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

// -*- mode: cpp; mode: fold -*-
// Description                                                          /*{{{*/
// $Id: acquire.cc,v 1.50 2004/03/17 05:17:11 mdz Exp $
/* ######################################################################

   Acquire - File Acquiration

   The core element for the schedule system is the concept of a named
   queue. Each queue is unique and each queue has a name derived from the
   URI. The degree of paralization can be controlled by how the queue
   name is derived from the URI.
   
   ##################################################################### */
                                                                        /*}}}*/
// Include Files                                                        /*{{{*/
#include <config.h>

#include <apt-pkg/acquire.h>
#include <apt-pkg/acquire-item.h>
#include <apt-pkg/acquire-worker.h>
#include <apt-pkg/configuration.h>
#include <apt-pkg/error.h>
#include <apt-pkg/strutl.h>
#include <apt-pkg/fileutl.h>

#include <algorithm>
#include <numeric>
#include <string>
#include <vector>
#include <iostream>
#include <sstream>
#include <iomanip>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <pwd.h>
#include <grp.h>
#include <dirent.h>
#include <sys/time.h>
#include <sys/select.h>
#include <errno.h>
#include <sys/stat.h>

#include <apti18n.h>
                                                                        /*}}}*/

using namespace std;

// Acquire::pkgAcquire - Constructor                                    /*{{{*/
// ---------------------------------------------------------------------
/* We grab some runtime state from the configuration space */
pkgAcquire::pkgAcquire() : LockFD(-1), d(NULL), Queues(0), Workers(0), Configs(0), Log(NULL), ToFetch(0),
                           Debug(_config->FindB("Debug::pkgAcquire",false)),
                           Running(false)
{
   Initialize();
}
pkgAcquire::pkgAcquire(pkgAcquireStatus *Progress) : LockFD(-1), d(NULL), Queues(0), Workers(0),
                           Configs(0), Log(NULL), ToFetch(0),
                           Debug(_config->FindB("Debug::pkgAcquire",false)),
                           Running(false)
{
   Initialize();
   SetLog(Progress);
}
void pkgAcquire::Initialize()
{
   string const Mode = _config->Find("Acquire::Queue-Mode","host");
   if (strcasecmp(Mode.c_str(),"host") == 0)
      QueueMode = QueueHost;
   if (strcasecmp(Mode.c_str(),"access") == 0)
      QueueMode = QueueAccess;

   // chown the auth.conf file as it will be accessed by our methods
   std::string const SandboxUser = _config->Find("APT::Sandbox::User");
   if (getuid() == 0 && SandboxUser.empty() == false) // if we aren't root, we can't chown, so don't try it
   {
      struct passwd const * const pw = getpwnam(SandboxUser.c_str());
      struct group const * const gr = getgrnam("root");
      if (pw != NULL && gr != NULL)
      {
         std::string const AuthConf = _config->FindFile("Dir::Etc::netrc");
         if(AuthConf.empty() == false && RealFileExists(AuthConf) &&
               chown(AuthConf.c_str(), pw->pw_uid, gr->gr_gid) != 0)
            _error->WarningE("SetupAPTPartialDirectory", "chown to %s:root of file %s failed", SandboxUser.c_str(), AuthConf.c_str());
      }
   }
}
                                                                        /*}}}*/
// Acquire::GetLock - lock directory and prepare for action             /*{{{*/
static bool SetupAPTPartialDirectory(std::string const &grand, std::string const &parent)
{
   std::string const partial = parent + "partial";
   mode_t const mode = umask(S_IWGRP | S_IWOTH);
   bool const creation_fail = (CreateAPTDirectoryIfNeeded(grand, partial) == false &&
         CreateAPTDirectoryIfNeeded(parent, partial) == false);
   umask(mode);
   if (creation_fail == true)
      return false;

   std::string const SandboxUser = _config->Find("APT::Sandbox::User");
   if (getuid() == 0 && SandboxUser.empty() == false) // if we aren't root, we can't chown, so don't try it
   {
      struct passwd const * const pw = getpwnam(SandboxUser.c_str());
      struct group const * const gr = getgrnam("root");
      if (pw != NULL && gr != NULL)
      {
         // chown the partial dir
         if(chown(partial.c_str(), pw->pw_uid, gr->gr_gid) != 0)
            _error->WarningE("SetupAPTPartialDirectory", "chown to %s:root of directory %s failed", SandboxUser.c_str(), partial.c_str());
      }
   }
   if (chmod(partial.c_str(), 0700) != 0)
      _error->WarningE("SetupAPTPartialDirectory", "chmod 0700 of directory %s failed", partial.c_str());

   return true;
}
bool pkgAcquire::Setup(pkgAcquireStatus *Progress, string const &Lock)
{
   Log = Progress;
   if (Lock.empty())
   {
      string const listDir = _config->FindDir("Dir::State::lists");
      if (SetupAPTPartialDirectory(_config->FindDir("Dir::State"), listDir) == false)
         return _error->Errno("Acquire", _("List directory %spartial is missing."), listDir.c_str());
      string const archivesDir = _config->FindDir("Dir::Cache::Archives");
      if (SetupAPTPartialDirectory(_config->FindDir("Dir::Cache"), archivesDir) == false)
         return _error->Errno("Acquire", _("Archives directory %spartial is missing."), archivesDir.c_str());
      return true;
   }
   return GetLock(Lock);
}
bool pkgAcquire::GetLock(std::string const &Lock)
{
   if (Lock.empty() == true)
      return false;

