partial merge #16670: Add Join helper to join a list of strings

src/Makefile.am

@@ -262,6 +262,7 @@ BITCOIN_CORE_H = \
   utilasmap.h \
   utilmemory.h \
   utilmoneystr.h \
+  utilstring.h \
   utiltime.h \
   validation.h \
   validationinterface.h \
@@ -587,6 +588,7 @@ libdash_util_a_SOURCES = \
   utilmoneystr.cpp \
   utilstrencodings.cpp \
   utiltime.cpp \
+  utilstring.cpp \
   $(BITCOIN_CORE_H)
 
 if GLIBC_BACK_COMPAT

src/test/util_tests.cpp

@@ -8,6 +8,7 @@
 #include <primitives/transaction.h>
 #include <sync.h>
 #include <utilstrencodings.h>
+#include <utilstring.h>
 #include <utilmoneystr.h>
 #include <test/test_dash.h>
 
@@ -95,6 +96,13 @@ BOOST_AUTO_TEST_CASE(util_HexStr)
     );
 }
 
+BOOST_AUTO_TEST_CASE(util_Join)
+{
+    // Normal version
+    BOOST_CHECK_EQUAL(Join({}, ", "), "");
+    BOOST_CHECK_EQUAL(Join({"foo"}, ", "), "foo");
+    BOOST_CHECK_EQUAL(Join({"foo", "bar"}, ", "), "foo, bar");
+}
 
 BOOST_AUTO_TEST_CASE(util_FormatISO8601DateTime)
 {

src/utilstring.cpp

@@ -0,0 +1,5 @@
+// Copyright (c) 2019 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <utilstring.h>

src/utilstring.h

@@ -0,0 +1,35 @@
+// Copyright (c) 2019 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_UTILSTRING_H
+#define BITCOIN_UTILSTRING_H
+
+#include <functional>
+#include <string>
+#include <vector>
+
+/**
+ * Join a list of items
+ *
+ * @param list       The list to join
+ * @param separator  The separator
+ * @param unary_op   Apply this operator to each item in the list
+ */
+template <typename T, typename UnaryOp>
+std::string Join(const std::vector<T>& list, const std::string& separator, UnaryOp unary_op)
+{
+    std::string ret;
+    for (size_t i = 0; i < list.size(); ++i) {
+        if (i > 0) ret += separator;
+        ret += unary_op(list.at(i));
+    }
+    return ret;
+}
+
+inline std::string Join(const std::vector<std::string>& list, const std::string& separator)
+{
+    return Join(list, separator, [](const std::string& i) { return i; });
+}
+
+#endif // BITCOIN_UTILSTRING_H