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