   // check for existence and possibly create auxiliary directories
   string const listDir = _config->FindDir("Dir::State::lists");
   string const archivesDir = _config->FindDir("Dir::Cache::Archives");

   if (Lock == listDir)
   {
      if (SetupAPTPartialDirectory(_config->FindDir("Dir::State"), listDir) == false)
         return _error->Errno("Acquire", _("List directory %spartial is missing."), listDir.c_str());
   }
   if (Lock == archivesDir)
   {
      if (SetupAPTPartialDirectory(_config->FindDir("Dir::Cache"), archivesDir) == false)
         return _error->Errno("Acquire", _("Archives directory %spartial is missing."), archivesDir.c_str());
   }

   if (_config->FindB("Debug::NoLocking", false) == true)
      return true;

   // Lock the directory this acquire object will work in
   if (LockFD != -1)
      close(LockFD);
   LockFD = ::GetLock(flCombine(Lock, "lock"));
   if (LockFD == -1)
      return _error->Error(_("Unable to lock directory %s"), Lock.c_str());

   return true;
}
                                                                        /*}}}*/
// Acquire::~pkgAcquire - Destructor                                    /*{{{*/
// ---------------------------------------------------------------------
/* Free our memory, clean up the queues (destroy the workers) */
pkgAcquire::~pkgAcquire()
{
   Shutdown();

   if (LockFD != -1)
      close(LockFD);

   while (Configs != 0)
   {
      MethodConfig *Jnk = Configs;
      Configs = Configs->Next;
      delete Jnk;
   }   
}
                                                                        /*}}}*/
// Acquire::Shutdown - Clean out the acquire object                     /*{{{*/
// ---------------------------------------------------------------------
/* */
void pkgAcquire::Shutdown()
{
   while (Items.empty() == false)
   {
      if (Items[0]->Status == Item::StatFetching)
         Items[0]->Status = Item::StatError;
      delete Items[0];
   }

   while (Queues != 0)
   {
      Queue *Jnk = Queues;
      Queues = Queues->Next;
      delete Jnk;
   }   
}
                                                                        /*}}}*/
// Acquire::Add - Add a new item                                        /*{{{*/
// ---------------------------------------------------------------------
/* This puts an item on the acquire list. This list is mainly for tracking
   item status */
void pkgAcquire::Add(Item *Itm)
{
   Items.push_back(Itm);
}
                                                                        /*}}}*/
// Acquire::Remove - Remove a item                                      /*{{{*/
// ---------------------------------------------------------------------
/* Remove an item from the acquire list. This is usually not used.. */
void pkgAcquire::Remove(Item *Itm)
{
   Dequeue(Itm);
   
   for (ItemIterator I = Items.begin(); I != Items.end();)
   {
      if (*I == Itm)
      {
         Items.erase(I);
         I = Items.begin();
      }      
      else 
         ++I;
   }
}
                                                                        /*}}}*/
// Acquire::Add - Add a worker                                          /*{{{*/
// ---------------------------------------------------------------------
/* A list of workers is kept so that the select loop can direct their FD
   usage. */
void pkgAcquire::Add(Worker *Work)
{
   Work->NextAcquire = Workers;
   Workers = Work;
}
                                                                        /*}}}*/
// Acquire::Remove - Remove a worker                                    /*{{{*/
// ---------------------------------------------------------------------
/* A worker has died. This can not be done while the select loop is running
   as it would require that RunFds could handling a changing list state and
   it can't.. */
void pkgAcquire::Remove(Worker *Work)
{
   if (Running == true)
      abort();
   
   Worker **I = &Workers;
   for (; *I != 0;)
   {
      if (*I == Work)
         *I = (*I)->NextAcquire;
      else
         I = &(*I)->NextAcquire;
   }
}
                                                                        /*}}}*/
// Acquire::Enqueue - Queue an URI for fetching                         /*{{{*/
// ---------------------------------------------------------------------
/* This is the entry point for an item. An item calls this function when
   it is constructed which creates a queue (based on the current queue
   mode) and puts the item in that queue. If the system is running then
   the queue might be started. */
void pkgAcquire::Enqueue(ItemDesc &Item)
{
   // Determine which queue to put the item in
   const MethodConfig *Config;
   string Name = QueueName(Item.URI,Config);
   if (Name.empty() == true)
      return;

   // Find the queue structure
   Queue *I = Queues;
   for (; I != 0 && I->Name != Name; I = I->Next);
   if (I == 0)
   {
      I = new Queue(Name,this);
      I->Next = Queues;
      Queues = I;
      
      if (Running == true)
         I->Startup();
   }

   // See if this is a local only URI
   if (Config->LocalOnly == true && Item.Owner->Complete == false)
      Item.Owner->Local = true;
   Item.Owner->Status = Item::StatIdle;
   
   // Queue it into the named queue
   if(I->Enqueue(Item)) 
      ToFetch++;
            
