Do not use MD5SumValue for Description_md5()

Our profile says we spend about 5% of the time transforming the
hex digits into the binary format used by HashsumValue, all for
comparing them against the other strings. That makes no sense
at all.

According to callgrind, this reduces the overall instruction
count from 5,3 billion to 5 billion in my example, which
roughly matches the 5%.

1 files changed, 11 insertions, 5 deletions

diff --git a/apt-pkg/pkgcachegen.h b/apt-pkg/pkgcachegen.h
index 228b9f71d..cb51c113a 100644
--- a/apt-pkg/pkgcachegen.h
+++ b/apt-pkg/pkgcachegen.h
@@ -41,7 +41,9 @@ class pkgCacheListParser;
 
 class APT_HIDDEN pkgCacheGenerator					/*{{{*/
 {
-   APT_HIDDEN map_stringitem_t WriteStringInMap(std::string const &String) { return WriteStringInMap(String.c_str()); };
+#ifdef APT_PKG_EXPOSE_STRING_VIEW
+   APT_HIDDEN map_stringitem_t WriteStringInMap(APT::StringView String) { return WriteStringInMap(String.data(), String.size()); };
+#endif
    APT_HIDDEN map_stringitem_t WriteStringInMap(const char *String);
    APT_HIDDEN map_stringitem_t WriteStringInMap(const char *String, const unsigned long &Len);
    APT_HIDDEN map_pointer_t AllocateInMap(const unsigned long &size);
@@ -117,13 +119,13 @@ class APT_HIDDEN pkgCacheGenerator					/*{{{*/
    map_pointer_t NewVersion(pkgCache::VerIterator &Ver, APT::StringView const &VerStr,
 			    map_pointer_t const ParentPkg, unsigned short const Hash,
 			    map_pointer_t const Next);
+   map_pointer_t NewDescription(pkgCache::DescIterator &Desc,const std::string &Lang, APT::StringView md5sum,map_stringitem_t const idxmd5str);
 #endif
    bool NewFileVer(pkgCache::VerIterator &Ver,ListParser &List);
    bool NewFileDesc(pkgCache::DescIterator &Desc,ListParser &List);
    bool NewDepends(pkgCache::PkgIterator &Pkg, pkgCache::VerIterator &Ver,
 		   map_pointer_t const Version, uint8_t const Op,
 		   uint8_t const Type, map_pointer_t* &OldDepLast);
-   map_pointer_t NewDescription(pkgCache::DescIterator &Desc,const std::string &Lang,const MD5SumValue &md5sum,map_stringitem_t const idxmd5str);
    bool NewProvides(pkgCache::VerIterator &Ver, pkgCache::PkgIterator &Pkg,
 		    map_stringitem_t const ProvidesVersion, uint8_t const Flags);
 
@@ -171,8 +173,10 @@ class APT_HIDDEN pkgCacheGenerator					/*{{{*/
 			   pkgCache::VerIterator &V);
    APT_HIDDEN bool AddImplicitDepends(pkgCache::VerIterator &V, pkgCache::PkgIterator &D);
 
+#ifdef APT_PKG_EXPOSE_STRING_VIEW
    APT_HIDDEN bool AddNewDescription(ListParser &List, pkgCache::VerIterator &Ver,
-	 std::string const &lang, MD5SumValue const &CurMd5, map_stringitem_t &md5idx);
+	 std::string const &lang, APT::StringView CurMd5, map_stringitem_t &md5idx);
+#endif
 };
 									/*}}}*/
 // This is the abstract package list parser class.			/*{{{*/
@@ -192,9 +196,9 @@ class APT_HIDDEN pkgCacheListParser
    inline map_stringitem_t StoreString(pkgCacheGenerator::StringType const type, const char *S,unsigned int Size) {return Owner->StoreString(type, S, Size);};
 #ifdef APT_PKG_EXPOSE_STRING_VIEW
    inline map_stringitem_t StoreString(pkgCacheGenerator::StringType const type, APT::StringView S) {return Owner->StoreString(type, S);};
+   inline map_stringitem_t WriteString(APT::StringView S) {return Owner->WriteStringInMap(S.data(), S.size());};
 #endif
 
-   inline map_stringitem_t WriteString(const std::string &S) {return Owner->WriteStringInMap(S);};
    inline map_stringitem_t WriteString(const char *S,unsigned int Size) {return Owner->WriteStringInMap(S,Size);};
 #ifdef APT_PKG_EXPOSE_STRING_VIEW
    bool NewDepends(pkgCache::VerIterator &Ver,APT::StringView Package, APT::StringView Arch,
@@ -217,7 +221,9 @@ class APT_HIDDEN pkgCacheListParser
 #endif
    virtual bool NewVersion(pkgCache::VerIterator &Ver) = 0;
    virtual std::vector<std::string> AvailableDescriptionLanguages() = 0;
-   virtual MD5SumValue Description_md5() = 0;
+#ifdef APT_PKG_EXPOSE_STRING_VIEW
+   virtual APT::StringView Description_md5() = 0;
+#endif
    virtual unsigned short VersionHash() = 0;
    /** compare currently parsed version with given version
     *