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@ -15,7 +15,7 @@ only accessible in read-only mode, through some clearly defined functions.
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In addition to "alpm.h", the interfaces of "alpm_list.h" have also been made
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available to the frontend. It is not a requirement for the frontend to use
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these list functions; however, it prevents frontends from having to reimplement
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possibly useful functions.
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a list data structure.
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Several structures and functions have been renamed compared to pacman 2.9 code.
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This was done at first for the sake of naming scheme consistency, and then
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@ -25,53 +25,68 @@ same name declared in both spaces. To avoid such conflicts, internal function
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names have been prepended with "_alpm_".
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In a general manner, public library functions are named "alpm_<type>_<action>"
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(examples: alpm_trans_commit(), alpm_lib_release(), alpm_pkg_getinfo(), ...).
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(examples: alpm_trans_commit(), alpm_release(), alpm_pkg_getinfo(), ...).
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Internal (and thus private) functions should be named "_alpm_XXX" for instance
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(examples: _alpm_needbackup(), _alpm_runscriplet(), ...). Functions defined and
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used inside a single file should be defined as "static".
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NOTE: The below descriptions may be severely outdated. Yes it needs updating,
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but it may be better done by doxygen comments and generated documentation.
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[HANDLE] (see handle.c)
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[Initialization]
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The "handle" object is the heart of the library. It is a global
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structure available from almost all other objects (althought some very
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low level objects should not be aware of the handle object, like chained
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list, package or groups structures.
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alpm_init() is used to initialize library internals and to create
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a transparent handle object. Before its call, the library can't be used.
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There is only one instance, created by the frontend upon
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"alpm_lib_init()" call, and destroyed upon "alpm_lib_release()" call.
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alpm_lib_init() is used to initialize library internals and to create
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the handle object (handle != NULL).
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Before its call, the library can't be used.
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alpm_lib_release() just does the opposite (memory used by the library is
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freed, and handle is set to NULL).
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After its call, the library is no more available.
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The aim of the handle is to provide a central placeholder for essential
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library parameters (filesystem root, pointers to database objects,
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configuration parameters, ...)
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The handle also allows to register a log callback usable by the frontend
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to catch all sort of notifications from the library.
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The frontend can choose the level of verbosity (i.e. the mask), or can
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simply choose to not use the log callback.
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A friendly frontend should care at least for WARNING and ERROR
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notifications.
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Other notifications can safely be ignored and are mainly available for
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troubleshooting purpose.
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Last, but not least, the handle holds a _unique_ transaction object.
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alpm_lib_release() just does the opposite (memory used by the library, and the
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handle is freed). After its call, the library is no longer available.
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[TRANSACTION] (see trans.c, and also alpm.c)
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[Options]
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In the future, the library will not use any configuration file. It will be up
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to the front end to The handle holds a
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number of configuration options instead (IGNOREPKG, SYSLOG usage,
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log file name, registered databases, ...).
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All of the following options have a alpm_option_get_* and alpm_option_set_*
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function for getting and setting the value. The cannot be set before the
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library is initialized.
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* logcb: The callback function for "log" operations.
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* dlcb: The callback function for download progress.
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* logmask: The logging mask for which level of output is sent to the logcb.
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* root: The root directory on which pacman operates (Default: /)
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* dbpath: The base path to pacman's databases (Default: var/lib/pacman)
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* cachedir: The base path to pacman's download cache (Default: var/cache/pacman)
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* logfile: The base path to pacman's log file (Default: var/log/pacman.log)
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* usesyslog: Log to syslog instead of `logfile` for file-base logging.
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* upgradedelay: The time span to wait before listing a package as an upgrade (Default: 0)
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* xfercommand: The command to use for downloading instead of pacman's internal
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downloading functionality.
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* nopassiveftp: Do not use passive FTP commands for ftp connections.
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* chomp: No way, easter eggs are secret!
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* usecolor: Unimplemented, but for the future. You can assume what it means.
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The following options also have a `alpm_option_add_*` function, as the values
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are list structures (NOTE: The add functions are NOT plural, as they're in
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english: alpm_option_get_noupgrades -> alpm_option_add_noupgrade).