   // Some trace stuff
   if (Debug == true)
   {
      clog << "Fetching " << Item.URI << endl;
      clog << " to " << Item.Owner->DestFile << endl;
      clog << " Queue is: " << Name << endl;
   }
}
                                                                        /*}}}*/
// Acquire::Dequeue - Remove an item from all queues                    /*{{{*/
// ---------------------------------------------------------------------
/* This is called when an item is finished being fetched. It removes it
   from all the queues */
void pkgAcquire::Dequeue(Item *Itm)
{
   Queue *I = Queues;
   bool Res = false;
   if (Debug == true)
      clog << "Dequeuing " << Itm->DestFile << endl;

   for (; I != 0; I = I->Next)
   {
      if (I->Dequeue(Itm))
      {
         Res = true;
         if (Debug == true)
            clog << "Dequeued from " << I->Name << endl;
      }
   }

   if (Res == true)
      ToFetch--;
}
                                                                        /*}}}*/
// Acquire::QueueName - Return the name of the queue for this URI       /*{{{*/
// ---------------------------------------------------------------------
/* The string returned depends on the configuration settings and the
   method parameters. Given something like http://foo.org/bar it can
   return http://foo.org or http */
string pkgAcquire::QueueName(string Uri,MethodConfig const *&Config)
{
   URI U(Uri);
   
   Config = GetConfig(U.Access);
   if (Config == 0)
      return string();
   
   /* Single-Instance methods get exactly one queue per URI. This is
      also used for the Access queue method  */
   if (Config->SingleInstance == true || QueueMode == QueueAccess)
      return U.Access;

   string AccessSchema = U.Access + ':',
        FullQueueName = AccessSchema + U.Host;
   unsigned int Instances = 0, SchemaLength = AccessSchema.length();

   Queue *I = Queues;
   for (; I != 0; I = I->Next) {
      // if the queue already exists, re-use it
      if (I->Name == FullQueueName)
         return FullQueueName;

      if (I->Name.compare(0, SchemaLength, AccessSchema) == 0)
         Instances++;
   }

   if (Debug) {
      clog << "Found " << Instances << " instances of " << U.Access << endl;
   }

   if (Instances >= (unsigned int)_config->FindI("Acquire::QueueHost::Limit",10))
      return U.Access;

   return FullQueueName;
}
                                                                        /*}}}*/
// Acquire::GetConfig - Fetch the configuration information             /*{{{*/
// ---------------------------------------------------------------------
/* This locates the configuration structure for an access method. If 
   a config structure cannot be found a Worker will be created to
   retrieve it */
pkgAcquire::MethodConfig *pkgAcquire::GetConfig(string Access)
{
   // Search for an existing config
   MethodConfig *Conf;
   for (Conf = Configs; Conf != 0; Conf = Conf->Next)
      if (Conf->Access == Access)
         return Conf;
   
   // Create the new config class
   Conf = new MethodConfig;
   Conf->Access = Access;
   Conf->Next = Configs;
   Configs = Conf;

   // Create the worker to fetch the configuration
   Worker Work(Conf);
   if (Work.Start() == false)
      return 0;

   /* if a method uses DownloadLimit, we switch to SingleInstance mode */
   if(_config->FindI("Acquire::"+Access+"::Dl-Limit",0) > 0)
      Conf->SingleInstance = true;
    
   return Conf;
}
                                                                        /*}}}*/
// Acquire::SetFds - Deal with readable FDs                             /*{{{*/
// ---------------------------------------------------------------------
/* Collect FDs that have activity monitors into the fd sets */
void pkgAcquire::SetFds(int &Fd,fd_set *RSet,fd_set *WSet)
{
   for (Worker *I = Workers; I != 0; I = I->NextAcquire)
   {
      if (I->InReady == true && I->InFd >= 0)
      {
         if (Fd < I->InFd)
            Fd = I->InFd;
         FD_SET(I->InFd,RSet);
      }
      if (I->OutReady == true && I->OutFd >= 0)
      {
         if (Fd < I->OutFd)
            Fd = I->OutFd;
         FD_SET(I->OutFd,WSet);
      }
   }
}
                                                                        /*}}}*/
// Acquire::RunFds - Deal with active FDs                               /*{{{*/
// ---------------------------------------------------------------------
/* Dispatch active FDs over to the proper workers. It is very important
   that a worker never be erased while this is running! The queue class
   should never erase a worker except during shutdown processing. */
void pkgAcquire::RunFds(fd_set *RSet,fd_set *WSet)
{
   for (Worker *I = Workers; I != 0; I = I->NextAcquire)
   {
      if (I->InFd >= 0 && FD_ISSET(I->InFd,RSet) != 0)
         I->InFdReady();
      if (I->OutFd >= 0 && FD_ISSET(I->OutFd,WSet) != 0)
         I->OutFdReady();
   }
}
                                                                        /*}}}*/
// Acquire::Run - Run the fetch sequence                                /*{{{*/
// ---------------------------------------------------------------------
/* This runs the queues. It manages a select loop for all of the
   Worker tasks. The workers interact with the queues and items to
   manage the actual fetch. */
static void CheckDropPrivsMustBeDisabled(pkgAcquire const &Fetcher)
{
   if(getuid() != 0)
      return;

   std::string SandboxUser = _config->Find("APT::Sandbox::User");
   if (SandboxUser.empty())
      return;

   struct passwd const * const pw = getpwnam(SandboxUser.c_str());
   if (pw == NULL)
      return;

   gid_t const old_euid = geteuid();
   gid_t const old_egid = getegid();
   if (setegid(pw->pw_gid) != 0)
      _error->Errno("setegid", "setegid %u failed", pw->pw_gid);
   if (seteuid(pw->pw_uid) != 0)
      _error->Errno("seteuid", "seteuid %u failed", pw->pw_uid);

   for (pkgAcquire::ItemCIterator I = Fetcher.ItemsBegin();
        I != Fetcher.ItemsEnd(); ++I)
   {
      std::string filename = (*I)->DestFile;
      if (filename.empty())
         continue;

