edsp: Add functionality to only write relevant packages

Add a variant of WriteLimitedScenario that does not take a pkgset,
but creates one on the fly based on the transitive closure of installed
packages, to be installed packages, and their dependencies and provides.

This includes more packages than strictly necessary, i.e. we do not
really need to include foo just because a package we want to install
Conflicts with it, but oh well, this is easy to read.

Trying to extend the filtering is hard as the dependencies being written
are also filtered...

2 files changed, 46 insertions, 0 deletions

diff --git a/apt-pkg/edsp.cc b/apt-pkg/edsp.cc
index 88569d3c4..2e6ef6271 100644
--- a/apt-pkg/edsp.cc
+++ b/apt-pkg/edsp.cc
@@ -327,6 +327,36 @@ bool EDSP::WriteLimitedScenario(pkgDepCache &Cache, FileFd &output,
       Progress->Done();
    return Okay;
 }
+
+static void MarkPackage(std::vector<bool> &pkgset, pkgCache::PkgIterator pkg)
+{
+   if (pkgset[pkg->ID])
+      return;
+   pkgset[pkg->ID] = true;
+   for (auto ver = pkg.VersionList(); not ver.end(); ++ver)
+   {
+      for (auto P = ver.ProvidesList(); not P.end(); ++P)
+	 MarkPackage(pkgset, P.ParentPkg());
+      for (auto D = ver.DependsList(); not D.end(); ++D)
+      {
+	 std::unique_ptr<pkgCache::Version *[]> targets(D.AllTargets());
+	 for (size_t i = 0; targets[i] != 0; ++i)
+	    MarkPackage(pkgset, pkgCache::VerIterator(*ver.Cache(), targets[i]).ParentPkg());
+
+	 MarkPackage(pkgset, D.TargetPkg());
+      }
+   }
+}
+
+bool EDSP::WriteLimitedScenario(pkgDepCache &Cache, FileFd &output,
+				OpProgress *Progress)
+{
+   std::vector<bool> pkgset(Cache.Head().PackageCount);
+   for (auto Pkg = Cache.PkgBegin(); not Pkg.end(); ++Pkg)
+      if (Cache[Pkg].Install() || Pkg->CurrentVer)
+	 MarkPackage(pkgset, Pkg);
+   return WriteLimitedScenario(Cache, output, pkgset, Progress);
+}
 									/*}}}*/
 // EDSP::WriteRequest - to the given file descriptor			/*{{{*/
 bool EDSP::WriteRequest(pkgDepCache &Cache, FileFd &output,
diff --git a/apt-pkg/edsp.h b/apt-pkg/edsp.h
index 0c37e231d..22767bd7b 100644
--- a/apt-pkg/edsp.h
+++ b/apt-pkg/edsp.h
@@ -91,6 +91,22 @@ namespace EDSP								/*{{{*/
 					 std::vector<bool> const &pkgset,
 					 OpProgress *Progress = NULL);
 
+	/** \brief creates a limited scenario representing the package universe
+	 *
+	 *  This method works similar to #WriteScenario as it works in the same
+	 *  way but doesn't send the complete universe to the solver but only
+	 *  packages reachable from installed packages or packages marked for
+	 *  install.
+	 *
+	 *  \param Cache is the known package universe
+	 *  \param output is written to this "file"
+	 *  \param Progress is an instance to report progress to
+	 *
+	 *  \return true if universe was composed successfully, otherwise false
+	 */
+	APT_PUBLIC bool WriteLimitedScenario(pkgDepCache &Cache, FileFd &output,
+					     OpProgress *Progress = NULL);
+
 	/** \brief waits and acts on the information returned from the solver
 	 *
 	 *  This method takes care of interpreting whatever the solver sends