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<div id="projectname">apt
 <span id="projectnumber">1.4.6</span>
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<div id="projectbrief">commandline package manager</div>
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<div class="title">Acquire system {{{</div> </div>
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<p>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 <a class="el" href="classpkgAcquire.xhtml" title="The core download scheduler. {{{. ">pkgAcquire</a>, 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.
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Files</h2></td></tr>
<tr class="memitem:acquire-item_8h"><td class="memItemLeft" align="right" valign="top">file  </td><td class="memItemRight" valign="bottom"><a class="el" href="acquire-item_8h.xhtml">acquire-item.h</a></td></tr>
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<tr class="memitem:acquire-worker_8h"><td class="memItemLeft" align="right" valign="top">file  </td><td class="memItemRight" valign="bottom"><a class="el" href="acquire-worker_8h.xhtml">acquire-worker.h</a></td></tr>
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<tr class="memitem:acquire_8h"><td class="memItemLeft" align="right" valign="top">file  </td><td class="memItemRight" valign="bottom"><a class="el" href="acquire_8h.xhtml">acquire.h</a></td></tr>
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Classes</h2></td></tr>
<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">class  </td><td class="memItemRight" valign="bottom"><a class="el" href="classpkgAcquire_1_1Item.xhtml">pkgAcquire::Item</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">Represents the process by which a <a class="el" href="classpkgAcquire.xhtml" title="The core download scheduler. {{{. ">pkgAcquire</a> object should retrieve a file or a collection of files. <a href="classpkgAcquire_1_1Item.xhtml#details">More...</a><br /></td></tr>
<tr class="separator:"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">class  </td><td class="memItemRight" valign="bottom"><a class="el" href="classpkgAcqTransactionItem.xhtml">pkgAcqTransactionItem</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">baseclass for the indexes files to manage them all together <a href="classpkgAcqTransactionItem.xhtml#details">More...</a><br /></td></tr>
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<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">class  </td><td class="memItemRight" valign="bottom"><a class="el" href="classpkgAcqMetaBase.xhtml">pkgAcqMetaBase</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">the manager of a transaction <a href="classpkgAcqMetaBase.xhtml#details">More...</a><br /></td></tr>
<tr class="separator:"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">class  </td><td class="memItemRight" valign="bottom"><a class="el" href="classpkgAcqMetaIndex.xhtml">pkgAcqMetaIndex</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">An item that is responsible for downloading the meta-index {{{ file (i.e., Release) itself and verifying its signature. <a href="classpkgAcqMetaIndex.xhtml#details">More...</a><br /></td></tr>
<tr class="separator:"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">class  </td><td class="memItemRight" valign="bottom"><a class="el" href="classpkgAcqMetaSig.xhtml">pkgAcqMetaSig</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">An acquire item that downloads the detached signature {{{ of a meta-index (Release) file, then queues up the release file itself. <a href="classpkgAcqMetaSig.xhtml#details">More...</a><br /></td></tr>
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<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">class  </td><td class="memItemRight" valign="bottom"><a class="el" href="classpkgAcqMetaClearSig.xhtml">pkgAcqMetaClearSig</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">An item repsonsible for downloading clearsigned metaindexes {{{. <a href="classpkgAcqMetaClearSig.xhtml#details">More...</a><br /></td></tr>
<tr class="separator:"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">class  </td><td class="memItemRight" valign="bottom"><a class="el" href="classpkgAcqBaseIndex.xhtml">pkgAcqBaseIndex</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">Common base class for all classes that deal with fetching indexes {{{. <a href="classpkgAcqBaseIndex.xhtml#details">More...</a><br /></td></tr>
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<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">class  </td><td class="memItemRight" valign="bottom"><a class="el" href="classpkgAcqIndex.xhtml">pkgAcqIndex</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">An acquire item that is responsible for fetching an index {{{ file (e.g., Packages or Sources). <a href="classpkgAcqIndex.xhtml#details">More...</a><br /></td></tr>
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<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">class  </td><td class="memItemRight" valign="bottom"><a class="el" href="classpkgAcqDiffIndex.xhtml">pkgAcqDiffIndex</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">An item that is responsible for fetching an index file of {{{ package list diffs and starting the package list's download. <a href="classpkgAcqDiffIndex.xhtml#details">More...</a><br /></td></tr>
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<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">struct  </td><td class="memItemRight" valign="bottom"><a class="el" href="structDiffInfo.xhtml">DiffInfo</a></td></tr>
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<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">class  </td><td class="memItemRight" valign="bottom"><a class="el" href="classpkgAcqIndexMergeDiffs.xhtml">pkgAcqIndexMergeDiffs</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">An item that is responsible for fetching client-merge patches {{{ that need to be applied to a given package index file. <a href="classpkgAcqIndexMergeDiffs.xhtml#details">More...</a><br /></td></tr>
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<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">class  </td><td class="memItemRight" valign="bottom"><a class="el" href="classpkgAcqIndexDiffs.xhtml">pkgAcqIndexDiffs</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">An item that is responsible for fetching server-merge patches {{{ that need to be applied to a given package index file. <a href="classpkgAcqIndexDiffs.xhtml#details">More...</a><br /></td></tr>