      // no need to drop privileges for a complete file
      if ((*I)->Complete == true)
         continue;

      // we check directory instead of file as the file might or might not
      // exist already as a link or not which complicates everything…
      std::string dirname = flNotFile(filename);
      if (unlikely(dirname.empty()))
         continue;
      // translate relative to absolute for DirectoryExists
      // FIXME: What about ../ and ./../ ?
      if (dirname.substr(0,2) == "./")
         dirname = SafeGetCWD() + dirname.substr(2);

      if (DirectoryExists(dirname))
         ;
      else
         continue; // assume it is created correctly by the acquire system

      if (faccessat(-1, dirname.c_str(), R_OK | W_OK | X_OK, AT_EACCESS | AT_SYMLINK_NOFOLLOW) != 0)
      {
         _error->WarningE("pkgAcquire::Run", _("Can't drop privileges for downloading as file '%s' couldn't be accessed by user '%s'."),
               filename.c_str(), SandboxUser.c_str());
         _config->Set("APT::Sandbox::User", "");
         break;
      }
   }

   if (seteuid(old_euid) != 0)
      _error->Errno("seteuid", "seteuid %u failed", old_euid);
   if (setegid(old_egid) != 0)
      _error->Errno("setegid", "setegid %u failed", old_egid);
}
pkgAcquire::RunResult pkgAcquire::Run(int PulseIntervall)
{
   _error->PushToStack();
   CheckDropPrivsMustBeDisabled(*this);

   Running = true;
   
   for (Queue *I = Queues; I != 0; I = I->Next)
      I->Startup();
   
   if (Log != 0)
      Log->Start();
   
   bool WasCancelled = false;

   // Run till all things have been acquired
   struct timeval tv;
   tv.tv_sec = 0;
   tv.tv_usec = PulseIntervall; 
   while (ToFetch > 0)
   {
      fd_set RFds;
      fd_set WFds;
      int Highest = 0;
      FD_ZERO(&RFds);
      FD_ZERO(&WFds);
      SetFds(Highest,&RFds,&WFds);
      
      int Res;
      do
      {
         Res = select(Highest+1,&RFds,&WFds,0,&tv);
      }
      while (Res < 0 && errno == EINTR);
      
      if (Res < 0)
      {
         _error->Errno("select","Select has failed");
         break;
      }

      RunFds(&RFds,&WFds);

      // Timeout, notify the log class
      if (Res == 0 || (Log != 0 && Log->Update == true))
      {
         tv.tv_usec = PulseIntervall;
         for (Worker *I = Workers; I != 0; I = I->NextAcquire)
            I->Pulse();
         if (Log != 0 && Log->Pulse(this) == false)
         {
            WasCancelled = true;
            break;
         }
      }      
   }   

   if (Log != 0)
      Log->Stop();
   
   // Shut down the acquire bits
   Running = false;
   for (Queue *I = Queues; I != 0; I = I->Next)
      I->Shutdown(false);

   // Shut down the items
   for (ItemIterator I = Items.begin(); I != Items.end(); ++I)
      (*I)->Finished();

   bool const newError = _error->PendingError();
   _error->MergeWithStack();
   if (newError)
      return Failed;
   if (WasCancelled)
      return Cancelled;
   return Continue;
}
                                                                        /*}}}*/
// Acquire::Bump - Called when an item is dequeued                      /*{{{*/
// ---------------------------------------------------------------------
/* This routine bumps idle queues in hopes that they will be able to fetch
   the dequeued item */
void pkgAcquire::Bump()
{
   for (Queue *I = Queues; I != 0; I = I->Next)
      I->Bump();
}
                                                                        /*}}}*/
// Acquire::WorkerStep - Step to the next worker                        /*{{{*/
// ---------------------------------------------------------------------
/* Not inlined to advoid including acquire-worker.h */
pkgAcquire::Worker *pkgAcquire::WorkerStep(Worker *I)
{
   return I->NextAcquire;
}
                                                                        /*}}}*/
// Acquire::Clean - Cleans a directory                                  /*{{{*/
// ---------------------------------------------------------------------
/* This is a bit simplistic, it looks at every file in the dir and sees
   if it is part of the download set. */
bool pkgAcquire::Clean(string Dir)
{
   // non-existing directories are by definition clean…
   if (DirectoryExists(Dir) == false)
      return true;

   if(Dir == "/")
      return _error->Error(_("Clean of %s is not supported"), Dir.c_str());

