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Dpkg::Deps(3)			 libdpkg-perl			 Dpkg::Deps(3)

NAME
       Dpkg::Deps - parse and manipulate dependencies of Debian packages

DESCRIPTION
       The Dpkg::Deps module provides objects implementing various types of
       dependencies.

       The most important function is deps_parse(), it turns a dependency line
       in a set of Dpkg::Deps::{Simple,AND,OR,Union} objects depending on the
       case.

FUNCTIONS
       All the deps_* functions are exported by default.

       deps_eval_implication($rel_p, $v_p, $rel_q, $v_q)
	   ($rel_p, $v_p) and ($rel_q, $v_q) express two dependencies as
	   (relation, version). The relation variable can have the following
	   values that are exported by Dpkg::Version: REL_EQ, REL_LT, REL_LE,
	   REL_GT, REL_GT.

	   This functions returns 1 if the "p" dependency implies the "q"
	   dependency. It returns 0 if the "p" dependency implies that "q" is
	   not satisfied. It returns undef when there's no implication.

	   The $v_p and $v_q parameter should be Dpkg::Version objects.

       my $dep = deps_concat(@dep_list)
	   This function concatenates multiple dependency lines into a single
	   line, joining them with ", " if appropriate, and always returning a
	   valid string.

       my $dep = deps_parse($line, %options)
	   This function parses the dependency line and returns an object,
	   either a Dpkg::Deps::AND or a Dpkg::Deps::Union. Various options
	   can alter the behaviour of that function.

	   use_arch (defaults to 1)
	       Take into account the architecture restriction part of the
	       dependencies.  Set to 0 to completely ignore that information.

	   host_arch (defaults to the current architecture)
	       Define the host architecture. By default it uses
	       Dpkg::Arch::get_host_arch() to identify the proper
	       architecture.

	   build_arch (defaults to the current architecture)
	       Define the build architecture. By default it uses
	       Dpkg::Arch::get_build_arch() to identify the proper
	       architecture.

	   reduce_arch (defaults to 0)
	       If set to 1, ignore dependencies that do not concern the
	       current host architecture. This implicitely strips off the
	       architecture restriction list so that the resulting
	       dependencies are directly applicable to the current
	       architecture.

	   use_profiles (defaults to 1)
	       Take into account the profile restriction part of the
	       dependencies. Set to 0 to completely ignore that information.

	   build_profiles (defaults to no profile)
	       Define the active build profiles. By default no profile is
	       defined.

	   reduce_profiles (defaults to 0)
	       If set to 1, ignore dependencies that do not concern the
	       current build profile. This implicitly strips off the profile
	       restriction list so that the resulting dependencies are
	       directly applicable to the current profiles.

	   reduce_restrictions (defaults to 0)
	       If set to 1, ignore dependencies that do not concern the
	       current set of restrictions. This implicitly strips off any
	       restriction list so that the resulting dependencies are
	       directly applicable to the current restriction.	This currently
	       implies "reduce_arch" and "reduce_profiles", and overrides them
	       if set.

	   union (defaults to 0)
	       If set to 1, returns a Dpkg::Deps::Union instead of a
	       Dpkg::Deps::AND. Use this when parsing non-dependency fields
	       like Conflicts.

	   build_dep (defaults to 0)
	       If set to 1, allow build-dep only arch qualifiers, that is
	       “:native”.  This should be set whenever working with build-
	       deps.

       deps_compare($a, $b)
	   Implements a comparison operator between two dependency objects.
	   This function is mainly used to implement the sort() method.

OBJECTS - Dpkg::Deps::*
       There are several kind of dependencies. A Dpkg::Deps::Simple dependency
       represents a single dependency statement (it relates to one package
       only).  Dpkg::Deps::Multiple dependencies are built on top of this
       object and combine several dependencies in a different manners.
       Dpkg::Deps::AND represents the logical "AND" between dependencies while
       Dpkg::Deps::OR represents the logical "OR". Dpkg::Deps::Multiple
       objects can contain Dpkg::Deps::Simple object as well as other
       Dpkg::Deps::Multiple objects.

       In practice, the code is only meant to handle the realistic cases
       which, given Debian's dependencies structure, imply those restrictions:
       AND can contain Simple or OR objects, OR can only contain Simple
       objects.

       Dpkg::Deps::KnownFacts is a special object that is used while
       evaluating dependencies and while trying to simplify them. It
       represents a set of installed packages along with the virtual packages
       that they might provide.

   COMMON FUNCTIONS
       $dep->is_empty()
	   Returns true if the dependency is empty and doesn't contain any
	   useful information. This is true when a Dpkg::Deps::Simple object
	   has not yet been initialized or when a (descendant of)
	   Dpkg::Deps::Multiple contains an empty list of dependencies.

       $dep->get_deps()
	   Returns a list of sub-dependencies. For Dpkg::Deps::Simple it
	   returns itself.

       $dep->output([$fh])
       "$dep"
	   Returns a string representing the dependency. If $fh is set, it
	   prints the string to the filehandle.

       $dep->implies($other_dep)
	   Returns 1 when $dep implies $other_dep. Returns 0 when $dep implies
	   NOT($other_dep). Returns undef when there's no implication. $dep
	   and $other_dep do not need to be of the same type.

       $dep->sort()
	   Sorts alphabetically the internal list of dependencies. It's a no-
	   op for Dpkg::Deps::Simple objects.

