drop stored StringItems in favor of in-memory mappings

Strings like Section names or architectures are needed vary often.
Instead of writing them each time we need them, we deploy sharing for
these special strings. Until now, this was done with a linked list of
strings in which we would search, which was stored in the cache.
It turns out we can do this just as well in memory as well with a bunch
of std::map's.

In memory means here that it isn't available anymore if we have a partly
invalid cache, but that isn't much of a problem in practice as the
status file is compared to the other files we parse very small and includes
mostly duplicates, so the space we would gain by storing is more or less
equal to the size of the stored linked list…

1 files changed, 2 insertions, 28 deletions

diff --git a/apt-pkg/pkgcache.h b/apt-pkg/pkgcache.h
index 8179e05aa..4284a318c 100644
--- a/apt-pkg/pkgcache.h
+++ b/apt-pkg/pkgcache.h
@@ -109,7 +109,6 @@ class pkgCache								/*{{{*/
    struct Description;
    struct Provides;
    struct Dependency;
-   struct StringItem;
    struct VerFile;
    struct DescFile;
    
@@ -186,7 +185,6 @@ class pkgCache								/*{{{*/
    Description *DescP;
    Provides *ProvideP;
    Dependency *DepP;
-   StringItem *StringItemP;
    char *StrP;
 
    virtual bool ReMap(bool const &Errorchecks = true);
@@ -290,12 +288,6 @@ struct pkgCache::Header
        The PackageFile structures are singly linked lists that represent
        all package files that have been merged into the cache. */
    map_pointer_t FileList;
-   /** \brief index of the first StringItem structure
-
-       The cache contains a list of all the unique strings (StringItems).
-       The parser reads this list into memory so it can match strings
-       against it.*/
-   map_pointer_t StringList;
    /** \brief String representing the version system used */
    map_pointer_t VerSysName;
    /** \brief native architecture the cache was built against */
@@ -438,7 +430,7 @@ struct pkgCache::Package
 struct pkgCache::PackageFile
 {
    /** \brief physical disk file that this PackageFile represents */
-   map_pointer_t FileName;        // StringItem
+   map_stringitem_t FileName;
    /** \brief the release information
 
        Please see the files document for a description of what the
@@ -606,7 +598,7 @@ struct pkgCache::Description
 struct pkgCache::Dependency
 {
    /** \brief string of the version the dependency is applied against */
-   map_stringitem_t Version;         // StringItem
+   map_stringitem_t Version;
    /** \brief index of the package this depends applies to
 
        The generator will - if the package does not already exist -
@@ -656,24 +648,6 @@ struct pkgCache::Provides
    map_pointer_t NextPkgProv;      // Provides
 };
 									/*}}}*/
-// StringItem structure							/*{{{*/
-/** \brief used for generating single instances of strings
-
-    Some things like Section Name are are useful to have as unique tags.
-    It is part of a linked list based at pkgCache::Header::StringList
-
-    All strings are simply inlined any place in the file that is natural
-    for the writer. The client should make no assumptions about the positioning
-    of strings. All StringItems should be null-terminated. */
-struct pkgCache::StringItem
-{
-   /** \brief string this refers to */
-   map_stringitem_t String;
-   /** \brief Next link in the chain */
-   map_stringitem_t NextItem;
-};
-									/*}}}*/
-
 
 inline char const * pkgCache::NativeArch()
 	{ return StrP + HeaderP->Architecture; }