   DIR *D = opendir(Dir.c_str());   
   if (D == 0)
      return _error->Errno("opendir",_("Unable to read %s"),Dir.c_str());
   
   string StartDir = SafeGetCWD();
   if (chdir(Dir.c_str()) != 0)
   {
      closedir(D);
      return _error->Errno("chdir",_("Unable to change to %s"),Dir.c_str());
   }
   
   for (struct dirent *Dir = readdir(D); Dir != 0; Dir = readdir(D))
   {
      // Skip some files..
      if (strcmp(Dir->d_name,"lock") == 0 ||
          strcmp(Dir->d_name,"partial") == 0 ||
          strcmp(Dir->d_name,".") == 0 ||
          strcmp(Dir->d_name,"..") == 0)
         continue;
      
      // Look in the get list
      ItemCIterator I = Items.begin();
      for (; I != Items.end(); ++I)
         if (flNotDir((*I)->DestFile) == Dir->d_name)
            break;
      
      // Nothing found, nuke it
      if (I == Items.end())
         unlink(Dir->d_name);
   };
   
   closedir(D);
   if (chdir(StartDir.c_str()) != 0)
      return _error->Errno("chdir",_("Unable to change to %s"),StartDir.c_str());
   return true;   
}
                                                                        /*}}}*/
// Acquire::TotalNeeded - Number of bytes to fetch                      /*{{{*/
// ---------------------------------------------------------------------
/* This is the total number of bytes needed */
APT_PURE unsigned long long pkgAcquire::TotalNeeded()
{
   return std::accumulate(ItemsBegin(), ItemsEnd(), 0,
      [](unsigned long long const T, Item const * const I) {
         return T + I->FileSize;
   });
}
                                                                        /*}}}*/
// Acquire::FetchNeeded - Number of bytes needed to get                 /*{{{*/
// ---------------------------------------------------------------------
/* This is the number of bytes that is not local */
APT_PURE unsigned long long pkgAcquire::FetchNeeded()
{
   return std::accumulate(ItemsBegin(), ItemsEnd(), 0,
      [](unsigned long long const T, Item const * const I) {
         if (I->Local == false)
            return T + I->FileSize;
         else
            return T;
   });
}
                                                                        /*}}}*/
// Acquire::PartialPresent - Number of partial bytes we already have    /*{{{*/
// ---------------------------------------------------------------------
/* This is the number of bytes that is not local */
APT_PURE unsigned long long pkgAcquire::PartialPresent()
{
   return std::accumulate(ItemsBegin(), ItemsEnd(), 0,
      [](unsigned long long const T, Item const * const I) {
         if (I->Local == false)
            return T + I->PartialSize;
         else
            return T;
   });
}
                                                                        /*}}}*/
// Acquire::UriBegin - Start iterator for the uri list                  /*{{{*/
// ---------------------------------------------------------------------
/* */
pkgAcquire::UriIterator pkgAcquire::UriBegin()
{
   return UriIterator(Queues);
}
                                                                        /*}}}*/
// Acquire::UriEnd - End iterator for the uri list                      /*{{{*/
// ---------------------------------------------------------------------
/* */
pkgAcquire::UriIterator pkgAcquire::UriEnd()
{
   return UriIterator(0);
}
                                                                        /*}}}*/
// Acquire::MethodConfig::MethodConfig - Constructor                    /*{{{*/
// ---------------------------------------------------------------------
/* */
pkgAcquire::MethodConfig::MethodConfig() : d(NULL), Next(0), SingleInstance(false),
   Pipeline(false), SendConfig(false), LocalOnly(false), NeedsCleanup(false),
   Removable(false)
{
}
                                                                        /*}}}*/
// Queue::Queue - Constructor                                           /*{{{*/
// ---------------------------------------------------------------------
/* */
pkgAcquire::Queue::Queue(string const &name,pkgAcquire * const owner) : d(NULL), Next(0),
   Name(name), Items(0), Workers(0), Owner(owner), PipeDepth(0), MaxPipeDepth(1)
{
}
                                                                        /*}}}*/
// Queue::~Queue - Destructor                                           /*{{{*/
// ---------------------------------------------------------------------
/* */
pkgAcquire::Queue::~Queue()
{
   Shutdown(true);
   
   while (Items != 0)
   {
      QItem *Jnk = Items;
      Items = Items->Next;
      delete Jnk;
   }
}
                                                                        /*}}}*/
// Queue::Enqueue - Queue an item to the queue                          /*{{{*/
// ---------------------------------------------------------------------
/* */
bool pkgAcquire::Queue::Enqueue(ItemDesc &Item)
{
   QItem **I = &Items;
   // move to the end of the queue and check for duplicates here
   HashStringList const hsl = Item.Owner->GetExpectedHashes();
   for (; *I != 0; I = &(*I)->Next)
      if (Item.URI == (*I)->URI || hsl == (*I)->Owner->GetExpectedHashes())
      {
         if (_config->FindB("Debug::pkgAcquire::Worker",false) == true)
            std::cerr << " @ Queue: Action combined for " << Item.URI << " and " << (*I)->URI << std::endl;
         (*I)->Owners.push_back(Item.Owner);
         Item.Owner->Status = (*I)->Owner->Status;
         return false;
      }

   // Create a new item
   QItem *Itm = new QItem;
   *Itm = Item;
   Itm->Next = 0;
   *I = Itm;
   
