};
+
+   /** \brief Advance to the next #Worker object.
+    *
+    *  \return the worker immediately following I, or \b NULL if none
+    *  exists.
+    */
+   Worker *WorkerStep(Worker *I);
+
+   /** \brief Get the head of the list of items. */
+   inline ItemIterator ItemsBegin() {return Items.begin();};
+
+   /** \brief Get the end iterator of the list of items. */
+   inline ItemIterator ItemsEnd() {return Items.end();};

    
    

-   pkgAcquire();
-   ~pkgAcquire();
+   // Iterate over queued Item URIs
+   class UriIterator;
+   /** \brief Get the head of the list of enqueued item URIs.
+    *
+    *  This iterator will step over every element of every active
+    *  queue.
+    */
+   UriIterator UriBegin();
+   /** \brief Get the end iterator of the list of enqueued item URIs. */
+   UriIterator UriEnd();
+   
+   /** Deletes each entry in the given directory that is not being
+    *  downloaded by this object.  For instance, when downloading new
+    *  list files, calling Clean() will delete the old ones.
+    *
+    *  \param Dir The directory to be cleaned out.
+    *
+    *  \return \b true if the directory exists and is readable.
+    */
+   bool Clean(string Dir);
+
+   /** \return the total size in bytes of all the items included in
+    *  this download.
+    */
+   double TotalNeeded();
+
+   /** \return the size in bytes of all non-local items included in
+    *  this download.
+    */
+   double FetchNeeded();
+
+   /** \return the amount of data to be fetched that is already
+    *  present on the filesystem.
+    */
+   double PartialPresent();
+
+   /** \brief Construct a new pkgAcquire.
+    *
+    *  \param Log The progress indicator associated with this
+    *  download, or \b NULL for none.  This object is not owned by the
+    *  download process and will not be deleted when the pkgAcquire
+    *  object is destroyed.  Naturally, it should live for at least as
+    *  long as the pkgAcquire object does.
+    */
+   pkgAcquire(pkgAcquireStatus *Log = 0);
+
+   /** \brief Destroy this pkgAcquire object.
+    *
+    *  Destroys all queue, method, and item objects associated with
+    *  this download.
+    */
+   virtual ~pkgAcquire();

 };
 
 };
 

-// List of possible items queued for download.
+/** \brief Represents a single download source from which an item
+ *  should be downloaded.
+ *
+ *  An item may have several assocated ItemDescs over its lifetime.
+ */
+struct pkgAcquire::ItemDesc
+{
+   /** \brief The URI from which to download this item. */
+   string URI;
+   /** brief A description of this item. */
+   string Description;
+   /** brief A shorter description of this item. */
+   string ShortDesc;
+   /** brief The underlying item which is to be downloaded. */
+   Item *Owner;
+};
+                                                                       /*}}}*/
+/** \brief A single download queue in a pkgAcquire object.             {{{
+ *
+ *  \todo Why so many protected values?
+ */

 class pkgAcquire::Queue
 {
 class pkgAcquire::Queue
 {

-   friend pkgAcquire;
+   friend class pkgAcquire;
+   friend class pkgAcquire::UriIterator;
+   friend class pkgAcquire::Worker;
+
+   /** \brief The next queue in the pkgAcquire object's list of queues. */

    Queue *Next;
    
    protected:
 
    Queue *Next;
    
    protected:
 

-   // Queued item
-   struct QItem 
+   /** \brief A single item placed in this queue. */
+   struct QItem : pkgAcquire::ItemDesc

    {
    {

+      /** \brief The next item in the queue. */

       QItem *Next;
       QItem *Next;

-      
-      string URI;
-      string Description;
-      Item *Owner;
+      /** \brief The worker associated with this item, if any. */

       pkgAcquire::Worker *Worker;
       pkgAcquire::Worker *Worker;

-   };   
+
+      /** \brief Assign the ItemDesc portion of this QItem from
+       *  another ItemDesc
+       */
+      void operator =(pkgAcquire::ItemDesc const &I)
+      {
+        URI = I.URI;
+        Description = I.Description;
+        ShortDesc = I.ShortDesc;
+        Owner = I.Owner;
+      };
+   };

    
    

-   // Name of the queue
+   /** \brief The name of this queue. */

    string Name;
 
    string Name;
 

