apt-pkg/acquire-worker.h

   1 // -*- mode: cpp; mode: fold -*-
   2 // Description                                                          /*{{{*/
   3 // $Id: acquire-worker.h,v 1.12 2001/02/20 07:03:17 jgg Exp $
   4 /* ######################################################################
   5
   6    Acquire Worker - Worker process manager
   7
   8    Each worker class is associated with exaclty one subprocess.
   9
  10    ##################################################################### */
  11                                                                         /*}}}*/
  12
  13 /** \addtogroup acquire
  14  *  @{
  15  *
  16  *  \file acquire-worker.h
  17  */
  18
  19 #ifndef PKGLIB_ACQUIRE_WORKER_H
  20 #define PKGLIB_ACQUIRE_WORKER_H
  21
  22 #include <apt-pkg/acquire.h>
  23
  24
  25 /** \brief A fetch subprocess.
  26  *
  27  *  A worker process is responsible for one stage of the fetch.  This
  28  *  class encapsulates the communications protocol between the master
  29  *  process and the worker, from the master end.
  30  *
  31  *  Each worker is intrinsically placed on two linked lists.  The
  32  *  Queue list (maintained in the #NextQueue variable) is maintained
  33  *  by the pkgAcquire::Queue class; it represents the set of workers
  34  *  assigned to a particular queue.  The Acquire list (maintained in
  35  *  the #NextAcquire variable) is maintained by the pkgAcquire class;
  36  *  it represents the set of active workers for a particular
  37  *  pkgAcquire object.
  38  *
  39  *  \todo Like everything else in the Acquire system, this has way too
  40  *  many protected items.
  41  *
  42  *  \sa pkgAcqMethod, pkgAcquire::Item, pkgAcquire
  43  */
  44 class pkgAcquire::Worker
  45 {
  46    friend class pkgAcquire;
  47
  48    protected:
  49    friend class Queue;
  50
  51    /** \brief The next link on the Queue list.
  52     *
  53     *  \todo This is always NULL; is it just for future use?
  54     */
  55    Worker *NextQueue;
  56
  57    /** \brief The next link on the Acquire list. */
  58    Worker *NextAcquire;
  59
  60    /** \brief The Queue with which this worker is associated. */
  61    Queue *OwnerQ;
  62
  63    /** \brief The download progress indicator to which progress
  64     *  messages should be sent.
  65     */
  66    pkgAcquireStatus *Log;
  67
  68    /** \brief The configuration of this method.  On startup, the
  69     *  target of this pointer is filled in with basic data about the
  70     *  method, as reported by the worker.
  71     */
  72    MethodConfig *Config;
  73
  74    /** \brief The access method to be used by this worker.
  75     *
  76     *  \todo Doesn't this duplicate Config->Access?
  77     */
  78    string Access;
  79
  80    /** \brief The PID of the subprocess. */
  81    pid_t Process;
  82
  83    /** \brief A file descriptor connected to the standard output of
  84     *  the subprocess.
  85     *
  86     *  Used to read messages and data from the subprocess.
  87     */
  88    int InFd;
  89
  90    /** \brief A file descriptor connected to the standard input of the
  91     *  subprocess.
  92     *
  93     *  Used to send commands and configuration data to the subprocess.
  94     */
  95    int OutFd;
  96
  97    /** \brief Set to \b true if the worker is in a state in which it
  98     *  might generate data or command responses.
  99     *
 100     *  \todo Is this right?  It's a guess.
 101     */
 102    bool InReady;
 103
 104    /** \brief Set to \b true if the worker is in a state in which it
 105     *  is legal to send commands to it.
 106     *
 107     *  \todo Is this right?
 108     */
 109    bool OutReady;
 110
 111    /** If \b true, debugging output will be sent to std::clog. */
 112    bool Debug;
 113
 114    /** \brief The raw text values of messages received from the
 115     *  worker, in sequence.
 116     */
 117    vector<string> MessageQueue;
 118
 119    /** \brief Buffers pending writes to the subprocess.
 120     *
 121     *  \todo Wouldn't a std::dequeue be more appropriate?
 122     */
 123    string OutQueue;
 124
 125    /** \brief Common code for the constructor.
 126     *
 127     *  Initializes NextQueue and NextAcquire to NULL; Process, InFd,
 128     *  and OutFd to -1, OutReady and InReady to \b false, and Debug
 129     *  from _config.
 130     */
 131    void Construct();
 132
 133    /** \brief Retrieve any available messages from the subprocess.
 134     *
 135     *  The messages are retrieved as in ::ReadMessages(), and
 136     *  MessageFailure() is invoked if an error occurs; in particular,
 137     *  if the pipe to the subprocess dies unexpectedly while a message
 138     *  is being read.
 139     *
 140     *  \return \b true if the messages were successfully read, \b
 141     *  false otherwise.
 142     */
 143    bool ReadMessages();
 144
 145    /** \brief Parse and dispatch pending messages.
 146     *
 147     *  This dispatches the message in a manner appropriate for its
 148     *  type.
 149     *
 150     *  \todo Several message types lack separate handlers.
 151     *
 152     *  \sa Capabilities(), SendConfiguration(), MediaChange()
 153     */
 154    bool RunMessages();
 155
 156    /** \brief Read and dispatch any pending messages from the
 157     *  subprocess.
 158     *
 159     *  \return \b false if the subprocess died unexpectedly while a
 160     *  message was being transmitted.