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* noupgrades: Files which will never be touched by pacman (extracted as .pacnew)
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* noextracts: Files which will never be extracted at all (no .pacnew file)
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* ignorepkgs: Packages to ignore when upgrading.
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* holdpkgs: Packages which must be upgraded before continuing.
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The following options are read-only, having ONLY alpm_option_get_* functions:
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* localdb: A pmdb_t structure for the local (installed) database
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* syncdbs: A list of pmdb_t structures to which pacman can sync from.
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[Transactions]
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The transaction sturcture permits easy manipulations of several packages
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at a time (i.e. adding, upgrade and removal operations).
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A transaction can be initiatied with a type (ADD, UPGRADE or REMOVE),
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A transaction can be initiated with a type (ADD, UPGRADE or REMOVE),
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and some flags (NODEPS, FORCE, CASCADE, ...).
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Note: there can only be one type at a time: a transaction is either
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@ -91,97 +106,60 @@ These targets represent the list of packages to be handled.
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Then, a transaction needs to be prepared (alpm_trans_prepare()). It
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means that the various targets added, will be inspected and challenged
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against the set of alreayd installed packages (dependency checkings,
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against the set of already installed packages (dependency checkings,
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Last, a callback is associated with each transaction. During the
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transaction resolution, each time a new step is started or done (i.e
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dependency or conflict checkings, package adding or removal, ...), the
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dependency or conflict checking, package adding or removal, ...), the
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callback is called, allowing the frontend to be aware of the progress of
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the resolution. Can be useful to implement a progress bar.
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[CONFIGURATION/OPTIONS] (see handle.c)
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[Package Cache]
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The library does not use any configuration file. The handle holds a
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number of configuration options instead (IGNOREPKG, SYSLOG usage,
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log file name, registered databases, ...).
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It is up to the frontend to set the options of the library.
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Options can be manipulated using calls to
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alpm_set_option()/alpm_get_option().
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Note: the file system root is a special option which can only be defined
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when calling alpm_lib_init(). It can't be modified afterwards.
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[CACHE] (see cache.c)
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Compared to pacman 2.9, there is now one cache object connected to each
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database object.
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There are both a package and a group cache.
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The cache is loaded only on demand (i.e the cache is loaded the first
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time data from it should be used).
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Note: the cache of a database is always updated by the library after
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libalpm maintains two caches for each DB. One is a general package cache, the
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other is a group cache (for package groups). These caches are loaded on demand,
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and freed when the libary is.
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It is important to note tha, as a general rule, package structures should NOT be
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freed manually, as they SHOULD be part of the cache.
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The cache of a database is always updated by the library after
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an operation changing the database content (adding and/or removal of
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packages).
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Beware frontends ;)
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|
packages). Beware frontends ;)
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[PACKAGE] (see package.c, and also db.c)
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[Package]
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The package structure is using three new fields, namely: origin, data,
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infolevel.
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The purpose of these fields is to know some extra info about data stored
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in package structures.
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The package structure maintains all information for a package. In general,
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packages should never be freed from front-ends, as they should always be part of
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the package cache.
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For instance, where is the package coming from (i.e origin)?
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Was it loaded from a file or loaded from the cache?
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If it's coming from a file, then the field data holds the full path and
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name of the file, and infolevel is set to the highest possible value
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(all package fields are reputed to be known).
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Otherwise, if the package comes from a database, data is a pointer to
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the database structure hosting the package, and infolevel is set
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according to the db_read() infolevel parameter (it is possible using
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db_read() to only read a part of the package datas).
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Indeed, to reduce database access, all packages data requested by the
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frontend are comming from the cache. As a consequence, the library needs
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to know exactly the level of information about packages it holds, and
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then decide if more data needs to be fetched from the database.
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In file alpm.c, have a look at alpm_pkg_getinfo() function to get an
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overview.
