Acquire system {{{

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. More...

Files
file	acquire-item.h
file	acquire-method.h
file	acquire-worker.h
file	acquire.h

Classes
struct	pkgAcquire
	Represents the process by which a pkgAcquire object should retrieve a file or a collection of files. More...
class	pkgAcqTransactionItem
	baseclass for the indexes files to manage them all together More...
class	pkgAcqMetaBase
	the manager of a transaction More...
class	pkgAcqMetaIndex
	An item that is responsible for downloading the meta-index {{{ file (i.e., Release) itself and verifying its signature. More...
class	pkgAcqMetaSig
	An acquire item that downloads the detached signature {{{ of a meta-index (Release) file, then queues up the release file itself. More...
class	pkgAcqMetaClearSig
	An item responsible for downloading clearsigned metaindexes {{{. More...
class	pkgAcqBaseIndex
	Common base class for all classes that deal with fetching indexes {{{. More...
class	pkgAcqIndex
	An acquire item that is responsible for fetching an index {{{ file (e.g., Packages or Sources). More...
struct	DiffInfo
class	pkgAcqDiffIndex
	An item that is responsible for fetching an index file of {{{ package list diffs and starting the package list's download. More...
class	pkgAcqIndexMergeDiffs
	An item that is responsible for fetching client-merge patches {{{ that need to be applied to a given package index file. More...
class	pkgAcqIndexDiffs
	An item that is responsible for fetching server-merge patches {{{ that need to be applied to a given package index file. More...
class	pkgAcqArchive
	An item that is responsible for fetching a package file. {{{. More...
class	pkgAcqChangelog
	Retrieve the changelog for the given version {{{. More...
class	pkgAcqFile
	Retrieve an arbitrary file to the current directory. {{{. More...
class	pkgAcqAuxFile
class	pkgAcqMethod
class	pkgAcquireStatus
	A monitor object for downloads controlled by the pkgAcquire class. {{{. More...

Detailed Description

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.