-   // Items queued into this queue
+   /** \brief The head of the list of items contained in this queue.
+    *
+    *  \todo why a by-hand list instead of an STL structure?
+    */

    QItem *Items;
    QItem *Items;

+
+   /** \brief The head of the list of workers associated with this queue.
+    *
+    *  \todo This is plural because support exists in Queue for
+    *  multiple workers.  However, it does not appear that there is
+    *  any way to actually associate more than one worker with a
+    *  queue.
+    *
+    *  \todo Why not just use a std::set?
+    */

    pkgAcquire::Worker *Workers;
    pkgAcquire::Worker *Workers;

+
+   /** \brief the download scheduler with which this queue is associated. */

    pkgAcquire *Owner;
    pkgAcquire *Owner;

+
+   /** \brief The number of entries in this queue that are currently
+    *  being downloaded.
+    */
+   signed long PipeDepth;
+
+   /** \brief The maximum number of entries that this queue will
+    *  attempt to download at once.
+    */
+   unsigned long MaxPipeDepth;

    
    public:
    
    
    public:
    

-   // Put an item into this queue
-   void Enqueue(Item *Owner,string URI,string Description);
+   /** \brief Insert the given fetch request into this queue. 
+    *
+    *  \return \b true if the queuing was successful. May return
+    *  \b false if the Item is already in the queue
+    */
+   bool Enqueue(ItemDesc &Item);
+
+   /** \brief Remove all fetch requests for the given item from this queue.
+    *
+    *  \return \b true if at least one request was removed from the queue.
+    */

    bool Dequeue(Item *Owner);
 
    bool Dequeue(Item *Owner);
 

-   // Find a Queued item
+   /** \brief Locate an item in this queue.
+    *
+    *  \param URI A URI to match against.
+    *  \param Owner A pkgAcquire::Worker to match against.
+    *
+    *  \return the first item in the queue whose URI is #URI and that
+    *  is being downloaded by #Owner.
+    */

    QItem *FindItem(string URI,pkgAcquire::Worker *Owner);
    QItem *FindItem(string URI,pkgAcquire::Worker *Owner);

+
+   /** Presumably this should start downloading an item?
+    *
+    *  \todo Unimplemented.  Implement it or remove?
+    */
+   bool ItemStart(QItem *Itm,unsigned long Size);
+
+   /** \brief Remove the given item from this queue and set its state
+    *  to pkgAcquire::Item::StatDone.
+    *
+    *  If this is the only queue containing the item, the item is also
+    *  removed from the main queue by calling pkgAcquire::Dequeue.
+    *
+    *  \param Itm The item to remove.
+    *
+    *  \return \b true if no errors are encountered.
+    */

    bool ItemDone(QItem *Itm);
    
    bool ItemDone(QItem *Itm);
    

+   /** \brief Start the worker process associated with this queue.
+    *
+    *  If a worker process is already associated with this queue,
+    *  this is equivalent to calling Cycle().
+    *
+    *  \return \b true if the startup was successful.
+    */

    bool Startup();
    bool Startup();

-   bool Shutdown();
+
+   /** \brief Shut down the worker process associated with this queue.
+    *
+    *  \param Final If \b true, then the process is stopped unconditionally.
+    *               Otherwise, it is only stopped if it does not need cleanup
+    *               as indicated by the pkgAcqMethod::NeedsCleanup member of
+    *               its configuration.
+    *
+    *  \return \b true.
+    */
+   bool Shutdown(bool Final);
+
+   /** \brief Send idle items to the worker process.
+    *
+    *  Fills up the pipeline by inserting idle items into the worker's queue.
+    */

    bool Cycle();
    bool Cycle();

+
+   /** \brief Check for items that could be enqueued.
+    *
+    *  Call this after an item placed in multiple queues has gone from
+    *  the pkgAcquire::Item::StatFetching state to the
+    *  pkgAcquire::Item::StatIdle state, to possibly refill an empty queue.
+    *  This is an alias for Cycle().
+    *
+    *  \todo Why both this and Cycle()?  Are they expected to be
+    *  different someday?
+    */

    void Bump();
    
    void Bump();
    