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The 'origin' data member indicates whether the package is from a file
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(i.e. -U operations) or from the package cache. In the case of a file, all data
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members available are present in the structure. Packages indicated as being
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from the cache have data members filled on demand. For this reason, the
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alpm_pkg_get_* functions will load the data from the DB as needed.
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[ERRORS] (error.c)
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[Errors]
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The library provides a global variable pm_errno.
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It aims at being to the library what errno is for C system calls.
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Almost all public library functions are returning an integer value: 0
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indicating success, whereas -1 would indicate a failure.
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indicating success, -1 indicating a failure.
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If -1 is returned, the variable pm_errno is set to a meaningful value
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(not always yet, but it should improve ;).
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Wise frontends should always care for these returned values.
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Note: the helper function alpm_strerror() can also be used to translate
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the error code into a more friendly sentence.
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[LIST] (see list.c, and especially list wrappers in alpm.c)
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[List - alpm_list_t]
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The alpm_list_t structure is a doubly-linked list for use with the libalpm
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|
routines. This type is provided publicly so that frontends are free to use it
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if they have no native list type (C++, glib, python, etc all have list types).
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See the proper man pages for alpm_list_t references.
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It is a double chained list structure, use only for the internal needs
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of the library.
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A frontend should be free to use its own data structures to manipulate
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|
packages.
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For instance, consider a graphical frontend using the gtk toolkit (and
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|
as a consequence the glib library). The frontend will make use of the
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glib chained lists or trees.
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As a consequence, the library only provides a simple and very small
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interface to retrieve pointers to its internal data (see functions
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alpm_list_first(), alpm_list_next() and alpm_list_getdata()), giving to
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the frontend the responsibility to copy and store the data retrieved
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from the library in its own data structures.
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|
|
PACMAN frontend overview & internals
|
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|
|
@ -189,7 +167,7 @@ PACMAN frontend overview & internals
|
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|
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|
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Here are some words about the frontend responsibilities.
|
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The library can operate only a small set of well defined operations and
|
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|
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dumy operations.
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dummy operations.
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High level features are left to the frontend ;)
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|
@ -212,7 +190,7 @@ remove.c and sync.c).
|
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|
|
[CONFIGURATION] (see conf.c)
|
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|
|
|
|
|
|
|
The frontend is using a configuration file, usually "/etc/pacman.conf".
|
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|
|
Part of these options are only usefull for the frontend only (mainly,
|
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|
|
Part of these options are only useful for the frontend only (mainly,
|
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|
|
the download stuffs, and some options like HOLDPKG).
|
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|
|
The rest is used to configure the library.
|
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|
|
@ -224,28 +202,8 @@ Nothing new here, excepted some reorganization.
|
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|
|
The file pacman.c has been divided into several smaller files, namely
|
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|
|
|
add.c, remove.c, sync.c and query.c, to hold the big parts: pacman_add,
|
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|
|
pacman_remove, pacman_sync.
|
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|
|
These 3 functions have been splitted too to ease the code reading.
|
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[DONWLOAD] (see download.c)
|
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|
|
The library is not providing download facilities. As a consequence, it
|
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|
|
is up the the frontend to retrieve packages from Arch Linux servers.
|
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|
|
To do so, pacman is linked against an improved version of libftp
|
|
|
|
|
supporting both http and ftp donwloads.
|
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|
|
As a consequence, the frontend is repsonsible for the directory
|
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|
|
/var/cache/pacman/pkgs.
|
|
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|
|
One can consider that this cache is a facility provided by pacman.
|
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|
|
|
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|
|
Note: other frontends have to download packages by themselves too,
|
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|
|
although the cache directory can be shared by several frontends.
|
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|
|
|
|
|
|
|
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|
|
[LIST] (see list.c)
|
|
|
|
|
|
|
|
|
|
Single chained list.
|
|
|
|
|
A minimalistic chained list implementation to store options from the
|
|
|
|
|
configuration file, and targets passed to pacman on the command line.
|
|
|
|
|
These 3 functions have been split to ease the code reading.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
LIMITATIONS/BEHAVIOR CHANGES COMPARED TO PACMAN 2.9
|
|
|
|
|
|
Aaron Griffin