From 6fc65a45985756ca3149b5d841198506a3372050 Mon Sep 17 00:00:00 2001
From: Maksim Korotkov <m.korotkov@postgrespro.ru>
Date: Tue, 17 Sep 2024 12:50:06 +0300
Subject: [PATCH] std::string concatenation has been removed to optimize loops

The join() template function is implemented
to convert stl containers to a string.

Signed-off-by: Maksim Korotkov <m.korotkov@postgrespro.ru>
---
 blobstamper/stamp_enumerator.cpp | 14 ++--------
 blobstamper/stamp_text.cpp       | 47 ++++++++++----------------------
 blobstamper/utils.h              | 39 ++++++++++++++++++++++++++
 3 files changed, 56 insertions(+), 44 deletions(-)
 create mode 100644 blobstamper/utils.h

diff --git a/blobstamper/stamp_enumerator.cpp b/blobstamper/stamp_enumerator.cpp
index 9419dd1..2ddc9dc 100644
--- a/blobstamper/stamp_enumerator.cpp
+++ b/blobstamper/stamp_enumerator.cpp
@@ -21,22 +21,12 @@
 #include"galley.h"
 #include"stamp.h"
 #include"blob.h"
-
-
+#include "utils.h" 
 
 std::string StampStrEnumerator::ExtractStr(std::shared_ptr<Blob> blob)
 {
   std::vector<std::string> data = ExtractStrVector(blob);
-  std::string res = "";
-
-  for(std::string s : data)
-  {
-    if (!res.empty())
-    {
-      res+= separator;
-    }
-    res+= s;
-  }
+  auto res = Utils::join(data, separator);
   res = left_bracket + res + right_bracket;
   return res;
 }
diff --git a/blobstamper/stamp_text.cpp b/blobstamper/stamp_text.cpp
index 7d8ade7..41978e7 100644
--- a/blobstamper/stamp_text.cpp
+++ b/blobstamper/stamp_text.cpp
@@ -15,56 +15,39 @@
  * limitations under the License.
  *
  ******************************************************************************/
+#include <sstream>
 
 #include"stamp_text.h"
+#include "utils.h"
 
 std::string
 StampTextPulp::ExtractStr(std::shared_ptr<Blob> blob)
 {
     std::vector<char> data = blob->Chop(minSize(), maxSize())->AsByteVector();
+  if (data.empty())
+  {
+    return {};
+  }
+  std::ostringstream ss;
 
-    std::vector<char>::iterator the_iterator;
-
-    the_iterator = data.begin();
-    std:: string res;
-    while (the_iterator != data.end())
-    {
-      if (*the_iterator == '\0') { *the_iterator = ' '; }
-      res.push_back(*the_iterator++);
-    }
+  for (auto sym : data)
+  {
+    if (sym == '\0') { sym = ' '; }
+    ss << sym;
+  }
 
-    return res;
+  return ss.str();
 }
 
 std::string StampTextPulpWords::ExtractStr(std::shared_ptr<Blob> blob)
 {
   std::vector<std::string> data = ExtractStrVector(blob);
-  std::string res = "";
-
-  for(std::string s : data)
-  {
-    if (!res.empty())
-    {
-      res+=" ";
-    }
-    res+= s;
-  }
-  return res;
+  return Utils::join(data, " ");
 }
 
 std::string StampTextDictWords::ExtractStr(std::shared_ptr<Blob> blob)
 {
   std::vector<std::string> data = ExtractStrVector(blob);
-  std::string res = "";
-
-  for(std::string s : data)
-  {
-    if (!res.empty())
-    {
-      res+=" ";
-    }
-    res+= s;
-  }
-  return res;
+  return Utils::join(data, " ");
 }
 
diff --git a/blobstamper/utils.h b/blobstamper/utils.h
new file mode 100644
index 0000000..63a4cce
--- /dev/null
+++ b/blobstamper/utils.h
@@ -0,0 +1,39 @@
+/******************************************************************************
+ *
+ * Copyright 2021-2024 Nikolay Shaplov (Postgres Professional)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ ******************************************************************************/
+#include <sstream>
+
+namespace Utils
+{
+template <typename T>
+    std::string join(const T &container, const std::string &delimiter)
+    {
+        std::ostringstream oss;
+        if (container.empty())
+        {
+            return {};
+        }        
+        for (auto it = container.cbegin(); it != container.cend(); ++it)
+        {
+            oss << *it << delimiter;
+        }
+
+        auto res = oss.str();
+        res.resize(res.size() - delimiter.size());
+        return res;
+    }
+}
\ No newline at end of file