 161     */
 162    bool InFdReady();
 163
 164    /** \brief Send any pending commands to the subprocess.
 165     *
 166     *  This method will fail if there is no pending output.
 167     *
 168     *  \return \b true if all commands were succeeded, \b false if an
 169     *  error occurred (in which case MethodFailure() will be invoked).
 170     */
 171    bool OutFdReady();
 172
 173    /** \brief Handle a 100 Capabilities response from the subprocess.
 174     *
 175     *  \param Message the raw text of the message from the subprocess.
 176     *
 177     *  The message will be parsed and its contents used to fill
 178     *  #Config.  If #Config is NULL, this routine is a NOP.
 179     *
 180     *  \return \b true.
 181     */
 182    bool Capabilities(string Message);
 183
 184    /** \brief Send a 601 Configuration message (containing the APT
 185     *  configuration) to the subprocess.
 186     *
 187     *  The APT configuration will be send to the subprocess in a
 188     *  message of the following form:
 189     *
 190     *  <pre>
 191     *  601 Configuration
 192     *  Config-Item: Fully-Qualified-Item=Val
 193     *  Config-Item: Fully-Qualified-Item=Val
 194     *  ...
 195     *  </pre>
 196     *
 197     *  \return \b true if the command was successfully sent, \b false
 198     *  otherwise.
 199     */
 200    bool SendConfiguration();
 201
 202    /** \brief Handle a 403 Media Change message.
 203     *
 204     *  \param Message the raw text of the message; the Media field
 205     *  indicates what type of media should be changed, and the Drive
 206     *  field indicates where the media is located.
 207     *
 208     *  Invokes pkgAcquireStatus::MediaChange(Media, Drive) to ask the
 209     *  user to swap disks; informs the subprocess of the result (via
 210     *  603 Media Changed, with the Failed field set to \b true if the
 211     *  user cancelled the media change).
 212     */
 213    bool MediaChange(string Message);
 214
 215    /** \brief Invoked when the worked process dies unexpectedly.
 216     *
 217     *  Waits for the subprocess to terminate and generates an error if
 218     *  it terminated abnormally, then closes and blanks out all file
 219     *  descriptors.  Discards all pending messages from the
 220     *  subprocess.
 221     *
 222     *  \return \b false.
 223     */
 224    bool MethodFailure();
 225
 226    /** \brief Invoked when a fetch job is completed, either
 227     *  successfully or unsuccessfully.
 228     *
 229     *  Resets the status information for the worker process.
 230     */
 231    void ItemDone();
 232
 233    public:
 234
 235    /** \brief The queue entry that is currently being downloaded. */
 236    pkgAcquire::Queue::QItem *CurrentItem;
 237
 238    /** \brief The most recent status string received from the
 239     *  subprocess.
 240     */
 241    string Status;
 242
 243    /** \brief How many bytes of the file have been downloaded.  Zero
 244     *  if the current progress of the file cannot be determined.
 245     */
 246    unsigned long CurrentSize;
 247
 248    /** \brief The total number of bytes to be downloaded.  Zero if the
 249     *  total size of the final is unknown.
 250     */
 251    unsigned long TotalSize;
 252
 253    /** \brief How much of the file was already downloaded prior to
 254     *  starting this worker.
 255     */
 256    unsigned long ResumePoint;
 257
 258    /** \brief Tell the subprocess to download the given item.
 259     *
 260     *  \param Item the item to queue up.
 261     *  \return \b true if the item was successfully enqueued.
 262     *
 263     *  Queues up a 600 URI Acquire message for the given item to be
 264     *  sent at the next possible moment.  Does \e not flush the output
 265     *  queue.
 266     */
 267    bool QueueItem(pkgAcquire::Queue::QItem *Item);
 268
 269    /** \brief Start up the worker and fill in #Config.
 270     *
 271     *  Reads the first message from the worker, which is assumed to be
 272     *  a 100 Capabilities message.
 273     *
 274     *  \return \b true if all operations completed successfully.
 275     */
 276    bool Start();
 277
 278    /** \brief Update the worker statistics (CurrentSize, TotalSize,
 279     *  etc).
 280     */
 281    void Pulse();
 282
 283    /** \return The fetch method configuration. */
 284    inline const MethodConfig *GetConf() const {return Config;};
 285
 286    /** \brief Create a new Worker to download files.
 287     *
 288     *  \param OwnerQ The queue into which this worker should be
 289     *  placed.
 290     *
 291     *  \param Config A location in which to store information about
 292     *  the fetch method.
 293     *
 294     *  \param Log The download progress indicator that should be used
 295     *  to report the progress of this worker.
 296     */
 297    Worker(Queue *OwnerQ,MethodConfig *Config,pkgAcquireStatus *Log);
 298
 299    /** \brief Create a new Worker that should just retrieve
 300     *  information about the fetch method.
 301     *
 302     *  Nothing in particular forces you to refrain from actually
 303     *  downloading stuff, but the various status callbacks won't be
 304     *  invoked.
 305     *
 306     *  \param Config A location in which to store information about
 307     *  the fetch method.
 308     */
 309    Worker(MethodConfig *Config);
 310
 311    /** \brief Clean up this worker.
 312     *
 313     *  Closes the file descriptors; if MethodConfig::NeedsCleanup is
 314     *  \b false, also rudely interrupts the worker with a SIGINT.
 315     */
 316    ~Worker();
 317 };
 318
 319 /** @} */
 320
 321 #endif