Avoid string copy and std::list penalty in strings::Format.

2 files changed, 31 insertions, 49 deletions

diff --git a/base/string_format.cpp b/base/string_format.cpp
index 122aeadc92..fb8b46f7f2 100644
--- a/base/string_format.cpp
+++ b/base/string_format.cpp
@@ -1,25 +1,27 @@
 #include "string_format.hpp"
-#include "logging.hpp"
+
+#include "../std/list.hpp"
+
 
 namespace strings
 {
-  string const FormatImpl(string const & s, list<string> const & l)
+  string const FormatImpl(string const & s, string arr[], size_t count)
   {
     size_t offs = 0;
     list<size_t> fieldOffs;
 
-    string temp = s;
+    string res = s;
 
     while (true)
     {
-      offs = temp.find("%", offs);
+      offs = res.find("%", offs);
       if (offs == string::npos)
         break;
       else
       {
-        if ((offs != 0) && (temp[offs - 1] == '\\'))
+        if ((offs != 0) && (res[offs - 1] == '\\'))
         {
-          temp = temp.erase(offs - 1, 1);
+          res = res.erase(offs - 1, 1);
           --offs;
         }
         else
@@ -30,18 +32,14 @@ namespace strings
     }
 
     offs = 0;
+    size_t i = 0;
 
-    string res = temp;
-
-    list<size_t>::const_iterator offsIt;
-    list<string>::const_iterator strIt;
-
-    for (offsIt = fieldOffs.begin(), strIt = l.begin();
-        (offsIt != fieldOffs.end()) && (strIt != l.end());
-        ++offsIt, ++strIt)
+    for (list<size_t>::const_iterator offsIt = fieldOffs.begin();
+        (offsIt != fieldOffs.end()) && (i < count);
+        ++offsIt, ++i)
     {
-      res.replace(*offsIt + offs, 1, *strIt);
-      offs += strIt->size() - 1;
+      res.replace(*offsIt + offs, 1, arr[i]);
+      offs += (arr[i].size() - 1);
     }
 
     return res;
diff --git a/base/string_format.hpp b/base/string_format.hpp
index d97a8faeb9..5bb29ca5de 100644
--- a/base/string_format.hpp
+++ b/base/string_format.hpp
@@ -1,73 +1,57 @@
 #pragma once
+#include "base.hpp"
+#include "macros.hpp"
 
 #include "../std/string.hpp"
 #include "../std/sstream.hpp"
-#include "../std/list.hpp"
+
 
 namespace strings
 {
   template <typename T>
-  string ToString(T t)
+  string ToString(T const & t)
   {
+    // May be we should use DebugPrint here. Not sure.
+
     ostringstream out;
     out << t;
     return out.str();
   }
 
-  string const FormatImpl(string const & s, list<string> const & l);
+  string const FormatImpl(string const & s, string arr[], size_t count);
 
   template <typename T1>
   string const Format(string const & s, T1 const & t1)
   {
-    list<string> l;
-    l.push_back(ToString(t1));
-
-    return FormatImpl(s, l);
+    string arr[] = { ToString(t1) };
+    return FormatImpl(s, arr, ARRAY_SIZE(arr));
   }
 
   template <typename T1, typename T2>
   string const Format(string const & s, T1 const & t1, T2 const & t2)
   {
-    list<string> l;
-    l.push_back(ToString(t1));
-    l.push_back(ToString(t2));
-
-    return FormatImpl(s, l);
+    string arr[] = { ToString(t1), ToString(t2) };
+    return FormatImpl(s, arr, ARRAY_SIZE(arr));
   }
 
   template <typename T1, typename T2, typename T3>
   string const Format(string const & s, T1 const & t1, T2 const & t2, T3 const & t3)
   {
-    list<string> l;
-    l.push_back(ToString(t1));
-    l.push_back(ToString(t2));
-    l.push_back(ToString(t3));
-
-    return FormatImpl(s, l);
+    string arr[] = { ToString(t1), ToString(t2), ToString(t3) };
+    return FormatImpl(s, arr, ARRAY_SIZE(arr));
   }
 
   template <typename T1, typename T2, typename T3, typename T4>
   string const Format(string const & s, T1 const & t1, T2 const & t2, T3 const & t3, T4 const & t4)
   {
-    list<string> l;
-    l.push_back(ToString(t1));
-    l.push_back(ToString(t2));
-    l.push_back(ToString(t3));
-    l.push_back(ToString(t4));
-
-    return FormatImpl(s, l);
+    string arr[] = { ToString(t1), ToString(t2), ToString(t3), ToString(t4) };
+    return FormatImpl(s, arr, ARRAY_SIZE(arr));
   }
 
   template <typename T1, typename T2, typename T3, typename T4, typename T5>
   string const Format(string const & s, T1 const & t1, T2 const & t2, T3 const & t3, T4 const & t4, T5 const & t5)
   {
-    list<string> l;
-    l.push_back(ToString(t1));
-    l.push_back(ToString(t2));
-    l.push_back(ToString(t3));
-    l.push_back(ToString(t4));
-    l.push_back(ToString(t5));
-
-    return FormatImpl(s, l);
+    string arr[] = { ToString(t1), ToString(t2), ToString(t3), ToString(t4), ToString(t5) };
+    return FormatImpl(s, arr, ARRAY_SIZE(arr));
   }
 }