   Item.Owner->QueueCounter++;   
   if (Items->Next == 0)
      Cycle();
   return true;
}
                                                                        /*}}}*/
// Queue::Dequeue - Remove an item from the queue                       /*{{{*/
// ---------------------------------------------------------------------
/* We return true if we hit something */
bool pkgAcquire::Queue::Dequeue(Item *Owner)
{
   if (Owner->Status == pkgAcquire::Item::StatFetching)
      return _error->Error("Tried to dequeue a fetching object");

   bool Res = false;

   QItem **I = &Items;
   for (; *I != 0;)
   {
      if (Owner == (*I)->Owner)
      {
         QItem *Jnk= *I;
         *I = (*I)->Next;
         Owner->QueueCounter--;
         delete Jnk;
         Res = true;
      }
      else
         I = &(*I)->Next;
   }

   return Res;
}
                                                                        /*}}}*/
// Queue::Startup - Start the worker processes                          /*{{{*/
// ---------------------------------------------------------------------
/* It is possible for this to be called with a pre-existing set of
   workers. */
bool pkgAcquire::Queue::Startup()
{
   if (Workers == 0)
   {
      URI U(Name);
      pkgAcquire::MethodConfig *Cnf = Owner->GetConfig(U.Access);
      if (Cnf == 0)
         return false;
      
      Workers = new Worker(this,Cnf,Owner->Log);
      Owner->Add(Workers);
      if (Workers->Start() == false)
         return false;
      
      /* When pipelining we commit 10 items. This needs to change when we
         added other source retry to have cycle maintain a pipeline depth
         on its own. */
      if (Cnf->Pipeline == true)
         MaxPipeDepth = _config->FindI("Acquire::Max-Pipeline-Depth",10);
      else
         MaxPipeDepth = 1;
   }
   
   return Cycle();
}
                                                                        /*}}}*/
// Queue::Shutdown - Shutdown the worker processes                      /*{{{*/
// ---------------------------------------------------------------------
/* If final is true then all workers are eliminated, otherwise only workers
   that do not need cleanup are removed */
bool pkgAcquire::Queue::Shutdown(bool Final)
{
   // Delete all of the workers
   pkgAcquire::Worker **Cur = &Workers;
   while (*Cur != 0)
   {
      pkgAcquire::Worker *Jnk = *Cur;
      if (Final == true || Jnk->GetConf()->NeedsCleanup == false)
      {
         *Cur = Jnk->NextQueue;
         Owner->Remove(Jnk);
         delete Jnk;
      }
      else
         Cur = &(*Cur)->NextQueue;      
   }
   
   return true;
}
                                                                        /*}}}*/
// Queue::FindItem - Find a URI in the item list                        /*{{{*/
// ---------------------------------------------------------------------
/* */
pkgAcquire::Queue::QItem *pkgAcquire::Queue::FindItem(string URI,pkgAcquire::Worker *Owner)
{
   for (QItem *I = Items; I != 0; I = I->Next)
      if (I->URI == URI && I->Worker == Owner)
         return I;
   return 0;
}
                                                                        /*}}}*/
// Queue::ItemDone - Item has been completed                            /*{{{*/
// ---------------------------------------------------------------------
/* The worker signals this which causes the item to be removed from the
   queue. If this is the last queue instance then it is removed from the
   main queue too.*/
bool pkgAcquire::Queue::ItemDone(QItem *Itm)
{
   PipeDepth--;
   for (QItem::owner_iterator O = Itm->Owners.begin(); O != Itm->Owners.end(); ++O)
   {
      if ((*O)->Status == pkgAcquire::Item::StatFetching)
         (*O)->Status = pkgAcquire::Item::StatDone;
   }

   if (Itm->Owner->QueueCounter <= 1)
      Owner->Dequeue(Itm->Owner);
   else
   {
      Dequeue(Itm->Owner);
      Owner->Bump();
   }

   return Cycle();
}
                                                                        /*}}}*/
// Queue::Cycle - Queue new items into the method                       /*{{{*/
// ---------------------------------------------------------------------
/* This locates a new idle item and sends it to the worker. If pipelining
   is enabled then it keeps the pipe full. */
bool pkgAcquire::Queue::Cycle()
{
   if (Items == 0 || Workers == 0)
      return true;

   if (PipeDepth < 0)
      return _error->Error("Pipedepth failure");

   // Look for a queable item
   QItem *I = Items;
   while (PipeDepth < (signed)MaxPipeDepth)
   {
      for (; I != 0; I = I->Next)
         if (I->Owner->Status == pkgAcquire::Item::StatIdle)
            break;

      // Nothing to do, queue is idle.
      if (I == 0)
         return true;

      I->Worker = Workers;
      for (auto const &O: I->Owners)
         O->Status = pkgAcquire::Item::StatFetching;
      PipeDepth++;
      if (Workers->QueueItem(I) == false)
         return false;
   }

