util: Add Join helper to join a list of strings

MarcoFalke · furszy · commit f6c28729ce51 · 2021-06-28T15:08:25.000-03:00
diff --git a/src/Makefile.am b/src/Makefile.am
@@ -286,6 +286,7 @@ BITCOIN_CORE_H = \
   util/memory.h \
   util/system.h \
   util/macros.h \
+  util/string.h \
   util/threadnames.h \
   utilstrencodings.h \
   utilmoneystr.h \
@@ -558,6 +559,7 @@ libbitcoin_util_a_SOURCES = \
   utilmoneystr.cpp \
   util/threadnames.cpp \
   utilstrencodings.cpp \
+  util/string.cpp \
   utiltime.cpp \
   $(BITCOIN_CORE_H) \
   $(LIBSAPLING_H)
diff --git a/src/test/util_tests.cpp b/src/test/util_tests.cpp
@@ -9,6 +9,7 @@
 #include "primitives/transaction.h"
 #include "sync.h"
 #include "utilstrencodings.h"
+#include "util/string.h"
 #include "utilmoneystr.h"
 #include "test/test_pivx.h"
 #include "util/vector.h"
@@ -85,6 +86,19 @@ BOOST_AUTO_TEST_CASE(util_HexStr)
         "04 67 8a fd b0");
 }
 
+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");
+
+    // Version with unary operator
+    const auto op_upper = [](const std::string& s) { return ToUpper(s); };
+    BOOST_CHECK_EQUAL(Join<std::string>({}, ", ", op_upper), "");
+    BOOST_CHECK_EQUAL(Join<std::string>({"foo"}, ", ", op_upper), "FOO");
+    BOOST_CHECK_EQUAL(Join<std::string>({"foo", "bar"}, ", ", op_upper), "FOO, BAR");
+}
 
 BOOST_AUTO_TEST_CASE(util_FormatISO8601DateTime)
 {
diff --git a/src/util/string.cpp b/src/util/string.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 <util/string.h>
diff --git a/src/util/string.h b/src/util/string.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_UTIL_STRING_H
+#define BITCOIN_UTIL_STRING_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_UTIL_STRENCODINGS_H
