comphelper: add string::join()

If there is a need for it, this could be extended later to work with uno
sequences and/or OUStrings as well.

Change-Id: Id0af8b1755c8e4b668720563d10a052337e1b2c9

comphelper/source/misc/string.cxx

@@ -270,6 +270,17 @@ uno::Sequence< OUString >
     return kws;
 }
 
+OString join(const OString& rSeparator, const std::vector<OString>& rSequence)
+{
+    OStringBuffer aBuffer;
+    for (size_t i = 0; i < rSequence.size(); ++i)
+    {
+        if (i != 0)
+            aBuffer.append(rSeparator);
+        aBuffer.append(rSequence[i]);
+    }
+    return aBuffer.makeStringAndClear();
+}
 
 sal_Int32 compareNatural( const OUString & rLHS, const OUString & rRHS,
     const uno::Reference< i18n::XCollator > &rCollator,

include/comphelper/string.hxx

@@ -23,6 +23,7 @@
 #include <sal/config.h>
 
 #include <cstddef>
+#include <vector>
 #include <comphelper/comphelperdllapi.h>
 #include <sal/types.h>
 #include <rtl/strbuf.hxx>
@@ -310,6 +311,9 @@ COMPHELPER_DLLPUBLIC sal_Int32 indexOfAny(OUString const& rIn,
 COMPHELPER_DLLPUBLIC OUString convertCommaSeparated(
     ::com::sun::star::uno::Sequence< OUString > const & i_rSeq);
 
+/// Return a string which is the concatenation of the strings in the sequence.
+COMPHELPER_DLLPUBLIC OString join(const OString& rSeparator, const std::vector<OString>& rSequence);
+
 /** Convert a decimal string to a number.
 
     The string must be base-10, no sign but can contain any