   return true;
}
                                                                        /*}}}*/
// Queue::Bump - Fetch any pending objects if we are idle               /*{{{*/
// ---------------------------------------------------------------------
/* This is called when an item in multiple queues is dequeued */
void pkgAcquire::Queue::Bump()
{
   Cycle();
}
                                                                        /*}}}*/
HashStringList pkgAcquire::Queue::QItem::GetExpectedHashes() const      /*{{{*/
{
   /* each Item can have multiple owners and each owner might have different
      hashes, even if that is unlikely in practice and if so at least some
      owners will later fail. There is one situation through which is not a
      failure and still needs this handling: Two owners who expect the same
      file, but one owner only knows the SHA1 while the other only knows SHA256. */
   HashStringList superhsl;
   for (pkgAcquire::Queue::QItem::owner_iterator O = Owners.begin(); O != Owners.end(); ++O)
   {
      HashStringList const hsl = (*O)->GetExpectedHashes();
      if (hsl.usable() == false)
         continue;
      if (superhsl.usable() == false)
         superhsl = hsl;
      else
      {
         // we merge both lists - if we find disagreement send no hashes
         HashStringList::const_iterator hs = hsl.begin();
         for (; hs != hsl.end(); ++hs)
            if (superhsl.push_back(*hs) == false)
               break;
         if (hs != hsl.end())
         {
            superhsl.clear();
            break;
         }
      }
   }
   return superhsl;
}
                                                                        /*}}}*/
APT_PURE unsigned long long pkgAcquire::Queue::QItem::GetMaximumSize() const    /*{{{*/
{
   unsigned long long Maximum = std::numeric_limits<unsigned long long>::max();
   for (auto const &O: Owners)
   {
      if (O->FileSize == 0)
         continue;
      Maximum = std::min(Maximum, O->FileSize);
   }
   if (Maximum == std::numeric_limits<unsigned long long>::max())
      return 0;
   return Maximum;
}
                                                                        /*}}}*/
void pkgAcquire::Queue::QItem::SyncDestinationFiles() const             /*{{{*/
{
   /* ensure that the first owner has the best partial file of all and
      the rest have (potentially dangling) symlinks to it so that
      everything (like progress reporting) finds it easily */
   std::string superfile = Owner->DestFile;
   off_t supersize = 0;
   for (pkgAcquire::Queue::QItem::owner_iterator O = Owners.begin(); O != Owners.end(); ++O)
   {
      if ((*O)->DestFile == superfile)
         continue;
      struct stat file;
      if (lstat((*O)->DestFile.c_str(),&file) == 0)
      {
         if ((file.st_mode & S_IFREG) == 0)
            unlink((*O)->DestFile.c_str());
         else if (supersize < file.st_size)
         {
            supersize = file.st_size;
            unlink(superfile.c_str());
            rename((*O)->DestFile.c_str(), superfile.c_str());
         }
         else
            unlink((*O)->DestFile.c_str());
         if (symlink(superfile.c_str(), (*O)->DestFile.c_str()) != 0)
         {
            ; // not a problem per-se and no real alternative
         }
      }
   }
}
                                                                        /*}}}*/
std::string pkgAcquire::Queue::QItem::Custom600Headers() const          /*{{{*/
{
   /* The others are relatively easy to merge, but this one?
      Lets not merge and see how far we can run with it…
      Likely, nobody will ever notice as all the items will
      be of the same class and hence generate the same headers. */
   return Owner->Custom600Headers();
}
                                                                        /*}}}*/

// AcquireStatus::pkgAcquireStatus - Constructor                        /*{{{*/
// ---------------------------------------------------------------------
/* */
pkgAcquireStatus::pkgAcquireStatus() : d(NULL), Percent(-1), Update(true), MorePulses(false)
{
   Start();
}
                                                                        /*}}}*/
// AcquireStatus::Pulse - Called periodically                           /*{{{*/
// ---------------------------------------------------------------------
/* This computes some internal state variables for the derived classes to
   use. It generates the current downloaded bytes and total bytes to download
   as well as the current CPS estimate. */
bool pkgAcquireStatus::Pulse(pkgAcquire *Owner)
{
   TotalBytes = 0;
   CurrentBytes = 0;
   TotalItems = 0;
   CurrentItems = 0;
   
   // Compute the total number of bytes to fetch
   unsigned int Unknown = 0;
   unsigned int Count = 0;
   bool UnfetchedReleaseFiles = false;
   for (pkgAcquire::ItemCIterator I = Owner->ItemsBegin(); 
        I != Owner->ItemsEnd();
        ++I, ++Count)
   {
      TotalItems++;
      if ((*I)->Status == pkgAcquire::Item::StatDone)
         ++CurrentItems;
      
      // Totally ignore local items
      if ((*I)->Local == true)
         continue;

      // see if the method tells us to expect more
      TotalItems += (*I)->ExpectedAdditionalItems;

      // check if there are unfetched Release files
      if ((*I)->Complete == false && (*I)->ExpectedAdditionalItems > 0)
         UnfetchedReleaseFiles = true;

      TotalBytes += (*I)->FileSize;
      if ((*I)->Complete == true)
         CurrentBytes += (*I)->FileSize;
      if ((*I)->FileSize == 0 && (*I)->Complete == false)
         ++Unknown;
   }
   
   // Compute the current completion
   unsigned long long ResumeSize = 0;
   for (pkgAcquire::Worker *I = Owner->WorkersBegin(); I != 0;
        I = Owner->WorkerStep(I))
   {
      if (I->CurrentItem != 0 && I->CurrentItem->Owner->Complete == false)
      {
         CurrentBytes += I->CurrentSize;
         ResumeSize += I->ResumePoint;

         // Files with unknown size always have 100% completion
         if (I->CurrentItem->Owner->FileSize == 0 &&
             I->CurrentItem->Owner->Complete == false)
            TotalBytes += I->CurrentSize;
      }
   }
   