+   /** \brief Create a new Queue.
+    *
+    *  \param Name The name of the new queue.
+    *  \param Owner The download process that owns the new queue.
+    */

    Queue(string Name,pkgAcquire *Owner);
    Queue(string Name,pkgAcquire *Owner);

+
+   /** Shut down all the worker processes associated with this queue
+    *  and empty the queue.
+    */

    ~Queue();
 };
    ~Queue();
 };

+                                                                       /*}}}*/
+/** \brief Iterates over all the URIs being fetched by a pkgAcquire object.    {{{*/
+class pkgAcquire::UriIterator
+{
+   /** The next queue to iterate over. */
+   pkgAcquire::Queue *CurQ;
+   /** The item that we currently point at. */
+   pkgAcquire::Queue::QItem *CurItem;
+   
+   public:
+   
+   inline void operator ++() {operator ++(0);};

 
 

-// Configuration information from each method
+   void operator ++(int)
+   {
+      CurItem = CurItem->Next;
+      while (CurItem == 0 && CurQ != 0)
+      {
+        CurItem = CurQ->Items;
+        CurQ = CurQ->Next;
+      }
+   };
+   
+   inline pkgAcquire::ItemDesc const *operator ->() const {return CurItem;};
+   inline bool operator !=(UriIterator const &rhs) const {return rhs.CurQ != CurQ || rhs.CurItem != CurItem;};
+   inline bool operator ==(UriIterator const &rhs) const {return rhs.CurQ == CurQ && rhs.CurItem == CurItem;};
+   
+   /** \brief Create a new UriIterator.
+    *
+    *  \param Q The queue over which this UriIterator should iterate.
+    */
+   UriIterator(pkgAcquire::Queue *Q) : CurQ(Q), CurItem(0)
+   {
+      while (CurItem == 0 && CurQ != 0)
+      {
+        CurItem = CurQ->Items;
+        CurQ = CurQ->Next;
+      }
+   }   
+};
+                                                                       /*}}}*/
+/** \brief Information about the properties of a single acquire method.        {{{*/

 struct pkgAcquire::MethodConfig
 {
 struct pkgAcquire::MethodConfig
 {

+   /** \brief The next link on the acquire method list.
+    *
+    *  \todo Why not an STL container?
+    */

    MethodConfig *Next;
    
    MethodConfig *Next;
    

+   /** \brief The name of this acquire method (e.g., http). */

    string Access;
 
    string Access;
 

+   /** \brief The implementation version of this acquire method. */

    string Version;
    string Version;

+
+   /** \brief If \b true, only one download queue should be created for this
+    *  method.
+    */

    bool SingleInstance;
    bool SingleInstance;

-   bool PreScan;
+
+   /** \brief If \b true, this method supports pipelined downloading. */

    bool Pipeline;
    bool Pipeline;

+
+   /** \brief If \b true, the worker process should send the entire
+    *  APT configuration tree to the fetch subprocess when it starts
+    *  up.
+    */

    bool SendConfig;
    bool SendConfig;

+
+   /** \brief If \b true, this fetch method does not require network access;
+    *  all files are to be acquired from the local disk.
+    */
+   bool LocalOnly;
+
+   /** \brief If \b true, the subprocess has to carry out some cleanup
+    *  actions before shutting down.
+    *
+    *  For instance, the cdrom method needs to unmount the CD after it
+    *  finishes.
+    */
+   bool NeedsCleanup;
+
+   /** \brief If \b true, this fetch method acquires files from removable media. */
+   bool Removable;

    
    

+   /** \brief Set up the default method parameters.
+    *
+    *  All fields are initialized to NULL, "", or \b false as
+    *  appropriate.
+    */

    MethodConfig();
 };
    MethodConfig();
 };