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<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">class  </td><td class="memItemRight" valign="bottom"><a class="el" href="classpkgAcqArchive.xhtml">pkgAcqArchive</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">An item that is responsible for fetching a package file. {{{. <a href="classpkgAcqArchive.xhtml#details">More...</a><br /></td></tr>
<tr class="separator:"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">class  </td><td class="memItemRight" valign="bottom"><a class="el" href="classpkgAcqChangelog.xhtml">pkgAcqChangelog</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">Retrieve the changelog for the given version {{{. <a href="classpkgAcqChangelog.xhtml#details">More...</a><br /></td></tr>
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<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">class  </td><td class="memItemRight" valign="bottom"><a class="el" href="classpkgAcqFile.xhtml">pkgAcqFile</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">Retrieve an arbitrary file to the current directory. {{{. <a href="classpkgAcqFile.xhtml#details">More...</a><br /></td></tr>
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<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">class  </td><td class="memItemRight" valign="bottom"><a class="el" href="classpkgAcqMethod.xhtml">pkgAcqMethod</a></td></tr>
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<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">class  </td><td class="memItemRight" valign="bottom"><a class="el" href="classpkgAcquire_1_1Worker.xhtml">pkgAcquire::Worker</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">A fetch subprocess. <a href="classpkgAcquire_1_1Worker.xhtml#details">More...</a><br /></td></tr>
<tr class="separator:"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">class  </td><td class="memItemRight" valign="bottom"><a class="el" href="classpkgAcquire.xhtml">pkgAcquire</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">The core download scheduler. {{{. <a href="classpkgAcquire.xhtml#details">More...</a><br /></td></tr>
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<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">struct  </td><td class="memItemRight" valign="bottom"><a class="el" href="structpkgAcquire_1_1MethodConfig.xhtml">pkgAcquire::MethodConfig</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">Information about the properties of a single acquire method. {{{. <a href="structpkgAcquire_1_1MethodConfig.xhtml#details">More...</a><br /></td></tr>
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<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">class  </td><td class="memItemRight" valign="bottom"><a class="el" href="classpkgAcquire_1_1UriIterator.xhtml">pkgAcquire::UriIterator</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">Iterates over all the URIs being fetched by a <a class="el" href="classpkgAcquire.xhtml" title="The core download scheduler. {{{. ">pkgAcquire</a> object. {{{. <a href="classpkgAcquire_1_1UriIterator.xhtml#details">More...</a><br /></td></tr>
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<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">class  </td><td class="memItemRight" valign="bottom"><a class="el" href="classpkgAcquire_1_1Queue.xhtml">pkgAcquire::Queue</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">A single download queue in a <a class="el" href="classpkgAcquire.xhtml" title="The core download scheduler. {{{. ">pkgAcquire</a> object. {{{. <a href="classpkgAcquire_1_1Queue.xhtml#details">More...</a><br /></td></tr>
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<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">struct  </td><td class="memItemRight" valign="bottom"><a class="el" href="structpkgAcquire_1_1ItemDesc.xhtml">pkgAcquire::ItemDesc</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">Represents a single download source from which an item should be downloaded. <a href="structpkgAcquire_1_1ItemDesc.xhtml#details">More...</a><br /></td></tr>
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<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">class  </td><td class="memItemRight" valign="bottom"><a class="el" href="classpkgAcquireStatus.xhtml">pkgAcquireStatus</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">A monitor object for downloads controlled by the <a class="el" href="classpkgAcquire.xhtml" title="The core download scheduler. {{{. ">pkgAcquire</a> class. {{{. <a href="classpkgAcquireStatus.xhtml#details">More...</a><br /></td></tr>
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<a name="details" id="details"></a><h2 class="groupheader">Detailed Description</h2>
<p>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 <a class="el" href="classpkgAcquire.xhtml" title="The core download scheduler. {{{. ">pkgAcquire</a>, 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. </p>
<p>Each file to download is represented by a subclass of <a class="el" href="classpkgAcquire_1_1Item.xhtml" title="Represents the process by which a pkgAcquire object should retrieve a file or a collection of files...">pkgAcquire::Item</a>. The files add themselves to the download queue(s) by providing their <a class="el" href="classURI.xhtml">URI</a> information to <a class="el" href="classpkgAcquire_1_1Item.xhtml#a3d592ee597936699b45a5b4356740c33" title="Insert this item into its owner's queue. ">pkgAcquire::Item::QueueURI</a>, which calls <a class="el" href="classpkgAcquire.xhtml#adff4865b0b932d7c8dae0aee44006c13" title="Insert the given fetch request into the appropriate queue. ">pkgAcquire::Enqueue</a>.</p>
<p>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.</p>
<dl class="todo"><dt><b><a class="el" href="todo.xhtml#_todo000015">Todo:</a></b></dt><dd>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 <a class="el" href="classpkgAcquire_1_1Item.xhtml" title="Represents the process by which a pkgAcquire object should retrieve a file or a collection of files...">pkgAcquire::Item</a> seems to actually use this capability. </dd></dl>
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