   // Normalize the figures and account for unknown size downloads
   if (TotalBytes <= 0)
      TotalBytes = 1;
   if (Unknown == Count)
      TotalBytes = Unknown;

   // Wha?! Is not supposed to happen.
   if (CurrentBytes > TotalBytes)
      CurrentBytes = TotalBytes;

   // debug
   if (_config->FindB("Debug::acquire::progress", false) == true)
      std::clog << " Bytes: " 
                << SizeToStr(CurrentBytes) << " / " << SizeToStr(TotalBytes) 
                << std::endl;
   
   // Compute the CPS
   struct timeval NewTime;
   gettimeofday(&NewTime,0);
   if ((NewTime.tv_sec - Time.tv_sec == 6 && NewTime.tv_usec > Time.tv_usec) ||
       NewTime.tv_sec - Time.tv_sec > 6)
   {    
      double Delta = NewTime.tv_sec - Time.tv_sec + 
                     (NewTime.tv_usec - Time.tv_usec)/1000000.0;
      
      // Compute the CPS value
      if (Delta < 0.01)
         CurrentCPS = 0;
      else
         CurrentCPS = ((CurrentBytes - ResumeSize) - LastBytes)/Delta;
      LastBytes = CurrentBytes - ResumeSize;
      ElapsedTime = (unsigned long long)Delta;
      Time = NewTime;
   }

   double const OldPercent = Percent;
   // calculate the percentage, if we have too little data assume 1%
   if (TotalBytes > 0 && UnfetchedReleaseFiles)
      Percent = 0;
   else
      // use both files and bytes because bytes can be unreliable
      Percent = (0.8 * (CurrentBytes/float(TotalBytes)*100.0) +
                 0.2 * (CurrentItems/float(TotalItems)*100.0));
   double const DiffPercent = Percent - OldPercent;
   if (DiffPercent < 0.001 && _config->FindB("Acquire::Progress::Diffpercent", false) == true)
      return true;

   int fd = _config->FindI("APT::Status-Fd",-1);
   if(fd > 0) 
   {
      ostringstream status;

      char msg[200];
      long i = CurrentItems < TotalItems ? CurrentItems + 1 : CurrentItems;
      unsigned long long ETA = 0;
      if(CurrentCPS > 0)
         ETA = (TotalBytes - CurrentBytes) / CurrentCPS;

      // only show the ETA if it makes sense
      if (ETA > 0 && ETA < 172800 /* two days */ )
         snprintf(msg,sizeof(msg), _("Retrieving file %li of %li (%s remaining)"), i, TotalItems, TimeToStr(ETA).c_str());
      else
         snprintf(msg,sizeof(msg), _("Retrieving file %li of %li"), i, TotalItems);

      // build the status str
      status << "dlstatus:" << i
             << ":"  << std::setprecision(3) << Percent
             << ":" << msg
             << endl;

      std::string const dlstatus = status.str();
      FileFd::Write(fd, dlstatus.c_str(), dlstatus.size());
   }

   return true;
}
                                                                        /*}}}*/
// AcquireStatus::Start - Called when the download is started           /*{{{*/
// ---------------------------------------------------------------------
/* We just reset the counters */
void pkgAcquireStatus::Start()
{
   gettimeofday(&Time,0);
   gettimeofday(&StartTime,0);
   LastBytes = 0;
   CurrentCPS = 0;
   CurrentBytes = 0;
   TotalBytes = 0;
   FetchedBytes = 0;
   ElapsedTime = 0;
   TotalItems = 0;
   CurrentItems = 0;
}
                                                                        /*}}}*/
// AcquireStatus::Stop - Finished downloading                           /*{{{*/
// ---------------------------------------------------------------------
/* This accurately computes the elapsed time and the total overall CPS. */
void pkgAcquireStatus::Stop()
{
   // Compute the CPS and elapsed time
   struct timeval NewTime;
   gettimeofday(&NewTime,0);
   
   double Delta = NewTime.tv_sec - StartTime.tv_sec + 
                  (NewTime.tv_usec - StartTime.tv_usec)/1000000.0;
   
   // Compute the CPS value
   if (Delta < 0.01)
      CurrentCPS = 0;
   else
      CurrentCPS = FetchedBytes/Delta;
   LastBytes = CurrentBytes;
   ElapsedTime = (unsigned long long)Delta;
}
                                                                        /*}}}*/
// AcquireStatus::Fetched - Called when a byte set has been fetched     /*{{{*/
// ---------------------------------------------------------------------
/* This is used to get accurate final transfer rate reporting. */
void pkgAcquireStatus::Fetched(unsigned long long Size,unsigned long long Resume)
{   
   FetchedBytes += Size - Resume;
}
                                                                        /*}}}*/

pkgAcquire::UriIterator::UriIterator(pkgAcquire::Queue *Q) : d(NULL), CurQ(Q), CurItem(0)
{
   while (CurItem == 0 && CurQ != 0)
   {
      CurItem = CurQ->Items;
      CurQ = CurQ->Next;
   }
}

APT_CONST pkgAcquire::UriIterator::~UriIterator() {}
APT_CONST pkgAcquire::MethodConfig::~MethodConfig() {}
APT_CONST pkgAcquireStatus::~pkgAcquireStatus() {}