split-up Dependency struct

Having dependency data separated from the link between version/package
and the dependency allows use to work on sharing the depdency data a bit
as it turns out that many dependencies are in fact duplicates. How many
are duplicates various heavily with the sources configured, but for a
single Debian release the ballpark is 2 duplicates for each dependency
already (e.g. libc6 counts 18410 dependencies, but only 45 unique). Add
more releases and the duplicates count only rises to get ~6 for 3
releases. For each architecture a user has configured which given the
shear number of dependencies amounts to MBs of duplication.

We can cut down on this number, but pay a heavy price for it: In my
many releases(3) + architectures(3) test we have a 10% (~ 0.5 sec)
increase in cache creationtime, but also 10% less cachesize (~ 10 MB).

Further work is needed to rip the whole benefits from this through, so
this is just the start.

Git-Dch: Ignore

1 files changed, 18 insertions, 9 deletions

diff --git a/apt-pkg/pkgcache.h b/apt-pkg/pkgcache.h
index 0042eac96..41709eae8 100644
--- a/apt-pkg/pkgcache.h
+++ b/apt-pkg/pkgcache.h
@@ -139,6 +139,7 @@ class pkgCache								/*{{{*/
    struct Description;
    struct Provides;
    struct Dependency;
+   struct DependencyData;
    struct StringItem;
    struct VerFile;
    struct DescFile;
@@ -226,6 +227,7 @@ class pkgCache								/*{{{*/
    Description *DescP;
    Provides *ProvideP;
    Dependency *DepP;
+   DependencyData *DepDataP;
    APT_DEPRECATED StringItem *StringItemP;
    char *StrP;
 
@@ -310,6 +312,7 @@ struct pkgCache::Header
    unsigned short VersionSz;
    unsigned short DescriptionSz;
    unsigned short DependencySz;
+   unsigned short DependencyDataSz;
    unsigned short ProvidesSz;
    unsigned short VerFileSz;
    unsigned short DescFileSz;
@@ -324,6 +327,7 @@ struct pkgCache::Header
    map_id_t VersionCount;
    map_id_t DescriptionCount;
    map_id_t DependsCount;
+   map_id_t DependsDataCount;
    map_fileid_t ReleaseFileCount;
    map_fileid_t PackageFileCount;
    map_fileid_t VerFileCount;
@@ -711,7 +715,7 @@ struct pkgCache::Description
     The base of the linked list is pkgCache::Version::DependsList.
     All forms of dependencies are recorded here including Depends,
     Recommends, Suggests, Enhances, Conflicts, Replaces and Breaks. */
-struct pkgCache::Dependency
+struct pkgCache::DependencyData
 {
    /** \brief string of the version the dependency is applied against */
    map_stringitem_t Version;
@@ -720,15 +724,7 @@ struct pkgCache::Dependency
        The generator will - if the package does not already exist -
        create a blank (no version records) package. */
    map_pointer_t Package;         // Package
-   /** \brief next dependency of this version */
-   map_pointer_t NextDepends;     // Dependency
-   /** \brief next reverse dependency of this package */
-   map_pointer_t NextRevDepends;  // Dependency
-   /** \brief version of the package which has the reverse depends */
-   map_pointer_t ParentVer;       // Version
 
-   /** \brief unique sequel ID */
-   should_be_map_id_t ID;
    /** \brief Dependency type - Depends, Recommends, Conflicts, etc */
    unsigned char Type;
    /** \brief comparison operator specified on the depends line
@@ -736,6 +732,19 @@ struct pkgCache::Dependency
        If the high bit is set then it is a logical OR with the previous record. */
    unsigned char CompareOp;
 };
+struct pkgCache::Dependency
+{
+   map_pointer_t DependencyData;  // DependencyData
+   /** \brief version of the package which has the depends */
+   map_pointer_t ParentVer;       // Version
+   /** \brief next reverse dependency of this package */
+   map_pointer_t NextRevDepends;  // Dependency
+   /** \brief next dependency of this version */
+   map_pointer_t NextDepends;     // Dependency
+
+   /** \brief unique sequel ID */
+   should_be_map_id_t ID;
+};
 									/*}}}*/
 // Provides structure							/*{{{*/
 /** \brief handles virtual packages