+                                                                       /*}}}*/
+/** \brief A monitor object for downloads controlled by the pkgAcquire class.  {{{
+ *
+ *  \todo Why protected members?
+ *
+ *  \todo Should the double members be uint64_t?
+ */
+class pkgAcquireStatus
+{
+   protected:
+   
+   /** \brief The last time at which this monitor object was updated. */
+   struct timeval Time;
+
+   /** \brief The time at which the download started. */
+   struct timeval StartTime;
+
+   /** \brief The number of bytes fetched as of the previous call to
+    *  pkgAcquireStatus::Pulse, including local items.
+    */
+   double LastBytes;
+
+   /** \brief The current rate of download as of the most recent call
+    *  to pkgAcquireStatus::Pulse, in bytes per second.
+    */
+   double CurrentCPS;
+
+   /** \brief The number of bytes fetched as of the most recent call
+    *  to pkgAcquireStatus::Pulse, including local items.
+    */
+   double CurrentBytes;
+
+   /** \brief The total number of bytes that need to be fetched.
+    *
+    *  \warning This member is inaccurate, as new items might be
+    *  enqueued while the download is in progress!
+    */
+   double TotalBytes;
+
+   /** \brief The total number of bytes accounted for by items that
+    *  were successfully fetched.
+    */
+   double FetchedBytes;
+
+   /** \brief The amount of time that has elapsed since the download
+    *   started.
+    */
+   unsigned long ElapsedTime;
+
+   /** \brief The total number of items that need to be fetched.
+    *
+    *  \warning This member is inaccurate, as new items might be
+    *  enqueued while the download is in progress!
+    */
+   unsigned long TotalItems;
+
+   /** \brief The number of items that have been successfully downloaded. */
+   unsigned long CurrentItems;
+   
+   public:
+
+   /** \brief If \b true, the download scheduler should call Pulse()
+    *  at the next available opportunity.
+    */
+   bool Update;
+
+   /** \brief If \b true, extra Pulse() invocations will be performed.
+    *
+    *  With this option set, Pulse() will be called every time that a
+    *  download item starts downloading, finishes downloading, or
+    *  terminates with an error.
+    */
+   bool MorePulses;
+      
+   /** \brief Invoked when a local or remote file has been completely fetched.
+    *
+    *  \param Size The size of the file fetched.
+    *
+    *  \param ResumePoint How much of the file was already fetched.
+    */
+   virtual void Fetched(unsigned long Size,unsigned long ResumePoint);
+   
+   /** \brief Invoked when the user should be prompted to change the
+    *         inserted removable media.
+    *
+    *  This method should not return until the user has confirmed to
+    *  the user interface that the media change is complete.
+    *
+    *  \param Media The name of the media type that should be changed.
+    *
+    *  \param Drive The identifying name of the drive whose media
+    *               should be changed.
+    *
+    *  \return \b true if the user confirms the media change, \b
+    *  false if it is cancelled.
+    *
+    *  \todo This is a horrible blocking monster; it should be CPSed
+    *  with prejudice.
+    */
+   virtual bool MediaChange(string Media,string Drive) = 0;
+   
+   /** \brief Invoked when an item is confirmed to be up-to-date.
+
+    * For instance, when an HTTP download is informed that the file on
+    * the server was not modified.
+    */
+   virtual void IMSHit(pkgAcquire::ItemDesc &/*Itm*/) {};
+
+   /** \brief Invoked when some of an item's data is fetched. */
+   virtual void Fetch(pkgAcquire::ItemDesc &/*Itm*/) {};
+
+   /** \brief Invoked when an item is successfully and completely fetched. */
+   virtual void Done(pkgAcquire::ItemDesc &/*Itm*/) {};
+
+   /** \brief Invoked when the process of fetching an item encounters
+    *  a fatal error.
+    */
+   virtual void Fail(pkgAcquire::ItemDesc &/*Itm*/) {};
+
+   /** \brief Periodically invoked while the Acquire process is underway.
+    *
+    *  Subclasses should first call pkgAcquireStatus::Pulse(), then
+    *  update their status output.  The download process is blocked
+    *  while Pulse() is being called.
+    *
+    *  \return \b false if the user asked to cancel the whole Acquire process.
+    *
+    *  \see pkgAcquire::Run
+    */
+   virtual bool Pulse(pkgAcquire *Owner);
+
+   /** \brief Invoked when the Acquire process starts running. */
+   virtual void Start();
+
+   /** \brief Invoked when the Acquire process stops running. */
+   virtual void Stop();
+   
+   /** \brief Initialize all counters to 0 and the time to the current time. */
+   pkgAcquireStatus();
+   virtual ~pkgAcquireStatus() {};
+};
+                                                                       /*}}}*/
+/** @} */

 
 #endif
 
 #endif