Avoid temporary strings in SubstVar.

Microoptimization, but still gives a measurable 2-3% improvement
when using commands with lots of output like `apt list`.

diff --git a/apt-pkg/contrib/strutl.cc b/apt-pkg/contrib/strutl.cc
index 5e641a02b23524396e68dfadf81eb2d0c3d3f266..242a78449a661487e2d8527d5729836b387a5e93 100644 (file)
--- a/apt-pkg/contrib/strutl.cc
+++ b/apt-pkg/contrib/strutl.cc
@@ -464,7 +464,9 @@ string SubstVar(const string &Str,const string &Subst,const string &Contents)
 
    if (OldPos >= Str.length())
       return Temp;
-   return Temp + string(Str,OldPos);
+
+   Temp.append(Str, OldPos, string::npos);
+   return Temp;
 }
 string SubstVar(string Str,const struct SubstVar *Vars)
 {