       $dep->arch_is_concerned($arch)
	   Returns true if the dependency applies to the indicated
	   architecture. For multiple dependencies, it returns true if at
	   least one of the sub-dependencies apply to this architecture.

       $dep->reduce_arch($arch)
	   Simplifies the dependency to contain only information relevant to
	   the given architecture. A Dpkg::Deps::Simple object can be left
	   empty after this operation. For Dpkg::Deps::Multiple objects, the
	   non-relevant sub-dependencies are simply removed.

	   This trims off the architecture restriction list of
	   Dpkg::Deps::Simple objects.

       $dep->get_evaluation($facts)
	   Evaluates the dependency given a list of installed packages and a
	   list of virtual packages provided. Those lists are part of the
	   Dpkg::Deps::KnownFacts object given as parameters.

	   Returns 1 when it's true, 0 when it's false, undef when some
	   information is lacking to conclude.

       $dep->simplify_deps($facts, @assumed_deps)
	   Simplifies the dependency as much as possible given the list of
	   facts (see object Dpkg::Deps::KnownFacts) and a list of other
	   dependencies that are known to be true.

       $dep->has_arch_restriction()
	   For a simple dependency, returns the package name if the dependency
	   applies only to a subset of architectures.  For multiple
	   dependencies, it returns the list of package names that have such a
	   restriction.

       $dep->reset()
	   Clears any dependency information stored in $dep so that
	   $dep->is_empty() returns true.

   Dpkg::Deps::Simple
       Such an object has four interesting properties:

       package
	   The package name (can be undef if the dependency has not been
	   initialized or if the simplification of the dependency lead to its
	   removal).

       relation
	   The relational operator: "=", "<<", "<=", ">=" or ">>". It can be
	   undefined if the dependency had no version restriction. In that
	   case the following field is also undefined.

       version
	   The version.

       arches
	   The list of architectures where this dependency is applicable. It's
	   undefined when there's no restriction, otherwise it's an array ref.
	   It can contain an exclusion list, in that case each architecture is
	   prefixed with an exclamation mark.

       archqual
	   The arch qualifier of the dependency (can be undef if there's
	   none).  In the dependency "python:any (>= 2.6)", the arch qualifier
	   is "any".

       METHODS

       $simple_dep->parse_string('dpkg-dev (>= 1.14.8) [!hurd-i386]')
	   Parses the dependency and modifies internal properties to match the
	   parsed dependency.

       $simple_dep->merge_union($other_dep)
	   Returns true if $simple_dep could be modified to represent the
	   union of both dependencies. Otherwise returns false.

   Dpkg::Deps::Multiple
       This is the base class for Dpkg::Deps::{AND,OR,Union}. It implements
       the following methods:

       $mul->add($dep)
	   Adds a new dependency object at the end of the list.

   Dpkg::Deps::AND
       This object represents a list of dependencies who must be met at the
       same time.

       $and->output([$fh])
	   The output method uses ", " to join the list of sub-dependencies.

   Dpkg::Deps::OR
       This object represents a list of dependencies of which only one must be
       met for the dependency to be true.

       $or->output([$fh])
	   The output method uses " | " to join the list of sub-dependencies.

   Dpkg::Deps::Union
       This object represents a list of relationships.

       $union->output([$fh])
	   The output method uses ", " to join the list of relationships.

       $union->implies($other_dep)
       $union->get_evaluation($other_dep)
	   Those methods are not meaningful for this object and always return
	   undef.

       $union->simplify_deps($facts)
	   The simplication is done to generate an union of all the
	   relationships.  It uses $simple_dep->merge_union($other_dep) to get
	   its job done.

   Dpkg::Deps::KnownFacts
       This object represents a list of installed packages and a list of
       virtual packages provided (by the set of installed packages).

       my $facts = Dpkg::Deps::KnownFacts->new();
	   Creates a new object.

       $facts->add_installed_package($package, $version, $arch, $multiarch)
	   Records that the given version of the package is installed. If
	   $version/$arch is undefined we know that the package is installed
	   but we don't know which version/architecture it is. $multiarch is
	   the Multi-Arch field of the package. If $multiarch is undef, it
	   will be equivalent to "Multi-Arch: no".

	   Note that $multiarch is only used if $arch is provided.

       $facts->add_provided_package($virtual, $relation, $version, $by)
	   Records that the "$by" package provides the $virtual package.
	   $relation and $version correspond to the associated relation given
	   in the Provides field. This might be used in the future for
	   versioned provides.

       my ($check, $param) = $facts->check_package($package)
	   $check is one when the package is found. For a real package, $param
	   contains the version. For a virtual package, $param contains an
	   array reference containing the list of packages that provide it
	   (each package is listed as [ $provider, $relation, $version ]).

	   This function is obsolete and should not be used.
	   Dpkg::Deps::KnownFacts is only meant to be filled with data and
	   then passed to Dpkg::Deps methods where appropriate, but it should
	   not be directly queried.

CHANGES
   Version 1.02
       ·   Add new Dpkg::deps_concat() function.

   Version 1.01
       ·   Add new $dep->reset() method that all dependency objects support.

       ·   Dpkg::Deps::Simple now recognizes the arch qualifier "any" and
	   stores it in the "archqual" property when present.

       ·   Dpkg::Deps::KnownFacts->add_installed_package() now accepts 2
	   supplementary parameters ($arch and $multiarch).

       ·   Dpkg::Deps::KnownFacts->check_package() is obsolete, it should not
	   have been part of the public API.

1.17.5				  2013-12-10			 Dpkg::Deps(3)
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